Electrochemical Biosensing Studies Based On Polymeric Bionanocomposites

The immobilization of biomolecules is the key step in constructing a biosensor. Immobilization of biomolecules with effective methods and highly biocompatible materials is essential to improve the biosensing performance. With the rapid development of nanotechnology, a variety of nanomaterials have been used to construct various biosensors. Preparation of multifunctional nanocomposite materials is important to develop a biosensor with high sensitivity and selectivity. In this thesis, we prepared several metal (or metal oxide)-polymer-enzyme nanocomposite materials for high performance glucose biosensing and thrombin aptasensing. The main contents are as follows,1. The classification of electrochemical biosensors, the immobilization method of the biomolecules, the classification and characteristics of nano-materials, as well as their application in biosensing, have been reviewed.2. One-pot chemical oxidation of 1,6-hexanedithiol (HDT) in its aqueous suspension containing glucose oxidase (GOx) and Fe3O4-Au nanocomposites by 1,4-benzoquinone yields novel Fe3O4-Au-poly(HDT) (PHDT)-GOx magnetic polymeric bionanocomposites (MPBNCs) with GOx immobilized at high load and high activity. Transmission/scanning electron microscopy and UV-Vis spectrophotometry are used to characterize the prepared MPBNCs. A Fe3O4-Au-PHDT-GOx/Au electrode has been prepared by facile and efficient magnetism separation/immobilization of the MPBNCs onto an Au magnetism-electrode for biosensing of glucose, which exhibits high detection sensitivity (110μA cm-2 mM-1), low detection limit (0.33μM, S/N= 3), rapid response time (< 5 s), and excellent anti-interferent ability and stability. The biosensor performs better than those based on the existing protocols of conventional electropolymerization and chemical preoxidation/electropolymerization of monomer.3. Novel bimetallic polymeric bionanocomposites (PBNCs) of polydopamine (PDA), AuNPs-PtNPs bimetallic nanoparticles were prepared. First, We prepared PDA-GOx nanocomposites with high-load/activity GOx entrapped via one-pot chemical protocol, namely, mixing biogenic dopamine (DA) as a monomer, GOx as a model molecule, and BQ as an oxidizing reagent to trigger DA polymerization to allow one-pot chemical synthesis; second, Au nanoparticles (AuNPs) was generated via in situ biochemical generation protocol, yielded PDA-GOx-AuNPs nanocomposites; the last, we synthesized the PDA-GOx-AuNPs-PtNPs nanocomposites by H2PtCl6 reduction onto the AuNPs surfaces with the AuNPs of PDA-GOx-AuNPs as the seed and ascorbic acid as the reductant. The PBNCs based biosensor via dip-dry method exhibits high detection sensitivity (195μA cm-2 mM-1), low detection limit (0.21μM, S/N= 3), rapid response time (< 5 s), and excellent anti-interferent ability and stability.4. A thrombin aptasensor was prepared by immobilizing a thiolated thrombin aptamer (TBA) onto the electrode modified with a PDA-GOx-AuNPs nanocomposite material prepared via in situ chemical/biochemical protocol. The measurement of the aptasensor was based on the inhibition of the amperometric response of the GOx-based electrode originated from the specific thrombin-aptamer binding. The aptasensor exhibits wide linear detection range (1-40 nM), low detection limit (0.125 nM, S/N=3), rapid response time (< 10 s), and excellent anti-interferent ability.