The Use Of Nano-Materials To Build A New Biosensor To Detect In Vivo Activity Of Specific Substances

The biosensor is a special kind of sensors, which is sensitive to the biological substances, like enzymes, antibodies, antigens, cells, nucleic acids and so on and converted into sound, light, electricity signal for analyzing and detection. It shows high sensitivity, good selectivity and operation. The performance of the sensor relies on the selection of carrier material and the fixed methods of biological substance. Therefore, it’s important work how to immobilize effectively on cleaned electrode with biological molecule in high amounts with retention of their bioactivity. In this work, we have constructed two kinds of biosensors immobilized molecule onto substrate electrodes based on graphene oxide (GO)-Prussian Blue (PB)-3,4,9,10-perylenetetracarboxylic dianhydride derivative (PTC-NH2) nanocomposite film, pretreated multi-wall carbon nanotubes/chitosan nanocomposite and hollow Pt nanospheres (HPts), gold nanoparticles (GNPs) as matrixes. Detailed are as follows:1. A sensitive glucose biosensor based on the abundant immobilization of glucose oxidase on hollow Pt nanospheres assembled on graphene oxide-Prussian Blue-PTC-NH2 nanocomposite filmA simple process in which a graphene oxide (GO)-Prussian Blue (PB)-3,4,9,10-perylenetetracarboxylic dianhydride derivative (PTC-NH2) nanocomposite film is spread onto a glassy carbon electrode (GCE) surface is described. Glucose oxidase (GOD) was adsorbed on the modified glass carbon electrode via the specific structure of hollow Pt nanospheres (HPts). This process was sufficient to prevent GOD from leaching away, and to improve the sensitivity of our sensor. To characterise the sensors, several techniques were employed, including transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV), electric impedance spectroscopy (EIS) and chronoamperometry. The resulting amperometric glucose biosensor exhibited a fast response time (within 5 s) and a good linear calibration range from 0.01±0.06 mM to 5.23±0.04 mM with a lower limit of detection of 3.3 M (S/N=3). Possible interferents, including ascorbic acid, L-cysteine, dopamine and ethanol, showed almost negligible electrochemical responses, indicating the high specificity of the proposed biosensor for glucose detection. The improved performance of the proposed electrode for detecting glucose in human serum was ascribed to the high surface-to-volume ratio and the excellent conductivity of the hollow Pt nanospheres. This skilful strategy of incorporating the GO/PB/PTC-NH2 nanocomposite film with hollow Pt nanospheres enhances the performance of the electrochemical sensor, which holds promising for application in bioassay analysis.2. Immunoassay for netrin 1 via a glassy carbon electrode modified with multi-wall carbon nanotubes, thionine and gold nanoparticlesA novel and ultrasensitive immnunosensor for the determination of netrin 1, a cardiovascular disease biomarker, has been successfully fabricated based on pretreated multi-wall carbon nanotubes (p-MWCNTs) and layer-by-layer (LBL) self-assemble strategy for the first time. This skilful strategy of incorporating the good conductivity of p-MWCNTs with the easy operation of LBL self-assemble strategy makes easy operation of the electrochemical sensor. Gold nanoparticles (GNPs) can be adsorbed firmly onto the electrode surface through electrostatic adsorption and covalent interaction between GNPs and thionine (Thi). GNPs not only can capture the anti-netrinl, but also amplify the electrochemical signal, thus increasing the sensitivity of the immunosensor. Construction of modified layers were carefully investigated using a broad range of techniques, such as cyclic voltammetrys (CVs), electrochemical impedance spectroscopy (EIS), UV-visible spectrophotometer, transmission electron microscopy (TEM) and X-ray diffraction (XRD). Under the optimal conditions, netrinl can be determined in the ranges from 0.09 pg mL-1 to 1800 pg mL-1 with a relative low detection limit of 0.03 pg mL-1 (S/N=3). Moreover, assays results of real human serum samples with the proposed immunosensor are in accordance with the reference values from the standard ELISA method. The satisfactory results allow it to possess a potential alternative tool for the detection of netrinl in clinical application and thereby prevent the occurrence of atherosclerotic as early as possible.