Porous silicon as an entrapping matrix for the immobilization of urease

Electrochemically anodized surface of p-type silicon (porous silicon) is reported to be an efficient entrapping template for immobilization of urease. The porosity and the amount of loading of the enzyme are optimized for obtaining highest efficiency. The effect of entrapment and therefore the activity retained by the porous silicon surface is monitored by colorimetric assay. The yield in photoluminescence of porous silicon at 610 nm is seen to get affected by the presence of enzyme. The change in the surface morphology has been studied by scanning electron microscopy and it is observed that the immobilized system has successfully retained urease enzyme. The immobilized system gives linear response for concentrations of urea ranging in values between 3.3 x 10(-5) and 2.4 x 10(-4) M Porous silicon is seen to be capable of holding the urease enzyme for repeated cyclic tests for five times. The system exhibited a shelf life of 15 days. (c) 2004 Elsevier B.V. All rights reserved.