Porous Silicon Carrier Matrices in Micro Enzyme Reactors-Influence of Matrix Depth

Abstract

The influence of the carrier matrix depth was investigated for porous silicon enzyme reactors. For the experiments, oriented silicon, p-type (20–70 Ω cm), was used. Porous silicon was generated on planar surfaces and on anisotropically pre-etched high aspect-ratio parallel channel reactors. For each type of sample the porous silicon layer was generated for three depths, controlled by the anodisation time, and two current densities, to yield different morphologies. Glucose oxidase (GOx) was immobilised on the porous matrix by standard procedures for immobilisation of enzymes on silica. The enzyme activity of the samples was monitored by a colorimetric assay. The results clearly display the influence of the matrix depth for both the planar and the reactor structures. A 170-fold increase in catalytic turn-over, in comparison to an identical non-porous reference, was recorded for a reactor with an average pore depth of 10 μm. At depths above 10 μm the increase in catalytic efficiency levelled off. For the planar samples the levelling off occurred at an average pore depth of 20 μm.