Comparison of simple aromatic amines for electrosynthesis of permselective polymers in biosensor fabrication

Abstract

A range of simple aromatic amines were used to modify Pt microcylinders with insulating electrosynthesised polymers generated amperometrically in the presence or absence of a typical globular protein, bovine serum albumin (BSA), at neutral pH. Sensitivity to a typical interference species, ascorbic acid (AA), and the most common electrochemical signal molecule for oxidase enzymes, H 2 O 2 , was used to compare the suitability of the resulting polymer-protein modified electrodes for biosensor applications. Pt modified with poly(aminobenzene), PANI, gave the lowest sensitivity to AA ( ~3000 times lower than bare Pt); incorporation of BSA into the polymer during synthesis had a detrimental effect on its AA-rejecting capability. The H 2 O 2 sensitivity of the PANI-based electrodes was poor ( ~7 times lower) compared to bare Pt. The behaviour of poly(1,2-diaminobenzene), PoPD, was different in many respects: its AA-blocking ability was enhanced 3-fold by the presence of BSA and its H 2 O 2 sensitivity was similar to bare Pt. EQCM data recorded in PBS indicated that PANI films electrosynthesised at pH 7.4 were two orders of magnitude thicker than for PoPD. These differences may be due, at least in part, to the 'ladder' structure with phenazine rings proposed for PoPD, since they were not duplicated by other mono-substituted derivatives of aniline, such as 2-methylaniline or 1,3-diaminobenzene.

Control of the Oxygen Dependence of an Implantable Polymer/Enzyme Composite Biosensor for Glutamate

“…A number of aspects of the structure and behavior of Pt/oxidase-PPD biosensors indicate that their response is determined by enzyme kinetics, and not by diffusion through the polymer/enzyme composite (PEC) layer. First, the thickness of these PPD-based insulating layers (10-30 nm), 46,56-58 serving as both permselective barrier and immobilization matrix, is of the order that has been shown theoretically not to be limited by diffusion within the enzymecontaining layer. 53,55 Second, the response time of oxidase/PPDbased biosensors is fast, 68 being determined by the mixing time in stirred solution.…”

“…[49][50][51][52][53] These complex analyses are often needed to understand and optimize the behavior of thick or conducting layers; 53,54 however, a recent study has shown that substrate diffusion is not limiting for PPD layers incorporating enzyme, 55 due to their relatively small thickness. 53 This allows a basic Michaelis-Menten analysis to be used here, offering more readily accessible insights into factors affecting the responsiveness of biosensors fabricated from ultrathin (10-30 nm) 46,56-58 insulating polymers, such as PPD.…”

“…Pt cylinders (Pt C , 125-µm diameter, 1 mm long) were fabricated from Teflon-coated Pt wire (Advent Research Materials, Suffolk, U.K.). GluOx (EC 1.4.3.11, 200 U mL -1 , Yamasa Corp., Japan) was deposited onto the metal surface by dip-evaporation (1-5 dips) 28 and immobilized by amperometric electropolymerization (+700 mV vs SCE) in 300 mM o-phenylenediamine containing 5 mg mL -1 bovine serum albumin in phosphate buffered saline (PBS, pH 7.4), 46 as described previously to form Pt C /GluOx/PPD biosensors. 28 Pt disks (Pt D ) were fabricated by cutting the Teflon-coated wire transversely to produce 125-µm diameter disks, and Pt D /GluOx/PPD biosensors were fabricated as for Pt C .…”

The efficiency of immobilised glutamate oxidase decreases with surface enzyme loading: an electrostatic effect, and reversal by a polycation significantly enhances biosensor sensitivity

“…These results are in line with literature reports that the H 2 O 2 sensitivity of Pt is not affected by PPD and PPD-protein composites made under the conditions described here. 29,33,34 Differences in J max across sensor designs should therefore be a good reflection of differences in the amount of active enzyme present.…”

Ascorbic Acid Rejection Characteristics of Modified Platinum Electrodes: A Shelf Life Investigation

“…This is in stark contrast to the PPD layer grown on bare Pt which can be controlled more efficiently due to the self-limiting characteristic associated with the polymer during the electropolymerisation process. A number of groups report the thickness of PPD polymers to be between 10 and 30 nm [12,40,41]. Similarly, Nafion ® has been electrodeposited onto carbon electrode surfaces as a method of incorporating a uniform reproducible layer to ameliorate issues associated with dip coating and annealing [3,32,42].…”