Does the incorporation of zinc into TiO2 on titanium surfaces increase bactericidal activity? A systematic review and meta-analysis.

STATEMENT OF PROBLEM: Infections associated with bacterial biofilm formation are an important cause of early implant failure. With the growing number of antibiotic-resistant bacteria, the incorporation of zinc into TiO2 coatings of titanium implants has emerged to promote osseointegration and inhibit bacterial proliferation. However, a systematic assessment of its efficacy is lacking. PURPOSE: The purpose of this systematic review and meta-analysis was to assess the bactericidal effect of zinc-modified TiO2 coatings on titanium or Ti-6Al-4V alloy. MATERIAL AND METHODS: The review was structured based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) checklist and the peer review of electronic search strategies (PRESS) guidelines. The search was performed in Science Direct, SCOPUS, Web of Science, and PubMed databases, including experimental in vitro studies that used titanium or Ti-6Al-4V as a control group and performed bacterial assays. Meta-analysis was performed by using the standardized mean differences of antibacterial effects. RESULTS: A total of 2519 articles were collected after duplicate removal. Then, eligibility criteria and a manual search were applied to select 20 studies for qualitative analysis and 16 studies for statistical analysis. The risk of bias revealed low-quality evidence. The meta-analysis showed that zinc positively affected the bactericidal activity of TiO2 coatings (-8.79, CI95%=-11.01 to -6.57, P<.001), with a high degree of heterogeneity (I2=78%). Subgroup analysis with TiO2 nanotubes produced by anodization and ZnO nanoparticles by hydrothermal synthesis reduced heterogeneity to 43%, with the removal of outliers (I2=46%), with a favorable antibacterial effect for zinc incorporation into TiO2. CONCLUSIONS: Bactericidal activity was identified for zinc incorporated into TiO2 coatings, making it an interesting option for titanium dental implants.

Preparation, characterization and biological test of 3D-scaffolds based on chitosan, fibroin and hydroxyapatite for bone tissue engineering.

This work describes the preparation and characterization of porous 3D-scaffolds based on chitosan (CHI), chitosan/silk fibroin (CHI/SF) and chitosan/silk fibroin/hydroxyapatite (CHI/SF/HA) by freeze drying. The biomaterials were characterized by X-ray diffraction, attenuated total reflection Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and energy dispersive spectroscopy. In addition, studies of porosity, pore size, contact angle and biological response of SaOs-2osteoblastic cells were performed. The CHI scaffolds have a porosity of 94.2±0.9%, which is statistically higher than the one presented by CHI/SF/HA scaffolds, 89.7±2.6%. Although all scaffolds were able to promote adhesion, growth and maintenance of osteogenic differentiation of SaOs-2 cells, the new 3D-scaffold based on CHI/SF/HA showed a significantly higher cell growth at 7 days and 21 days and the level of alkaline phosphatase at 14 and 21 days was statistically superior compared to other tested materials.

Nucleation and growth of octacalcium phosphate on treated titanium by immersion in a simplified simulated body fluid.

A simplified simulated body fluid solution (S-SBF) was used to study the kinetics and mechanism of nucleation and growth of octacalcium phosphate (OCP) on the surfaces of alkali and heat-treated titanium samples. After the alkali and heat treatments, the samples were soaked in S-SBF for periods varying up to 24 h. A thin layer of poorly crystallized calcium titanate was formed after 15 min of immersion, allowing for the deposition of another layer of amorphous calcium phosphate (ACP). After 2.5 h of immersion, OCP nuclei were observed on the surface of the ACP layer. After 5 h of immersion in S-SBF solution, the specimens were completely covered with a homogeneous plate-like layer of OCP. Analyses by transmission electron microscopy revealed that nucleation and growth of OCP occurred concomitantly to the crystallization of ACP in hydroxyapatite (HA). This transformation took place by solid-state diffusion, forming a needle-like HA structure underneath the OCP film.