Antibacterial ability and osteogenic activity of polyphenol-tailored calcium silicate bone cement.

Calcium silicate-based cement (CSC) has attracted much interest because of its favourable osteogenic effect that supports its clinical use. Although CSC has antibacterial activity, this activity still needs to be improved when used in an infected bone defect. Natural polyphenols have been considered antimicrobial reagents. To this end, three different types of polyphenols (gallic acid (GA), pyrogallol (PG) and tannic acid (TA)) with different concentrations as a liquid phase were mixed with bioactive calcium silicate to enhance the antibacterial activity of CSC. The setting time, antibacterial activity, and osteogenic activity of CSC were studied. Evaluation of antibacterial ability and reactive oxygen species (ROS) was performed using Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria, while a human osteoblast-like cell line (MG63) was used to examine osteogenic activity. The experimental results showed that the addition of polyphenols did not remarkably affect the phase composition and morphology of CSC, but changed the setting time and diametral tensile strength. At the same concentration of 1 wt%, the setting time of TA (21 min) was significantly shorter than that of PG (26 min) and GA (68 min), and was indistinguishable from the control cement (20 min). GA had a significantly higher antioxidant activity than PG and TA. As expected, higher concentrations of polyphenols had a more positive impact on ROS generation. More importantly, the incorporation of polyphenols greatly enhanced the antibacterial activity of CSC against E. coli and S. aureus, but had little effect on the in vitro osteogenic activity of MG63 cells and the cytotoxicity of L929 cells. It was concluded that among the three phenolic compounds, the optimal concentration of the liquid phase in the hybrid cement was 5 wt% TA in terms of setting time, strength, antibacterial activity and in vitro osteogenic activity.

Mechanical Biocompatibility, Osteogenic Activity, and Antibacterial Efficacy of Calcium Silicate-Zirconia Biocomposites.

Zirconia ceramics with high mechanical properties have been used as a load-bearing implant in the dental and orthopedic surgery. However, poor bone bonding properties and high elastic modulus remain a challenge. Calcium silicate (CaSi)-based ceramic can foster osteoblast adhesion, growth, and differentiation and facilitate bone ingrowth. This study was to prepare CaSi-ZrO2 composites and evaluate their mechanical properties, long-term stability, in vitro osteogenic activity, and antibacterial ability. The Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria and human mesenchymal stem cells (hMSCs) were used to evaluate the antibacterial and osteogenic activities of implants in vitro, respectively. Results indicated that the three-point bending strength of ZrO2 was 486 MPa and Young's modulus was 128 GPa, which were much higher than those of the cortical bone. In contrast, the bending strength and modulus of 20% (201 MPa and 48 GPa, respectively) and 30% CaSi (126 MPa and 20 GPa, respectively) composites were close to the reported strength and modulus of the cortical bone. As expected, higher CaSi content implants significantly enhanced cell growth, differentiation, and mineralization of hMSCs. It is interesting to note the induction ability of CaSi in osteogenic differentiation of hMSCs even when cultured in the absence of an osteogenic differentiation medium. The composite with the higher CaSi contents exhibited the greater bacteriostatic effect against E. coli and S. aureus. In conclusion, the addition of 20 wt % CaSi can effectively improve the mechanical biocompatibility, osteogenesis, and antibacterial activity of ZrO2 ceramics, which may be a potential choice for load-bearing applications.

Component effects of bioactive glass on corrosion resistance and in vitro biological properties of apatite-matrix coatings.

BACKGROUND: Surface modification of metallic implants is critical for improving the clinical performance of the dental and orthopedic devices. Bioactive glasses exhibit different levels of cellular function and physicochemical behavior; however, there have been few previous studies on the effect of constituents of the bioactive glasses on the in vitro osteogenic activity and corrosion resistance of apatite-based coatings. OBJECTIVE: The objective of this work was to investigate the effect of SiO2, CaO, Na2O, and P2O5 on plasma-sprayed apatite coatings on Ti alloy substrates for tailoring the properties of implants making them suitable for clinical applications. METHODS: The corrosion potential and corrosion current of various coatings in simulated body fluid (SBF) were examined. MG63 cell proliferation, differentiation, and mineralization of plasma-sprayed apatite-matrix coatings were evaluated. RESULTS: The SiO2 and CaO-containing HA (HSC) coating had a higher corrosion potential than the other three coatings, while SiO2-containing HA (HS) coating displayed the highest corrosion current among all coatings. The effect of the oxides on cell functions followed the order SiO2 > CaO > P2O5 > Na2O in terms of cell attachment, proliferation, differentiation, and mineralization. CONCLUSIONS: The flexibility in oxide doping may allow for the tunable biological properties and corrosion-resistant ability of the apatite coatings.