title: On-chip micro-biosensor for the detection of human CD4(+) cells based on AC impedance and optical analysis.
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.
authors.affiliation: Wadsworth Center, NYS Department of Health (NYSDOH), ESP, P-1 South, Albany, NY 12201-0509, USA.
authors.forename: Nirankar N
authors.initials: NN
authors.lastname: Mishra
authors.forename: Scott
authors.initials: S
authors.lastname: Retterer
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Zieziulewicz
authors.forename: Michael
authors.initials: M
authors.lastname: Isaacson
authors.forename: Donald
authors.initials: D
authors.lastname: Szarowski
authors.forename: Donald E
authors.initials: DE
authors.lastname: Mousseau
authors.forename: David A
authors.initials: DA
authors.lastname: Lawrence
authors.forename: James N
authors.initials: JN
authors.lastname: Turner
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D018791:CD4 Lymphocyte Count / Q000295:instrumentation* / Q000379:methods; D002469:Cell Separation / Q000295:instrumentation* / Q000379:methods; D002478:Cells, Cultured; D017097:Electric Impedance; D004563:Electrochemistry / Q000295:instrumentation / Q000379:methods; D004574:Electromagnetic Fields; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation* / Q000379:methods; D008856:Microscopy, Fluorescence / Q000295:instrumentation* / Q000379:methods; D055095:Optics and Photonics / Q000295:instrumentation