In Vitro Bioactivity and Biocompatibility of Bio-Inspired Ti-6Al-4V Alloy Surfaces Modified by Combined Laser Micro/Nano Structuring

Abstract

The bioactivity and biocompatibility play key roles in the success of dental and orthopaedic implants. Although most commercial implant systems use various surface microstructures, the ideal multi-scale topographies capable of controlling osteointegration have not yielded conclusive results. Inspired by both the isotropic adhesion of the skin structures in tree frog toe pads and the anisotropic adhesion of the corrugated ridges on the scales of Morpho butterfly wings, composite micro/nano-structures, including the array of micro-hexagons and oriented nano-ripples on titanium alloy implants, were respectively fabricated by microsecond laser direct writing and femtosecond laser-induced periodic surface structures, to improve cell adherence, alignment and proliferation on implants. The main differences in both the bioactivity in simulated body fluid and the biocompatibility in osteoblastic cell MC3T3 proliferation were measured and analyzed among Ti-6Al-4V samples with smooth surface, micro-hexagons and composite micro/nano-structures, respectively. Of note, bioinspired micro/nano-structures displayed the best bioactivity and biocompatibility after in vitro experiments, and meanwhile, the nano-ripples were able to induce cellular alignment within the micro-hexagons. The reasons for these differences were found in the topographical cues. An innovative functionalization strategy of controlling the osteointegration on titanium alloy implants is proposed using the composite micro/nano-structures, which is meaningful in various regenerative medicine applications and implant fields.

mTORC2 regulates hierarchical micro/nano topography‐induced osteogenic differentiation via promoting cell adhesion and cytoskeletal polymerization

“… 8 , 9 Notably, mimicking the natural bone structure which consists of micro‐scale collagen fibers and nano‐scale hydroxyapatite, the hierarchical micro/nano topography titanium surface provides a better microenvironment than that with signal micro‐scale topography for cell‐surface interaction. 10 , 11 , 12 , 13 , 14 , 15 In our previous study, we have revealed that the hierarchical micro/nano topography was superior to the SLA titanium surface in improving the osteogenesis. 16 , 17 However, the elaborate regulation process of the cell‐surface interaction and the underlying mechanism have remained to be elucidated.…”

“…Recently, the hierarchical micro/nano topography has attracted extensive attention since the nano‐scale feature can increase the adsorption of proteins and subsequently enhance cell attachment 8,9 . Notably, mimicking the natural bone structure which consists of micro‐scale collagen fibers and nano‐scale hydroxyapatite, the hierarchical micro/nano topography titanium surface provides a better microenvironment than that with signal micro‐scale topography for cell‐surface interaction 10‐15 . In our previous study, we have revealed that the hierarchical micro/nano topography was superior to the SLA titanium surface in improving the osteogenesis 16,17 .…”

Characterization and evaluation of a femtosecond laser-induced osseointegration and an anti-inflammatory structure generated on a titanium alloy

“…It may be that the HAp is only deposited on the surface, while the rest of the samples with surface structure can be deposited in the voids or gaps resulting in non-standard sampling. However, in other reports, femtosecond laser-modified surfaces have shown good HAp deposition capabilities [ 57 ]. The LDH assay was applied to assess the effect of molten metal on cytotoxicity and showed that the combination of femtosecond laser treatment and sandblasting increased cytotoxicity to some extent, but the cytotoxicity of the resulting surfaces was still lower than that of the polished titanium surface.…”

Multifunctional Coatings of Titanium Implants Toward Promoting Osseointegration and Preventing Infection: Recent Developments

“…The surface was more conducive to the polarization of macrophage to anti-inflammatory type M2 and induced osteoblasts to exhibit more mineralization nodules. Inspired by the skin structures of the tree frog toe pads and the adhesion of the corrugated ridges on the scales of Morpho butterfly wings, Li et al generated micro-hexagons and nano-ripples on titanium surface by microsecond laser ( Li et al, 2020a ). This structure provided microscale space for cell behaviors, enhancing mechanical interlocking at the boneimplant interface.…”