Surface charge of PLA microparticles in regulation of antigen loading, macrophage phagocytosis and activation, and immune effects in vitro

The use of microparticles (MPs) as adjuvants has attracted increasing interest in vaccine delivery systems. Many physiochemical characteristics of MPs including hydrodynamic size, surface properties, and morphology can regulate the immune response. Surface charge is an important characteristic of MPs, but how it affects their adjuvanticity remains unknown. In this study, we prepared uniform-sized polylactide MPs coated with various polymers of different positive charge, and investigated how the surface charge affected antigen loading and macrophage phagocytosis and activation in vitro. A higher surface charge greatly enhanced antigen loading and antigen internalization into macrophages, promoted the expression of MHC II and CD80, and increased the secretion level of TNF-alpha. Taken together, these results indicated that surface charge was an important parameter for improving the adjuvanticity of MPs. (C) 2014 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.