Construction Of Electrochemical Biosensor By Phosphonic Acid Cross - Linked Polymer

The electrochemical biosensors have been paid a widely public attention in the past few years in the field of clinical diagnosis, environmental monitoring, industrial production and bio-analysis because they may provide fast, simple, low-cost, specific selective and high sensitive detection capabilities. The current research for improving the ability of electrochemical biosensors is focused on immobilizing electroactive species. Compared with the traditional absorption, covalent binding and crosslinking, the advantages of encapsulation are the higher active recovery rate and stability. Based on the above reasons, we prepare the electrochemical sensors through the-PO3H2groups on organic phosphonate to crosslink with-NH2groups on polymer to encapsulate the electroactive species for hydrogen peroxide sensing.1. Based on the polyphosphonate-assisted coacervation of chitosan, a simple and versatile procedure for the encapsulation of proteins/enzymes in chitosan-carbon nanotubes (CNTs) composites matrix was developed. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrum (EDS) mapping demonstrated the hemoglobin (Hb) uniformly distributed into chitosan-CNTs composites matrix. Raman measurements indicated the CNTs in composites matrix retained the electronic and structural integrities of the pristine CNTs. Fourier transform infrared (FT-IR), ultraviolet-visible (UV-vis) and circular dichroism (CD) spectroscopy displayed the encapsulated Hb preserved their near-native structure, indicating the polyphosphonate-chitosan-CNTs composites possessed excellent biocompatibility for the encapsulation of proteins/enzymes. Electrochemical measurements indicated the encapsulated Hb could directly exchange electron with the substrate electrode. Moreover, the modified electrode showed excellent bioelectrocatalytic activity for the reduction of hydrogen peroxide. Under optimum experimental conditions, the fabricated electrochemical sensor displayed the fast response (less than3s), wide linear range (7.0×10-7to2.0×10-3M) and low detection limit (4.0×10-7M) for the determination of hydrogen peroxide.2. A nonenzymatic iron(Ⅲ) diethylenetriaminepentaacetic acid (Fe-DETPA) complex based amperometric sensor for the analytical determination of hydrogen peroxide was developed. By combining the electrostatic interaction between Fe-DETPA complex and polyallylamine (PAH) functionalized multiwalled carbon nanotubes (MWCNTs) as well as the ionotropic crosslinking interaction between PAH and ethylenediamine-tetramethylene phosphonic acid (EDTMP), the electroactive Fe-DETPA complex was successfully incorporated within the MWCNTs matrix, and firmly immobilized on the Au substrate electrode. The fabricated electrochemical sensor was characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM) spectroscopy and electrochemical methods. The influences of solution pH and ionic strength on the electrochemical sensor were investigated. The prepared electrochemical sensor had a fast response of hydrogen peroxide (<3s) and excellent linear range of concentration from1.25×10-8to4.75×10-3M with the detection limit of6.3×10-9M under the optimum conditions.3. The switchable/tunable electrocatalysis is of great importance in both fundamental and application research. We synthesize the CS-Fe(notpH3) hybrids film by the simple one-step electrodeposition technique (CS:chitosan; Fe(notpH3):1,4,7-triazacyclononane-1,4,7-triyl-tris methylene-phosphonic acid iron(Ⅲ) complex). The stable immobilization of Fe(notpH3) in CS polymer originates from the strong electrostatic and/or hydrogen bonding interactions between Fe(notpH3) and CS, which also enhances the insolubility of CS in acidic solution. The immobilized Fe(notpH3) complex undergoes an effective direct electron transfer reaction and shows a particular pH-sensitive electrochemical property. Based on the particular formal potential hopping mechanism of Fe(notpH3) complex, the CS-Fe(notpH3) hybrids film can be further used to realize pH-controlled switchable electrocatalysis toward H2O2reduction.