The influence of different mode of power density during antimicrobial photodynamic therapy for photokilling of Streptococcus mutans.

BACKGROUND: The aim of this study was to evaluate the inactivation potency of riboflavin and curcumin plus blue diode laser against Streptococcus mutans with different power densities. MATERIALS AND METHODS: In this in vitro study, standard-strain S. mutans was exposed to curcumin and riboflavin plus blue diode laser with different power densities (0.4-1.0 W/cm2) as well as chlorhexidine (CHX). The colony forming units (CFUs)/mL was calculated. Data were analyzed by one-way ANOVA. RESULTS: Antibacterial analysis indicated that the blue diode laser irradiation with curcumin and riboflavin provided a satisfactory reduction of the S. mutans level. In addition, S. mutans was more affected by curcumin + blue diode laser when the power density was set to 1.0 W/cm2 (P < 0.0001). Meanwhile, bacterial suspensions treated with CHX showed maximum colony number reduction, compared with the control (P < 0.0001). CONCLUSION: This study showed the blue diode laser along with curcumin had strong bactericidal effect on S. mutans, and this effect improved by increasing the power density.

In vitro study of nanoliposomes containing curcumin and doxycycline for enhanced antimicrobial photodynamic therapy against Aggregatibacter actinomycetemcomitans.

The excessive inappropriate use of systemic antibiotics has contributed to the emergence of antibiotic-resistant pathogens, which pose a significant risk to the success of treatment. This study has approached this problem by developing doxycycline-loaded liposome doped with curcumin (NL-Cur+Dox) for combination antibacterial therapy against Aggregatibacter actinomycetemcomitans. The characterization of formulation revealed encapsulation of both drugs in NL-Cur+Dox with an average size of 239 nm and sustained release behavior. Transmission electron microscopy analysis confirmed the vesicular-shaped nanocarriers without any aggregation or crystallization. The cytotoxic and hemolytic activities of NL-Cur+Dox were evaluated. The anti-biofilm and anti-metabolic effects of NL-Cur+Dox -mediated antimicrobial photodynamic therapy (aPDT) were examined. The data indicated that NL-Cur+Dox -mediated aPDT led to a significant reduction of biofilm (82.7%, p = 0.003) and metabolic activity (75%, p < 0.001) of A. actinomycetemcomitans compared to the control. NL-Cur+Dox had no significant cytotoxicity to human gingival fibroblast cells under selected conditions (p = 0.074). In addition, the hemolytic activity of NL-Cur+Dox were negligible (< 5%). These findings demonstrate the potential application of such potent formulations in reducing one of the main bacteria causing periodontitis where the NL-Cur+Dox could be exploited to achieve an improved phototherapeutic efficiency.

An in vitro study on the efficacy of hydrogen peroxide mediated high-power photodynamic therapy affecting Enterococcus faecalis biofilm formation and dispersal.

OBJECTIVE: Biofilms are involved in failure of root canal treatment due to their high resistance to antimicrobial agents, which make their removal as a big challenge. The present study aims at utilizing hydrogen peroxide (HP) plus high frequency laser reinforced antimicrobial photodynamic therapy (a-PDT) as a complementary therapy against Enterococcus faecalis (E. faecalis) at planktonic and biofilm stages. MATERIALS AND METHODS: E. faecalis at planktonic and biofilm stages was treated with the photosensitizer HP, followed by no irradiation or irradiation with a power of 2.5 W (ʎ = 980 nm). The cell viability, anti-biofilm, anti-metabolic potential, and temperature changes were evaluated. RESULTS: The combination of HP and 980 nm diode laser intensely boosted antibacterial and anti-biofilm efficacy compared with either component alone, affirming HP reinforcement as a bacteriostatic agent. The maximum effect on biofilm occurs in 5.25% sodium hypochlorite (NaOCl) group. During laser irradiations, the mean of temperature changes remains below 5.6 °C. CONCLUSIONS: It could be concluded that the HP could improve anti-biofilm efficacy as a photosensitizer in a-PDT.

The Potential Application of Natural Photosensitizers Used in Antimicrobial Photodynamic Therapy against Oral Infections.

Oral health problems and the emergence of antimicrobial resistance among pathogenic bacterial strains have become major global challenges and are essential elements that negatively affect general well-being. Antimicrobial photodynamic therapy (APDT) is based on a light source and oxygen that activates a nontoxic photosensitizer, resulting in microbial destruction. Synthetic and natural products can be used to help the APDT against oral microorganisms. The undesirable consequences of conventional photosensitizers, including toxicity, and cost encourage researchers to explore new promising photosensitizers based on natural compounds such as curcumin, chlorella, chlorophyllin, phycocyanin, 5-aminolevulinic acid, and riboflavin. In this review, we summarize in vitro studies describing the potential use of APDT therapy conjugated with some natural products against selected microorganisms that are considered to be responsible for oral infections.

Comparison of bacterial disinfection efficacy using blue and red lights on dental implants contaminated with Aggregatibacter actinomycetemcomitans.

OBJECTIVES: The purpose of this study was to determine the bacterial disinfection efficacy of four photosensitizers (PSs; curcumin, riboflavin, toluidine blue O, and phycocyanin) with blue diode laser (Blue DL) and blue light-emitting diode (Blue LED) or Red DL and Red LED in dental implants contaminated with Aggregatibacter actinomycetemcomitans. MATERIALS AND METHODS: A total of 60 dental implants were contaminated with A. actinomycetemcomitans. All implants were then randomized into ten different disinfection modalities (n = 6 implants per group). The irradiation wavelength in Blue DL and Blue LED or Red DL and Red LED was 450, 430-460, 635, and 630 nm, respectively and its applied energy density was 60 J/cm2 in all groups. Group IX was served as the control group and in group X disinfection was performed with 0.2% chlorhexidine. After the treatments, the colony forming units (CFUs)/ml were calculated to determine antimicrobial effects of each treatment. RESULTS: All disinfection methods significantly reduced bacteria amounts of dental implants inoculated with A. actinomycetemcomitans compared to control group. The CFU/ml in LED group was significantly lower than the DL in all studied groups. CONCLUSION: aPDT could be an effective supplement in dental implants disinfection. The LED, proved to be better in reducing CFU/ml of A. actinomycetemcomitans on dental implants surface than DL.

Combinatorial therapy of chitosan hydrogel-based zinc oxide nanocomposite attenuates the virulence of Streptococcus mutans.

BACKGROUND: Biofilm formation is an important causative factor in the expansion of the carious lesions in the enamel. Hence, new approaches to efficient antibacterial agents are highly demanded. This study was conducted to evaluate the antimicrobial-biofilm activity of chitosan hydrogel (CS gel), zinc oxide/ zeolite nanocomposite (ZnONC) either separately or combined together [ZnONC / CS gel (ZnONC-CS)] against Streptococcus mutans biofilm. RESULTS: MTT assay demonstrated that the ZnONC-CS exhibits a non-cytotoxic effect (> 90% cell viability) toward human gingival fibroblast cells at different dosages (78.1-625 µg/mL) within 72 h. In comparison with CS gel and ZnONC, ZnONC-CS was superior at biofilm formation and metabolic activity reduction by 33 and 45%, respectively; (P < 0.05). The field emission scanning electron microscopy micrographs of the biofilms grown on the enamel slabs were largely in concordance with the quantitative biofilm assay results. Consistent with the reducing effect of ZnONC-CS on biofilm formation, the expression levels of gtfB, gtfC, and ftf significantly decreased. CONCLUSIONS: Taken together, excellent compatibility coupled with an enhanced antimicrobial effect against S. mutans biofilm has equipped ZnONC-CS as a promising candidate for dental biofilm control.

Propolis nanoparticle enhances the potency of antimicrobial photodynamic therapy against Streptococcus mutans in a synergistic manner.

Less invasive removal approaches have been recommended for deep caries lesions. Antimicrobial photodynamic therapy (aPDT) and propolis nanoparticle (PNP) are highlighted for the caries management plan. Evidence is lacking for an additive effect of combination PNP with photosensitizer (PS) in aPDT. This study aimed to investigate the individual and synergistic effects of chlorophyllin-phycocyanin mixture (PhotoActive+) and toluidine blue O (TBO) as PSs in combination with PNP in the aPDT process (aPDTplus) against major important virulence factors of Streptococcus mutans. Following characterization, biocompatibility of the PSs alone, or in combination with PNP were investigated on human gingival fibroblast cell. The in vitro synergy of PhotoActive+ or TBO and PNP was evaluated by the checkerboard method. The bacteria's virulence properties were surveyed in the presence of the PSs, individually as well as in combination. When the PSs were examined in combination (synergistic effect, FIC Index < 0.5), a stronger growth inhibitory activity was exhibited than the individual PSs. The biofilm formation, as well as genes involved in biofilm formation, showed greater suppression when the PSs were employed in combination. Overall, the results of this study suggest that the combination of PhotoActive+ or TBO with PNP with the least cytotoxicity effects and the highest antimicrobial activites would improve aPDT outcomes, leading to synergistic effects and impairing the virulence of S. mutans.

Anti-biofilm and anti-metabolic effects of antimicrobial photodynamic therapy using chlorophyllin-phycocyanin mixture against Streptococcus mutans in experimental biofilm caries model on enamel slabs.

BACKGROUND: Partial (selective) removal of dental caries is a suitable manner to treat deep carious lesions in vital teeth with asymptomatic pulps. Antimicrobial photodynamic therapy (aPDT) was proposed as a promising ancillary approach for reduction of the residual bacteria from the cavity. Therefore, the focus of this study was to investigate the influence of aPDT using diode laser (DL) plus PhotoActive+ (chlorophyllin-phycocyanin mixture [CHL-PC]) as photosensitizer (PS) on metabolic activity and the reduction in the number of living bacteria within the preformed biofilm caries model on enamel slabs of Streptococcus mutans. MATERIALS AND METHODS: The lethal and sub-significant inhibitory (SSI) potential of aPDT using CHL-PC and 635 nm DL against experimental biofilm caries model on enamel slabs and metabolic activity of S. mutans was analyzed using crystal violet and XTT reduction assays, respectively. Intracellular ROS formation by DCFH-DA assay was measured in CHL-PC mediated aPDT treated bacterial samples. Tooth discoloration and cell cytotoxicity of CHL-PC were assessed in the CIEL*a*b* color space and neutral red assay, respectively. RESULTS: In this study aPDT at a maximum concentration level of CHL-PC (5000 µg/mL) with 3 min DL irradiation time (103.12 J/cm2) reduced the ex-vivo cariogenic biofilm of S. mutans by 36.93 % (P <  0.05). Although chlorhexidine (CHX) had an anti-biofilm effect about 1.7 fold compared to CHL-PC mediated aPDT, this difference was not significant (36.93 in comparison to 63.05 %; P >  0.05). CHL-PC mediated aPDT demonstrated a significant reduction in bacterial metabolic activity, with rates of 77 % at a SSI dose (using 156 µg/mL of CHL-PC and 3 min DL irradiation time with the energy density of 103.12 J/cm2). The treated bacterial cells exhibited significant (P < 0.05) increment in the ROS generation. The least color change (ΔE) was found using CHL-PC at a concentration of 156 µg/mL (ΔE = 2.74). CHL-PC in different concentrations showed no significant reduction in human gingival fibroblasts (HGFs) cell survival (P >  0.05). CONCLUSION: CHL-PC mediated aPDT not only reduces the number of living bacteria within the biofilms of S. mutans in an experimental biofilm caries model on enamel slabs but also its influences microbial virulence by reducing the metabolic activity of the S. mutants.