Protein-covered silica nano-particles adsorbing onto synthetic vesicles

Abstract

Silica nano-particles with surface acid groups were reacted with coupling agents and, then, with lysozyme, to get functionalized entities. The procedure functionalizes surface sites and ensures moderate coverage. The amount of bound lysozyme, estimated from UV-vis, is 5 molecules per nano-particle. Electro-phoretic mobility indicates variations in surface charge density of functionalized nano-particles compared to the original ones. Protein-functionalized nano-particles form clusters, re-dispersible by application of shear. Such nano-particles interact with vesicles comparable in size. The kinetic pathways of the interactions between them were investigated. Adsorption onto vesicles and clustering are diffusion controlled. The process is governed by repulsive and attractive interactions between such entities. Nano-particle/vesicle adducts precipitate as fine powders, or form large floating objects, depending on vesicle size, charge, and [vesicles/nano-particles] ratios. Attempts were made to rationalize such behavior as the combination of electro-phoretic mobility and diffusive contributions of the interacting species.