Cellular Binding of Nanoparticles in the Presence of Serum Proteins

Abstract

Nanoparticles have important biomedical applications ranging from the treatment of human disease with gene therapy to understanding basic cellular function. For cellular uptake of nanoparticles to occur, the particle must first bind to the cell surface. We sought to understand how nanoparticles interact with the cell surface in the presence of serum proteins. Cell culture medium supplemented with serum is a highly complex mixture of amino acids, vitamins, inorganic salts, glucose and proteins. Characterization of cationic, fluorescent nanoparticles in the presence of cell culture medium demonstrated that the particles rapidly bind a mixture of proteins present in the serum resulting in an anionic nanoparticle that essentially presents a surface of serum proteins to the cell surface. Probing the interaction of this serum protein-nanoparticle complex with the cell surface was achieved using fluorescently labeled proteins and monitoring the colocalization of nanoparticle and protein signal with two-color fluorescence microscopy over time. Our results indicated that both nanoparticle and protein were highly colocalized at early times and this was found to decrease with increased incubation time. Displacement of the serum proteins from the nanoparticles was found to be protein dependent. This study has important implications for the rational design of nanoparticles and ligands for delivery in a cellular environment as it demonstrates the significance of serum protein-nanoparticle interactions. Such interactions can ultimately influence the cellular binding of the nanoparticle to the cell surface.[1][1] G. W. Doorley and C. K. Payne, “ Cellular Binding of Nanoparticles in the Presence of Serum Proteins” Chem. Commun., 2010, in press