Adsorption of bovine serum albumin on polyelectrolyte-coated glass substrates: applications to colloidal lithography.

The adsorption of bovine serum albumin (BSA) labeled with fluorescein isothiocyanate (FITC) on polyelectrolyte-coated glass substrates was investigated using fluorescence microscopy. Glass substrates may inhibit adsorption of proteins due to electrostatic repulsion. However, when the substrate is modified with a thin film of positively charged polyelectrolytes, proteins can be adsorbed due to the attractive electrostatic interactions. In this study, poly(allylamine-hydrochloride) (PAH) molecules, which have positively charged amino groups at pH 7, were used to generate a positively charged layer on the glass substrate. A surfactant, sodium dodecyl sulphate (SDS), was used to alter the glass-protein interaction and subsequently modulate the coverage of adsorbed protein. We applied this technique to control the heterogeneously charged microscopic patterns of biomolecules created when the adsorption of protein is done in conjunction with colloidal lithography.