CaCO3-Encapsulated Au Nanoparticles Modulate Macrophages toward M1-like Phenotype

Macrophage cells are plastic and can be polarized into opposing phenotypes, pro-inflammatory (M1-like cells) or anti-inflammatory (M2-like cells). Reprograming of M2-like cells into M1 phenotype will contribute significantly to combatting cancer. Gold nanoparticles (AuNPs) are intensively studied in various fields for their distinctive photo-chemical properties. However, the immune response of AuNPs is still unclear. In this study, AuNPs and CaCO3-encapsulated Au nanoparticles (Au@CaCO3 NPs) were synthesized as stimuli for macrophage modulation. Co-incubation of AuNPs and macrophages leads to a dramatically elongated macrophage cell morphology. Moreover, increased expression of M2 biomarker and M2-inducing cytokines suggests that AuNPs induce macrophage polarization toward M2 phenotype. More interestingly, the co-incubation of Au@CaCO3 NPs and macrophage cells resulted in a round cellular morphology and induced the secretion of M1 biomarker and inflammatory cytokines. Our studies demonstrate that the strategy of CaCO3-encapsulated Au nanoparticles can be used in modulating the polarization of M1 macrophages. Our strategy provides an efficient method for activating inflammation in macrophages, which will be useful for the application of nanoparticles in cancer therapy.