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.

A Label-Free and Ultrasensitive Immunosensor for Detection of Human Chorionic Gonadotrophin Based on Graphene FETs

“…Based on our measurement, the lowest concentration our graphene aptasensor detected was 1 pg·mL −1 , and a concentration-response calibration curve showed a good fitting (R 2 = 0.97) in the range of concentration evaluated, which is advantageous for the detection of hCG having wide-ranging expression profiles in the different stages of diagnosis i.e., pregnancy or cancer development. The obtained limit of detection (LOD) was 600 times more sensitive than the one achieved with the previously published hCG biosensor on BG-gFET [ 15 ] and twenty times better than one obtained with polysilicon nanogap [ 32 ]. In addition, our biosensor was capable of clearly monitoring the anti-hCG + hCG interaction at concentration as low as 1 pg·mL −1 directly without pre- or post-amplification process.…”

Electroanalytical Sensor for Diabetic Foot Ulcer Monitoring with Integrated Electronics for Connected Health Application

“…The limit of detection (LoD) and sensitivity of the electrochemical sensor was calculated [54] to be 0.75 nM and 84.52 Ω/nM/mm 2 respectively. The LoD obtained using screen printed band-aid was found to be superior as compared to those reported in recent studies (Table 1).…”

Sensors Based on Bio and Biomimetic Receptors in Medical Diagnostic, Environment, and Food Analysis

“…Nevertheless, only some of them have found real practical application today [ 298 ]. Examples are “Contour” for glucose determination, “OneTouch” for glucose and cholesterol determination [ 299 , 300 ], test strips sensitive to hCG [ 301 ], a lactose biosensor [ 302 , 303 ], and portable systems for enzyme immunoassay and polymerase chain reaction analysis [ 304 , 305 , 306 , 307 ]. Despite a large number of publications, the potential field of application for biosensors is huge, and many existing developments are far from where we should expect them to be, usually due to their low reliability and the complexity of their design.…”