Blood cell counting at Point-of-care

Blood cell counting at Point-of-care

The blood cell count is one of the most ubiquitous tests performed in health care settings for disease diagnostics and its management. Irregular leukocyte and its differential count are observed in many diseases including leukemia, immunodeficiency, bone marrow failure etc. CD4+ T cell count is used as a diagnostic test for HIV/AIDS and is also used for monitoring the effectiveness of the antiretroviral therapy drugs on HIV infected patients. Similarly, the cancer patients undergoing chemo/radiation therapy, suffers with very low total leukocyte count in particular absolute neutrophil count. The current standard to obtain cell counts require a trained technician to operate a large and expensive equipment i.e. flow cytometer. We have a developed an immune-capture assay to electrically enumerate specific leukocytes in a microfluidic biochip with a drop of blood.

Ten microliters of whole blood is infused in biochip with the lysing buffer (composed of saponin and formic acid) to lyse all erythrocytes. To preserve the remaining leukocytes, the lysed solution is quenched to halt the lysing process and maintain the pH of the solution. The leukocytes are electrically counted as they pass through the counting channel bonded with microfabricated platinum electrodes. The specific leukocytes, e.g. CD4+T cells or neutrophils are captured in their respective capture chambers where their respective CD4 and CD66b antibody is adsorbed. The remaining cells are counted at the exit of the capture chamber by second electrical counter. The difference in cell counts of two counters gives the CD4+ T cell count and absolute neutrophil count. Figure shows the comparison of CD4 T cell counts from HIV infected individuals using our biochip and control counts obtained from Carle Foundation Hospital.

Future goal of the project is to develop a bio-chip capable of performing a complete blood cell count. Our main focus is to perform absolute count of red blood cell, platelets, white blood cells and its 3-part differential (Lymphocytes, Monocytes and Neutrophils) from a drop of blood (finger-prick).

Schematic of Set-up

This material was originally published on the website of the Laboratory of Integrated Biomedical Micro/Nanotechnology & Applications (LIBNA).