Applications of Microstructured Porous Silicon as a Biocatalytic Surface

The use of porous silicon (PS) as an efficient surface enlarging carrier matrix for immobilised enzymes is demonstrated. An optimal porous matrix in p-type silicon (10–20 Ωcm) with respect to enzymatic substrate turn-over was obtained when anodising the sample at 100 mA/cm2 for 5 min. An increase in glucose turn-over of ≈︂220 times as compared to an enzyme activated polished surface was recorded. The highest increase in turn-over was found to be 350 times for an n-epilayer on n+ substrate. The application of glucose monitoring is demonstrated showing a linear range to 15 mM glucose with a satisfactory storage and operational stability. The use of ascorbate oxidase activated porous silicon for the elimination of ascorbate (an electrochemical interferent) in glutamate monitoring is reported. An upper elimination level of 1 mM ascorbate was found. PS is also reported as an efficient protein cleavage surface when activated with proteases. Cleavage times normally ranging between 6 and 24 h were found to be 60 s in the microreactor. Myoglobin cleaved on a trypsin microreactor is shown with the corresponding mass spectra having a sequence coverage of 79%.