Development and characterization of an ELISA assay in PDMS microfluidic channels

This report describes the first preliminary evaluation of a heterogeneous sandwich enzyme-linked immunoassay in a PDMS microfluidic device. The PDMS devices were fabricated using replica molding against a patterned photoresist generated by photolithographic techniques. With this experimental setup, the microfluidic sensor chip was successfully used to quantify a model analyte (sheep IgM) with sensitivity down to 17 nM. The conventional blocking cocktail used in nearly all polystyrene microtiter plate-based ELISA assays failed to block the nonspecific adsorption of the analyte and secondary antibody. This report describes the successful use of surface modification chemistries and a modified blocking cocktail to reduce background due to nonspecific adsorption and to thereby increase the sensitivity of the assay. These protocols can be extended to the detection of a variety of analytes by immunoassay in PDMS microchannels.