Antibacterial, remineralising and matrix metalloproteinase inhibiting scandium-doped phosphate glasses for treatment of dental caries.

OBJECTIVES: Antibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc3+ ions. METHODS: Sc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated. RESULTS: The developed glass system showed linear Sc3+ ions release over time. The released Sc3+ shows statistically significant inhibition of S. mutans biofilm (1.2 log10 CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats. SIGNIFICANCE: Since Sc3+ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria.

Potential use of gallium-doped phosphate-based glass material for periodontitis treatment.

This study aimed at evaluating the potential effect of gallium-incorporated phosphate-based glasses towards periodontitis-associated bacteria, Porphyromonas gingivalis, and matrix metalloproteinase-13. Periodontitis describes a group of inflammatory diseases of the gingiva and supporting structures of the periodontium. They are initiated by the accumulation of plaque bacteria, such as the putative periodontal pathogen Porphyromonas gingivalis, but the host immune response such as elevated matrix metalloproteinases are the major contributing factor for destruction of periodontal tissues. Antibacterial assays of gallium-incorporated phosphate-based glasses were conducted on Porphyromonas gingivalis ATCC 33277 using disc diffusion assay on fastidious anaerobe agar and liquid broth assay in a modified tryptic soy broth. In vitro study investigated the effect of gallium on purified recombinant human matrix metalloproteinase-13 activity using matrix metalloproteinase assay kit. In vivo biocompatibility of gallium-incorporated phosphate-based glass was evaluated in rats as subcutaneous implants. Antibacterial assay of gallium displayed activity against Porphyromonas gingivalis (inhibition zone of 22 ± 0.5 mm compared with 0 mm for control glass, c-PBG). Gallium in the glass contributed to growth inhibitory effect on Porphyromonas gingivalis (up to 1.30 reductions in log 10 values of the viable counts compared with control) in a modified tryptic soy broth. In vitro study showed gallium-incorporated phosphate-based glasses inhibited matrix metalloproteinase activity significantly (p ≤ 0.01) compared with c-PBG. Evaluation of in vivo biocompatibility of gallium-incorporated phosphate-based glasses in rats showed a non-toxic and foreign body response after 2 weeks of implantation. The results indicate that gallium ions might act on multiple targets of biological mechanisms underlying periodontal disease. Moreover, gallium-incorporated phosphate-based glasses are biocompatible in a rat model. The findings warrant further investigation and will have important clinical implications in the future treatment and management of periodontitis.

Poly(3-hydroxybutyrate) multifunctional composite scaffolds for tissue engineering applications.

Poly(3-hydroxybutyrate) (P(3HB)) foams exhibiting highly interconnected porosity (85% porosity) were prepared using a unique combination of solvent casting and particulate leaching techniques by employing commercially available sugar cubes as porogen. Bioactive glass (BG) particles of 45S5 Bioglass grade were introduced in the scaffold microstructure, both in micrometer ((m-BG), <5 microm) and nanometer ((n-BG), 30 nm) sizes. The in vitro bioactivity of the P(3HB)/BG foams was confirmed within 10 days of immersion in simulated body fluid and the foams showed high level of protein adsorption. The foams interconnected porous microstructure proved to be suitable for MG-63 osteoblast cell attachment and proliferation. The foams implanted in rats as subcutaneous implants resulted in a non-toxic and foreign body response after one week of implantation. In addition to showing bioactivity and biocompatibility, the P(3HB)/BG composite foams also exhibited bactericidal properties, which was tested on the growth of Staphylococcus aureus. An attempt was made at developing multifunctional scaffolds by incorporating, in addition to BG, selected concentrations of Vitamin E or/and carbon nanotubes. P(3HB) scaffolds with multifunctionalities (viz. bactericidal, bioactive, electrically conductive, antioxidative behaviour) were thus produced, which paves the way for next generation of advanced scaffolds for bone tissue engineering.