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Cheap, rapid check to quantify CD4 developed
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Nov 2, 2005, 19:00 GMT
ALBANY, NY, United States (UPI) -- Scientists from two New York universities say they`ve developed an inexpensive, hand-held sensor that can check a HIV patient`s immune system in seconds.
Prices of antiretroviral therapy for HIV have dropped in poorer nations, but a lack of cheap, simple diagnostics to enable doctors to use those treatments remains a stumbling block.
The sensor measures the quantity of key immune cells called CD4+ cells in the blood. Physicians rely on CD4+ measurements to decide when to start drug treatments and to gauge how a patient is responding to treatment.
To make the device, researchers from Cornell University in Ithaca and the University at Albany coated electrodes with antibodies specific to CD4+ cells. When a small sample of blood is placed on a chip bearing those electrodes, the antibodies grab hold of the CD4+ cells. The captured cells then impede the flow of current across the electrodes, allowing the density of CD4+ cells to be calculated.
The study appears in the journal Biosensors & Bioelectronics.
"On-chip micro-biosensor for the detection of human CD4+ cells based on AC impedance and optical analysis"
Nirankar N. Mishraa, Scott Rettererd, Thomas J. Zieziulewiczb, Michael Isaacsond, Donald Szarowskia, Donald E. Mousseaua, David A. Lawrencea, c and James N. Turnera, c,
aWadsworth Center, NYS Department of Health (NYSDOH), ESP, P-1 South, Albany, NY 12201-0509, USA
bDepartment of Environmental Health and Toxicology, SUNY-SPH, Albany, NY, USA
cBiomedical Sciences, School of Public Health, The University at Albany, NY, USA
dBiomedical Engineering, Cornell University, Ithaca, NY, USA
Biosensors and Bioelectronics
Volume 21, Issue 5 , 15 November 2005, Pages 696-704
Abstract
The current study was undertaken to fabricate a small micro-electrode on-chip to rapidly detect and quantify human CD4+ cells in a minimal volume of blood through impedance measurements made with simple electronics that could be battery operated implemented in a hand held device. The micro-electrode surface was non-covalently modified sequentially by incubation with solutions of protein G_, human albumin, monoclonal mouse anti-human CD4, and mouse IgG. The anti-human CD4 antibody served as the recognition and capture molecule for CD4+ cells present in human blood. The binding of these biomolecules to the micro-electrodes was verified by impedance and cyclic voltammetry measurements. An increase in impedance was detected for each layer of protein adsorbed onto the micro-electrode surface. This process was shown to be highly repeatable. Increased impedance was measured when CD4+ cells were captured on the micro-electrode, and the impedance also increased as the number of captured cells increased. Fluorescence microscopy of captured cells immunolabeled with anti-human CD4, CD8, and CD19 antibodies, and the nuclear label DAPI, confirmed that only CD4+ cells were captured. The results were highly dependent on the specimen preparation method used. We conclude that the on-chip capture system can efficiently quantify the number of CD4+ cells.
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