Adsorption of avidin on microfabricated surfaces for protein biochip applications

The adsorption of the protein avidin from hen egg white on patterns of sili con dioxide and platinum surfaces on a microchip and the use of fluorescent microscopy to detect binding of biotin are described. A silicon dioxide mi crochip was formed using plasma-enhanced chemical vapor deposition while pl atinum was deposited using radiofrequency sputtering. After cleaning using a plasma are, the chips were placed into solutions containing avidin or bov ine serum albumin. The avidin was adsorbed onto the microchips from phospha te-buffered sa line (PBS) or fro m PBS to which ammonium sulfate had been a dded. Avidin was also adsorbed onto bovine serum albumin (BSA)-coated surfa ces of oxide and platinum. Fluorescence microscopy was used to confirm adso rption of labeled protein, or the binding of fluorescently labeled biotin o nto previously adsorbed, unlabeled avidin. When labeled biotin in PBS was p resented to avidin adsorbed onto a BSA-coated microchip, the fluorescence s ignal was significantly higher than for avidin adsorbed onto the biochip al one. The results show that a simple, low-cost adsorption process can deposi t active protein onto a chip in an approach that has potential application in the development of protein biochips for the detection of biological spec ies. (C) 2001 John Wiley & Sons, Inc.