title: A Point-of-Care Immunosensor for Human Chorionic Gonadotropin in Clinical Urine Samples Using a Cuneated Polysilicon Nanogap Lab-on-Chip.
abstract: Human 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.
authors.affiliation: Biomedical Nano Diagnostics Research Group, Institute of Nano Electronic Engineering (INEE), Universiti Malaysia Perlis (UniMAP), Kangar, Perlis, Malaysia.
authors.forename: S R
authors.initials: SR
authors.lastname: Balakrishnan
authors.affiliation: Biomedical Nano Diagnostics Research Group, Institute of Nano Electronic Engineering (INEE), Universiti Malaysia Perlis (UniMAP), Kangar, Perlis, Malaysia.
authors.forename: U
authors.initials: U
authors.lastname: Hashim
authors.affiliation: Biomedical Nano Diagnostics Research Group, Institute of Nano Electronic Engineering (INEE), Universiti Malaysia Perlis (UniMAP), Kangar, Perlis, Malaysia.
authors.forename: Subash C B
authors.initials: SC
authors.lastname: Gopinath
authors.affiliation: School of Microelectronic Engineering, University Malaysia Perlis (UniMAP), Kuala Perlis, Perlis, Malaysia.
authors.forename: P
authors.initials: P
authors.lastname: Poopalan
authors.affiliation: Department of Obstetrics and Gynaecology, Hospital Tuanku Fauziah, Kangar, Perlis, Malaysia.
authors.forename: H R
authors.initials: HR
authors.lastname: Ramayya
authors.affiliation: University Health Centre, Universiti Malaysia Perlis (UniMAP), Kuala Perlis, Perlis, Malaysia.
authors.forename: M
authors.initials: M
authors.lastname: Iqbal Omar
authors.affiliation: Biomedical Nano Diagnostics Research Group, Institute of Nano Electronic Engineering (INEE), Universiti Malaysia Perlis (UniMAP), Kangar, Perlis, Malaysia.
authors.forename: R
authors.initials: R
authors.lastname: Haarindraprasad
authors.affiliation: Biomedical Nano Diagnostics Research Group, Institute of Nano Electronic Engineering (INEE), Universiti Malaysia Perlis (UniMAP), Kangar, Perlis, Malaysia.
authors.forename: P
authors.initials: P
authors.lastname: Veeradasan
mesh_terms: D000328:Adult; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods*; D006063:Chorionic Gonadotropin / Q000652:urine*; D005260:Female; D006801:Humans; D056656:Lab-On-A-Chip Devices; D019095:Point-of-Care Systems; D011247:Pregnancy / Q000652:urine*
chemical_list: D006063:Chorionic Gonadotropin