Antibacterial Thermosensitive Silver-Hydrogel Nanocomposite Improves Wound Healing.

Bacterial infection and poor cell recruitment are among the main factors that prolong wound healing. To address this, a strategy is required that can prevent infection while promoting tissue repair. Here, we have created a silver nanoparticle-based hydrogel composite that is antibacterial and provides nutrients for cell growth, while filling cavities of various geometries in wounds that are difficult to reach with other dressings. Silver nanoparticles (AgNPs) were synthesized by chemical reduction and characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), and inductively coupled plasma-mass spectroscopy (ICP-MS). Using varying concentrations of AgNPs (200, 400, and 600 ppm), several collagen-based silver-hydrogel nanocomposite candidates were generated. The impact of these candidates on wound healing was assessed in a rat splinted wound model, while their ability to prevent wound infection from a contaminated surface was assessed using a rat subcutaneous infection model. Biocompatibility was assessed using the standard MTT assay and in vivo histological analyses. Synthesized AgNPs were spherical and stable, and while hydrogel alone did not have any antibacterial effect, AgNP-hydrogel composites showed significant antibacterial activity both in vitro and in vivo. Wound healing was found to be accelerated with AgNP-hydrogel composite treatment, and no negative effects were observed compared to the control group. The formulations were non-cytotoxic and did not differ significantly in hematological and biochemical factors from the control group in the in vivo study. By presenting promising antibacterial and wound healing activities, silver-hydrogel nanocomposite offers a safe therapeutic option that can be used as a functional scaffold for an acceleration of wound healing.

Exploring the use of a Ruthenium complex incorporated into a methacrylate-based dental material for antimicrobial photodynamic therapy.

OBJECTIVES: To evaluate the effects of a blue light photosensitizer (PS), Ruthenium II complex (Ru), on the chemical, physical, mechanical, and antimicrobial properties of experimental dental resin blends. METHODS: The experimental resin (BisEMA, TEEGDMA, HPMA, ethanol, and photoinitiator) was loaded with Ru at 0.00%, 0.07%, 0.14%, 0.28%, 0.56%, 1.12%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% w/w. Samples were evaluated for the degree of conversion (DC) after 30 and 60 s curing-time (n = 6). Selected formulations (0.00%, 0.28%, 0.56%, 1.12%) were further tested for shear bond strength (SBS) (n = 15); flexural strength (FS) (n = 12); and antimicrobial properties (CFUs), in dark and light conditions. These latter tests were performed on specimens stored for 24-h or 2-month in 37°C water. Water sorption (WS) and solubility (SL) tests were also performed (n = 12). Data were analyzed either by a one- or two-factor general linear model (α = 0.05). RESULTS: Overall, Ru concentration above 1.2% resulted in reduced DC. In SBS results, only the 1.12%Ru resin blend samples had statistically lower values compared to the 0.00%Ru resin blend at 24-h storage (p = 0.004). In addition, no differences in SBS were detected among the experimental groups after 2-month storage in water. Meanwhile, FS increased for all experimental groups under similar aging conditions (p < 0.001). Antimicrobial properties were improved upon inclusion of Ru and application of light (p < 0.001 for both) at 24-h and 2-month storage. Lastly, no detectable changes in WS or SL were observed for the Ru-added resins compared to the 0.00%Ru resin blend. However, the 0.28% Ru blend presented significantly higher WS compared to the 0.56% Ru blend (p = 0.007). CONCLUSIONS: Stable SBS, improved FS, and sustained antimicrobial properties after aging gives significant credence to our approach of adding the Ruthenium II complex into dental adhesive resin blends intended for an aPDT approach.

Characterization of polymethylmethacrylate microspheres loaded with silver and doxycycline for dental materials applications.

OBJECTIVES: The manufacturing of polymethylmethacrylate(PMMA) microspheres loaded with doxycycline(DOX) and/or silver sulfate(Ag2SO4) to be incorporated into glass ionomer cement(GIC). METHODS: PMMA microspheres were manufactured with Ag2SO4(1-5%) and/or DOX(5-15%). Particle size, encapsulation efficiency and drug release were measured by light microscope, ICP, and HPLC. Microspheres were added to a dental GIC(20%w/w). Drug release and DTS were investigated. Minimum inhibitory concentration and antibacterial effects of PMMA microspheres into GIC materials were tested. RESULTS: The median diameter of 50 µm was obtained for microspheres. DOX was encapsulated at an efficiency of 8.3% using a theoretical loading of 15%DOX + 5%Ag2SO4. The Ag2SO4 encapsulation efficiency was 0.63% using a theoretical loading of 5%AgSO4. All groups showed burst release within the first day and continued released up to 15 days, with 60-83% of DOX and approximately 30% of silver. For GIC, approximately 15% of DOX and 0.18% of silver were released in a 7-day period. Microbiological results showed an antimicrobial effect against S. mutans when the lead formulation of microspheres was added. The DTS was reduced by the inclusion of microspheres. SIGNIFICANCE: PMMA microspheres containing DOX and Ag2SO4 offer a sustained antimicrobial activity for dental applications and promising potential for the biomedical field.

Potassium iodide potentiated photodynamic inactivation of Enterococcus faecalis using Toluidine Blue: Comparative analysis and post-treatment biofilm formation study.

BACKGROUND: Photodynamic Inactivation (PDI) has recently gained interest as an alternative modality to fight pathogenic entities and its effect can be further enhanced by using certain inorganic salts. Here, the Potassium Iodide (KI)-mediated PDI effect on Enterococcus faecalis using Toluidine Blue Ortho (TBO) as photosensitizer (PS) has been evaluated, and subsequent Biofilm formation extent is accounted for. METHODS: The comparative photoinactivation of TBO and TBO/KI on E.faecalis was investigated by quantifying surviving bacterial colonies after laser irradiation with 30,60, and 180 s exposure times and different PS/Potentiator concentrations. The biofilm formation capability of E.faecalis was observed by calculating Optical Density (OD595) of samples 24,48, and 72 h post-PDI treatment. Scanning Electron Microscopy (SEM) was used as a qualitative measure of bacterial biofilm growth. RESULTS: More than 4 LOGS of photokilling was obtained for experimental groups with the highest PS/KI concentrations at 180 s exposure time. All KI-potentiated groups showed enhancement in PDI effect when compared to non-potentiated counterparts. The degree of recurring biofilm for laser-treated groups also showed to be much less than that of control group, as confirmed by both OD595 measurement and SEM imaging.