Fabrication of anodic and atomic layer deposition-alumina coated titanium implants for effective osteointegration applications.

Biomimicking the chemical, mechanical, and topographical properties of bone on an implant model is crucial to obtain rapid and effective osteointegration, especially for the large-area fractures of the skeletal system. Titanium-based biomaterials are more frequently preferred in clinical use in such cases and coating these materials with oxide layers having chemical/nanotopographic properties to enhance osteointegration and implantation success rates has been studied for a long time. The objective of this study is to examine the high and rapid mineralization potential of anodized aluminum oxide (AAO) coated and atomic layer deposition (ALD)-alumina coated titanium substrates on large deformation areas with difficult spontaneous healing. AAO-coated titanium (AAO@Ti) substrates were fabricated via anodization technique in different electrolytes and their osteogenic potential was analyzed by comparing them to the bare titanium surface as a control. In order to investigate the effect of the ionic characters gained by the surfaces through anodization, the oxidized nanotopographic substrates were additionally coated with an ultrathin alumina layer via ALD (ALD@AAO@Ti), which is a sensitive and conformal coating vapor deposition technique. Besides, a bare titanium sample was also coated with pure alumina by ALD (ALD@Ti) to investigate the effect of nanoscale surface morphology. XPS analysis after ALD coating showed that the ionic character of each surface fabricated by anodization was successfully suppressed. In vitro studies demonstrated that, among the substrates investigated, the mineralization capacity of MG-63 osteosarcoma cells were highest when incubated on ALD-treated and bare AAO@Ti samples that were anodized in phosphoric acid (H3PO4_AAO@Ti and ALD@H3PO4_AAO@Ti). Mineralization on these substrates also increased consistently beginning from day 2 to day 21. Moreover, immunocytochemistry for osteopontin (OPN) demonstrated the highest expression for ALD@H3PO4_AAO@Ti, followed by the H3PO4_AAO@Ti sample. Consequently, it was observed that, although ALD treatment improves cellular characteristics on all samples, effective mineralization requires more than a simple ALD coating or the presence of a nanostructured topography. Overall, ALD@H3PO4_AAO@Ti substrates can be considered as an implant alternative with its enhanced osteogenic differentiation potential and rapid mineralization capacity.

Bioinspired Collagen/Gelatin Nanopillared Films as a Potential Implant Coating Material.

Collagen-based Sharpey's fibers are naturally located between alveolar bone and tooth, and they have critical roles in a well-functioning tooth such as mechanical stability, facile differentiation, and disease protection. The success of Sharpey's fibers in these important roles is due to their unique location, vertical alignment with respect to tooth surface, as well as their micronanofiber architecture. Inspired by these structures, herein, we introduce the use of nanoporous anodic aluminum oxide molds in a drop-casting setup to fabricate biopolymeric films possessing arrays of uniform Collagen:Gelatin (Col:Gel) nanopillars. Obtained structures have diameters of ∼90 nm and heights of ∼300 nm, yielding significantly higher surface roughness values compared to their flat counterparts. More importantly, the nanostructures were parallel to each other but perpendicular to the underlying film surface imitating the natural collagenous structures of Sharpey's fibers regarding nanoscale morphology, geometrical orientation, as well as biochemical content. Viability testing showed that the nanopillared Col:Gel films have high cell viabilities (over 90%), and they display significantly improved attachment (ca. ∼ 2 times) and mineralization for Saos-2 cells when compared to flat Col:Gel films and Tissue Culture Polystyrene (TCPS) controls, plausibly due to their largely increased surface roughness and area. Hence, such Sharpey's fiber-inspired bioactive nanopillared Col:Gel films can be used as a dental implant coating material or tissue engineering platform with enhanced cellular and osteogenic properties.