Stimuli responsive coatings offer a versatile method by which to manipulate interfacial interactions of proteins in a desired way. That said, there exists little guidance as to how structure of a responsive polymer coating influences adsorption of proteins. In this study, we have investigated the adsorption behavior of immuglobulin-G (IgG) on poly(N-isopropylacryamide) (PNIPAAm) hydrogel coatings as a function of thickness.  PNIPAAm exhibits a hydrophilic to hydrophobic transition above a critical temperature of 32�C in aqueous solutions, thus favoring adsorption above 32 oC. Through the use of ellipsometry and QCM-D, we have observed thickness dependent adsorption that becomes less reversible as the film thickness increases. To better understand these results, we performed hydrodynamic shear force assay in a spinning disk configuration in order to quantify adhesion of poly(styrene) probe spheres (10�m) to the PNIPAAm coatings in both the solvated (hydrophilic) and collapsed (hydrophobic) state.  Measurements show a linear dependence between mean particle adhesion strength and PNIPAAm film thikness in the hydrophilic state. In the collapsed state, the adhesion strength depends strongly on coating thickness.

Quantification of adhesion strength of thermoresponsive coatings through hydrodynamic detachment shear stresses

244th National Meeting (2012)

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