ADSORPTION OF STREPTAVIDIN ONTO POLYSTYRENE SURFACE

Abstract: Microparticles of various sizes carrying different surface modifications have numerous technological and biomedical applications, for example to create a larger target for a molecular receptor by binding multiply ligands to the surface of the microparticle. The aim of the present work is to study how to most efficiently couple protein molecules to the surface of such microparticles. In the current study I have focused on the coupling of Streptavidin-Alexa Flour 488 (SA-AF 488) to polystyrene microparticles (PSMs). The passive adsorption of SA-AF 488 onto PSMs with diameter 6 µm was first investigated at two different pH. It was found that maximal adsorption occurs when pH is in the neighbourhood of SA-AF’s isoelectric point. However, the protein adsorption on the PSMs was uneven for the passive adsorption. To obtain a more even protein adsorption I then investigated covalent coupling of the same protein on carboxyl-modified PSMs (PSM-COOH) as well as amine modified PSMs (PSM-NH2) with diameter 1 µm. This approach resulted in more even protein coverage on the PSMs and of the two covalently-coupled PSMs it was found that the PSM-COOH bound more proteins in comparison to PSM-NH2. The study shows that efficiently coupling of protein molecules can be achieved to microparticles, opening up for different proteins such as antibodies to be coupled to microspheres of various sizes.