U.S. patent application number 17/230027 was filed with the patent office on 2021-07-29 for cartridge for bead-milling-based testing of erythrocyte mechanical fragility.
The applicant listed for this patent is Blaze Medical Devices, Inc.. Invention is credited to Kenneth Alfano, Terrance Boyd, Aaron Kehrer, Steven Meines, Gene Parunak, Michael Tarasev.
Application Number | 20210231640 17/230027 |
Document ID | / |
Family ID | 1000005512333 |
Filed Date | 2021-07-29 |
United States Patent
Application |
20210231640 |
Kind Code |
A1 |
Alfano; Kenneth ; et
al. |
July 29, 2021 |
Cartridge for Bead-Milling-Based Testing of Erythrocyte Mechanical
Fragility
Abstract
A bead mill and an associated bead-mill-based machine for
testing mechanical fragility of red blood cells, employing a
cartridge configured to contain a sample while cells get stressed
via bead oscillation and, in the case of the fragility testing
machine, also while lysis levels get detected, for presentation of
fragility information.
Inventors: |
Alfano; Kenneth; (Canton,
MI) ; Tarasev; Michael; (Pinckney, MI) ;
Meines; Steven; (Ypsilanti, MI) ; Boyd; Terrance;
(Jackson, MI) ; Kehrer; Aaron; (Ypsilanti, MI)
; Parunak; Gene; (Saline, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Blaze Medical Devices, Inc. |
Ann Arbor |
MI |
US |
|
|
Family ID: |
1000005512333 |
Appl. No.: |
17/230027 |
Filed: |
April 14, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
16408927 |
May 10, 2019 |
11009500 |
|
|
17230027 |
|
|
|
|
14773137 |
Sep 4, 2015 |
10495629 |
|
|
PCT/US2014/012583 |
Jan 22, 2014 |
|
|
|
16408927 |
|
|
|
|
61773790 |
Mar 6, 2013 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 21/17 20130101;
B01L 3/508 20130101; G01N 33/49 20130101; G01N 2203/0089 20130101;
B02C 19/06 20130101; G01N 3/08 20130101; G01N 2203/0087
20130101 |
International
Class: |
G01N 33/49 20060101
G01N033/49; B01L 3/00 20060101 B01L003/00; B02C 19/06 20060101
B02C019/06; G01N 3/08 20060101 G01N003/08; G01N 21/17 20060101
G01N021/17 |
Claims
1. A cartridge for use in testing mechanical fragility of red blood
cells (RBC), the cartridge comprising: a body having a first
portion configured for securely mounting the cartridge within a
mechanical fragility testing device; a second portion defining a
chamber for holding a sample containing red blood cells (RBC);
first and second end portions disposed at opposite longitudinal
ends of the second portion of the body and enclosing each end of
the chamber, at least one of the first and second end portions
defining a sealable passage for inserting the sample into the
chamber; a bead disposed within the chamber and configured for
movement that progressively lyses the RBC within the chamber in
response to forces imparted by the mechanical fragility testing
device; wherein the second portion of the body includes a flexible,
transparent portion configured to be in contact with at least a
representative portion of the sample, the flexible, transparent
portion configured to be pinched and permit repeated projections of
light therethrough, while the sample and the bead are within the
chamber, to produce optical measurements for ascertaining levels of
hemolysis present in the sample at a plurality of points in
time.
2. The cartridge of claim 1, wherein the end portions comprise
plugs.
3. The cartridge of claim 1, wherein said flexible, transparent
portion comprises a flexible plastic tube for containing the
sample.
4. The cartridge of claim 3, further comprising a rigid tube that
substantially encases the flexible plastic tube.
5. The cartridge of claim 1, wherein the chamber is substantially
without air when sealed.
6. The cartridge of claim 1, wherein said movement is oscillation
at a frequency of up to 30 Hz
7. The cartridge of claim 1, wherein said forces are magnetic.
8. The cartridge of claim 7, wherein said forces are from an audio
transducer in the testing device.
9. The cartridge of claim 1, wherein the bead has grooves, ridges,
a textured surface, and/or varying diameters along its length.
10. The cartridge of claim 1, wherein the bead is coated for
biocompatibility with the sample.
11. A cartridge for use in testing mechanical fragility of red
blood cells (RBC), the cartridge comprising: a body having a first
portion configured for securely mounting the cartridge within a
mechanical fragility testing device; a second portion defining a
plurality of chambers for holding respective subsamples, the
subsamples each comprising a portion of a sample containing red
blood cells (RBC); first and second end portions disposed at
opposite longitudinal ends of the second portion of the body and
enclosing each end of each chamber of the plurality of chambers, at
least one of the first and second end portions defining a sealable
passage for inserting the sample into the second portion of the
body and splitting the sample into the subsamples in each chamber
of the plurality of chambers; a plurality of beads, each bead
disposed within a respective chamber of the plurality of chambers
and configured for movement that progressively lyses the RBC within
the respective chamber in response to forces imparted by the
mechanical fragility testing device; wherein the second portion of
the body includes for each chamber a flexible, transparent portion
configured to be in contact with at least a representative portion
of the subsample contained in the chamber, the flexible,
transparent portion configured to be pinched and permit repeated
projections of light therethrough, while the subsample and a
corresponding bead of the plurality of beads are within the
chamber, to produce optical measurements for ascertaining levels of
hemolysis present in the subsample at a plurality of points in
time.
12. The cartridge of claim 11, wherein the end portions comprise
plugs.
13. The cartridge of claim 11, wherein the flexible, transparent
portion of each chamber comprises a flexible plastic tube for
containing the subsample in the chamber.
14. The cartridge of claim 13, further comprising a plurality of
rigid tubes, each of the plurality of rigid tubes substantially
encasing a corresponding flexible plastic tube.
15. The cartridge of claim 11, wherein each chamber is
substantially without air when said second portion of the body is
sealed.
16. The cartridge of claim 11, wherein said movement is oscillation
at a frequency of up to 30 Hz.
17. The cartridge of claim 11, wherein said forces are
magnetic.
18. The cartridge of claim 17, wherein said forces are from an
audio transducer in the testing device.
19. The cartridge of claim 11, wherein at least one bead of the
plurality of beads has grooves, ridges, a textured surface, and/or
varying diameters along its length.
20. The cartridge of claim 11, wherein at least one bead of the
plurality of beads is coated for biocompatibility with the sample.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. patent application
Ser. No. 16/408,927 filed May 10, 2019 and incorporated herein by
reference in its entirety, which is a divisional of U.S. patent
application Ser. No. 14/773,137 filed Sep. 4, 2015 and incorporated
herein by reference in its entirety, which is a U.S. national stage
application of International Application No. PCT/US2014/012583
designating the United States of America and filed Jan. 22, 2014
and incorporated herein by reference in its entirety, which claims
the priority benefit of U.S. Provisional Patent Application No.
61/773,790, filed Mar. 6, 2013 and which is incorporated herein by
reference in its entirety.
TECHNICAL FIELD
[0002] This disclosure relates to laboratory instruments and
medical devices, and associated methods and components. More
particularly, it relates to bead mills in general as well as
associated tests for mechanical fragility of red blood cells.
BACKGROUND ART
[0003] The statements in this section merely provide background
information related to the present disclosure. Accordingly, such
statements are not intended to constitute an admission of prior
art.
[0004] Red blood cell (RBC, erythrocyte) membrane fragility can be
measured in various ways, principally either osmotically or
mechanically. In general, it involves subjecting a sample of cells
to a stress and measuring how much hemolysis occurs as a result of
the applied stress. In the case of mechanical fragility (MF), cell
membranes are exposed to some kind of mechanical disturbance such
as a shear stress--which may vary in intensity, duration, or other
parameters--while the proportion of cells lysing is tracked. This
enables cells' overall susceptibility to hemolysis to be
characterized and presented (comprehensively or selectively) in
various ways. Fragility indices or profiles (single-parameter or
multi-parameter) for erythrocytes may be desirable for research
purposes or for clinical purposes. Applications may include blood
product quality testing, diagnostics, clinical research, or basic
research on RBC of humans or other species.
SUMMARY OF INVENTION
[0005] This section briefly and non-exhaustively summarizes certain
subject matter of this disclosure.
[0006] This disclosure includes description of an MF tester
configurable for testing erythrocyte membrane mechanical fragility,
the machine comprising: a sample miller for moving a bead residing
within a sample comprising erythrocytes within a stressing chamber,
wherein the stressing chamber is configured to cause hemolysis in
said sample; a chamber pincher for reversibly compressing an
optically transparent portion of said stressing chamber to a
thickness(es) suitable for an optical measurement to quantify said
hemolysis; an optical detector for said optical measurement to
quantify said hemolysis; and a light source for said optical
detector.
[0007] The sample miller can include various configurations of cams
(e.g. scotch yoke), or non-cam mechanical linear actuators, or
non-mechanical linear actuators can present some alternative sorts
of bead-milling mechanisms. In this respect, this disclosure
pertains to an integratable, general-purpose mechanical fragility
testing system utilizing a bead mill principle or the like for
stressing the samples. In some embodiments, a motion-control system
provides directly or indirectly lysis-inducing movement, while also
providing upon defined intervals of stress sufficient optical
proximity for effective detection of the extent of resultant lysis
in a given sample of cells being tested. Moreover, in some
embodiments no fluidic transfer is needed between stressing and
detection of respective portions of a sample, and/or a disposable
cartridge is employed to house the sample during testing. Another
class of aspects or embodiments may involve a magnetic or
electromagnetic bead mill, some embodiments of which allow moving a
bead within a sample without needing to move the cartridge or any
associated carriage.
[0008] Chamber pincher embodiments include, for example, vertical
poles on one or two lateral sides of the cartridge, with a pole on
both sides being preferred for stronger and more uniform and stable
compression. In this case, a top and/or a bottom bar having flat
surfaces may slide vertically toward each other by sliding at least
one of them (with a rigid probe accompanying or embodying the fiber
optic from at least one vertical direction, e.g. to enable pushing
down on the flexible tube/chamber), driven by a stepper motor, to
compress the chamber for optical detection when needed.
Alternatively, the orientation of components can be altered such
that the pinching occurs horizontally, or any other known pinching
mechanism could be substituted and adapted appropriately.
[0009] Optical detector embodiments include, for example, a
spectrophotometer configured to measure light absorption, such as
for example in a wavelength range of about 390-460 nm if using the
preferred spectral approach described herein. Alternatively, a
spectrometer may be configured to measure scatter, or the optical
detector may be a cell counter utilizing light microscopy. Light
source embodiments include, for example, a 420 nm and a white (e.g.
4000-5500 Kelvin) Light Emitting Diodes (LEDs), or other
appropriate LED configurations, or bright-field microscopy bulbs
(all depending in significant part, of course, upon the optical
detection means and approach being employed). The pincher ensures
that fiber optics from the top (e.g. illuminating fiber) and bottom
(e.g. detecting fiber) of the chamber get near enough to each other
to enable the optical detection/measurement.
[0010] This disclosure also includes description of a
sample-holding cartridge for an MF tester, the cartridge
comprising: a cartridge body for containing a sample, said
cartridge body comprising an optically transparent material at a
place where at least a portion of said sample can be reversibly
dispersed upon pinching to be a thickness(es) suitable for optical
detection of red blood cell hemolysis, said optically transparent
material being flexible, or compressible, or being in direct or
indirect connection with a flexible or compressible portion; and a
bead(s) for milling said sample within the cartridge.
[0011] In some embodiments, said cartridge is "multiplexed" and
thus comprises multiple such cartridges in combination together for
testing distinct samples and/or for testing sub-samples of a given
sample(s), perhaps simultaneously to conserve time and/or effort.
In this respect, this disclosure pertains to a sample-holding
cartridge, preferably disposable, and preferably single-use to
minimize cleaning or risk of contamination (as for non-multiplex
cartridges as well), for the aforementioned testing system, which
may comprise an optically transparent portion at an area of said
cartridge where said sample can be brought to dispersed or thinned
to achieve a thickness which may or may not be predetermined
(depending on the approach for this used in a given embodiment)
upon a pinching of said cartridge, said optically transparent
portion being either also a flexible portion and/or in direct or
indirect contact with a flexible portion to facilitate said
pinching--which may be temporary or reversible so as to enable
repeated such pinching, either between different extents of
mechanical stress application and/or for repeat measurement any
given single point of the same.
[0012] This disclosure also includes a description of an
electromagnetic (EM) bead mill, of the kind employed in some
embodiments herein of an MF tester, and which is also utilizable
alone for any general purpose for which bead mills are currently
used (e.g. disruption of a biological sample). The present EM bead
mill comprises a holding place for positioning a cartridge
containing a sample and a bead, and an electromagnet configured to
cause said bead to oscillate within said cartridge, to disrupt said
sample. Preferred embodiments of the EM based embodiments utilize
adaptations of existing developed audio transducers to produce the
EM fields. The configuration can be set to work by either moving
the entire cartridge, in which case the bead would not need to be
magnetic, or it can be set to just move the bead, in which case the
cartridge could remain still and the bead would need to be
sufficiently magnetic. Unlike the use of beads in ultrasound-based
cell disruption, which (when supplemented with beads) typically
utilizes beads no more than about 500 microns in diameter induced
to oscillate by ultrasound in the kHz-MHz (i.e., at least 1000 Hz)
frequency range, the bead(s) in the present bead mill should be
larger and/or heavier, at least one or more millimeter(s) in
diameter, with oscillating frequencies in the Hz (under 1000 Hz)
range. Moreover, the present invention is capable of providing
non-ultrasonic bead-induced mechanical shear stress to the sample.
In the case of a general bead mill, the vial or tube or cartridge
is typically a single-use disposable product (simpler than the
cartridges needed for fragility testing), and in those cases the
bead is typically reusable. Associated methods include using the
system to measure RBC MF, and also making the sample-holding
cartridge.
[0013] The scope of the invention is defined by the claims, which
are incorporated into this section by reference. A more complete
understanding of the present disclosure (including other filings
that are incorporated herein by reference) and associated
embodiments will be afforded to those skilled in the art, as well
as the realization of additional advantages thereof, in
consideration of the overall disclosure including drawings where
applicable. Reference will be made to the appended sheets of
drawings that will first be described briefly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] All drawings are for illustrative and explanatory purposes
only and not intended to limit the present invention to any of the
example embodiments depicted.
[0015] FIG. 1 shows embodiments of a sample cartridge.
[0016] FIG. 2 shows a chart of bead velocity versus time.
[0017] FIG. 3 shows a bead-mill-based MF tester embodiment,
exterior view.
[0018] FIG. 4 shows a bead-mill-based MF tester embodiment,
interior view.
[0019] FIG. 5 shows a bead-mill-based MF tester embodiment,
interior view without casing.
[0020] FIG. 6 shows a "pre-run" screen.
[0021] FIG. 7 shows the pre-run screen with planned data point
collection times.
[0022] FIG. 8 shows an example screen with an attempted run that
failed a hardware check.
[0023] FIG. 9 shows the screen when the system is waiting for the
temperature to reach the set point.
[0024] FIG. 10 shows the screen with a run attempt that has failed
an optical density check.
[0025] FIG. 11 shows the example screen with a run in-progress.
[0026] FIG. 12 shows an example of a data structure.
[0027] FIG. 13 shows a settings embodiment.
[0028] FIG. 14 shows a csv file with field identifiers.
[0029] FIG. 15 shows a generalized software architecture
diagram.
[0030] FIG. 16 shows an activity model.
[0031] FIG. 17 shows a software context diagram.
[0032] FIG. 18 shows a high-level system-architecture diagram.
[0033] FIG. 19 shows a system-architecture diagram.
[0034] FIG. 20 shows a block diagram of system elements.
[0035] FIG. 21 shows a block diagram of a sample-holding
cartridge.
[0036] FIG. 22 shows a translation of rotary motion to linear
motion.
[0037] FIG. 23 shows pinch mechanics and optics.
[0038] FIG. 24 shows a multi-plexed cartridge.
[0039] FIG. 25A shows a perspective view of a plastic-tubing based
embodiment of a single-sample-holding cartridge.
[0040] FIG. 25B shows a top view of a plastic-tubing based
embodiment of a single-sample-holding cartridge.
[0041] FIG. 25C shows a cross-section view of a plastic-tubing
based embodiment of a single-sample-holding cartridge.
[0042] FIG. 26 shows examples of non-conventional bead designs.
[0043] FIGS. 27A and 27B show an electro-magnetic (EM) embodiment
of a bead-mill.
[0044] FIGS. 28A and 28B show a mechanical fragility tester
utilizing an EM bead-mill.
MODE(S) FOR CARRYING OUT THE INVENTION
[0045] This section contains descriptive content for this
disclosure. It is also to be understood that the terminology and
phraseology used herein is for explanatory and exemplary purposes
and not intended to be limiting.
[0046] Erythrocyte mechanical fragility testing combines controlled
physical (and more specifically, mechanical) stressing of cells
along with a measurement of how much hemolysis occurs during such
stressing. A wide range of research and clinical applications are
possible for such metrics. There are many ways to provide the
mechanical stress in a fragility assay, as well as many ways to
measure the resulting hemolysis. Mechanical fragility testable by
utilizing a low-energy mechanical stress such as via bead mill,
tends to more directly reflect erythrocyte membrane properties (as
compared to high-energy mechanical stress such as via ultrasound).
Sometimes stressors can be combined, such as when evaluating
changes in mechanical fragility under differing osmolarities;
relatedly, temperature or pressure or other factors can in some
cases be relevant stress conditions.
[0047] There are also many ways that a fragility assay can in
effect measure the hemolysis resulting from the mechanical stress.
One way is by cell counting before and after a given stressing
interval (discussed for example in US Patent Application
Publication No. US20110300574, incorporated herein by reference in
its entirety). Such an approach could use any known principle of
cell counting, preferably optical, such as those using light
microscopy like the commercial Cellometer.TM. line. But whenever
the particular advantages of cell-counting are not needed or
desired, the preferred approach herein is to use the Blood
Hemolysis Analyzer invented by Michael Tarasev and discussed for
example in U.S. Pat. No. 7,790,464, issued Sep. 7, 2010,
incorporated herein by reference in its entirety. This approach
exploits the fact that the spectral peak in the Soret region
(un)flattens in relative proportion to the extent of hemolysis in a
given sample. [This optical system/method involves projecting light
into a sample to allow the light to pass through the sample,
wherein a first portion of the light, having a wavelength of about
390-460 nm, is absorbed by a cell-free hemoglobin derivative, and a
second portion of the light, having a wavelength of about 390-460
nm, is absorbed by a cellular hemoglobin derivative contained
within erythrocytes; and measuring light absorption with an
absorption detector configured to determine the light absorption of
the sample, within a wavelength range of about 390-460 nm, and to
provide an at least partially flattened spectra commensurate with
the ratio between cell-free and cellular hemoglobin, to thereby
determine the relative cell free hemoglobin concentration within
the sample, from which the proportion of hemolysed cells can then
be inferred.] This notably avoids the need for any separation steps
such as for example centrifugation or other known means for
separating solid from liquid elements; the main aspects of this
approach involve utilizing a difference in apparent (not actual)
spectral absorption between intracellular and extracellular
hemoglobin, in order to infer what fraction of RBC in a given
sample are lysed at a given time (of course, this unique approach
to lysis measurement is only suitable for RBC). Another
consideration is that determining fractional hemolysis requires
knowing or measuring the original hematocrit or a reasonable proxy
such as total hemoglobin concentration (which can be address by
various possible means).
[0048] A fragility assay can involve outputting various kinds or
amounts of fragility data--including specific values or indices,
single-variable-parameter fragility profiles, and/or
multi-variable-parameter ("multi-dimensional") fragility profiles.
(Note that "parameter" can be used to refer to either a stress
parameter or a fragility parameter.) Data matrices reflecting how
much lysis occurs under various combinations of stress parameters
can be used to give profile-based parameters characterizing the
sample tested (or the source it represents). Data of interest could
comprise how much lysis would be expected under a given set of
stress parameters, what stress condition(s) would be expected to
result in a given lysis level, or slopes or shapes of any such
curves/trajectories--the latter of which can reveal subpopulations
within a sample with their own discernible profiles. The particular
fragility parameter(s) sought will likely depend on what is deemed
most clinically or scientifically relevant for each particular
application. Notably, a single-value index parameter can itself be
determined from a profile, such as through an interpolation.
[0049] Depending on the stress/lysis method employed for a given MF
testing approach, it may be important to dilute samples to ensure
that all samples (or subsamples) have the same concentration of red
cells (hematocrit) in order to have consistency in the
rate/efficiency of hemolysis when subjected to stress.
Additionally, such dilution can be used to ensure the uniformity of
the cells' environment when comparing different RBC samples.
Another consideration is that dilution may be be necessary to bring
the spectral absorbance of the RBC or blood sample within the
dynamic range of the detection system used (e.g. cell counting
apparatus or spectrophotometer). Also, in the case of red cell
samples experiencing aggregation or coagulation, it can be useful
to ascertain the role of such on the cells' susceptibility to
induced hemolysis, along with the overall biochemical and fluidic
environment in any given sample of cells.
[0050] Sensitivity with regard to spectrally-based measures of
hemolysis can be enhanced by accounting for multiple forms of
hemoglobin (Hb)--namely oxy, deoxy, meth, and/or carboxy Hb forms.
Oxygenated (Oxy) Hb typically constitutes the vast majority in
aerated blood or RBC , with other Hb forms present in negligible
amounts. It's uncommon to determine the concentration of all four
types, and could be unnecessary for the amount of precision
typically needed, but nevertheless remains an option that could be
implemented with sufficient spectral resolution. Multi-wavelength
analysis methods for such implementation are well known. The main
three wavelengths used in the preferred optical approach include
418 nm (the peak of the soret region), 576 nm (the peak for oxy
Hb), and 685 nm for a base-line. Other absorbent proteins (e.g.
bilirubin) that may potentially interfere with hemoglobin
measurements can also be accounted for with multi-wavelength
analysis, if desired, and overall sensitivity can potentially be
enhanced by using first and second derivatives of the optical
spectra.
[0051] Benefits pertaining to various desirable aspects of RBC MF
testing can be substantially enhanced by employing a disposable
chip or cartridge component or the like to self-contain the blood
sample during testing; usage in general of a disposable component
in RBC mechanical fragility testing is a principal focus of U.S.
patent application Ser. No. 13/708,980, Publication US20130098163,
filed Dec. 8, 2012, which is hereby incorporated by reference in
its entirety. However, this present disclosure specifically
describes disposable cartridges that are configured to be used with
bead-mill based systems. [U.S. Pat. No. 8,268,244, which is hereby
incorporated by reference in its entirety, discloses a
concentric-cylinder based approach to such cartridge based
modularization (e.g. FIGS. 3 and 4 of that patent)--in that context
targeting assessments of RBCs' quality or transfusion
suitability.]
[0052] Two kinds of possible approaches for agitating a bead in a
"bead-mill-based" approach to lysing cells can include a motor/CAM
approach which shakes the sample containing the bead, or an
electromagnetic-field based approach to actuating the bead's
movement within the sample (directly or indirectly). These are both
compatible with using a disposable (ideally single-use) sample
cartridge that can serve in effect as both a stressing chamber (for
applying mechanical stress) and an optical cuvette (for measuring
lysis or indicia thereof). [Various experiments and certain other
research discussed or referenced in the description herein were
conducted by one or more co-inventor(s), sometimes with assistance
from other technical personnel of applicant company or a contracted
service provider(s), and may include experiments done via
test-beds, preliminary subsystems, mock-ups, or anything else whose
results may be potentially relevant to the present disclosure.]
[0053] This disclosure next describes an electromagnetic approach
to stressing a test sample, specifically by actuating the bead,
which some embodiments may utilize. There are situations where its
advantages (e.g., less moving parts and vibration and noise,
potentially smaller size and less ramp-up/ramp-down time for
oscillation speed, etc.) prove worthwhile. Of course, any
particular system's specifications are likely to be significantly
configuration-specific; hence generalizable principles are
explained here using empirical and/or other research results, from
which appropriate adaptations may be inferred and extrapolated as
needed. The experiments discussed here next aid with understanding
how to adapt various EM configurations as needed for various
possible bead-milling applications.
[0054] An electromagnetic (EM) bead mill can use a changing
magnetic field as the method of moving a magnet in a fluid. In a
preliminary setup and associated experiments, two 12 volt solenoids
opposing each other were used. These were powered by a function
generator which alternates the current direction according to a
chosen frequency. A switching circuit controlled the fields of both
solenoids, so at any given point in time one solenoid was pushing
the magnet away from it, and the opposing solenoid was pulling the
magnet towards it. The bead was suspended in a fluid contained by
the plastic tube.
[0055] A test was performed in order to see the effects of
different variables on the displacement of the magnet during one
period of oscillation. The variables considered were the voltage
applied across the solenoids, the distance between the solenoids,
the frequency applied, and the offset of the tube from the central
solenoid axis. The displacement of the bead magnet was calculated
by taking high speed video of the bead oscillating in the tube with
a steel rule in frame. In order to keep the tube centered for
different solenoid-to-solenoid distances, 3 different length tubes
were used. FIG. 1 depicts examples of such tubes 101, each with
plugs 102 on the ends and a magnetic bead 103 inside with liquid
104. It also illustrates conceptually how an electromagnet can be
positioned (externally) relative to such tubes, to force the
contained magnet's movement on-demand.
[0056] As voltage applied increased, the displacement at a constant
frequency generally increased. As solenoid distance increased,
displacement at a constant frequency decreased. As frequency
increased, displacement at a constant voltage decreased. An offset
from the central solenoid axis decreases displacement. As the
solenoid distance increased, the rate at which the displacement
increased per volt applied at a constant frequency decreased.
[0057] The closer the solenoids were, the stronger the force on the
bead was, and the higher the displacement for a constant voltage
and frequency. Another observation was that the rate at which the
displacement increased per volt at a given frequency was also
higher. The slopes of the displacements were found by taking linear
trend lines of the displacement vs. voltage graphs for each of the
three distances tested.
[0058] The results from 60 Hz measurements at low voltages were at
the threshold of the digital scale resolution. The testing approach
would need to be modified for applications where reliable data from
this frequency range is essential. However, for most expected
applications, 30 Hz is likely to be sufficient (for the high end of
intensities to be employed). The slope of the displacement vs.
voltage curve could in principle be used to find the voltage needed
for a specific displacement, but this would involve a working
assumption of linearly proportional behavior of the bead in a
fluid. For maximum displacement, if desired, the frequency should
be low, the solenoid distance minimized (or a single-solenoid with
alternating current can be used), the voltage maximized, and the
tube centered on the solenoid axis. Repulsive as well as attractive
magnetic force could potentially be utilized.
[0059] Also significantly, other experiments showed that, in
contrast to when the entire cartridge/sample is moved to move the
bead indirectly (whether via CAM or magnetism), moving the bead
"directly" in this manner introduces more possibility for
separation of the parameters for force or sustained bead "velocity"
versus motion "amplitude" or net relative bead movement, both of
which can be affected by oscillation "frequency," which should be
taken into account if "intensity" of stress is desired to be truly
a significantly separate parameter from aggregated net "duration"
(the true total and distribution of which can also to some extent
be a function of "frequency.")). Finally, issues with power needed
(and thus heat generated also) can be alleviated by configuring the
electromagnet(s) such that the field is optimal for efficient
longitudinal bead oscillation. [See later below for additional
description of particular EM-based approaches, including utilizing
available off-the-shelf motion actuators.]
[0060] Another class of magnetically-based embodiments for a bead
mill (or a bead-mill-based MF tester) involves having mechanical
motion outside of the sample chamber that corresponds to moving a
(non-electro) permanent magnet within the chamber (i.e., analogous
to magnetic stir bars). This could comprise counter-rotating discs
just outside either side of the cartridge, with permanent magnets
placed to engage the bead at respective points in its journey. In a
preliminary test-bed prototype evaluated for this approach, a
magnet outside the cartridge on each side was able to controllably
"carry" the magnet back and forth with good reliability and
reasonable positioning tolerances at a target frequency of 30 Hz or
oscillations/sec. Notably, magnetically trapping the bead between
magnets for such carrying proved more controllable--especially at
higher frequencies--than either "pushing" or "pulling" via direct
attraction or repulsion.
[0061] This disclosure next describes certain example approaches
and embodiments for a motorized cam-based approach to agitating the
bead. Two example kinds of motorized approaches evaluated include a
"horizontal" bead shaker/mill and a "vertical" one, using
respective versions of the TissueLyser.TM. commercial bead mills
sold by Qiagen.
[0062] The horizontal version has two cam driven arms that create a
horizontal motion (somewhat non-linear, due to angular or
partially-circular motion) to drive a bead in a sample tube, and it
is used for some of the present experiments because some
embodiments of the present system employ some of its principles. To
compare the motion of the bead in this mechanically driven lyser
with that of the aforementioned EM approach, high-speed video (HSV)
of the moving bead was taken and analyzed. Initial tests were run
using a 5 mm stainless steel bead in a solution of buffer with
Albumin. It was found that at higher oscillation frequencies the
solution foamed too much to be able to see the bead. Subsequent
runs were performed using buffer without Albumin (in general, the
biochemical environment of RBC during the testing can notably
impact lysis efficiency, which should be taken into account in a
testing protocol). Also notable is that the angular/semi-circular
nature of the motion resulted in some inconsistent stress
application at different locations in the holder of the multiple
samples.
[0063] High speed video was employed to determine the ramp up and
ramp down time lengths at the beginning and end of each discrete
stressing interval, as this also needs to be accounted for when
adapting any bead milling technology to a fragility test which
requires accurate knowledge and quantitation of stress being
applied. This presents another advantage for direct EM driven
movement of the bead itself.
[0064] As with the horizontal mill, the vertical mill is not
specifically designed for "fragility" testing purposes and hence
experiments were needed to assess the relative suitability to be
adapted for sufficiently precise and controlled application of
mechanical stress on-demand. And conversely, of course, any kind of
new or custom lyser for a fragility tester is likely to be readily
adequate to perform basic and generalized bead-milling functions if
desired (and in some cases may do so more desirably).
[0065] The vertical mill was analyzed to find the frequency of
oscillation and the velocity of the mill. Velocity vs. time was
plotted for the vertical bead mill, with the plot 200 shown in FIG.
2. The vertical bead mill is comprised of an electric motor with a
horizontal output shaft connected to a cam. The bead/tube carriage
is threaded onto a vertical shaft connected to the cam. There is a
control circuit board that handles the numerical display on the top
of the frequency and timer, and also a feedback circuit to regulate
the motor speed with information from an encoder on the motor.
Other notable differences between vertical and horizontal bead mill
approaches such as those above include that, in a vertical bead
mill, the bead comes out above the surface of a liquid sample and
impacts said surface upon every re-entry. This of course assumes
that the tube is not entirely filled, yet with a horizontal
approach the fluid dynamic implications are different in that even
an un-filled tube would not result in such periodic separation of
the bead from the sample.
[0066] Overall, for adapting these two example cam bead bills to
mechanical fragility (MF) testing, the greater linearity of the
vertical approach is preferable to the angular movement of the
horizontal mill (due to the greater accuracy/consistency), yet all
else being equal a horizontal motion is more conducive to the
preferred approaches to optical detection.
[0067] This disclosure next conceptually describes an example
embodiment for an overall MF testing system; such embodiments
feature essentially linear (i.e., non-angular) and horizontal
motion of a sample/cartridge/carriage, to shake a bead, to induce
sample rupture. Associated example embodiments of particular (often
changeable) sub-systems for this are briefly explained first in
principle, before being described later in the context of drawings.
This example embodiment (various aspects and optional features of
which can be selectively employed and/or mixed-and-matched in
enumerable combinations or permutations, to comprise various
possible embodiments) can be thought of as involving the following
six sub-systems.
[0068] First, an optics sub-system contains a spectrometer
connected to the electronics or PC, and elements to generate and
collect light from the sample and focus it on the spectrometer.
Custom and/or off-the-shelf light sources and/or spectrophotometers
may potentially be employed. Some combination of half-silvered
mirrors, dichroic mirrors, and/or beam-splitters might be
employed.
[0069] Second, a "sampling" or "pinching" sub-system contains two
moving (or one moving and one stationary) elements that pinch the
cuvette. These elements contain fiber optics to deliver and collect
light from the sample, and mechanical stops to set a particular
optics gap during pinch/release cycle (unless pinching essentially
to contact with readings collected serially during each compression
or de-compression, or compressing until reaching a predetermined
reading based on spectral characteristics of such compressed sample
irrespective of the actual gap magnitude), with two linear
actuators that control the position of the moving elements. After
pinching, they are used to retract the moving elements out of the
way so lysing can occur. There is also an electromagnet that can
pull the bead to one side of the cuvette during pinch/release cycle
(in some embodiments this function may be achieved via
gravitational tilt/pause, beveled "pusher," permanent magnet, or
other means). Preliminary experiments also show that it is best to
pinch in a manner (e.g. from the top down, maintaining a fixed/flat
bottom) that prevents gravity from pulling the sample away from
where readings will be taken, and decrease or minimize any
intra-sample separation such as cell precipitation in an RBC
suspension. The gap between compressed cartridge walls, and thus
the thickness of the sample in the optically tested area, can be
established based on the attenuation of the probing light, within
the used spectral range, due to sample absorption and optionally
scattering, such that the resultant changes in light intensity are
within the dynamic range of the detection system (e.g.
spectrophotometer). Alternatively, scattering, cumulative and/or
within a set angular range can be used to evaluate the number of
scatter-causing intact cells within the sample thus providing an
estimate of hemolysis.
[0070] Third, a lysing (or stressing) sub-system contains a cuvette
carriage that oscillates on linear rails. This carriage also has a
slot for the cuvette to be inserted.
[0071] Fourth, a carriage motion sub-system contains a motor that
controls the speed and position of the cuvette carriage during
lysing, and also moves the cuvette to the correct position during
pinch/release cycle.
[0072] Fifth, a cartridge or "cuvette" sub-system (which can also
be deemed a distinct device) contains a container consisting of a
membrane formed by two sheets of plastic film and a plastic
overmold. The membrane is flexible to allow for stretching during
sampling/pinching. This container can hold the blood and the bead
during both lysis/stressing and optical detection (to find
resultant lysis), thereby serving as both a stressing chamber and
an optical cuvette. The container can be open at one end for
loading of a sample; it also can comprise a cap that can screw on
to the container after loading.
[0073] Sixth, an electronics sub-system contains motion-control
circuitry for motor speed and angular position, and pinch/release
circuitry for pinching linear actuators and switching the
electromagnet on/off.
[0074] FIGS. 3-5 show a conceptual example system design. FIG. 3
shows an outer casing 301, on the front of which is a door 302
which here is open, thus exposing an access cavity 303, in which
there is a port 304 for inserting a cartridge (not shown). Then
FIG. 4 shows a zoom view of said access cavity, and shows a
cartridge 400 for containing a testing sample, which features
winged sides 401 to facilitate entry into corresponding slits 402
on said port, as well as a flexible and optically-transparent
membrane portion 403 (in the middle) with a hard-plastic partial
over-mold 404 for structural definition. FIG. 5 shows the interior
of the system without said casing, thus exposing the base plate
501, a motor-driven cam 502 for horizontal agitation of said
cartridge, a motor-driven pinching mechanism 503 for compressing
said membrane portion for optical readings between agitation
increments, and the control electronics 504.
[0075] The following listed conceptual steps are involved in this
example machine's operation, each employing appropriate respective
aspect(s) of the above-noted subsystems: pinch/release cycle,
moving bead aside during pinch/release cycle, optics gap distance
setting, cartridge insertion path, orienting cartridge to optics,
accommodations for blood volume displaced during pinch/release, and
disposable cuvette loading.
[0076] This disclosure next describes associated software for
running RBC MF testing system embodiments such as introduced above,
beginning with conceptual visualizations of software graphical
interface screens (the examples shown here being for a research-use
focused version of the system). [For the simulated screenshots,
note that anything labeled "sonication" should herein instead read
as "bead milling."] In many respects, these software related
aspects are readily adaptable to various kinds of embodiments--or
in some cases even non-bead-based MF testing. Note that on a high
enough level of abstraction, the software that operates the overall
system can generally be conceptually approached somewhat
independently of the particular hardware and mechanics employed for
the fragility testing unit--but at certain levels of detail they do
become interdependent, and examples provided herein are intended to
be illustrative and exemplary in a manner understood as adaptable
in various ways consistent with the full range of possible
embodiments.
[0077] FIG. 6 shows a "pre-run screen." It contains a field box for
the user to supply a run's key parameters including what level of
stress intensity (should read here "Bead Oscillation Frequency,
Hz") the device will provide 601, the total duration over which
such stress will be provided 602, and the number of data-point
intervals at which the stressing will pause to determine hemolysis
level in the sample 603. Note that the timing/spacing of the data
points, which will constitute the profile, can be customized with
further user options 604. If desired, temperature of the test
sample can be set and monitored via another sub-window 605. [Note
that a temperature control system may be included in the device, at
varying levels of sophistication employing established techniques,
as desired, to provide users with a range of testing-temperatures
to choose from (e.g. .about.5-45 deg. C). At a basic level, it may
simply keep ambient room temperature maintained within an
appropriate tolerance, such as via cooling fan(s) and perhaps
thermal baffle(s).] Data points to be collected are listed along
with identifiers (not to be confused with the sample's identifier
box 606) in a display sub-window 607 and as collected will be
plotted as a profile on a graph 608, while this progress is tracked
with a progress bar 609 for operator information and convenience
(relatedly, the cumulative amount of hemolysis in the sample is
also reported nearby 610). (Note that the profile plot may be
withheld, flagged, or disclaimed if unperformed mathematical
correction or additional measurement would be needed for a
particular sample in order to have acceptable accuracy.)
[0078] FIG. 7 shows the pre-run screen with planned data point
collection times represented by numeric text 701 being manually
adjustable (as opposed to using strictly linear or logarithmic data
point spacing) upon being generated in said display sub-window. In
this case, cycle time 702 refers to how much additional stressing
occurs for each incremental data point, while elapsed time 703
refers to the cumulative amount of stress exposure for the sample
up to any given point. And note that each data point may represent
multiple measurements repeated (e.g. for averaging) at any given
level of hemolysis.
[0079] FIG. 8 shows an example screen with an attempted run that
failed a hardware check. The warning window 801 lists possible
reasons 802 for the failure. This is an important aspect of
integrating software that operates a special machine--as the
software of the present invention is not merely abstract or
computational. Relatedly, subsequent screen examples discussed
below depict other system-related considerations such as the test
sample's temperature monitoring and optical density; moreover, an
error window (not shown) pops up if the loading door is not
securely closed when attempting to run the system for a test.
[0080] FIG. 9 shows the screen when the system is waiting for the
temperature to reach the set point, as indicated by the run status
bar 901 and system status button 902.
[0081] FIG. 10 shows the screen with a run attempt that has failed
an optical density check, as indicated by an appropriate warning
window 1001 as well as said status bar 901 and status button
902.
[0082] FIG. 11 shows the example screen with a run in-progress, as
accruing data point identifiers are being added 1101 to said
display window, with such data points being used for a partial
profile 1102 in said graph, and a correspondingly filled portion
1103 of said progress bar.
[0083] Examples of data structures include FIG. 12 which covers
example device-specific calibration and records, with field
identifiers for Device ID 1201, Spectrophotometer calibration 1202,
LED calibration 1203, LED hours 1204, and # Runs 1205.
[0084] FIG. 13 covers example settings, with field identifiers for
# repeats per rich-parameter data point (a "rich parameter" being a
stress parameter for which data points are more densely
concentrated--which is often more easily so for stress duration
versus stress intensity, for example) 1301, with the corresponding
field value representing how many pinch-release cycles (repeats of
squeezing the sample down to a readable gap-height) occur per such
data point (lysis cycle) 1302; the # spectra taken per such repeat
1303, with the corresponding field value representing how many
times a cmos sensor is scanned per pinch-release cycle 1304; the
integration time per such spectra 1305, with the corresponding
field value representing how long the sensor is on during each scan
1306; the white LED power 1307, with the corresponding field value
representing the set point determined for such value 1308; the 400
nm power 1309, with the corresponding field value representing the
set point determined for such value 1310; and the acceptable
starting hemoglobin range 1311, with the corresponding field value
representing the concentration of RBC in the sample fluid 1312.
[0085] As represented by FIG. 14, a ".csv" file may be employed
with field identifiers for run parameters 1401 as well as for
select raw data 1402.
[0086] This disclosure next addresses certain aspects of the
software architecture for a MF testing system embodiment such as
above--to help visualize the logical flow of operation in the
software that controls the blood fragility unit (testing
components), as well as the associated hardware and connections
necessary to interface with the blood fragility unit. Graphical
representations of the logical flow of the software during
operation of the MF tester are accompanied by those also helping to
visualize the main system hardware components of the blood
fragility testing unit and the control computer and their
connections to each other (system diagrams).
[0087] FIG. 15 shows a generalized software architecture diagram
1500.
[0088] FIG. 16 shows an activity model 1600.
[0089] FIG. 17 is a software context diagram to help illustrate how
the described software architecture model fits in the context of
the overall system 1700.
[0090] This disclosure next describes system integration for
overall operation of MF testing. While certain example components
may be indicated depending on the level of detail exhibited in any
given example diagram, these depictions can largely apply
interchangeably to various combinations of components or subsystems
that are consistent with any embodiment in the overall inventive
scope (e.g., electromagnetic motion vs. mechanical motion of bead,
spectral vs. cell-counting detection of lysis, etc.), and should be
interpreted accordingly.
[0091] FIG. 18 shows various described aspects of the present
invention, in the context of a "high-level" system-architecture
diagram 1800.
[0092] FIG. 19 then elaborates on the high-level diagram with a
more detailed system-architecture diagram 1900.
[0093] This disclosure next details an example embodiment of a MF
testing machine of a linear horizontal bead-milling type, in the
context of included drawings.
[0094] The main system components for this example embodiment are:
a sample cuvette/cartridge assembly (contains the sample and a bead
to mechanically lyse cells), a carriage (holds sample cuvette
during operation and rides on linear rails), miller (in this case,
a motor that drives a crank and connecting rod to turn rotary
motion into linear motion in the carriage that drives the ball
through the sample, with a position sensor that tells system when a
safe carriage position has been reached to perform analysis),
pincher (in this case, a motor and connecting arms that
address/bring the illumination and detections optics to the sample;
this system creates proper sample thickness(es) for analysis, which
might be defined by a predetermined gap length or predetermined
characteristics for the optical results; this system also controls
a magnet that draws the ball out of the pinch-zone during its
operation), LED light sources (wide spectrum (VIS+UV) combined
light source to illuminate the sample), spectrometer (detector that
collects and analysis the wavelengths of light from the sources
transmitted through the sample), analysis optics (components that
connect the source illumination and detector to the sample
cuvette), control electronics (to connect the system to the system
GUI to control operations of the other sub-systems; includes power
distribution from the supply and detection of sensor and switches
(including door interlock)).
[0095] A block diagram depicting a "top view" of system components
appears in FIG. 20. The shown elements of this example embodiment
interact as follows: To agitate and stress a sample, a mill motor
2001 turns a crank 2002 and thus a connecting rod 2003 to translate
rotary motion to linear motion for the carriage 2004. To take
optical readings intermittently, the carriage is pinched by a pinch
motor 2005 which turns a long threaded screw connected to two
joined sliding members to translate the rotary motion to dual
linear motion to concurrently bring in a light terminal from the
top and a spectral detector from the bottom (not shown).
[0096] A block diagram of a sample-holding cartridge (which also
serves as a "cuvette" in this case) appears in FIG. 21. The shown
elements of this example embodiment relate to each other as
follows: The cuvette main body 2101 is where a testing sample gets
placed via an opening 2102 that is closed with a cap 2103. Any
suitable (e.g. sufficiently strong) capping means could be employed
here (e.g. threaded screw type, snap type, etc.). A bead 2104 also
goes in said main body, whether manufactured to be there initially
or placed by a user. The closed/capped cartridge or "cuvette" then
goes in the carriage.
[0097] The translation of rotary motion to linear motion is
specifically depicted by FIG. 22, which shows the crank 2002
(turned by the mill motor) which moves the connecting rod 2003, to
cause the carriage 2004 (which holds the cuvette, which contains
the bead) to move back and forth.
[0098] Pinch mechanics and optics are specifically depicted in FIG.
23. The pinch motor 2005 causes two sliding members 2007 to push
and pull the LED output source 2301 and spectrometer input detector
2302 to and from the cuvette in the carriage 2004, to reach an
appropriate thickness for optical readings between intervals of
bead agitation of the sample. A magnet 2303 on one side pulls the
(magnetic, in this case) bead out of the way for the pinching. The
sliding-members approach, via screw threads turned by a
stepper-motor, translates rotary motion to linear (and in this
case, vertical) motion; this, or a similarly translational
mechanism, is preferred over using two separate motors.
[0099] The pinching motor strength should be commensurate with any
resistance offered by the flexible material or portion(s) thereof
to be compressed (for adequate speed/control of compression), which
may in turn depend in part upon the thickness of the material(s)
being used for the compressible portion (see below for relevant
discussion on the cartridge). Any stepper motors employed would
likely be controlled via firmware, as an intermediary between the
software and the actuators, as is common with such
electro-mechanical technologies.
[0100] This disclosure next details possible materials and
configurations for embodiments of a sample-holding cartridge device
(preferably disposable, and preferably designed for single-use) for
embodiments of an RBC MF tester. Refer back to FIG. 4 for a
generalized illustration of an embodiment of a sample-holding
cartridge (in the context of an overall testing system), and the
description thereof for an overview of the main aspects of such
embodiment. Also, see FIG. 24 for a depiction of such a cartridge
"multiplexed" 2400 or multiplied in parallel to enable testing of
multiple distinct samples or sub-samples concurrently.
[0101] There are several industry standard (i.e., pre-manufactured)
plastic materials already in use in blood related applications such
as intravenous tubes or surgical operations. Custom compounded
and/or coated or treated formulations may also be employed if
desired. Tygon.RTM. material in general, currently formulated and
produced as a proprietary family of robust plastic or polymer
tubing varying in base materials constituencies, can in many cases
offer good reversibility of compression (i.e., de-compressibility)
upon release, and (somewhat relatedly) is manufactured in
relatively high thicknesses--this can present a challenge for
optical detection in some cases; a solution to this that still
retains the overall thickness and post-compression "spring-back" is
to have small shaved or otherwise thinned "window" portion(s) of
the tube for optics, while the majority of the tube constitutes
much or all of the rest of the longitudinal body of a cylindrical
cartridge (which still may have end caps and/or a structural
component such as an overmold or exoskeleton, in addition to the
flexible tube material). Alternatively, an appropriate balance or
tradeoff among tubing thickness, flexibility, resilience, and
transparency may be selected from existing products to allow using
tubing as-is "off the shelf." Resistance to flex-fatigue is an
important consideration for repeatably-reversible pinching or other
compression over sustained usage.
[0102] An alternative to flexible tubing could employ sheets of
LDPE, or low-density polyethylene, as an example material for a
membrane portion(s) of a disposable cartridge. Sheets or "films"
(which are manufactured with notable differences from "tubing" such
as the above-noted Tygon) could be heat-staked about a rigid
skeleton--which in the above example cylindrical cartridge includes
"wings" alongside the cylinder (i.e., aiding with
handling/insertion guidance and subsequent stability, as well as
definitional structure) and circular "rings" at either end of the
cylinder. Of course, cylindrical/round shaping is not needed--but
may facilitate the use of spherical beads as well as other
non-custom parts. If using plastic "tubing," rather than
sheets/films, the extent of structure needed to be provided from an
overmold/skeleton or the like can become somewhat simpler such as a
cage or mesh or the like (in part depending on the properties and
tolerances of the tubing), and in some cases could be omitted
altogether (though some sort of structural assistance is preferred,
or at least a tacking point(s) to hold securely in position during
testing). Alternatively, it could use an essentially full
encasement, such as with a rigid tube exterior to the flexible
tube.
[0103] In the example cartridge embodiment depicted in FIGS. 25A,
25B, and 25C, the overall cartridge 2500 includes a cartridge body
2501 featuring ventilation holes 2502 and a capturing hook 2503 for
attaching to the machine (described below). Said body
holds/contains a piece of pre-manufactured flexible clear tubing of
appropriate thickness to be sufficiently compressible and
resilient, which provides a sample cavity 2504. Barbed plugs 2505
are on each end of the tube, confining a coated magnetic bead 2506,
with the "top" one of said plugs being hollowed to provide a
capillary 2508 for inserting the sample (e.g. via pipette tip, such
as used for loading electrophoresis gels) before the sealing plug
2507 is secured (e.g. via screw-threads). Upon pinching at the
cavity area between successive intervals of milling, sample inside
is temporarily pushed away from the light path as part of the
tubing shape gets reversibly compressed to allow taking an optical
reading through said tubing. There may be a separate window to
facilitate calibration or base-lining (not shown), which
alternatively could be located on the machine itself (note this may
be for example a piece of the clear plastic tubing being used in
the cartridge, for the "clear/light" calibration, as well as having
an opaque portion to be used for "blackout/dark" calibration). A
fill-line may be set to allow for a small/acceptable amount of air
to remain after sealing by the user, to minimize risk of sample
spillage or overflow. [Note that it may be acceptable in some cases
to specify that users should only use samples with minimal
auto-hemolysis, to simplify determination of a "0% lysis"
measurement. For determining "100% lysis," as a fractional
denominator, options include either running the test until a
fragility profile plateaus (and thus renders the total hemoglobin
approximately inferable), or employing spectral measurement in the
visible range (via known means).]
[0104] Whatever form the body of such a cartridge takes, portion(s)
must be strong enough to withstand any force from repeated bead
impact (e.g. via end-caps, plugs, or the like), while at least part
of the wall(s) be relatively manipulable for pinchability (e.g.
plastic-based film or tubing, likely polymer-based). It is possible
for the entire cartridge body to be non-rigid, provided sufficient
strength (e.g. end-welds/seals) and structural definition exist. In
general, a reversibly flexible and pinchable portion is the
preferred way to achieve a compressible portion of a stressing
chamber to achieve an optically-appropriate gap, to in turn
facilitate lysis measurement after or between defined stressing
session(s), and various possible plastic formulations could serve
sufficiently for such. And in general, the optimal materials and
configuration may depend in each case on a variety of
application-specific factors, and can be fairly adapted accordingly
as desired. It may also facilitate optimal function to take
measures to minimize sample foaming during agitation, whether
through anti-foam interior cartridge material properties or
treatments and/or appropriate dimensional or volume or
fill-fraction considerations (e.g. through minimizing or trapping
residual air within the cartridge interior), etc.; the latter may
require a balance of concerns, as filling to near-capacity for
example may be more functionally feasible with a relatively more
flexible tube. Sample insertion or filling (and subsequent
closing/sealing) by the user can be done by various means,
depending on how much convenience is being prioritized over
cartridge complexity. It has been observed that consistent fill
fraction is important to the results, so designs (e.g. via end tip
configuration) which ensure essentially 100% filling may be
preferred because this provides both consistency and foam
minimization (the latter being due to the lack of air in the
cartridge), though a small amount can still be acceptable.
[0105] Regarding the bead or slug or plug or like object(s) within
the cartridge to facilitate sample lysis, preliminary
experimentation has found that a typical single smooth spherical
bead may not provide the desired lysis efficiency. For example, a
conjoinment or other combination of multiple beads of varying or
alternating shapes or diameters (such as alternating small-large),
or some resemblance of this approach via a single object, may
improve lysis efficiency. The pitch, width, number, and depth of
the grooves/ridges or surface texturing, as well as the relative
length of the bead and cartridge interior, can all contribute to
lysis efficiency; this can be experimentally calibrated for any
given configuration to determine the desired level of efficiency.
Preliminary experimentation with non-conventional beads indicates
that factors such as cartridge interior shape/geometry,
size/dimensionality, volume, and fill-fraction (for example) can be
relevant and should be considered. For cylindrical tubing as the
chamber, an essentially cylindrical bead was found to be superior
to spherical beads in lysis efficiency, and ridges further improved
upon this, as did a knurled surface. Moreover, the ratio between
the bead/slug length and the interior length of the lysis chamber
was a significant factor, with a ratio between 0.5 and 0.8 being
most efficient for lysis in cases where the chamber is fully
filled. Anything that can improve lysis efficiency can be desirable
for making the test faster and/or reducing the energy use and
associated heat generation, etc. Instead of or in conjunction with
grooves or ridges, having multiple objects nested (e.g.
concentrically) can also provide additional stress, though this
approach would work better when using non-magnetic beads/objects.
Also possible is to texturize the interior surface or the cartridge
wall. If a small gap between the bead and the cartridge wall
interior is desired to aid stressing efficiency, then for a
non-cylindrical cartridge the bead would not be round or
cylindrical but would have a similar cross-sectional shape to that
of the cartridge. FIG. 26 shows some possible alternative bead
configurations, with the one 2601 being conjoined spheres of
differing diameters and another 2602 having a longitudinal rod with
spaced discs.
[0106] This disclosure next describes select approaches to
electromagnetic actuation for a bead mill (whether for general use
or for an MF tester). One example found by inventors to be
well-adaptable to controllable bead-milling, whether as part of
fragility testing or for other bead milling, is to make an
electromagnetic actuator of the sort from an audio speaker, which
was found to be appropriately controllable to give an adequate
range of linear excursion at a useful range of oscillation
frequencies (going as low as 1 Hz, and as high as at least 30 Hz,
and adjustable in increments as fine as 1 Hz). Note that higher
frequencies were found to reduce the range of motion, so the
particular parameters would ideally (but not necessarily,
particularly for plain bead-milling rather than MF testing) be
selected and/or modified to ensure adequate distance travel over
the full desired range of frequencies. A difference from an
"electromagnetic bead mill" as described earlier herein is that
there the electromagnet targeted the bead itself--rather than the
cartridge as in this case.
[0107] Inventors found through experimentation that there are
commercially-available electromagnetic (EM) actuators (e.g.
ButtKicker.TM., a line of low-frequency audio transducers utilized
to agitate special seats in movie theatres, instead of certain
voice coil shakers or other tactile devices) that can be readily
adapted to propel either an entire cartridge containing a bead or
just a magnetic bead therein, albeit more readily so for the
latter. (A tradeoff to consider when selecting between these two
approaches is that to move only the bead, the bead is limited in
composition to sufficiently magnetic material. This may require an
exterior biocompatible coating, especially as oxidation can be a
greater risk with magnetic or otherwise magnetically-susceptible
objects versus stainless steel (for example). Moving only the bead
also notably minimizes vibration, which is often a priority.) For
multiplexing, a more custom coil-based EM configuration might be
preferable to provide more flexibility on the spatial orientation
(at least for use in a MF tester, to facilitate accessibility for
optical detection--which would of course not be needed for simple
bead-milling in general). More details about the technologies
employed in some seat-agitation types of products can be found for
example in International Patent Application Publication Numbers
WO2003069299 (entitled "Electromagnetic Shaker") and WO2000005805
(entitled "Low Frequency Vibrator).
[0108] In the example bead miller embodiment depicted in FIG. 27A
and FIG. 27B, which employs the magnetic-bead approach that avoids
having to shake the entire cartridge, a low-frequency audio
transducer serving as an electromagnetic bead actuator 2701 here
essentially is adapted from one of the commercially-available
seat-agitation products noted above. FIG. 27A is a perspective
front view and FIG. 27B is a perspective back view. (By default it
comes with a magnetically suspended piston that moves precisely in
response to amplified audio signal input; the mass can generate a
high force that can be accurately transferred to whatever the
housing is attached to (which is more relevant for the
"cartridge-shaking" embodiments, rather than the direct
"bead-moving" embodiments.) For embodiments like this one, wherein
the cartridge is stationary and the bead is moved by direct
magnetism, the cartridge is positioned such that the magnetic bead
inside of the cartridge is directly movable by the transducer. In
practical use, most plain bead mills will be multi-plexed to allow
several samples to be milled simultaneously; this can be done by
using multiple of such audio transducers or other coil-based EM
actuators, and/or the direct "bead-moving" approach) by placing
multiple tubes in the EM "sweet spot" (the particular location and
size of which depends upon the particular configuration employed)
where the field causes magnet oscillation. And of course, for just
a plain bead mill without fragility testing, no flexible or
"pinchable" portion for pinching/compressing is needed in the
tube(s). Because the bead miller version shown in FIG. 27 is
specifically designed to be incorporated in the fragility-testing
machine (described subsequently), which is an embodiment designed
to incorporate a commercially-available EM actuator, it also
depicts a cartridge carrier 2702 that slides along a cartridge rail
2703 as driven by a cartridge loading motor 2704, to provide
movement of the cartridge(s) to and from the region of bead
actuation/movement (such as to and from the region of optical
detection, after respective stressing intervals). A thermal baffle
2705 may be employed to direct air flow from fan(s) (not shown), as
desired (note that temperature is more often a concern with
fragility-testing versus with plain bead-milling).
[0109] FIGS. 28A and 28B then show an example of an overall MF
tester utilizing the bead miller shown earlier in FIG. 27. FIG. 28A
is a perspective view and FIG. 28B is a top view. In addition to
elements discussed above, there is a pole-and-bar based pinching
mechanism 2801 driven by a pinch drive motor 2802 to repeatedly
compress the cartridge between milling intervals while the sampling
fiber optic 2803 gathers readings for the spectrophotometer 2804
indicating what fraction of hemoglobin is extracellular versus
intracellular (as indicative of percentage hemolysis) per the
above-noted optical technology. A fiber-coupled light source 2805
and associated LED controller 2806 serve to provide the light
during these readings, through an illuminating fiber optic 2807.
Said fiber optics can be brought toward the cartridge/sample during
the pinching. Also, if taking multiple optical readings (e.g., for
confirmation or averaging) upon each respective stressing
increment, the controlling program can if desired have the
cartridge slide once past the magnet, via the rail, in order to let
the bead essentially "mix" the sample between said repeat
readings.
[0110] This disclosure next addresses a few miscellaneous general
points regarding the overall test system and approach.
[0111] In general, fixed or normalized dilution of cell
concentrations can be performed either by the user or be automated
in the system. Alternatively, the consumable/disposable piece could
be pre-filled with appropriate buffer from manufacture. Depending
on the limitations of any given version/embodiment configuration,
usage instructions may specify a range for hematocrit or red cell
concentration that users should stay within--to maintain a given
level of accuracy.
[0112] It's important to contrast any kind of RBC "fragility" with
the related property of cell "deformability"--which is a broad
concept covering many different kinds of tests that all in some way
seek to determine how well a cell can deform or change shape under
stress. Moreover, fragility (MF in particular) is particularly well
suited for multi-parameter (>1) stressing to give
multi-dimensional (>2) profiles showing how hemolysis depends on
two or more stress variables such as extent/degree of intensity and
extent/degree of duration (for one or more given type/kind) of
mechanical stress. Indeed, merely providing the available option of
such data richness can potentially enhance the general utility of
embracing MF over other membrane-related metrics.
[0113] The fragility testing system described herein could also
potentially be adapted to test mechanical fragility of material
other than red blood cells. Of course the stressor(s)' selection
and overall system configuration would need to be empirically
assessed and modified as appropriate to suit such alternative
material, and for a type of cells or tissue (for example) other
than red blood cells an appropriately modified spectral or
cell-counting approach (if applicable) to detection of
lysis/rupture would be needed.
[0114] For purposes herein, "bead" and like terms includes broadly
any item or object whose presence in a sample serves to directly or
indirectly cause or facilitate rupture or disruption, such as cell
lysis. "Mill" and its variants refers broadly to any use of bead
movement to create mechanical stress. "Cartridge" refers to any
container that holds a sample while it gets milled, and in the
context of RBC fragility testers, also contains the sample while
hemolysis gets detected, preferably via pinching (and preferably in
the same portion of the cartridge, to avoid a need to transfer the
sample between the stressing and the detection). "Pinching" causes
at least a portion of a sample to thin in shape, to facilitate
detection.
[0115] This disclosure is enabling to those of ordinary skill in
the art, while maintaining adequate flexibility for reasonable
adaptation. Moreover, those skilled in the art will appreciate
variations of the examples and principles described herein, which
are also intended to be within the scope of the present invention.
Any references herein to "the invention" or the like are thus
intended in this spirit, always in consideration of the respective
context.
* * * * *