Adsorption of antibody onto Pluronic F68-covered nanoparticles: link with surface properties

Abstract

The use of nanoparticles as drug delivery systems is an emerging application to improve intravenous therapy. Controlling the biocompatibility of the nanoparticles is a crucial step towards the optimal implementation of these systems. Adsorption of serum components onto the nanoparticles is driven mainly by hydrophobic forces. Thus, incorporation of hydrophilic polymers such as polyethylene oxide (PEO) derivatives to the nanostructure surface reduces the interaction of nanoparticles with blood stream components (IgG). The effectiveness of the poloxamer for reducing protein adsorption depends on the resistance of this coating layer. A fundamental understanding of the properties of this surface coating is crucial towards the rational design of these systems. Here, we have used an innovative combination of experimental techniques to evaluate the properties of the nanoparticles and more specifically, the mechanical properties of the coating. Electrophoretic mobility and colloidal stability data suggest similar surface characteristics between IgG–Pluronic–polystyrene (PS) and IgG–PS complexes, indicating that the protein adsorption is just slightly reduced by the presence of poloxamer. Nevertheless, the biological activity of the adhered antibodies suggests that the Pluronic F68 significantly altered their immunoactivity. The decrease in the activity might indicate a partial denaturation of the protein and/or changes in the preferential orientation when adsorbing caused by the surfactant–protein interactions. The surface characterisation of the IgG layers adsorbed onto a Pluronic covered surface importantly provides evidence of the conformational change undergone by the protein, supporting the partial protein denaturation suggested by the loss of immunoreactivity in the IgG–Pluronic–PS particles. The use of surface tension to obtain structural and mechanical information about the coating procedure is a novel approach to understand generic features of the biocompatibility of colloidal systems. These results may help to understand why drug nanocarriers coated by poloxamers improve their long-circulating properties in comparison with uncoated particles.