Depending on the requirements of specific applications, implanted materials including metals, ceramics, and polymers have been used in various disciplines of medicine. Titanium and its alloys as implant materials play a critical role in the orthopedic and dental procedures. However, they still require the utilization of surface modification technologies to not only achieve the robust osteointegration but also to increase the antibacterial properties, which can avoid the implant-related infections. This article aims to provide a summary of the latest advances in surface modification techniques, of titanium and its alloys, specifically in biomedical applications. These surface techniques include plasma spray, physical vapor deposition, sol-gel, micro-arc oxidation, etc. Moreover, the microstructure evolution is comprehensively discussed, which is followed by enhanced mechanical properties, osseointegration, antibacterial properties, and clinical outcomes. Future researches should focus on the combination of multiple methods or improving the structure and composition of the composite coating to further enhance the coating performance.

The propose of this review was to summarize the advances in multi-scale surface technology of titanium implants to accelerate the osseointegration process. The several multi-scaled methods used for improving wettability, roughness, and bioactivity of implant surfaces are reviewed. In addition, macro-scale methods (e.g., 3D printing (3DP) and laser surface texturing (LST)), micro-scale (e.g., grit-blasting, acid-etching, and Sand-blasted, Large-grit, and Acid-etching (SLA)) and nano-scale methods (e.g., plasma-spraying and anodization) are also discussed, and these surfaces are known to have favorable properties in clinical applications. Functionalized coatings with organic and non-organic loadings suggest good prospects for the future of modern biotechnology. Nevertheless, because of high cost and low clinical validation, these partial coatings have not been commercially available so far. A large number of in vitro and in vivo investigations are necessary in order to obtain in-depth exploration about the efficiency of functional implant surfaces. The prospective titanium implants should possess the optimum chemistry, bionic characteristics, and standardized modern topographies to achieve rapid osseointegration.

The Ste2p receptor for alpha-factor, a tridecapeptide mating pheromone of the yeast Saccharomyces cerevisiae, belongs to the G protein-coupled family of receptors. In this paper we report on the synthesis of peptides corresponding to five of the seven transmembrane domains (M1-M5) and two homologues of the sixth transmembrane domain corresponding to the wild-type sequence and a mutant sequence found in a constitutively active receptor. The secondary structures of all new transmembrane peptides and previously synthesized peptides corresponding to domains 6 and 7 were assessed using a detailed CD analysis in trifluoroethanol, trifluoroethanol-water mixtures, sodium dodecyl sulfate micelles, and dimyristoyl phosphatidyl choline bilayers. Tryptophan fluorescence quenching experiments were used to assess the penetration of the membrane peptides into lipid bilayers. All peptides were predominantly (40-80%) helical in trifluoroethanol and most trifluoroethanol-water mixtures. In contrast, two of the peptides M3-35 (KKKNIIQVLLVASIETSLVFQIKVIFTGDNFKKKG) and M6-31 (KQFDSFHILLINleSAQSLLVPSIIFILAYSLK) formed stable beta-sheet structures in both sodium dodecyl sulfate micelles and DMPC bilayers. Polyacrylamide gel electrophoresis showed that these two peptides formed high molecular aggregates in the presence of SDS whereas all other peptides moved as monomeric species. The peptide (KKKFDSFHILLIMSAQSLLVLSIIFILAYSLKKKS) corresponding to the sequence in the constitutive mutant was predominantly helical under a variety of conditions, whereas the homologous wild-type sequence (KKKFDSFHILLIMSAQSLLVPSIIFILAYSLKKKS) retained a tendency to form beta-structures. These results demonstrate a connection between a conformational shift in secondary structure, as detected by biophysical techniques, and receptor function. The aggregation of particular transmembrane domains may also reflect a tendency for intermolecular interactions that occur in the membrane environment facilitating formation of receptor dimers or multimers.