Growth and characterisation of diffusion junctions between paired gold electrodes: diffusion effects in generator–collector mode

A dual-electrode flow sensor fabricated using track-etched microporous membranes

A new dual-electrode flow sensor has been fabricated by piling the microporous membrane electrodes which have 7-10μm thickness. The electrode was prepared by sputtering of platinum onto both sides of the membrane filter which contain a smooth flat surface as well as cylindrical pores with uniform diameters. The electrolysis is performed when the sample solution flows through the membrane electrode, and a generated analyte on the first working electrode is instantaneously transported to the surface of second working electrode which is located at the downstream of the first one. In this case, the sample solution surely flows through the pores of the membrane filters. As the result, highly efficient electrolysis was achieved at each electrode, and the collection efficiency values as high as 100% were obtained in the wide range of flow rate. Good responses to the injections of sample solutions were also confirmed in the FIA system.

Probing fundamental film parameters of immobilized enzymes--towards enhanced biosensor performance. Part II-Electroanalytical estimation of immobilized enzyme performance

The method of immobilization of a protein has a great influence on the overall conformation, and hence, functioning of the protein. Thus, a greater understanding of the events undergone by the protein during immobilization is key to manipulating the immobilization method to produce a strategy that influences the advantages of immobilization while minimizing their disadvantages in biosensor design. In this, the second paper of a two-part series, we have assessed the kinetic parameters of thin-film laccase monolayers, covalently attached to SAMs differing in spacer-arm length and lateral density of spacer arms. This was achieved using chronoamperometry and an electroactive product (p-benzoquinone), which was modeled in a non-linear regressional fashion to extract the relevant parameters. Finally, comparisons between the kinetic parameters presented in this paper and the rheological parameters of laccase monolayers immobilized in the same manner (Part I of this two paper series) were performed. Improvements in the maximal enzyme-catalysed current, i(max), the apparent Michaelis-Menten constant, K(m) and the apparent biosensor sensitivity were noted for most of the surfaces with increasing linker length. Decreasing the lateral density of the spacer-arms brought about a general improvement in these parameters, which is attributed to the decrease in multiple points of immobilization undergone by functional proteins. Finally, comparisons between rheological data and kinetics data showed that the degree of viscosity exhibited by protein films has a negative influence on attached protein layers, while enhanced protein hydration levels (assessed piezoelectrically from data obtained in Paper 1) has a positive effect on those surfaces comprising rigidly bound protein layers.