Submonolayer measurements of adsorbed proteins in microfluidic channels

Microelectromechanical systems (MEMS), and soon nanoelectromechanical systems (NEMS), are projected to have a major impact in systems for toxin detection, proteomics and biomedical applications. This chapter describes experimental systems that were developed in our labs, as well as those being developed elsewhere, that are being used to understand protein deposition at sub-monolayer coverages in these devices. Modeling tools, used in conjunction with experimental results, can also be utilized for predicting the interactions of proteins with these microsystems, under static and flow conditions, with the goal of creating biocompatible MEMS devices that can be easily integrated with biologically based assay systems. The long-term combination and integration of biological and electronic components requires a thorough understanding of surface/biomolecule interactions in these devices. The use of surface modification techniques has allowed the tailoring of the interface between biological/nonbiological materials, independent of the bulk composition of the nonbiological material, to enable reproducible experimental design. Our results to date have indicated we can measure protein adsorption down to less that 1% of a monolayer and that static results are very different than those observed under flow conditions, and this has been supported by the modeling results. Thus, data obtained under static conditions cannot be used as a predictor for behavior under flow conditions, which should be the predominant situation in most biological assay systems.