Engineering nano-structures with controllable dimensional features on micro-topographical titanium surfaces to modulate the activation degree of M1 macrophages and their osteogenic potential

Modulating the activation state and degree of macrophages still remains as a challenge for the topographical design of Ti-based implants. In this work, micro/nano-structured coatings were prepared on Ti substrates by micro-arc oxidation (MAO) and subsequent hydrothermal (HT) treatment. By varying the HT conditions, plate-like nano-structures with an average length of 80, 440 or 780 nm were obtained on MAO-prepared micro-topographical surfaces. Depending on the dimensional features of nano-plates, the specimens were noted as Micro, Micro/Nano-180, Micro/Nano-440 and Micro/Nano-780, respectively. The in vitro results showed that the activation state and degree of macrophages could be effectively modulated by the micro/nano-structured surfaces with various dimensional features. Compared to the Micro surface, the Micro/Nano-180 surface activated both M1 and M2 phenotype in macrophages, while the Micro/Nano-440 and Micro/Nano-780 surfaces polarized macrophages to their M1 phenotype. The activation degree of M1 macrophages followed the trend: Micro < Micro/Nano-180 < Micro/Nano-440 < Micro/Nano-780. However, the osteogenic potential of the activated macrophages in response to various surfaces were in the order: Micro approximate to Micro/Nano-780 < Micro/Nano-180 < Micro/Nano-440. Together, the findings presented in this work indicate that engineering nano-structures with controllable dimensional features is a promising strategy to modulate macrophage activation state and degree. In addition, it is essential to determine the appropriate activation degree of M1 macrophages for enhanced osteogenesis. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.