Electrochemical and bioelectrocatalytical properties of novel block-copolymers containing interacting ferrocenyl units

The electrochemical characterization of three different polystyrene-b-polybutadiene block copolymers functionalized with ferrocenyl units electronically communicated, PSm-PBn(HSiMeFc2)p where m=615, n=53, p=39 (1), m=375, n=92, p=76 (2) and m=455, n=204, p=170 (3), has been carried out both in solution and electrochemically deposited onto platinum electrodes. The bioelectrocatalytical properties of electrodes modified with the polymers in the nicotinamide dinucleotide (NADH) and glucose oxidase (GOx) oxidations have been investigated as a function of the constitution and structure of the polymers. The analytical properties of electrodes modified with these polymers as sensors of NADH and GOx are described. In addition, an amperometric biosensor for glucose, prepared by electrostatic immobilization of glucose oxidase onto a platinum electrode modified with one of the ferrocenyl block copolymers as an example, has been developed. The results confirm that electrodes modified with the examined copolymers act as efficient redox mediators for the electrocatalytic oxidation of both reduced nicotinamide dinucleotide cofactor and glucose oxidase. The reaction with NADH proceeds via formation of a charge-transfer intermediate before yielding the reaction products. This is a novel example of electrodes modified with ferrocene derivatives that can be applied to the determination of NADH without the use of diaphorase. The redox copolymers co-immobilized with glucose-oxidase have been successfully used as amperometric biosensors for glucose determinations. As expected these compounds allow using lower working potentials. The sensitivities and detection limits obtained are comparable or even better than those of other ferrocene-modified polymers mediator electrodes

Thiolated DAB Dendrimer-Gold Nanoparticles Self-Assembled Monolayer as Covalent Support for Direct Electrochemistry of HRP and Sensing Applications

A thiolated DAB dendrimer has been employed to bond gold nanoparticles of several sizes in order to obtain an electrocatalytic framework for the covalent immobilization and direct electrochemistry of horseradish peroxidase (HRP). This biosensor must represent the basis for developing a lot of oxidase-peroxidase bienzymatic biosensors and heavy metals biosensors based on the HRP inhibition. The kinetic study of the modified electrodes showed that the 5 nm and 16 nm gold nanoparticles are the most efficient to contact with the HRP active centre and the optimized biosensor allow to measure hydrogen peroxide at -0.3 V applied potential in linear ranges of 1-5000 and 1-140 or 140-5000 respectively with high sensitivities of 418.6 and 266.3 u A mM-1 cm-2 respectively too with low detection limits of 5 and 9 nM and fast response. The obtained apparent Michaelis-Menten constants, were 0.16 and 0.84 mM respectively. Both are significantly lower than the intrinsic K´M revealing the very high enzymatic efficiency of the developed devices