Dual-ion delivery for synergistic angiogenesis and bactericidal capacity with silica-based microsphere

Inhibition of bacterial growth with the simultaneous promotion of angiogenesis has been challenging in the repair and regeneration of infected tissues. Here, we aim to tackle this issue through the use of cobalt doped silicate microspheres that can sustainably release dual ions (silicate and cobalt) at therapeutically relevant doses. The cobalt was doped up to 2.5 wt% within a sol-gel silicate glass network, and microspheres with the size of similar to 300 mu m were generated by an emulsification method. The cobalt and silicate ions released were shown to synergistically upregulate key angiogenic genes, such as HIF1-alpha, VEGF and the receptor KDR. Moreover, the incorporation of ions promoted the polarization, migration, homing and sprouting angiogenesis of endothelial cells. Neo-vascular formation was significantly higher in the dual-ion delivered microspheres, as evidenced in a chicken chorioallantoic membrane model. When cultured with bacterial species, the cobalt-doped microspheres effectively inhibited bacteria growth in both indirect or direct contacts. Of note, the bacteria/endothelial cell coculture model proved the efficacy of dual-ion releasing microcarriers for maintaining the endothelial survivability against bacterial contamination and their cell-cell junction. The current study demonstrates the multiple actions (proangiogenic and antibacterial) of silicate and cobalt ions released from microspheres, and the concept provided here can be extensively applied to repair and regenerate infected tissues as a growth factor- or drug-free delivery system. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.