第673回千葉医学会整形外科例会 28.

Description of patients included at each time point in each of the development and validation samples. (DOC 37 kb

第702回千葉医学会例会・第1内科教室同門会例会 17.

Description of patients included at each time point in each of the development and validation samples. (DOC 37 kb

Stiffness Dependent Separation of Cells in a Microfluidic Device

<div><p>Abnormal cell mechanical stiffness can point to the development of various diseases including cancers and infections. We report a new microfluidic technique for continuous cell separation utilizing variation in cell stiffness. We use a microfluidic channel decorated by periodic diagonal ridges that compress the flowing cells in rapid succession. The compression in combination with secondary flows in the ridged microfluidic channel translates each cell perpendicular to the channel axis in proportion to its stiffness. We demonstrate the physical principle of the cell sorting mechanism and show that our microfluidic approach can be effectively used to separate a variety of cell types which are similar in size but of different stiffnesses, spanning a range from 210 Pa to 23 kPa. Atomic force microscopy is used to directly measure the stiffness of the separated cells and we found that the trajectories in the microchannel correlated to stiffness. We have demonstrated that the current processing throughput is 250 cells per second. This microfluidic separation technique opens new ways for conducting rapid and low-cost cell analysis and disease diagnostics through biophysical markers.</p></div

Effect of channel flow rate on Jurkat and HeyA8 cell separation.

<p><i>Numbers presented represent the averages of the trails conducted.</i></p><p>At fast flow rate, the hydrodynamic force was dominant and pushed stiff cells migrated to soft outlet which resulted in the lowest enrichment. At slow flow rate, cells were stuck to the ridges and occluded the channel which resulted in the lowest throughput. We determined channel flow rate at provided the best separation result. The cell retention is defined by calculating the ratio of cells collected at the outlet and total number of cells injected in the inlet. For example, the stiff outlet retention is . The total retention is the sum of cells collected at the two outlets.</p

Cell size is weakly correlated to cell stiffness and cell transverse displacement.

<p>Pearson coefficients are used to measure the strength of correlation. Except for K562 CD, which showed medium level of correlations, the other data showed weak correlations. The transverse displacement, cell diameter, and Young's modulus are represented as mean ± standard deviation. Sample size for K562 transverse displacement versus cell diameter is for each cell population. Sample size for K562 Young's modulus versus cell diameter is for each cell population. Sample size for HeyA8 and Jurkat Young's modulus versus cell diameter is and respectively.</p

HeyA8 cells and Jurkat cells have similar cell diameters but different stiffnesses and can be separated.

<p>(A) Flow cytometry analyses of the initial mixture of cells and the cells collected at the stiff and soft outlets show the enrichment for HeyA8 cells (<i>E</i> =  kPa) was 5.7-fold and for Jurkat cells (<i>E</i> =  kPa) was 3.1-fold (<i>N</i> = 6). HeyA8 cells were fluorescently labeled green for these studies and Jurkat cells were labeled red. (B) AFM measurement of Young's modulus of Jurkat cells and HeyA8 cells initially, before mixing and flowing, show that HeyA8 cells and Jurkat cells differ greatly in Young's modulus (cells for each cell type). (C) HeyA8 cells and Jurkat cells are similar in cell diameter when suspended (, respectively). (D) Separated cells at outlets were measured by AFM ( for each outlet). Nonparametric Wilcoxon signed-rank tests were used to test statistical significance, with * indicating a p<0.001 and ns indicating no significance.</p

K562 cells and stiffened K562 cells separation.

<p>(A) Flow cytometry analyses of the initial mixture of cells and the cells collected at the stiff and soft outlets show an enrichment of both cell types at the stiff and soft outlet respectively. 4% formaldehyde treated K562 cells (<i>E</i> =  kPa) were enriched 6.7-fold at the stiff outlet and untreated K562 cells (<i>E</i> = ) were enriched 2.3-fold at the soft outlet (<i>N</i> = 2). (B) Cell stiffness was measured with AFM and quantified in terms of Young's modulus. A nonparametric Wilcoxon signed-rank test was used to test statistical significance, with ** indicating a p<0.0001.</p

Numerical simulations that demonstrate the separation principle.

<p>(A) Cells experience both a hydrodynamic force, , and an elastic force, , as the cells are deformed by the ridges. The elastic force varies with cell stiffness. The net transverse displacement is a result of interplay between the hydrodynamic force and stiffness-dependent elastic force. (B) The free energy associated with cell compression, , increases to a maximum as the cell passes through the ridge and varies as a function of cell Young's modulus. The difference in the gradient of free energy of soft and stiff cells gives rise to different transverse forces that deflect cell trajectories in the microchannel perpendicular to the ridge and dependent on cell mechanical stiffness. (C) Simulation of velocity field and the resulting streamlines. The diagonal ridges create secondary flows (blue arrows represent velocity vector of the flow) that circulate underneath the ridges which propels soft cells in the negative transverse direction. The trajectory of soft cells follows closely to the streamline due to the minimal elastic force.</p

Cell trajectories are a function of cell stiffness.

<p>(A) Overlay of still frames from a video of an untreated and 2 CD softened K562 cells flowing in a channel. Each micrograph is an overlay of 10 still frames at equal 10 ms time intervals from a video taken at 1200 fps. Green and red solid lines represent numerical simulations of the flow trajectory stiff and soft capsules. (B) Cell transverse displacement per ridge (n = 110 cells for each cell population) for untreated K562 cells and 2 CD softened K562 cells are and respectively. (C) Young's modulus ( for each cell population) for untreated K562 cells and 2 CD treated K562 cells are and respectively. The error bars represent the standard deviation. Nonparametric Wilcoxon signed-rank tests were used to test statistical significance between the two cell populations, with ** indicating a p<0.0001.</p

Additional file 1: Table S1. of Predicting invasive fungal disease due to Candida species in non-neutropenic, critically ill, adult patients in United Kingdom critical care units

Site of Candida invasive fungal disease (N = 359). (DOC 31 kb