Sharma Rao A/l BalakrishnanU. HashimSubash C. B. GopinathP. PoopalanH. R. RamayyaM. Iqbal OmarR. HaarindraprasadP. Veeradasan2024-05-282024-05-282015Balakrishnan SR, Hashim U, Gopinath SCB, Poopalan P, Ramayya HR, Iqbal Omar M, et al. (2015) A Point-of-Care Immunosensor for Human Chorionic Gonadotropin in Clinical Urine Samples Using a Cuneated Polysilicon Nanogap Lab-on-Chip. PLoS ONE 10(9): e0137891. doi:10.1371/journal. pone.01378911932-62032112-310.1371/journal.pone.0137891https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0137891https://oarep.usim.edu.my/handle/123456789/5384Human chorionic gonadotropin (hCG), a glycoprotein hormone secreted from the placenta, is a key molecule that indicates pregnancy. Here, we have designed a cost-effective, label-free, in situ point-of-care (POC) immunosensor to estimate hCG using a cuneated 25 nm polysilicon nanogap electrode. A tiny chip with the dimensions of 20.5 × 12.5 mm was fabricated using conventional lithography and size expansion techniques. Furthermore, the sensing surface was functionalized by (3-aminopropyl)triethoxysilane and quantitatively measured the variations in hCG levels from clinically obtained human urine samples. The dielectric properties of the present sensor are shown with a capacitance above 40 nF for samples from pregnant women; it was lower with samples from non-pregnant women. Furthermore, it has been proven that our sensor has a wide linear range of detection, as a sensitivity of 835.88 μA mIU-1 ml-2 cm-2 was attained, and the detection limit was 0.28 mIU/ml (27.78 pg/ml). The dissociation constant Kd of the specific antigen binding to the anti-hCG was calculated as 2.23 ± 0.66 mIU, and the maximum number of binding sites per antigen was Bmax = 22.54 ± 1.46 mIU. The sensing system shown here, with a narrow nanogap, is suitable for high-throughput POC diagnosis, and a single injection can obtain triplicate data or parallel analyses of different targets.enArticle117109