Self-Assembled Dipeptide- Gold Nanoparticles Composite Based Electrochemical Biosensor Research

Recent years, water pollution, food safety and other livelihood problems promoted the development of analytical detection industry. Electrochemical sensor, as a kind of electroanalysis method, it attracts a lot of attentions because it possesses many advantages, such as cheapness, sensitiveness, high efficiency, etc., and diversities of matrix structure. Among them, the electrochemical enzyme sensor, with biological enzyme high catalytic activity and the advantages of electrochemical technology, is becoming a research hotspot. Currently, the main problems of electrochemical enzyme sensor are the immobilization of enzyme, fast electron transfer between and enzyme activity. The direction to solve these problems mainly focuses on how to choose more suitable materials, or how to build diverse structures. With the development of biological science, using biological structure material with excellent biocompatibility to build electrochemical biosensor has become extremely potential direction.Diphenylalanine dipeptide (FF) molecule is the simplest block for building biological micro-nano structure materials. It can spontaneously self-assemble into diverse structures, and be easy to joint functional molecules, which can be potential electrochemical sensor matrix. However, its electroconductivity needs to be further improved. Therefore, this thesis is mainly based on dipeptide molecule and its derivatives. By preparing dipeptide based composite improves electroconductivity and the immobilization of enzyme molecules, and constructs a series of electrochemical enzyme sensors, realizing effective detection of the analytes. This work is demonstrated in detail:1. Based on dipeptide self-assemby, we prepared the dipeptide-gold nanoparticles hybrid sphere (DP-AuNPs HS) and firstly fixed it on the glassy carbon electrode (GCE) as the matrix of horseradish peroxidase (HRP), building a kind of hydroquinone (HQ) as the electronic mediator hydrogen peroxide (H2O2) sensor. We found that gold nanoparticles embedded in the internal and external surface of the hybrid sphere. That will help improve the dipeptide material itself electron transfer ability, and is advantageous to the immobilization of enzyme. We discussed the mechanism of formation of the hybrid sphere and investigated the electrochemical behaviors of the sensor. In addition, the analyte H2O2 was analyzed, obtaining satisfied high sensitivity (28.3 μA·mmol-1·L), wide linear range (0.5-970 μmol·L-1), and low detection limit (0.1 μmol·L-1) test results.2. Based on the FF’s derivative, N-fluorenylmethoxycarbonyl diphenylalanine (Fmoc-FF), we firstly prepared the dipeptide-gold nanoparticles composite hydrogel (DP-AuNPs HG) by the one-pot reduction for immobilizing glucose oxidase (GOx) molecule.3D network hydrogel structure is beneficial to providing good micro-environment for enzyme molecule and porous channels can help mass transfer of analytes. Additionally, uniform distribution of gold nanoparticles on the fibrous structure can promote electron transfer and be advantageous to the direct electron transfer (DET) of GOx, which lay a foundation for building a glucose biosensor.