Size Effect of Mesoporous Bioactive Glass on Macrophage Polarization

Macrophages, one of the key immune cells, are closely associated with various diseases and play critical roles in tissue regeneration via proper polarization. Mesoporous bioactive glass (MBG) has been widely used in bone tissue regeneration; thus, it is charming and beneficial to understand the interactions between MBG and the immune system. Herein, MBG particles with sizes of about 75 nm (MBG-1), 200 nm (MBG-2), and 500 nm (MBG-5) were prepared, and their size effects on macrophage polarization were investigated. The results demonstrated that small MBG particles (75 nm) promoted macrophage polarization toward the M2 phenotype while inhibiting M1 polarization at an early stage (3 days). Meanwhile, medium-sized MBG particles (200 nm) induce a mild inflammatory response in the early stage and promote a high proportion of anti-inflammatory M2 macrophages in the late stage. In contrast, large-sized MBG particles (500 nm) trigger a strong multidirectional activation of macrophages during the early stage, accompanied by a marked upregulation in the expression of both M1 and M2 phenotypic markers. This work preliminarily investigates the relationship between the particle size of MBG and polarization of macrophages, providing insights for the design and further applications of MBG-based biomaterials.