[Biosensors and Bioelectronics] Microfluidic-integrated patterned ITO immunosensor for rapid detecti
An optically transparent patterned indium tin oxide (ITO) three-electrode sensor integrated with a microfluidic channel was designed for label-free immunosensing of prostate-specific membrane antigen (PSMA), a prostate cancer (PCa) biomarker, expressed on prostate tissue and circulating tumor cells but also found in serum. The sensor relies on cysteamine capped gold nanoparticles (N-AuNPs) covalently linked with anti-PSMA antibody (Ab) for target specificity. A polydimethylsiloxane (PDMS) microfluidic channel is used to efficiently and reproducibly introduce sample containing soluble proteins/cells to the sensor. The PSMA is detected and quantified by measuring the change in differential pulse voltammetry signal of a redox probe ([Fe(CN)6]3–/[Fe(CN)6]4–) that is altered upon binding of PSMA with PSMA-Ab immobilized on N-AuNPs/ITO. Detection of PSMA expressing cells and soluble PSMA was tested. The limit of detection (LOD) of the sensor for PSMA-based PCa cells is 6/40 µL (i.e., 150 cells/mL) (n=3) with a linear range of 15–400 cells/40 µL (i.e., 375–10,000 cells/mL), and for the soluble PSMA is 0.499 ng/40 µL (i.e., 12.5 ng/mL) (n=3) with the linear range of 0.75–250 ng/40 µL (i.e., 19–6250 ng/mL), both with an incubation time of 10 min. The results indicate that the sensor has a suitable sensitivity and dynamic range for routine detection of PCa circulating tumor cells and can be adapted to detect other biomarkers/cancer cells.
Rajesh Seenivasan a, Chandra K. Singh b, Jay W. Warrick c, , Nihal Ahmad b, Sundaram Gunasekaran a, a Department of Biological Systems Engineering, University of Wisconsin–Madison, 460 H Mall, Madison, WI 53706, USA b Department of Dermatology, University of Wisconsin–Madison, 1300 University Avenue, Madison, WI 53706, USA c Department of Biomedical Engineering, University of Wisconsin–Madison, 1111 Highland Avenue, Madison, WI, 53705, USA Received 23 January 2017, Revised 30 March 2017, Accepted 10 April 2017, Available online 11 April 2017