Application of anodized aluminium oxide as a biochip substrate for a Fabry-Perot interferometer

Background: Non-uniform distribution of pore size and depth of porous Si chip for a Fabry-Perot interferometer, in a previous study, led to relatively low sensitivity with poor reproducibility when its surface was immobilized with calyx crown derivative (Prolinker A). In this study, porous anodized aluminium oxide (AAO) was used as an alternative biochip substrate for detecting P-galactosidase, and chip fabrication and surface functionalization methods were optimized. Results: According to structural and spectral analysis of the AAO surface, an optimal operating voltage for anodization was determined as 40 V, which gave the best uniformity in pore size (about 30 nm) and fringe pattern. The Delta EOT (difference in effective optical thickness) showed a linear relationship (R-2 = 0.9932) with beta-galactosidase concentration in the range 0.05-5 units enzyme mL(-1), corresponding to 0.07-7.0 mu g protein mL(-1). Conclusions: With uniformly porous AAO immobilized with Prolinker A, sensitivity was enhanced about 200 times compared with the lowest detection concentration of 10 units mL(-1) with the porous Si chip used in the previous study. (C) 2007 Society of Chemical Industry