The Studies On Novel Bioelectrochemical Sensors Based On Nanomaterials

Bioelectrochemical sensors are the common focus in the electrochemistry andbiology fields. Nano-materials were introduced to develop the novel biosensors. Theelectrochemical peformance of biosensors were studied. At the same time, theconformation and bioactivity of enzyme have been investigated based on same opticalmethods. This work mainly covered the following areas:1. A facile and effective electrochemical sensing platform for the detection ofglucose and urea in a sample without separation was developed usingchitosan-reduced graphene oxide (CS-RGO)/concanavalin A (Con A) as sensing layer.The CS-RGO/Con A with pH-dependent surface net charges exhibited pH-switchableresponse to negatively charged Fe(CN)63-. The principle for glucose and ureadetection was essentially based on in situ pH-switchable enzyme-catalyzed reaction inwhich the oxidation of glucose catalyzed by glucose oxidase or hydrolyzation of ureacatalyzed by urease resulted in pH change of electrolyte solution to give differentelectrochemical response toward Fe(CN)63-. It was verified by cyclic voltammograms,differential pulse voltammograms and electrochemical impedance spectroscopy. Theresistance to charge transfer or amperometric current changed proportionally towardglucose from1.0to10.0mM and urea from1.0to7.0mM. Based on human serumexperiments, the sensing platform was proved to be suitable to simultaneous assay ofglucose and urea in a practical biosystem.2. Glucose oxidase (GOD) and Cytochrome c (Cyt c) were co-entrapped in thepoly(diallyldimethylammonium chloride)-reduced graphene oxide-goldnanoparticles (PDDA-RGO-AuNPs) hybrid nanocomposites modified glassy carbonelectrode to prepare a novel bi-protein bio-interphase. Electron transfer andelectrocatalysis of the bi-protein bio-interpahse were investigated in detail. The resultsshowed that the PDDA-RGO-AuNPs nanocomposites accelerated the electron transferbetween proteins and electrode. The bi-protein exhibited effective direct electrontransfer (DET) reaction with an apparent rate constant (ks) of2.36s-1. The optimalmolar ratio and total amount of Cyt c and GOD in the bio-interphase for DET of GODwas estimated to be about3:1and1.40nmol, respectively. The bi-proteinbio-interphase could be used to detect glucose based on the consumption of O2with the oxidation of glucose catalyzed by GOD. The resulted biosensor exhibits widelinear range from2.0to18.0mM.3. A series of gold nanoparticles (AuNPs)-glucose oxidase (GOD)nanocomposites, such as AuNPs-GOD, AuNPs-mercaptohexadecyl acid (MHA)-GODand AuNPs-mercaptoundecanoic acid (MUA)-GOD, have been prepared to study theeffects of conformation and bioactivity of GOD on AuNPs and surface chemistry ofAuNPs on electroanalytical performance of GOD. It was found that the conformationand bioactivity of GOD on AuNPs surface greatly depended on the surface chemistryof AuNPs. The second conformation and bioactivity of GOD were more or lesschanged after it was immobilized on AuNPs surface. The direct electrochemistry ofGOD became better and better as the change degree of second conformation GODincreased. When the AuNPs-GOD nanocomposites were used to develop a glucosebiosensor based on the reduction of O2, the closed-packed MHA and MUA layeraround AuNPs surface seriously disrupted the performance of biosensors.4. GOD and Bilirubin Oxidase (BOD) were immobilized on PDDA-RGO hybridnanocomposites to deveplop two electrodes, respectively. And the anode and cathodewere concatenated to form a self-powered biosensor. The PDDA-RGO hybridnanocomposites promoted proteins exhibited well bioactivity. The amplification ofmediator in the electrochemical of anode have been investigated in details. The resultsexhibited that the effect of the mediator existed on the surface of electrode was betterthan that existed in the solution. The optimal electrodes have been used in thedevelopment of self-powered biosensors, the biosensor exhibited well catalytic effecttowards glucose.