Universal Antifouling and Photothermal Antibacterial Surfaces Based on Multifunctional Metal-Phenolic Networks for Prevention of Biofilm Formation.

Biofilms formed from the pathogenic bacteria that attach to the surfaces of biomedical devices and implantable materials result in various persistent and chronic bacterial infections, posing serious threats to human health. Compared to the elimination of matured biofilms, prevention of the formation of biofilms is expected to be a more effective way for the treatment of biofilm-associated infections. Herein, we develop a facile method for endowing diverse substrates with long-term antibiofilm property by deposition of a hybrid film composed of tannic acid/Cu ion (TA/Cu) complex and poly(ethylene glycol) (PEG). In this system, the TA/Cu complex acts as a multifunctional building block with three different roles: (i) as a versatile "glue" with universal adherent property for substrate modification, (ii) as a photothermal biocidal agent for bacterial elimination under irradiation of near-infrared (NIR) laser, and (iii) as a potent linker for immobilization of PEG with inherent antifouling property to inhibit adhesion and accumulation of bacteria. The resulted hybrid film shows negligible cytotoxicity and good histocompatibility and could prevent biofilm formation for at least 15 days in vitro and suppress bacterial infection in vivo, showing great potential for practical applications to solve the biofilm-associated problems of biomedical materials and devices.

UV-activated 7-dehydrocholesterol-coated titanium implants promote differentiation of human umbilical cord mesenchymal stem cells into osteoblasts.

Vitamin D metabolites are essential for bone regeneration and mineral homeostasis. The vitamin D precursor 7-dehydrocholesterol can be used after UV irradiation to locally produce active vitamin D by osteoblastic cells. Furthermore, UV-irradiated 7-dehydrocholesterol is a biocompatible coating for titanium implants with positive effects on osteoblast differentiation. In this study, we examined the impact of titanium implants surfaces coated with UV-irradiated 7-dehydrocholesterol on the osteogenic differentiation of human umbilical cord mesenchymal stem cells. First, the synthesis of cholecalciferol (D3) was achieved through the incubation of the UV-activated 7-dehydrocholesterol coating for 48 h at 23℃. Further, we investigated in vitro the biocompatibility of this coating in human umbilical cord mesenchymal stem cells and its potential to enhance their differentiation towards the osteogenic lineage. Human umbilical cord mesenchymal stem cells cultured onto UV-irradiated 7-dehydrocholesterol-coated titanium implants surfaces, combined with osteogenic supplements, upregulated the gene expression of several osteogenic markers and showed higher alkaline phosphatase activity and calcein blue staining, suggesting increased mineralization. Thus, our results show that the use of UV irradiation on 7-dehydrocholesterol -treated titanium implants surfaces generates a bioactive coating that promotes the osteogenic differentiation of human umbilical cord mesenchymal stem cells, with regenerative potential for improving osseointegration in titanium-based bone anchored implants.

Evaluation of experimental coating to improve the zirconia-veneering ceramic bond strength.

PURPOSE: To evaluate the shear bond strength (SBS) between zirconia and veneering ceramic following different surface treatments of zirconia. The efficacy of an experimental zirconia coating to improve the bond strength was also evaluated. MATERIALS AND METHODS: Zirconia strips were fabricated and were divided into four groups as per their surface treatment: polished (control), airborne-particle abrasion, laser irradiation, and application of the experimental coating. The surface roughness and the residual monoclinic content were evaluated before and after the respective surface treatments. A scanning electron microscope (SEM) analysis of the experimental surfaces was performed. All specimens were subjected to shear force in a universal testing machine. The SBS values were analyzed with one-way ANOVA followed by Bonferroni post hoc for groupwise comparisons. The fractured specimens were examined to observe the failure mode. RESULTS: The SBS (29.17 MPa) and roughness values (0.80) of the experimental coating group were the highest among the groups. The residual monoclinic content was minimal (0.32) when compared to the remaining test groups. SEM analysis revealed a homogenous surface well adhered to an undamaged zirconia base. The other test groups showed destruction of the zirconia surface. The analysis of failure following bond strength testing showed entirely cohesive failures in the veneering ceramic in all study groups. CONCLUSION: The experimental zirconia surface coating is a simple technique to increase the microroughness of the zirconia surface, and thereby improve the SBS to the veneering ceramic. It results in the least monoclinic content and produces no structural damage to the zirconia substructure.

Treatment of peri-implantitis around TiUnite-surface implants using Er:YAG laser microexplosions.

Implant therapy can lead to peri-implantitis, and none of the methods used to treat this inflammatory response have been predictably effective. It is nearly impossible to treat infected surfaces such as TiUnite (a titanium oxide layer) that promote osteoinduction, but finding an effective way to do so is essential. Experiments were conducted to determine the optimum irradiation power for stripping away the contaminated titanium oxide layer with Er:YAG laser irradiation, the degree of implant heating as a result of Er:YAG laser irradiation, and whether osseointegration was possible after Er:YAG laser microexplosions were used to strip a layer from the surface of implants placed in beagle dogs. The Er:YAG laser was effective at removing an even layer of titanium oxide, and the use of water spray limited heating of the irradiated implant, thus protecting the surrounding bone tissue from heat damage.

Using thermal energy produced by irradiation of Mn-Zn ferrite magnetic nanoparticles (MZF-NPs) for heat-inducible gene expression.

One of the main advantages of gene therapy over traditional therapy is the potential to target the expression of therapeutic genes in desired cells or tissues. To achieve targeted gene expression, we developed a novel heat-inducible gene expression system in which thermal energy generated by Mn-Zn ferrite magnetic nanoparticles (MZF-NPs) under an alternating magnetic field (AMF) was used to activate gene expression. MZF-NPs, obtained by co-precipitation method, were firstly surface modified with cation poly(ethylenimine) (PEI). Then thermodynamic test of various doses of MZF-NPs was preformed in vivo and in vitro. PEI-MZF-NPs showed good DNA binding ability and high transfection efficiency. In AMF, they could rise to a steady temperature. To analyze the heat-induced gene expression under an AMF, we combined P1730OR vector transfection with hyperthermia produced by irradiation of MZF-NPs. By using LacZ gene as a reporter gene and Hsp70 as a promoter, it was demonstrated that expression of a heterogeneous gene could be elevated to 10 to 500-fold over background by moderate hyperthermia (added 12.24 or 25.81 mg MZF-NPs to growth medium) in tissue cultured cells. When injected with 2.6 or 4.6 mg MZF-NPs, the temperature of tumor-bearing nude mice could rise to 39.5 or 42.8 degrees C, respectively, and the beta-gal concentration could increase up to 3.8 or 8.1 mU/mg proteins accordingly 1 day after hyperthermia treatment. Our results therefore supported hyperthermia produced by irradiation of MZF-NPs under an AMF as a feasible approach for targeted heat-induced gene expression. This novel system made use of the relative low Curie point of MZF-NPs to control the in vivo hyperthermia temperature and therefore acquired safe and effective heat-inducible transgene expression.

Dose inhomogeneities on surfaces of different dental implants during irradiation with high-energy photons.

OBJECTIVES: The aim of this study was to determine the radiation doses in mucosa and bone close to the surface of different dental implant materials. METHODS: Radiation dose was measured at the interface of bone or soft tissue and various implant materials for 6 MV photons generated by a medical linear accelerator using a phantom and ultrathin thermoluminescent dosemeters. RESULTS: Increasing thickness of implant materials resulted in a dose decrease in bone immediately behind the implants. Directly in front of titanium implants, dose increases of 18.2% and 30.4% were found in bone and soft tissue, respectively, independent of implant thickness and surface structure (polished/plasma coated). Even a titanium coating with 70 microm hydroxyapatite did not affect the scattering dose. In contrast, for aluminium oxide ceramics, a scatter-induced notable dose increase could not be assessed. CONCLUSIONS: During irradiation with high-energy photons, an implant-induced dose enhancement could be reduced in bone using the technique of multiple fields and in soft tissue using ceramic abutments.