Influence of electrostatic interactions on the surface adsorption of a viral protein cage.

The Cowpea chlorotic mottle virus (CCMV) provides a useful protein-cage architecture that can be used for the size- and shape-constrained chemistry of nanomaterials. The control of surface assembly is necessary for the realization of many applications of these nanoscale reaction vessels. Electrostatic interactions provide a useful (and reversible) method for controlled surface assembly. CCMV absorption behavior was studied on Formvar, bare Si, Formvar-coated Si, and Si modified by aminopropyltriethoxysilane (APS). Transmission electron microscopy (TEM), atomic force microscopy (AFM), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) were used to characterize the CCMV surface adsorption. Combined AFM and ATR-FTIR data indicated that the viral coverage on the modified surfaces was approximately 84% of the jamming limit predicted by the random sequential adsorption (RSA) model. According to the ATR-FTIR results, surface coverage was not increased at higher ionic strengths nor at a pH near the isoelectric point (pI) of the virus. The Langmuir model was used to provide a description of the kinetic absorption behavior.