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.
Highlights
Advancements of surface treatments in metallic biomaterials have allowed the production of better or longer lasting dental and orthopedic implants
Considering the previous study [28] revealing that the size of the pores on implants should in the range of 100~200 μm for better cell adherence and osseointegration, the side length of the be in the range of 100~200 μm for better cell adherence and osseointegration, the side length of the micro-hexagon was set to 150~300 μm and the width of channels between micro-hexagons was set to micro-hexagon was set to 150~300 μm and the width of channels between micro-hexagons was set to
Considering the corrugated ridges on the scales of Morpho butterfly wings directional adhesion in Figure 1b, fs-laser-induced periodic surface structures (LIPSS) were fabricated on the array of micro-hexagons using the with directional adhesion in Figure 1b, fs-LIPSS were fabricated on the array of micro-hexagons using femtosecond laser to create nano-ripples with the controlled orientation and the spatial periodicity the femtosecond laser to create nano-ripples with the controlled orientation and the spatial close to the size of cellular filopodia in the range 250~400 nm [29]
Summary
Advancements of surface treatments in metallic biomaterials have allowed the production of better or longer lasting dental and orthopedic implants. Inspired by the remarkable adhesion of both the skin structures in tree frog toe pads and the corrugated ridges on the scales of Morpho butterfly wings, biomimetic hierarchical surface structures on titanium alloy implants are fabricated by combined laser surface structuring in this work, to improve cell adherence, orientation and proliferation on implants. A microsecond laser was used to generate the primary array of micro-hexagons like hexagonal cells of tree frog toe pads, and secondly, a femtosecond laser was applied to directly induce nano-ripples with a controlled orientation on the micro-hexagons like the corrugated ridges of wing scales in Morpho butterflies.
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