tA highly sensitive and non-invasive label-free biosensor was demonstrated for glucose detection using(3-aminopropyl)triethoxysilane (APTES) and glucose oxidase (GOx) surface modified polysilicon nanogap(PSNG) lab-on-chip. Fabricated gap size below 100 nm nanogap (NG) was used to discriminate the detec-tion of the prepared dextrose monohydrate (DEX) which used as reference. The results were comparedwith salivary glucose (SAL) samples and an on spot blood glucometer. A simple immobilization step ofAPTES and GOx was demonstrated and the result shows an excellent catalytic activity toward the oxi-dation of glucose with a current sensitivity of 42.08 A mM?1cm?2(or NG conductance sensitivity of165.3 nS cm?1). It was found that the working capability of this enzyme based biosensor was extremelywide linear ranging from 5 M to 50 mM, and the limit of detection (LOD) can be achieved down to0.6 M. Moreover, the amperometric response has affectively distinguished, the sensor response timeof 3 s is achieved. The reproducibility and stability of the enzymatic activity of biosensor were success-fully distinguished for glucose sensing. AC dielectric and impedance spectroscopy measurement alsoshows insignificant effect of polarization which is due to the accumulation of ions (double layers) onthe surface of PSNG electrodes. Therefore, this glucose biosensor could be an attractive candidate for commercialization as a point-of-care clinical diagnostic tool.

ZnO is synthesized by using conventional chemical route which is known as the “sol – gel” method and deposited on glass and silicon substrate. Morphological and optical properties have been investigated using XRD, AFM, FESEM and UV – vis test. In order to optimize the synthesized ZnO thin film, the ZnO thin film is coated with thin film of different thickness associated with various annealing temperature. Thicknesses of ZnO thin film coated for 3, 5 and 9 coating cycles of coating are 40 nm2, 60 nm2 and 200 nm2, respectively. The data report that the grain size of the seed solution increases from 80 nm to 110 nm as the thickness of ZnO thin film increases. As the thin film is treated with annealing temperature from 200 °C to 450 °C, the grain size of thin film also increases from 100 nm2 to 450 nm2. The RMS value of thin film also increases due to intense surface roughness on ZnO thin film. The band gap value of thin film decreased from 3.26 eV to 3.18 eV for coating ZnO thin film with thickness 40 nm2 – 200 nm2.

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.

Rationally designed biosensing system supports multiplex analyses is warranted for medical diagnosis to determine the level of analyte interaction. The chemically functionalized novel multi-electrode polysilicon nanogap (PSNG) lab-on-chip is designed in this study, facilitates multiplex analyses for a single analyte. On the fabricated 69 nm PSNG, biocompatibility and structural characteristics were verified for the efficient binding of Human Chorionic Gonadotropin (hCG). With the assistance of microfluidics, hCG sample was delivered via single-injection to 3-Aminopropyl(triethoxy)silane (APTES) and Glycidoxypropyl(trimethoxy)silane (GPMS) modified PSNG electrodes and the transduced signal was used to investigate the dielectric mechanisms for multiplex analyses. The results from amperometric response and impedance measurement delivered the scale of interaction between anti-hCG antibody and hCG that exhibited 6.5 times higher sensitivity for the chemical linker, APTES than GPMS. Under optimized experimental conditions, APTES and GPMS modified immunosensor has a limit of detection as 0.56 mIU/ml and 2.93 mIU/ml (at S/N=3), with dissociation constants (Kd) of 5.65±2.5 mIU/ml and 7.28±2.6 mIU/ml, respectively. These results suggest that multiplex analysis of single target could enhance the accuracy of detection and reliable for real-time comparative analyses. The designed PSNG is simple, feasible, requires low sample consumption and could be applied for any given multiplex analyses.