Effects of photodynamic therapy on Streptococcus mutans and enamel remineralization of multifunctional TiO2-HAP composite nanomaterials.

BACKGROUND: As photosensitizer and photocatalyst, titanium dioxide (TiO2) can produce a photodynamic reaction for antibacterial treatment. This study aims to explore a Titanium dioxide/nano-hydroxyapatite (TiO2-HAP) composite combined with the dental curing lamp (385-515 nm) in clinical which could inhibit the dental plaque biofilm formed by Streptococcus mutans (S. mutans) and promote the enamel surface remineralization simultaneously. METHODS: X-ray Diffraction (XRD) and high resolution transmission electron microscope (HRTEM) were used to detect the characterization of TiO2-HAP composite nanomaterials. Photodynamic properties of TiO2-HAP were detected by Diffuse reflectance spectrum (DRS) and fluorescence spectroscopy. Bacterial growth was measured by reading the absorbance of bacterial cultures and confocal microscope was used to observe the biofilm removal ability of nanomaterials. The ability of TiO2-HAP to promote enamel remineralization was measured by Scanning electron microscope (SEM). RESULTS: The OD 600 of S. mutans was 0.76 in the control group and 0.13 in group of TiO2-HAP with exposure to light-emitting diode (LED) (150 mW/cm2) for 5 min, suggesting its sustained antibacterial potency and inhibition of the metabolic activity of dental plaque microcosm biofilm. Also, the release of calcium and phosphorus ions in TiO2-HAP can promote enamel mineralization simultaneously. After 15 days of remineralization, the Ca/P ratio of demineralized enamel surface increased from 1.28 to 1.67, which was similar to that of normal enamel. CONCLUSIONS: The TiO2-HAP exhibit a promising anti-bacterial activity and remineralization capacity which can prevent the occurrence of caries to the greatest extent and promote the biomimetic mineralization of dental tissues.

High-performance free-standing microbial fuel cell anode derived from Chinese date for enhanced electron transfer rates.

Traditional anode materials have disadvantages like low specific surface area and poor electrical conductivity. Herein, carbonized Chinese dates (CCD) were synthesized as microbial fuel cells (MFC) anodes. The obtained materials exhibited excellent biocompatibility with fast start-up (within one day) and charge transfer (Rct 4.0 Ω). Their porous structure allows efficient ion transport and microbial community succession, favorable for long-term operation. The biomass analysis shows that CCD anodes can load higher weight of biomass. High-throughput sequencing (16S rRNA) discovered that CCD anode can enrich Geobacter spp., with highest abundance of 73.4%, much higher than carbon felt (CF, 39.2%). Benefit from these properties, the MFC with CCD anodes possess a maximum power density of 12.17 W m-3 (1.62 times of commercial carbon felt). In all, the CCD anode exhibits high performance with low cost and easy fabrication, certificating it a promising candidate for an ideal MFC anode material.