Surface biopassivation of replicated poly(dimethylsiloxane) microfluidic channels and application to heterogeneous immunoreaction with on-chip fluorescence detection

Poly(dimethylsiloxane) (PDMS) appeared recently as a material of choice for rapid and accurate replication of polymer-based microfluidic networks. How ever, due to its hydrophobicity, the surface strongly interacts with apolar analytes or species containing apolar domains, resulting in significant un controlled adsorption on channel walls. This contribution describes the app lication and characterization of a PDMS surface treatment that considerably decreases adsorption of low and high molecular mass substances to channel walls while maintaining a modest cathodic electroosmotic. flow. Channels ar e modified with a three-layer biotin-neutravidin sandwich coating, made of biotinylated IgG, neutravidin, and biotinylated dextran. By replacing bioti nylated dextran with any biotinylated reagent, the modified surface can be readily patterned with biochemical probes, such as antibodies. Combination of probe immobilization chemistry with low nonspecific binding enables affi nity binding assays within channel networks. The example of an electrokinet ic driven, heterogeneous immunoreaction for human IgG is described.