The main aim of bone tissue engineering is to fabricate highly biocompatible, osteoconductive and/or osteoinductive biomaterials for tissue regeneration. Bone implants should support bone growth at the implantation site via promotion of osteoblast adhesion, proliferation, and formation of bone extracellular matrix. Moreover, a very desired feature of biomaterials for clinical applications is their osteoinductivity, which means the ability of the material to induce osteogenic differentiation of mesenchymal stem cells toward bone-building cells (osteoblasts). Nevertheless, the development of completely biocompatible biomaterials with appropriate physicochemical and mechanical properties poses a great challenge for the researchers. Thus, the current trend in the engineering of biomaterials focuses on the surface modifications to improve biological properties of bone implants. This review presents the most recent findings concerning surface modifications of biomaterials to improve their osteoconductivity and osteoinductivity. The article describes two types of surface modifications: (1) Additive and (2) subtractive, indicating biological effects of the resultant surfaces in vitro and/or in vivo. The review article summarizes known additive modifications, such as plasma treatment, magnetron sputtering, and preparation of inorganic, organic, and composite coatings on the implants. It also presents some common subtractive processes applied for surface modifications of the biomaterials (i.e., acid etching, sand blasting, grit blasting, sand-blasted large-grit acid etched (SLA), anodizing, and laser methods). In summary, the article is an excellent compendium on the surface modifications and development of advanced osteoconductive and/or osteoinductive coatings on biomaterials for bone regeneration.

https://www.mdpi.com/2079-6412/10/10/971/pdf

Osteoconductive and Osteoinductive Surface Modifications of Biomaterials for Bone Regeneration: A Concise Review

The problem of treatment of household and biomedical waste containing toxic substances is becoming increasingly important. In contrast to the conventional incineration, plasma gasification of the waste provides reliable destruction of highly toxic dioxins, benzo(a)pyrene and furans. This article presents the results of thermodynamic analysis and experiments on gasification of the waste of various origins in the plasma reactor. The calculations have shown that the maximum yield of synthesis gas in the waste plasma gasification in the air and steam medium was achieved at a temperature not higher than 1600 K. It is shown that in the process of air-plasma and steam-plasma gasification of bone tissue, it is possible to obtain synthesis gas with concentrations 53.4 and 84.9 vol.% having heat of combustion 3510 and 5664 kJ/kg, respectively. In the air and steam plasma gasification of household waste a high-calorific synthesis gas with concentrations 82.4 and 94.5 vol.%, respectively, can be obtained. Its heat of combustion amounts to 13,620 and 18,497 kJ/kg respectively for air and steam gasification. A comparison between the experiment and the calculations showed a good agreement. According to the results of investigations of the waste plasma gasification, no harmful impurities were detected. From the waste organic and mineral mass, respectively, high-calorific synthesis gas and a neutral slag were obtained.

Processing of Biomedical Waste in Plasma Gasifier

Titanium, stainless steel, and CoCrMo alloys are the most widely used biomaterials for orthopedic applications. The most common causes of orthopedic implant failure after implantation are infections, inflammatory response, least corrosion resistance, mismatch in elastic modulus, stress shielding, and excessive wear. To address the problems associated with implant materials, different modifications related to design, materials, and surface have been developed. Among the different methods, coating is an effective method to improve the performance of implant materials. In this article, a comprehensive review of recent studies has been carried out to summarize the impact of coating materials on metallic implants. The antibacterial characteristics, biodegradability, biocompatibility, corrosion behavior, and mechanical properties for performance evaluation are briefly summarized. Different effective coating techniques, coating materials, and additives have been summarized. The results are useful to produce the coating with optimized properties.

Recent Developments in Coatings for Orthopedic Metallic Implants

Incorporating TiO2 nanoparticles to enhance corrosion resistance, cytocompatibility, and antibacterial properties of PEO ceramic coatings on titanium

Systematic optimization of corrosion, bioactivity, and biocompatibility behaviors of calcium-phosphate plasma electrolytic oxidation (PEO) coatings on titanium substrates

Surface treatment and bioactive metal ion incorporation are effective methods for the modification of titanium alloys to be used as biomaterials. However, few studies have demonstrated the use of air-plasma treatment in orthopedic biomaterial development. Additionally, no study has performed a direct comparison between unmodified titanium alloys and air-plasma-treated alloys with respect to their biocompatibility and osteogenesis. In this study, the biological activities of unmodified titanium alloys, air-plasma-treated titanium alloys, and air-plasma-treated strontium-doped/undoped calcium phosphate (CaP) coatings were compared. The strontium-doped CaP (Sr-CaP) coating on titanium alloys were produced by selective laser melting (SLM) technology as well as micro-arc oxidation (MAO) and air-plasma treatment. The results revealed that rapid air-plasma treatment improved the biocompatibility of titanium alloys and that Sr-CaP coating together with air-plasma treatment significantly enhanced both the biocompatibility and osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs). Overall, this study demonstrated that low temperature air-plasma treatment is a fast and effective surface modification which improves the biocompatibility of titanium alloys. Additionally, air-plasma-treated Sr-CaP coatings have numerous practical applications and may provide researchers with new tools to assist in the development of orthopedic implants.

/pdf/improved-osteogenesis-of-selective-laser-melted-titanium-4c66w3htbf.pdf

Improved Osteogenesis of Selective-Laser-Melted Titanium Alloy by Coating Strontium-Doped Phosphate With High-Efficiency Air-Plasma Treatment.

Comparative evaluation of Sr-incorporated calcium phosphate and calcium silicate as bioactive osteogenesis coating orthopedics applications

Synthesis and Antibacterial Properties of ZIF-8/Ag-Modified Titanium Alloy

Tantalum (Ta) is an element with high chemical stability and ductility that is used in orthopedic biomaterials. When utilized, it can produce a bioactive surface and enhance cell–material interactions, but currently, there exist scarce effective methods to introduce the Ta element onto the surface of implants. This work reported a sol–gel-assisted approach combined with micro-arc oxidation (MAO) to introduce Ta onto the surface of the titanium (TC4) substrate. Specifically, this technique produced a substrate with a hierarchically rough structured topography and introduced strontium ions into the film. The films were uniform and continuous with numerous crater-like micropores. Compared with the TC4 sample (196 ± 35 nm), the roughness of Ta (734 ± 51 nm) and Ta–Sr (728 ± 85 nm) films was significantly higher, and both films (Ta and Ta–Sr) showed increased hydrophilicity when compared with TC4, promoting cell attachment. Additionally, the in vitro experiments indicated that Ta and Ta–Sr films have the potential to enhance the recruitment of cells in the initial culture stages, and improve cell proliferation. Overall, this work demonstrated that the application of Ta and Ta–Sr films to orthopedic implants has the potential to increase the lifetime of the implants. Furthermore, this study also describes an innovative strategy to incorporate Ta into implant films.

/pdf/sol-gel-assisted-micro-arc-oxidation-synthesis-and-4adhut1fcb.pdf

Yongjie Wei

Papers

Improved Osteogenesis of Selective-Laser-Melted Titanium Alloy by Coating Strontium-Doped Phosphate With High-Efficiency Air-Plasma Treatment.

Comparative evaluation of Sr-incorporated calcium phosphate and calcium silicate as bioactive osteogenesis coating orthopedics applications

Synthesis and Antibacterial Properties of ZIF-8/Ag-Modified Titanium Alloy

Sol–gel-assisted micro-arc oxidation synthesis and characterization of a hierarchically rough structured Ta–Sr coating for biomaterials

Synthesis and Antibacterial Properties of ZIF-8/Ag-Modified Titanium Alloy