Poly(lactic acid/caprolactone) bilayer membrane blocks bacterial penetration.

BACKGROUND AND OBJECTIVE: The clinical outcomes of guided tissue regeneration (GTR) or guided bone regeneration (GBR) procedures can be impaired if a bacterial infection develops at the surgical site. Membrane exposure is one of the causes of the onset of bacterial infection. Previously, we have fabricated a poly(lactic acid/caprolactone) (PLCL) bilayer membrane composed of a porous layer and a compact layer. The compact layer acts as a barrier against connective tissue and epithelial cells, and we hypothesized that it could also be an effective barrier against bacterial cells. The objective of this study was to evaluate the ability of the PLCL bilayer membrane to block bacterial cell penetration, which would be useful for preventing postoperative infections. METHODS: Porphyromonas gingivalis, Streptococcus mutans, and multispecies bacteria collected from human saliva were used in this study. Bacteria were seeded directly on the compact layer of a PLCL bilayer membrane, and bacterial adhesion to the membrane, as well as penetration into the membrane's structure, were assessed. Bacterial adhesion was evaluated by the number of colonies formed at 6, 24, and 72 h, and penetration was observed using a scanning electron microscope at 24 and 72 h. Commercially available membranes, composed of poly(lactic-co-glycolic acid) or type I collagen, were used as controls. RESULTS: P. gingivalis, S. mutans, and the multispecies bacteria obtained from human saliva adhered onto all the membranes after only 6 h of incubation. However, fewer adherent cells were observed for the PLCL bilayer membrane compared with the controls for all experimental periods. The PLCL membrane was capable of blocking bacterial penetration, and no bacterial cells were observed in the structure. In contrast, bacteria penetrated both the control membranes and were observed at depths of up to 80 µm after 72 h of incubation. CONCLUSION: Membrane characteristics may influence how bacterial colonization occurs. The PLCL membrane had reduced bacterial adhesion and blocked bacterial penetration, and these characteristics could contribute to a favorable outcome for regenerative treatments. In the event of membrane exposure at GTR/GBR surgical sites, membranes with an efficient barrier function, such as the PLCL bilayer membrane, could simplify the management of GTR/GBR complications.

Fabrication of pH-Responsive Zn2+-Releasing Glass Particles for Smart Antibacterial Restoratives.

The on-demand release of antibacterial components due to pH variations caused by acidogenic/cariogenic bacteria is a possible design for smart antibacterial restorative materials. This study aimed to fabricate pH-responsive Zn2+-releasing glass particles and evaluate their solubilities, ion-releasing characteristics, and antibacterial properties in vitro. Three kinds of silicate-based glass particles containing different molar ratios of Zn (PG-1: 25.3; PG-2: 34.6; PG-3: 42.7 mol%) were fabricated. Each particle was immersed in a pH-adjusted medium, and the solubility and concentration of the released ions were determined. To evaluate the antibacterial effect, Streptococcus mutans was cultured in the pH-adjusted medium in the presence of each particle, and the bacterial number was counted. The solubility and concentration of Zn2+ released in the medium increased with a decrease in medium pH. PG-3 with a greater content of Zn demonstrated higher concentrations of released Zn2+ compared with PG-1 and PG-2. PG-2 exhibited bactericidal effects at pH 5.1, whereas PG-3 demonstrated bactericidal effects at pH values of 5.1 and 6.1, indicating that PG-3 was effective at inhibiting S. mutans even under slightly acidic conditions. The glass particle with 42.7 mol% Zn may be useful for developing smart antibacterial restoratives that contribute to the prevention of diseases such as caries on root surfaces with lower acid resistance.

Poly(lactic acid/caprolactone) bilayer membrane achieves bone regeneration through a prolonged barrier function.

Guided bone regeneration (GBR) is a treatment strategy used to recover bone volume. Barrier membranes are a key component of GBR protocols, and their properties can impact treatment outcomes. This study investigated the efficacy of an experimental, slow-degrading, bilayer barrier membrane for application in GBR using in vivo animal models. A synthetic copolymer of poly(lactic acid/caprolactone) (PLCL) was used to prepare a slow-degrading bilayer membrane. The biodegradability of PLCL was evaluated by subcutaneous implantation in a rat model. The barrier function of the PLCL membrane was investigated in a rat calvaria defect model and compared with commercially available membranes composed of type I collagen (Col) and poly(lactic-co-glycolic acid) (PLGA). An alveolar bone defect model in beagle dogs was used to simulate GBR protocols to evaluate the bone regeneration ability of the experimental PLCL membrane. The PLCL membrane showed slow biodegradation, resulting in an efficient and prolonged barrier function compared with commercial materials. In turn, this barrier function enabled the space-making ability of PLCL membrane and facilitated bone regeneration. In the alveolar bone defect model, significantly greater regeneration was achieved by treatment with PLCL membrane compared with Col and PLGA membranes. Additionally, a continuous alveolar ridge contour was observed in PLCL-treated bone defects. In conclusion, the PLCL bilayer membrane is a promising biomaterial for use in GBR given its slow degradation and prolonged barrier function.

Development of Antibacterial Resin Composites Incorporating Poly(METAC) Clusters.

This study examined the antibacterial effects and physical properties of a novel resin composite incorporating poly[{2-(methacryloyloxy)ethyl}trimethylammonium chloride] (poly(METAC)), a methacrylate cationic polymer comprising quaternary ammonium compounds (QACs). Resin composites incorporating poly(METAC) were fabricated by adding 6 wt.% METAC aqueous solution to a commercially available resin composite. The FE-SEM/EDS and Raman spec-troscopy analyses showed that METAC was assembled and polymerized in the resin composites after curing. The antibacterial effect was evaluated by inoculating Streptococcus mutans or Strepto-coccus sobrinus suspensions on the surface of cured resin composites, and the experimental resin composites incorporating poly(METAC) clusters exhibited bactericidal effects even after 28 days of ageing. The physical properties of the experimental resin composites were within the ISO-stipulated ranges. Newly fabricated resin composites containing the QAC-based poly(METAC) cluster ex-hibited long-term bactericidal effects against oral bacteria on their surfaces and demonstrated ac-ceptable physical properties for clinical use.

Metal-doped silicate and phosphate glasses for antibacterial dental biomaterials.

Owing to the development of glass 45S5 (Bioglass®) comprising 45 mol% SiO2, 24.5 mol% Na2O, 24.5 mol% CaO, and 6 mol% P2O5, different compositions of silicate glasses have been developed. When these silicate glasses contact an aqueous environment, such as body fluids, they induce apatite layer formation on their surfaces owing to ion exchange. In addition to promoting hard tissue formation, researchers have sought to enhance the antibacterial properties of these glasses, thereby resulting in the development of metal-doped silicate glasses. The addition of antibacterial metals (silver, copper, zinc, and gallium) to silicate glass offers a promising avenue for combating oral pathogens. In recent years, there has been growing interest in metal-doped phosphate glasses. The release of metal ions can be regulated by modifying the dissolution rate of the phosphate glasses. This review summarizes the metal-doped silicate and phosphate glasses that confer antibacterial activity. Future strategies for the development of dental biomaterials that incorporate metal-doped glass and exhibit antibacterial effects are discussed.

Incorporation of chlorhexidine in self-adhesive resin cements.

The aim of this study was to evaluate the maximum amount of chlorhexidine (CHX) that could be incorporated to self-adhesive resin cements to add antibacterial effect without affecting the physical properties. The CHX was incorporated into a commercial self-adhesive resin cement at mass fractions of 0.5-15 wt%, and the CHX-release profile, antibacterial effect, flexural and bond strengths of experimental cements were evaluated. Increasing the CHX content from 5 to 15 wt% resulted in a higher released concentration of CHX. In agar diffusion tests, experimental cements containing 5, 10, and 15 wt% CHX produced inhibition zones against oral bacteria. In flexural strength and shear bond strength to dentin, no significant reduction was observed with the incorporation of 5 wt% CHX. This in vitro study suggests that the addition of 5 wt% CHX yielded an antibacterial self-adhesive cement and had no adverse effect on the flexural and shear bond strengths.

Establishment of novel in vitro culture system with the ability to reproduce oral biofilm formation on dental materials.

Intensive research has been conducted with the aim of developing dental restorative/prosthetic materials with antibacterial and anti-biofilm effects that contribute to controlling bacterial infection in the oral cavity. In situ evaluations were performed to assess the clinical efficacy of these materials by exposing them to oral environments. However, it is difficult to recruit many participants to collect sufficient amount of data for scientific analysis. This study aimed to assemble an original flow-cell type bioreactor equipped with two flow routes and assess its usefulness by evaluating the ability to reproduce in situ oral biofilms formed on restorative materials. A drop of bacterial suspension collected from human saliva and 0.2% sucrose solution was introduced into the assembled bioreactor while maintaining the incubation conditions. The bioreactor was able to mimic the number of bacterial cells, live/dead bacterial volume, and volume fraction of live bacteria in the in situ oral biofilm formed on the surface of restorative materials. The usefulness of the established culture system was further validated by a clear demonstration of the anti-biofilm effects of a glass-ionomer cement incorporating zinc-releasing glasses when evaluated by this system.

Evaluation of ion release and the recharge ability of glass-ionomer cement containing BioUnion filler using an in vitro saliva-drop setting assembly.

OBJECTIVE: A glass-ionomer cement (GIC) containing BioUnion filler has been reported to release Zn2+ under acidic conditions and to inhibit oral bacteria on its surface. However, previous results are based on in vitro experiments under static conditions. This study aimed to assemble an in vitro saliva-drop setting to simulate in vivo conditions of the oral cavity and to investigate the ion releasing and recharging properties of the GIC containing BioUnion filler. METHODS: The effective concentrations of Zn2+ and F- against Streptococcus mutans and saliva-derived multi-species biofilms were determined. Artificial saliva was dropped on the GIC containing BioUnion filler using the in vitro saliva-drop setting assembly and was periodically replaced with acetic acid. Ion release/recharge properties were investigated by measuring the release concentrations of Zn2+ and F-. RESULTS: The concentration of Zn2+ released from the BioUnion filler-containing GIC during seven days with repeated exposure to acid could be maintained at the level to inhibit S. mutans and saliva-derived multi-species biofilm formation. Moreover, the BioUnion filler-containing GIC could be recharged with Zn2+ and F- by the application of a tooth gel containing Zn2+ and F-. The release concentration of Zn2+ after recharging was significantly higher than the effective concentration of Zn2+ to hinder S. mutans and saliva-derived multi-species biofilm formation on material surfaces. SIGNIFICANCE: The GIC containing BioUnion filler was shown to have the potential to inhibit biofilm formation in the oral cavity. In addition, recharging Zn2+ and F- would further enhance the effect of the GIC containing BioUnion filler.

Antibacterial effects and physical properties of a glass ionomer cement containing BioUnion filler with acidity-induced ability to release zinc ion.

BioUnion filler is a bioactive glass particle that releases Zn2+ in an acidic environment. In this study, the ion release, antibacterial, and physical properties of a glass ionomer cement (GIC) incorporating BioUnion filler (CA) were assessed in vitro. The concentration of Zn2+ released from CA into acetic acid was higher than that released into water and its minimum inhibitory concentrations against six oral bacterial species. Moreover, the concentration of Zn2+-release was maintained during all the seven times it was exposed to acetic acid. Compared to a conventional cement and resin composite, CA significantly inhibited the growth of oral bacteria and hindered their adhesion on the material surface. Thus, our study outcomes show that the release of Zn2+ from CA in the acidic environment does not affect its compressive strength.

Barrier membranes for tissue regeneration in dentistry.

Background: In dentistry, barrier membranes are used for guided tissue regeneration (GTR) and guided bone regeneration (GBR). Various membranes are commercially available and extensive research and development of novel membranes have been conducted. In general, membranes are required to provide barrier function, biosafety, biocompatibility and appropriate mechanical properties. In addition, membranes are expected to be bioactive to promote tissue regeneration. Objectives: This review aims to organize the fundamental characteristics of the barrier membranes that are available and studied for dentistry, based on their components. Results: The principal components of barrier membranes are divided into nonbiodegradable and biodegradable materials. Nonbiodegradable membranes are manufactured from synthetic polymers, metals or composites of these materials. The first reported barrier membrane was made from expanded polytetrafluoroethylene (e-PTFE). Titanium has also been applied for dental regenerative therapy and shows favorable barrier function. Biodegradable membranes are mainly made from natural and synthetic polymers. Collagens are popular materials that are processed for clinical use by cross-linking. Aliphatic polyesters and their copolymers have been relatively recently introduced into GTR and GBR treatments. In addition, to improve the tissue regenerative function and mechanical strength of biodegradable membranes, inorganic materials such as calcium phosphate and bioactive glass have been incorporated at the research stage. Conclusions: Currently, there are still insufficient guidelines for barrier membrane choice in GTR and GBR, therefore dentists are required to understand the characteristics of barrier membranes.

Acidity-induced release of zinc ion from BioUnionTM filler and its inhibitory effects against Streptococcus mutans.

BioUnion filler incorporated into restorative/coating materials is a new bio-functional glass powder. The most unique function of BioUnion filler is its ability to release Zn2+ in acidic environments. In this study, the ion release profile of BioUnion filler under acidic conditions and its antibacterial effects against Streptococcus mutans were evaluated. The concentrations of Zn2+ released from BioUnion fillers into acetic acids were greater than those released into water. S. mutans inhibition by BioUnion fillers was greater with sucrose than without sucrose, reflecting a decrease in suspension pH in response to the addition of sucrose. Exposure to acids increased Zn2+ release from BioUnion fillers, and the fillers after repeated exposure to acids demonstrated inhibitory effects against S. mutans. These findings suggest that BioUnion filler accelerated the release of Zn2+ under acidic conditions, which induced bactericidal/inhibitory effects against S. mutans.

Cutting-edge filler technologies to release bio-active components for restorative and preventive dentistry.

Advancements in materials used for restorative and preventive treatment is being directed toward "bio-active" functionality. Incorporation of filler particles that release active components is a popular method to create bio-active materials, and many approaches are available to develop fillers with the ability to release components that provide "bio-protective" or "bio-promoting" properties; e.g. metal/calcium phosphate nanoparticles, multiple ion-releasing glass fillers, and non-biodegradable polymer particles. In this review paper, recent developments in cutting-edge filler technologies to release bio-active components are addressed and summarized according to their usefulness and functions, including control of bacterial infection, tooth strengthening, and promotion of tissue regeneration.

Fabrication of novel poly(lactic acid/caprolactone) bilayer membrane for GBR application.

OBJECTIVE: Guided bone regeneration (GBR) often involves the use of membranes as barriers for soft tissues. Commercially available membranes, however, do not possess an adequately low degradation rate, resulting in limited barrier function. The purpose of this study was to develop and assess the physicochemical and biological characteristics of a novel poly(l-lactic acid/caprolactone) (PLCL) bilayer membrane and determine its usefulness for GBR application. METHODS: The experimental bilayer membrane was prepared via a two-step freezing and lyophilization process with a PLCL solution. Next, the PLCL membrane was investigated regarding tensile strength, surface roughness, in vitro degradation and clinical operability. In addition, cell proliferation and differentiation were investigated on each layer of the experimental membrane. For all experiments, a commercially available poly(lactic-co-glycolic) acid membrane was used as a control. RESULTS: In vitro analysis of the PLCL bilayer membrane revealed suitable mechanical strength combined with high breaking strain, which contributed to membrane operability. In addition, the PLCL bilayer membrane had enhanced stability compared to the commercial control due to its slower degradation, and was capable of supporting cell growth and osteogenic differentiation. SIGNIFICANCE: The current study confirmed that the PLCL membrane possessed a high biocompatibility and slow degradation rate that contributes to prolonged barrier function and bone regeneration. Altogether, it was considered that the PLCL bilayer membrane developed in this study was applicable for GBR treatment.

Comprehensive analysis of circulating microRNAs as predictive biomarkers for sorafenib therapy outcome in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is the third leading cause of cancer-related death worldwide. Clinical management has improved the prognosis of early HCC, but that of advanced HCC remains poor. Sorafenib, an oral multikinase inhibitor, provided a treatment option for advanced-stage HCC, and prolonged the survival and inhibited tumor progression as first-line therapy in patients with advanced HCC. In this study, we investigated if specific microRNAs could act as predictive biomarkers of sorafenib effectiveness and indicate the best time to switch to second-line therapies. Sorafenib inhibited the proliferation of the Li-7, Hep3B, HepG2 and Huh7 liver cancer cell lines (effective group), but not that of the HLE, HLF and ALEX cancer cell lines (non-effective group). A microRNA (miRNA/miR) analysis was performed comparing sorafenib-effective and non-effective cells lines as well as serum samples from patients with HCC from sorafenib-effective (complete response/partial response) and -non-effective (progressive disease) groups before sorafenib administration and detected three differentially-expressed miRNAs that were common among the in vivo and in vitro samples. The increase rate (effective/non-effective) of hsa-miR-30d in the medium was higher than that in the cancer cells. hsa-miR-30d was highly expressed in the serum and exosomes of patients with HCC in the effective group when compared to those of the non-effective group. Additionally, the hsa-miR-30d expression in the medium of cancer cell lines was highly upregulated in the effective group compared with the non-effective group. These results suggested that hsa-miR-30d might be secreted by the cancer cells to the serum through the exosomes. We identified a specific circulating miRNA that is related to refractory HCC under sorafenib therapy. Therefore, hsa-miR-30d might serve as a predictive biomarker for the efficacy of sorafenib therapy in HCC.