Studies On Enzyme Immobilization And Amperometric Enzyme Electrodes Based On Several Bifunctional Boronic Acid Derivatives

Boronic acid derivatives can react with 1,2- or 1,3-diols, which has found wide applications in separation chemistry, synthesis chemistry and analytical chemistry. The amperometric enzyme sensors use enzymes as their molecular recognition element and output amperometric signals from redox chemistry of the enzyme systems, which possess many advantages such as high sensitivity and selectivity. Enzyme immobilization is the key step in fabricating an amperometric enzyme sensor, and enzyme immobilization through various nanocomposites has become the recent research focus in this field. In this thesis, first we briefly review the recent progress of electrochemical enzyme sensors and boric acid-diols reactions, then some researches are conducted on enzyme immobilization and biosensing mainly based on the reactions of several bifunctional bronic acid derivatives with the glycosyl groups of enzymes. The contents are as follows.1. A glucose oxidase(GOx)-poly(3-anilineboronic acid)(PABA)-Pd nanoparticles(Pd NPs) bionanocomposite was synthesized in an one-step manner based on the chemical oxidation polymerization of 3-anilineboronic acid(ABA) by Na2 Pd Cl4 and the chemical interaction of glycoprotein enzyme’s diols with boronic acid groups. An appropriate amount of the bionanocomposite was cast-coated on a Pd-plated multiwalled carbon nanotubes(MWCNTs)-modified Au electrode, followed by electrode-modification with an outer-layer chitosan(CS) film, to yield a CS/GOx-PABA-Pd NPs/Pdplate/MWCNTs/Au enzyme electrode. In the first-generation biosensing mode, the enzyme electrode exhibited a linear amperometric response to glucose concentration from 2.0 μM to 4.5 m M with a sensitivity of 160 μA m M-1 cm-2 and a limit of detection(S/N = 3) of 0.1 μM. Excellent analytical performance was also obtained in the second-generation biosensing mode. In addition, a glucose/O2 biofuel cell(BFC) was constructed using this enzyme electrode as the anode and a Pt/MWCNTs/Au electrode as the cathode, and this biofuel cell as a self-powered biosensing device showed a linear voltage response to glucose concentration from 100 μM to 13.5 m M with a sensitivity of 43.5 m V m M-1 cm-2.2. A GOx-4-mercaptophenylboronic acid(MBA)-Au nanoparticles(Aunano) bionanocomposite was synthesized in an one-step manner based on the chemical interaction of glycoprotein enzyme’s diols with boronic acid groups and the strong Au-S binding. An appropriate amount of the bionanocomposite was cast-coated on an Au-plated multiwalled carbon nanotubes(MWCNTs)-modified Au electrode, followed by electrode-modification with an outer-layer CS film, to yield a CS/GOx-MBA-Au NPs/Auplate/MWCNTs/Au enzyme electrode. In the first-generation biosensing mode, the enzyme electrode exhibited a linear amperometric response to glucose concentration from 10.0 μM to 3.1 m M with a sensitivity of 121.5 μA m M-1 cm-2 and a limit of detection(S/N = 3) of 1.0 μM.3. A uricase(UOx)-poly(furan-3-boronic acid)(PFBA)-Pd NPs bionanocomposite bionanocomposite was synthesized in an one-step manner based on the chemical oxidation polymerization of furan-3-boronic acid(FBA) by Na2 Pd Cl4 and the chemical interaction of glycoprotein enzyme’s diols with boronic acid groups. In the first-generation biosensing mode, the similarly prepared CS/UOx-PFBA-Pd NPs/Pdplate/MWCNTs/Au enzyme electrode exhibited a linear amperometric response to uric acid(UA) concentration from 1.0 μM to 2.5 m M with a sensitivity of 490 μA m M-1 cm-2 and a limit of detection(S/N = 3) of 0.1 μM. Furthermore, a monopolar UA BFC was fabricated by using the enzyme electrode as the bioanode and a Pt/MWCNTs/Au electrode as the cathode, giving an open-circuit cell voltage of 0.394 V, a short-circuit current density of 857 μA cm-2 and the maximum power density of 70 μW cm-2 at 0.22 V under simulated physiological conditions.