Optofluidic device for label-free cell classification from whole blood

Abstract

We demonstrated a unique optofluidic lab-on-a-chip device that can measure optically encoded forward scattering signals. From the design of the spatial pattern, we can measure the position and velocity of each cell in the flow and generate a 2-D cell distribution plot over the cross section of the channel. Moreover, we have demonstrated that the cell distribution is highly sensitive to its size and stiffness. The latter is an important biomarker for cell classification and our method offers a simple and unequivocal method to classify cells by their size and stiffness. We have proved the concept using live and fixed HeLa cells. Due to the stiffness and size difference of neutrophils compared to other types of white blood cells, we have demonstrated detection of neutrophils from other blood cells. Finally, we have performed the test using 5 μL of human blood. In a greatly simplified blood preparation process, skipping the usual steps of anticoagulation, centrifuge, antibody labelling or staining, filtering, etc., we have demonstrated that our device and detection principle can count neutrophils in whole human blood. Our system is compact, inexpensive and simple to fabricate and operate, having a commodity laser diode and a Si PIN photoreceiver as the main pieces of hardware. Although the results are still preliminary, the studies indicate that this optofluidic device holds promise to be a point-of-care and home care device to measure neutrophil concentration, which is the key indicator of the immune functions for cancer patients undergoing chemotherapy.

Fig. 1

(a) A schematic representation of the encoded microfluidic device and the system setup. (b) An encoded forward scattering signal detected by the silicon PIN photoreceiver.

Fig. 2

Population distribution plots for fixed HeLa cells (left) and live HeLa cells (right) over the cross section (100 μm × 45 μm) of the microfluidic channel. The Reynolds number of the sample is 11.2.

Fig. 3

WBCs and RBCs tested separately at Re = 5.6. (a) A histogram of WBCs and RBCs using cell velocity as the parameter. (b) Superimposed population distributions for WBCs and RBCs within the microfluidic channel.

Fig. 4

(a) A velocity histogram of white blood cells from 5 μL RBC-lysed whole blood sample (870 × dilution) at Re = 16.8. The histogram shows a distinguishable population of neutrophils due to their high deformability. The peak on the left of the neutrophil (i.e. V < 30 cm s⁻¹) is the signal from other WBC types plus RBC residues, since the sample did not go through a centrifuge. (b) The distribution of RBC-lysed whole blood sample converted from (a) shows a separate band for neutrophils (red) from other cells (green). (c) A scatter plot of 5 μL RBC-lysed diluted whole blood sample (870 × vdilution) measured with a commercial flow cytometer (Accuri C6). Three populations clearly exhibit major WBC groups as the gating indicated.