A sensor for glucose formed in a one-step process is described based on a new doped polyindole film coated onto a platinum surface; a polymer-entrapped glucose oxidase electrode can be operated as an amperometric glucose sensor. The new glucose sensor has fast response time (25–40 s) with high storage and operational stability ( > 35 days). Electrochemical rate constants for the new enzyme electrode have been calculated using the expressions derived by Albery et al.(J. Chem. Soc., Faraday Trans. 1, 1986, 82, 1033). It has been found that unsaturated enzyme kinetics are rate-limiting for conducting polymer-coated enzyme electrodes formed in a one-step process.

In this manuscript, recent advancements in the area of minimally-invasive transdermal biosensing and drug delivery are reviewed. The administration of therapeutic entities through the skin is complicated by the stratum corneum layer, which serves as a barrier to entry and retards bioavailability. A variety of strategies have been adopted for the enhancement of transdermal permeation for drug delivery and biosensing of various substances. Physical techniques such as iontophoresis, reverse iontophoresis, electroporation, and microneedles offer (a) electrical amplification for transdermal sensing of biomolecules and (b) transport of amphiphilic drug molecules to the targeted site in a minimally invasive manner. Iontophoretic delivery involves the application of low currents to the skin as well as the migration of polarized and neutral molecules across it. Transdermal biosensing via microneedles has emerged as a novel approach to replace hypodermic needles. In addition, microneedles have facilitated minimally invasive detection of analytes in body fluids. This review considers recent innovations in the structure and performance of transdermal systems.

The in situ synthesis is reported of noble metal nanoparticlesvia3-glycidoxypropyltrimethoxysilane mediated reduction of 3-aminopropyltrimethoxysilane treated metal salts during sol–gel processing. The method described involves the synthesis of uniform spherical nanoparticles of gold, silver and palladium with controlled size that can be directly utilized for thin film preparation. A detailed study of the synthesis and application of gold nanoparticles to the electrochemical detection of hydrogen peroxide was carried out and reveals that the amplification of hydrogen peroxide sensing is size-dependent. In addition, these nanoparticles exhibit excellent compatibility towards composite preparation. As an example, a nanocomposite with Prussian Blue (PB) is synthesized and found to be useful for the fabrication of chemically modified electrodes (CME). The resulting CME shows dramatic improvement in the electrochemistry of PB with gradual enhancement in electrocatalytic efficiency towards hydrogen peroxide sensing. The nanocomposite is used to study the direct and horseradish peroxidase (HRP)-catalyzed reduction of hydrogen peroxide. The results recorded for hydrogen peroxide analysis show an improvement in sensitivity and limit of detection on decreasing the size of gold nanoparticles in all cases.

A microsensor for urea is described which is based on immobilised urease on the tip of a 10 µm diameter ammonia gas electrode made from a polypyrrole film coated on to a platinum wire. The sensor responds rapidly, reaching a steady state within 20–40 s when the concentration of urea in solution is changed from 0.0001 to 0.05 M. The enzymatic response is current limiting. Responses in a wide range of substrate concentrations were achieved (0.001–0.05 M). High storage and operational stability (more than 32 d) have been recorded for the urea microsensor.