Scientists have developed a new highly sensitive biosensor that accurately count sub-populations of white blood cells for HIV diagnose.
The biosensor is based on a differential immuno-capture technology. As part of a small, disposable biochip, the microfluidic biosensor can count CD4+/CD8+ T cells quickly and accurately for AIDS diagnosis in the field. The findings were published in the journal Nature Protocols in August 2017. “An important diagnostic biomarker for HIV/AIDS is the absolute count of the CD4+ and CD8+ T lymphocytes in the whole blood. The current diagnostic tool – a flow cytometer – is expensive, requires large blood volume, and a trained technician to operate,” said Rashid Bashir from University of Illinois in the US. “We have developed a microfluidic biosensor based on a differential immuno-capture electrical cell counting technology to enumerate specific cells in 20 minutes using 10 microlitres of blood.”
Human blood comprises 45% of cells with 5 million erythrocytes as compared to only 7,000 leukocytes in one microlitre of blood. Biochip incorporates separate ports for lysing reagents and quenching buffers that preserve the leukocytes for counting by the microfabricated electrodes. Specific leukocytes such as CD4 T cells get captured as they interact with the antibodies in the capture chamber. The difference in the respective cell counts give the concentration of the cells captured. Electrical cell counting can differentiate cells based on size and membrane properties depending on the frequency of the interrogation signal. However, differentiating cells of same morphology is a challenging.
According to Biochips Market report published by Coherent Market Insights, biochip performs a large number of biological reactions in a few seconds such as analyzing contamination and gene decoding. In clinical trials, the differential immuno-capture biochip achieved more than 90% correlation with a flow cytometer for cell counts using HIV infected blood samples. The novel biosensor has the potential to be an automated portable blood cell counter for point-of-care applications in developed and resource-limited regions worldwide.