Porous Organic Materials in Tissue Engineering: Recent Advances and Applications for Severed Facial Nerve Injury Repair.

The prevalence of facial nerve injury is substantial, and the restoration of its structure and function remains a significant challenge. Autologous nerve transplantation is a common treatment for severed facial nerve injury; however, it has great limitations. Therefore, there is an urgent need for clinical repair methods that can rival it. Tissue engineering nerve conduits are usually composed of scaffolds, cells and neurofactors. Tissue engineering is regarded as a promising method for facial nerve regeneration. Among different factors, the porous nerve conduit made of organic materials, which has high porosity and biocompatibility, plays an indispensable role. This review introduces facial nerve injury and the existing treatment methods and discusses the necessity of the application of porous nerve conduit. We focus on the application of porous organic polymer materials from production technology and material classification and summarize the necessity and research progress of these in repairing severed facial nerve injury, which is relatively rare in the existing articles. This review provides a theoretical basis for further research into and clinical interventions on facial nerve injury and has certain guiding significance for the development of new materials.

Bifunctional defect mediated direct Z-scheme g-C3N4-x/Bi2O3-y heterostructures with enhanced piezo-photocatalytic properties for efficient tooth whitening and biofilm eradication.

Biofilm-associated dental diseases and tooth discoloration have recently become the major barriers to achieve healthy teeth. However, there are few effective strategies to address these issues. Herein, the piezo-photocatalytic process is first proposed to be applied for biofilm eradication and tooth whitening with well-designed direct Z scheme g-C3N4-x/Bi2O3-y heterostructures. DFT calculation and XPS results verify the formation of direct Z scheme g-C3N4/Bi2O3 heterostructures theoretically and experimentally. Using the direct Z scheme g-C3N4-x/Bi2O3-y heterostructure, excellent piezo-photocatalytic effects for tooth whitening and biofilm removal are achieved. For piezo-photocatalytic degradation of the typical food colorant of indigo carmine the degradation rate constant is about quadruple that of piezocatalytic and 2.6 times of photocatalytic treatment. Tooth whitening experiments indicate that g-C3N4-x/Bi2O3-y could whiten the stained teeth through the synergistic piezo-photocatalysis. In addition, excellent antibacterial performances can be obtained on the g-C3N4-x/Bi2O3-y heterostructure through piezo-photocatalytic treatment. Not only the planktonic S. mutans but also those bacteria embedded in biofilms can be effectively killed. The analyses of the piezo-photocatalytic mechanism indicates that the enhanced piezo-photocatalytic performance of the g-C3N4-x/Bi2O3-y heterostructure could be attributed to the much higher separation efficiency of photoexcited charge carriers, increased production amounts of ROS and superior adsorption ability for bacteria than those with bare semiconductors of g-C3N4-x and Bi2O3-y and those treated only with ultrasonic vibration or irradiation. Biosafety results show that the g-C3N4-x/Bi2O3-y heterostructure is biologically safe and piezo-photocatalytic treatment has no harm the tooth structure, demonstrating the great potential of piezo-photocatalytic effect based new tooth whitening and antibacterial technology in future dental care fields.

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.

Experimental investigation on characteristics of graphene acoustic transducers driven by electrostatic and electromagnetic forces.

Acoustic transducers with graphene film have high sensitivity and wide bandwidth of frequency response as receivers. However, they exist in transmitting mode with low radiation performance. We propose an effective approach to enhance radiation performance of the graphene acoustic transducer by embedding a coil in insulating layer, and investigate the characteristics of graphene acoustic transducers by experiments. A graphene acoustic transducer is designed and fabricated. The highest receiving sensitivity of the transducer is -30 dB. The output sound pressure level of the transducer is more than 3 dB on average in the range of 2 âˆ¼ 16 kHz compared without a coil. And the sound pressure level increases by 6 dB on average in the range of 40 âˆ¼ 45 kHz. These results demonstrate that the graphene transducer maintains high receiving performance, and also improves acoustic radiation performance, which greatly expands its application field.