Channel-specific coatings on microfabricated chips

This paper reports channel-specific immobilization of fluorescein-5-isothio cyanate (FITC)-labeled bovine serum albumin and beta -galactosidase on micr ochips with a central channel and two crossing channels; referred to as a d ouble cross channel configuration. Solvent wells at the termini of all chan nels were used to store reagents. Coatings were applied in multiple steps u sing electroosmotically driven flow to deliver reagents to specific channel s in the chip. The first step in all coating reactions was derivatization o f the capillary walls with an organosilane having a reactive pendant functi onal group. As the silylating reagent was transported from the reagent stor age well to a specific waste well, capillary walls in the route of transpor t were silylated. Flow was maintained throughout a reaction. The route of t ransport, and thus the specificity of channel coating, were controlled by t he well to which negative potential was applied. Flow in a multichannel net work takes the shortest route between the electrodes delivering the motive potential. The second reagent in the reaction was delivered from a differen t well and took a different path through the channel network, as did other reagents. Only the channel being coated was in the flow path of all the rea gents used in the coating process. The zone of immobilization in the case o f FITC-labeled albumin was determined with confocal fluorescence microscopy . Enzyme activity of immobilized beta -galactosidase (beta -Gal) was monito red by following the hydrolysis of fluorescein mono-beta -D-galactopyranosi de to fluorescein with laser-induced fluorescence. (C) 2001 Published by El sevier Science B.V.