Pulsed laser deposition of nanostructured bioactive glass and hydroxyapatite coatings: Microstructural and electrochemical characterization

Preparation and physicochemical characterization of whitlockite/PVA/Gelatin composite for bone tissue regeneration

This work used a straightforward solvent casting approach to synthesize bone whitlockite (WH) based PVA/Gelatin composites. WH nanoparticles (NPs) were synthesized using the wet precipitation method, followed by their addition into the PVA/Gelatin matrix at concentrations from 1% to 10%. The physicochemical characterization of the prepared PVA/Gelatin/WH composite was carried out using ATR-FTIR, Optical profilometry, a Goniometer, a Universal tensile testing machine (UTM), and scanning electron microscopy (SEM) techniques. The ATR-FTIR analysis confirmed the formation of noncovalent interactions between polymeric chains and WH NPs and the incorporation of WH NPs into the polymer cavities. SEM analysis demonstrated increased surface roughness with the addition of WH NPs, supporting the results obtained through optical profilometry analysis. The mechanical properties of the prepared composite showed an increase in the tensile strength with the addition of WH filler up to 7% loading. The prepared composite has demonstrated an excellent swelling ability and surface wettability. The reported results demonstrate the exceptional potential of the prepared composite for bone tissue regeneration.

Modification of titanium orthopedic implants with bioactive glass: a systematic review of in vivo and in vitro studies

Bioactive glasses (BGs) are ideal biomaterials in the field of bio-restoration due to their excellent biocompatibility. Titanium alloys are widely used as a bone graft substitute material because of their excellent corrosion resistance and mechanical properties; however, their biological inertness makes them prone to clinical failure. Surface modification of titanium alloys with bioactive glass can effectively combine the superior mechanical properties of the substrate with the biological properties of the coating material. In this review, the relevant articles published from 2013 to the present were searched in four databases, namely, Web of Science, PubMed, Embase, and Scopus, and after screening, 49 studies were included. We systematically reviewed the basic information and the study types of the included studies, which comprise in vitro experiments, animal tests, and clinical trials. In addition, we summarized the applied coating technologies, which include pulsed laser deposition (PLD), electrophoretic deposition, dip coating, and magnetron sputtering deposition. The superior biocompatibility of the materials in terms of cytotoxicity, cell activity, hemocompatibility, anti-inflammatory properties, bioactivity, and their good bioactivity in terms of osseointegration, osteogenesis, angiogenesis, and soft tissue adhesion are discussed. We also analyzed the advantages of the existing materials and the prospects for further research. Even though the current research status is not extensive enough, it is still believed that BG-coated Ti implants have great clinical application prospects.

Microstructure and Mechanical Characteristics of Ti-Ta Alloys before and after NaOH Treatment and Their Behavior in Simulated Body Fluid

In the present study, the microstructure and mechanical properties of Ti-xTa (x = 5%, 15%, and 25% wt. Ta) alloys produced by using an induced furnace by the cold crucible levitation fusion technique were investigated and compared. The microstructure was examined by scanning electron microscopy and X-ray diffraction. The alloys present a microstructure characterized by the α' lamellar structure in a matrix of the transformed β phase. From the bulk materials, the samples for the tensile tests were prepared and based on the results and the elastic modulus was calculated by deducting the lowest values for the Ti-25Ta alloy. Moreover, a surface alkali treatment functionalization was performed using 10 M NaOH. The microstructure of the new developed films on the surface of the Ti-xTa alloys was investigated by scanning electron microscopy and the chemical analysis revealed the formation of sodium titanate and sodium tantanate along with titanium and tantalum oxides. Using low loads, the Vickers hardness test revealed increased hardness values for the alkali-treated samples. After exposure to simulated body fluid, phosphorus and calcium were identified on the surface of the new developed film, indicating the development of apatite. The corrosion resistance was evaluated by open cell potential measurements in simulated body fluid before and after NaOH treatment. The tests were performed at 22 °C as well as at 40 °C, simulating fever. The results show that the Ta content has a detrimental effect on the investigated alloys' microstructure, hardness, elastic modulus, and corrosion behavior.

Recent Advancements in Materials and Coatings for Biomedical Implants

Metallic materials such as stainless steel (SS), titanium (Ti), magnesium (Mg) alloys, and cobalt-chromium (Co-Cr) alloys are widely used as biomaterials for implant applications. Metallic implants sometimes fail in surgeries due to inadequate biocompatibility, faster degradation rate (Mg-based alloys), inflammatory response, infections, inertness (SS, Ti, and Co-Cr alloys), lower corrosion resistance, elastic modulus mismatch, excessive wear, and shielding stress. Therefore, to address this problem, it is necessary to develop a method to improve the biofunctionalization of metallic implant surfaces by changing the materials' surface and morphology without altering the mechanical properties of metallic implants. Among various methods, surface modification on metallic surfaces by applying coatings is an effective way to improve implant material performance. In this review, we discuss the recent developments in ceramics, polymers, and metallic materials used for implant applications. Their biocompatibility is also discussed. The recent trends in coatings for biomedical implants, applications, and their future directions were also discussed in detail.

Graphene oxide encapsulated forsterite scaffolds to improve mechanical properties and antibacterial behavior

It is very desirable to have good antibacterial properties and mechanical properties at the same time for bone scaffolds. Graphene oxide (GO) can increase the mechanical properties and antibacterial performance, while forsterite (Mg2SiO4) as the matrix can increase forsterite/GO scaffolds' biological activity for bone tissue engineering. Interconnected porous forsterite scaffolds were developed by space holder processes for bone tissue engineering in this research. The forsterite/GO scaffolds had a porosity of 76-78% with pore size of 300-450 μm. The mechanism of the mechanical strengthening, antibacterial activity, and cellular function of the forsterite/GO scaffold was evaluated. The findings show that the compressive strength of forsterite/1wt.% GO scaffold (2.4±0.1 MPa) was significantly increased, in comparison to forsterite scaffolds without GO (1.4±0.1 MPa). Validation of the samples' bioactivity was attained by forming a hydroxyapatite (HAp) layer on the forsterite/GO surface within in vitro immersion test. The results of cell viability demonstrated that synthesized forsterite scaffolds with low GO did not show cytotoxicity and enhanced cell proliferation. Antibacterial tests showed that the antibacterial influence of forsterite/GO scaffold was strongly correlated with GO concentration from 0.5 to 2 wt.%. The scaffold encapsulated with 2wt.% GO had the great antibacterial performance with bacterial inhibition rate around 90%. As results show, the produced forsterite/1wt.% GO can be an attractive option for bone tissue engineering.

Effect of Doping Element and Electrolyte’s pH on the Properties of Hydroxyapatite Coatings Obtained by Pulsed Galvanostatic Technique

Hydroxyapatite (HAp) is the most widely used calcium phosphate as a coating on metal implants due to its biocompatibility and bioactivity. The aim of this research is to evaluate the effect of the pH’s electrolyte and doping element on the morphology, roughness, chemical, and phasic composition of hydroxyapatite-based coatings obtained by pulsed galvanostatic electrochemical deposition. As doping elements, both Sr and Ag were selected due to their good osseoinductive character and antibacterial effect, respectively. The electrolytes were prepared at pH 4 and 5, in which specific concentrations of Sr, Ag, and Sr + Ag were added. In terms of morphology, all coatings consist in ribbon-like crystals, which at pH 5 appear to be a little larger. Addition of Sr did not affect the morphology of HAp, while Ag addition has led to the formation of flower-like crystals agglomeration. When both doping elements were added, the flowers like agglomerations caused by the Ag have diminished, indicating the competition between Sr and Ag. X-Ray Diffraction analysis has highlighted that Sr and/or Ag have successfully substituted the Ca in the HAp structure. Moreover, at higher pH, the crystallinity of all HAp coatings was enhanced. Thus, it can be said that the electrolyte’s pH enhances to some extent the properties of HAp-based coatings, while the addition of Sr and/or Ag does not negatively impact the obtained features of HAp, indicating that by using pulsed galvanostatic electrochemical deposition, materials with tunable features dictated by the function of the coated medical device can be designed.