Effect of methylene blue-induced photodynamic therapy on a Streptococcus mutans biofilm model

Postbiotic mediators derived from Lactobacillus species enhance riboflavin-mediated antimicrobial photodynamic therapy for eradication of Streptococcus mutans planktonic and biofilm growth

BACKGROUND

Streptococcus mutans has been implicated as a primary causative agent of dental caries and one of its important virulence properties is an ability to form biofilm on tooth surfaces. Thus, strategies to prevent and control S. mutans biofilms are requested. The present study aimed to examine the eradication of S. mutans planktonic and biofilm cells using riboflavin (Rib)-mediated antimicrobial photodynamic therapy (aPDT) enhanced by postbiotic mediators derived from Lactobacillus species.

MATERIALS AND METHODS

Minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of Rib and postbiotic mediators were determined. The antimicrobial and anti-biofilm effects of Rib-mediated aPDT (Rib plus blue light), Rib-mediated aPDT in combination with postbiotic mediators derived from Lactobacillus casei (LC) (aPDT+ LC), and Rib-mediated aPDT in combination with postbiotic mediators derived from Lactobacillus plantarum (LP) (aPDT+ LP) were evaluated. The anti-virulence potential of Rib-mediated aPDT, aPDT+ LC, and aPDT+ LP were assessed by measuring the expression of the gtfB gene using quantitative real-time polymerase chain reaction (qRT-PCR) at the highest concentrations of Rib, LC, and LP, at which the S. mutans had proliferation as the same as in the control (non-treated) group.

RESULTS

According to the results, the MIC doses of LC, LP, and Rib were 64 µg/mL, 128 µg/mL, and 128 µg/mL, respectively, while the MBC values of LC, LP, and Rib were 128 µg/mL, 256 µg/mL, and 256 µg/mL, respectively. Rib-mediated aPDT, aPDT+ LP, and aPDT+ LC showed a significant reduction in Log10 CFU/mL of S. mutans compared to the control group (4.2, 4.9, and 5.2 Log10 CFU/mL, respectively; all P < 0.05). The most destruction of S. mutans biofilms was observed after treatment with aPDT+ LC followed by aPDT+ LP and Rib-mediated aPDT (77.5%, 73.3%, and 67.6%, respectively; all P < 0.05). The concentrations of 31.2 µg/mL, 62.5 µg/mL, and 62.5 µg/mL were considered as the highest concentrations of LC, LP, and Rib, respectively, at which S. mutans replicates as same as the control group and were used for gtfB gene expression assay using qRT-PCR during Rib-mediated aPDT, aPDT+ LP, and aPDT+ LC treatments. Gene expression results revealed that aPDT+ LP and aPDT+ LC could decrease the gene expression level of gtfB by 6.3- and 5.7-fold, respectively (P < 0.05), while only 5.1-fold reduction was observed after Rib-mediated aPDT (P < 0.05).

CONCLUSION

Our findings indicate that aPDT+ LP and aPDT+ LC hold promise for use as a treatment to combat S. mutans planktonic and biofilms growth as well as anti-virulence as a preventive strategy to inhibit biofilms development via reduction of gtfB gene expression.

Effect of Laser Irradiation Modes and Photosensitizer Types on Antimicrobial Photodynamic Therapy (aPDT) for Streptococcus sobrinus in the Crown Dentin of Bovine Teeth: An Experimental In Vitro Study

This study aimed to assess the impact of different laser irradiation modes and photosensitizer types on the bactericidal efficacy of antimicrobial photodynamic therapy (aPDT). Dentin plates were prepared by sectioning the crown dentin of bovine teeth infected with Streptococcus sobrinus (n = 11). Nine aPDTs involving the combination of three 1% solutions of photosensitizers (brilliant blue, BB; acid red, AR; and methylene blue, MB) and three irradiation modes of semiconductor lasers (50 mW for 120 s, 100 mW for 60 s, and 200 mW for 30 s) were performed for each infected dentin plate, and the control consisted of the specimens not applied with aPDT. The bactericidal effects in 10 groups were evaluated using both assays of the colony count (colony-forming-unit: CFU) and adenosine triphosphate (ATP) (relative-light-unit: RLU). The data obtained were analyzed using the Kruskal-Wallis test (α = 0.05). The most aPDT groups exhibited significantly lower RLU and CFU values compared with the control (p < 0.05). The effect of irradiation modes on RLU and CFU values was significant in the aPDT group using BB (p < 0.05) but not in the aPDT group using AR or MB. The aPDT performed with AR or MB exerted a remarkable bactericidal effect.

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.

First in human measurements of abscess cavity optical properties and methylene blue uptake prior to photodynamic therapy by in vivo diffuse reflectance spectroscopy

Significance

Efficacious photodynamic therapy (PDT) of abscess cavities requires personalized treatment planning. This relies on knowledge of abscess wall optical properties, which we report for the first time in human subjects.

Aim

The objective was to extract optical properties and photosensitizer concentration from spatially-resolved diffuse reflectance measurements of abscess cavities prior to methylene blue (MB) PDT, as part of a Phase 1 clinical trial.

Approach

Diffuse reflectance spectra were collected at the abscess wall of 13 human subjects using a custom fiber-optic probe and optical spectroscopy system, before and after MB administration. A Monte Carlo lookup table was used to extract optical properties.

Results

Pre-MB abscess wall absorption coefficients at 665 nm were 0.15±0.1 cm -1 (0.03-0.36 cm -1 ) and 10.74±15.81 cm -1 (0.08-49.3 cm -1 ) post-MB. Reduced scattering coefficients at 665 nm were 8.45±2.37 cm -1 (4.8-13.2 cm -1 ) and 5.6±2.26 cm -1 (1.6-9.9 cm -1 ) for pre-MB and post-MB, respectively. Oxygen saturations were found to be 58.83±35.78% (5.6-100%) pre-MB and 36.29±25.1% (0.0001-76.4%) post-MB. Determined MB concentrations were 71.83±108.22 µM (0-311 µM).

Conclusions

We observed substantial inter-subject variation in both native wall optical properties and methylene blue uptake. This underscores the importance of making these measurements for patient-specific treatment planning.

Evaluation of Antibacterial Efficacy of High-Intensity Focused Ultrasound Versus Photodynamic Therapy Against Enterococcus faecalis-Infected Root Canals

OBJECTIVE

The high incidence of endodontic failure is associated with the remnants of Enterococcus faecalis present within the intricate anatomies of the root canal system (RCS), often inaccessible by the current endodontic practices. This study was aimed at evaluating the effect of high-intensity focused ultrasound (HIFU) and photodynamic therapy (PDT) on E. faecalis biofilms in artificially infected root canals for the potential application in current endodontic practices.

METHODS

Forty-five single-rooted extracted teeth were instrumented using hand files, sterilized in an autoclave, infected with E. faecalis and incubated for 4 wk. The specimens were treated and identified as follows: Control, 4% sodium hypochlorite (NaOCl); riboflavin (1 mg/mL); light only; HIFU (250 kHz, 20 W, 60s); PDT; riboflavin/HIFU; light/HIFU; and riboflavin/HIFU/light. Bactericidal efficacy was determined by colony-forming units (CFU), (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) (MTT) assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM).

RESULTS

Enterococcus faecalis biofilm exhibited significantly lower metabolic activity when treated with HIFU (250 kHz, 20 W, 60 s) compared with the control (4% NaOCl) and PDT groups. A similar phenomenon was observed with the CFU assay. HIFU remained the most effective treatment modality, with consistent results in CLSM and SEM.

CONCLUSION

This study highlighted the potential application of HIFU as an adjunct drug-free, non-destructive root canal disinfection method for endodontic treatment, suggesting an alternative to the current gold standard of 4% NaOCl and PDT.

Photodynamic antimicrobial therapy (AmPDT) using 1,9-Dimethyl-Methylene Blue zinc chloride double salt - DMMB and λ640 ± 5ηm LED light in patients undertaking orthodontic treatment

Orthodontic treatment involves the use of apparatuses that impairs oral hygiene making patients susceptible to periodontal diseases and caries. To prevent increased antimicrobial resistance AmPDT has shown itself a feasible option. The aim of this investigation was to assess the efficiency of AmPDT employing 1,9-Dimethyl-Methylene Blue zinc chloride double salt - DMMB as a photosensitizing agent combined with red LED irradiation (λ640 ± 5 ηm) against oral biofilm of patients undertaking orthodontic treatment. Twenty-one patients agreed to participate. Four biofilm collections were carried out on brackets and gingiva around inferior central incisors; first was carried out before any treatment (Control); second followed five minutes of pre-irradiation, the third was immediately after the first AmPDT, and the last after a second AmPDT. Then, a microbiological routine for microorganism growth was carried out and, after 24-h, CFU counting was performed. There was significant difference between all groups. No significant difference was seen between Control and Photosensitizer and AmpDT1 and AmPDT2 groups. Significant differences were observed between Control and AmPDT1 and AmPDT2 groups, Photosensitizer and AmPDT1 and AmPDT2 groups. It was concluded that double AmPDT using DMBB in nano concentration and red LED was capable to meaningfully decrease the number of CFUs in orthodontic patients.

The role of the light source in antimicrobial photodynamic therapy

Antimicrobial photodynamic therapy (APDT) is a promising approach to fight the growing problem of antimicrobial resistance that threatens health care, food security and agriculture. APDT uses light to excite a light-activated chemical (photosensitiser), leading to the generation of reactive oxygen species (ROS). Many APDT studies confirm its efficacy in vitro and in vivo against bacteria, fungi, viruses and parasites. However, the development of the field is focused on exploring potential targets and developing new photosensitisers. The role of light, a crucial element for ROS production, has been neglected. What are the main parameters essential for effective photosensitiser activation? Does an optimal light radiant exposure exist? And finally, which light source is best? Many reports have described the promising antibacterial effects of APDT in vitro, however, its application in vivo, especially in clinical settings remains very limited. The restricted availability may partially be due to a lack of standard conditions or protocols, arising from the diversity of selected photosensitising agents (PS), variable testing conditions including light sources used for PS activation and methods of measuring anti-bacterial activity and their effectiveness in treating bacterial infections. We thus sought to systematically review and examine the evidence from existing studies on APDT associated with the light source used. We show how the reduction of pathogens depends on the light source applied, radiant exposure and irradiance of light used, and type of pathogen, and so critically appraise the current state of development of APDT and areas to be addressed in future studies. We anticipate that further standardisation of the experimental conditions will help the field advance, and suggest key optical and biological parameters that should be reported in all APDT studies. More in vivo and clinical studies are needed and are expected to be facilitated by advances in light sources, leading to APDT becoming a sustainable, alternative therapeutic option for bacterial and other microbial infections in the future.

Antimicrobial photodynamic therapy mediated by methylene blue-loaded polymeric micelles against Streptococcus mutans and Candida albicans biofilms

BACKGROUND

Streptococcus mutans and Candida albicans can colonize the teeth, the oral cavity as biofilm and can cause oral infections. Thus, strategies to prevent and control oral biofilms are requested. The present study aims the development and characterization of methylene blue (MB)-loaded polymeric micelles for antimicrobial photodynamic therapy (aPDT) against Streptococcus mutans and Candida albicans biofilms METHODS: MB-loaded polymeric micelles were produced and characterized by particle size, polydispersity index, morphology, zeta potential, stability, MB release profile, and antimicrobial effect against S. mutans and C. albicans biofilms.

RESULTS

MB-loaded polymeric micelles showed a reduced particle size, moderate polydisperse profile, spherical and neutral shape, which demonstrated to be promising features to allow micelles penetration into biofilms. Antimicrobial effect against bacterial and yeast biofilms was demonstrated once MB was irradiated by light under 660 nm (aPDT). Furthermore, MB-loaded polymeric micelles showed significant inhibition of S. mutans and C. albicans biofilms. Furthermore, the treatment with MB-micelles incubated with high pre-incubation times (15 and 30 min) were more effective than 5 min. It can be explained by the time required for this nanosystem to penetrate the innermost layer of biofilms and release MB for aPDT.

CONCLUSION

MB-loaded polymeric micelles can effectively decrease the bacteria and yeast viability and it may cause positive impacts in the clinical practice. Thus, the developed formulation showed potential in the treatment to remove oral biofilms, but clinical studies are needed to confirm its potential.

Optical spectral diagnostics of the oxygenation level in periodontal tissues and photodynamic therapy using methylene blue in children with cerebral palsy

Dental diseases occur in children with cerebral palsy three times higher than in healthy children. Low values of the unstimulated salivation rate (<0.3 ml per minute), pH and buffer capacity, changes in enzyme activity and sialic acid concentration, as well as increased saliva osmolarity and total protein concentration, which indicates impaired hydration, are the factors in the development of a gingiva disease in case of cerebral palsy. This leads to increased bacterial agglutination and the formation of acquired pellicle and biofilm, leading to the formation of dental plaque. There is a tendency toward an increase in the concentration of hemoglobin and a decrease in the degree of hemoglobin oxygenation, as well as an increase in the generation of reactive oxygen and nitrogen species. Photodynamic therapy (PDT) with the use of photosensitizer methylene blue improves blood circulation and the degree of oxygenation in periodontal tissues, as well as eliminates a bacterial biofilm. Analysis of back diffuse reflection spectra makes it possible to conduct non-invasive monitoring determine tissue areas with a low level of hemoglobin oxygenation for precision photodynamic exposure.

Aim

To improve the effectiveness of phototheranostics methods using, namely PDT with simultaneous optical-spectral control, for the treatment of gingivitis in children with complex dental and somatic status (cerebral palsy).

Methods

The study involved 15 children (6-18 y.o.) with various forms of cerebral palsy, in particular, spastic diplegia and atonic-astatic form and with gingivitis. The degree of hemoglobin oxygenation was measured in tissues before PDT and on the 12th day. PDT was performed using laser radiation (λ = 660 nm) with a power density of 150 mW/cm² with a five-minute application of 0.01% MB. The total light dose was 45 ± 15 J/cm². For statistical evaluation of the results, a paired Student's t-test was used.

Results

The paper presents the results of phototheranostics using methylene blue in children with cerebral palsy. An increase in the level of hemoglobin oxygenation from 50 to 67% (p < 0.001) and a decrease in blood volume in the microcirculatory bed of periodontal tissues were shown.

Conclusion

Photodynamic therapy methods with application of methylene blue make it possible to assess the state of the gingival mucosa tissue diseases objectively in real time, and to provide effective targeted therapy for gingivitis in children with cerebral palsy. There is a prospect that they can become widely used clinical methods.

Does potassium iodide help in the microbial reduction of oral microcosm biofilms after photodynamic therapy with methylene blue and red laser?

OBJECTIVE

To evaluate the efficacy of methylene blue (MB)-mediated antimicrobial photodynamic therapy (aPDT) doped with potassium iodide (KI) against oral microcosms biofilms cultured in dentin.

METHODS

A saliva-glycerol stock formed from pooled human saliva was diluted in McBain artificial saliva with 1% sucrose (1:1), inoculated on bovine dentin blocks, and refreshed daily for 5 days. The biofilms were divided (n = 9/group) and treated with 0.9% NaCl (C), 0.2% chlorhexidine (CX), 0.01% MB + low-power laser 15 J, 88 mW, 180 s (PL), and 0.01% MB + 50 mM KI + laser (PKIL). Serial dilution was performed, and cellular viability (CFU/mL) was evaluated for total microorganisms, total lactobacilli, total streptococci, and S. mutans. Additional biofilms were cultured and treated (n = 4) for biomass determination (%BMR). The microscopic structure of the biofilms was observed by SEM. One-way ANOVA and Tukey tests were conducted (α=5%).

RESULTS

Total microorganisms and total streptococci significantly reduced in biofilms treated with CX and PKIL when compared to C, but the CX, PKIL, and PL treatments did not differ from each other. Total lactobacilli and S. mutans showed a significant reduction in the CX, PL, and PKIL groups when compared to C, but with no difference between them. Biomass analysis showed a significantly reduction for CX and PKIL compared to C. SEM micrographs showed noticeable changes in bacterial membrane integrity for the PKIL and CX groups.

CONCLUSION

The addition of KI to methylene blue-mediated aPDT in microcosm biofilms was effective in reducing oral microorganisms, but the effect was group dependent.

Application of antimicrobial photodynamic therapy to treat subgingival multidrug-resistant bacterial infections in ICU patients

BACKGROUND

Drug-resistant bacterial infections have received much attention in recent years. Antimicrobial photodynamic therapy (aPDT) is an effective antimicrobial strategy. This study aimed to evaluate the therapeutic effect of methylene blue (MB)-mediated aPDT against subgingival multidrug-resistant (MDR) bacterial infections in intensive care unit (ICU) patients.

METHODS

Eighty-three patients who were hospitalized in the ICU of the Second Affiliated Hospital of Nanchang University from July 2019 to June 2021 were selected. The intraoral partitioned control test was conducted. Teeth that met the criteria were selected from different quadrants of the same patient, randomly divided into three groups, namely, A, B, and C, and treated with aPDT, chlorhexidine gargle, or normal saline. The counts of MDR bacteria in the gingival crevicular fluid were assessed in the different groups at different time points before and after treatment.

RESULTS

The MDR bacterial count decreased immediately after aPDT and was significantly different from that in the chlorhexidine gargle rinse group and the normal saline rinse group (P<0.05). There was no significant difference among the three groups at 6, 12, and 24 hours after treatment (P>0.05).

CONCLUSION

aPDT can be used to treat subgingival MDR bacterial infections, but the long-term effects of treatment need to be further studied.

Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy

Knowledge of photo-oxidative stress responses in bacteria that survive antimicrobial photodynamic therapy (aPDT) is scarce. Whereas aPDT is attracting growing clinical interest, subsequent stress responses are crucial to evaluate as they may lead to the up-regulation of pathogenic traits. Here, we aimed to assess transcriptional responses to sublethal aPDT-stress and identify potential connections with virulence-related genes. Six Enterococcus faecalis strains were investigated; ATCC 29212, three dental root-canal isolates labelled UmID1, UmID2 and UmID3 and two vancomycin-resistant isolates labelled A1 and A2. TMPyP was employed as a photosensitiser. A viability dose-response curve to increasing concentrations of TMPyP was determined by culture plating. Differential expression of genes involved in oxidative stress responses (dps and hypR), general stress responses (dnaK, sigma-factor^V and relA), virulence-related genes (ace, fsrC and gelE) and vancomycin-resistance (vanA) was assessed by reverse-transcription qPCR. TMPyP-mediated aPDT inactivated all strains with comparable efficiencies. TMPyP at 0.015 μM was selected to induce sublethal photo-oxidative stress. Despite heterogeneities in gene expression between strains, transcriptional profiles revealed up-regulations of transcripts dps, hypR as well as dnaK and sigma factor^V after exposure to TMPyP alone and to light-irradiated TMPyP. Specifically, the alternative sigma factor^V reached up to 39 ± 113-fold (median ± IQR) (p = 0.0369) in strain A2. Up-regulation of the quorum sensing operon, fsr, and its downstream virulence-related gelatinase gelE were also observed in strains ATCC-29212, A1, A2 and UmID3. Finally, photo-oxidative stress induced vanA-type vancomycin-resistance gene in both carrier isolates, reaching up to 3.3 ± 17-fold in strain A2 (p = 0.015). These findings indicate that, while aPDT successfully inactivates vancomycin-resistant and naïve strains of E. faecalis, subpopulations of surviving cells respond by co-ordinately up-regulating a network of genes involved in stress survival and virulence. This includes the induction of vancomycin-resistance genes in carrier isolates. These data may provide the mechanistic basis to circumvent bacterial responses and improve future clinical protocols.

Influence of antimicrobial photodynamic therapy with different pre-irradiation times on children's dental biofilm: randomized clinical trial

PURPOSE

Photodynamic therapy (PDT) is effective in reducing pathogenic microorganisms in the oral cavity and in preventing dental diseases. This study evaluated the pre-irradiation time using PDT (diode laser associated with 0.01% methylene blue) to decrease the number of microorganisms in the visible plaque in permanent teeth.

METHODS

This randomized clinical trial included 108 homologous lower permanent first molars (36 and 46) with biofilm from 54 children aged six to 12 years. PDT was performed (0.01% methylene blue photosensitizer/therapeutic laser-InGaAIP), according to the following protocols: Group 1, biofilm collection of the distal area of the lingual surface of 36 µm before PDT; group 2, mesial area of the lingual surface of 36 µm 1 min after PDT; group 3, area of the lingual surface of 46 µm before PDT; and group 4, mesial area of the lingual surface of 46 µm 5 min after PDT.

RESULTS

After statistical analysis, significant differences were observed between the groups (p = 0.000). In groups 2 and 4, the number of bacteria tended to decrease, with a more evident bacterial reduction in group 4.

CONCLUSIONS

Pre-irradiation reduced the number of colony-forming units of mature bacterial biofilms in vivo. A time of 5 min resulted in a greater reduction in the number of colony-forming units.

CLINICAL TRIAL REGISTRATION

ReBEC Identifier: RBR-6bqfp3; Date of Register: March 2nd, 2020. Retrospectively Registered.

Quorum quenching of Streptococcus mutans via the nano-quercetin-based antimicrobial photodynamic therapy as a potential target for cariogenic biofilm

Background

Quorum sensing (QS) system can regulate the expression of virulence factors and biofilm formation in Streptococcus mutans. Antimicrobial photodynamic therapy (aPDT) inhibits quorum quenching (QQ), and can be used to prevent microbial biofilm. We thereby aimed to evaluate the anti-biofilm potency and anti-metabolic activity of nano-quercetin (N-QCT)-mediated aPDT against S. mutans. Also, in silico evaluation of the inhibitory effect of N-QCT on the competence-stimulating peptide (CSP) of S. mutans was performed to elucidate the impact of aPDT on various QS-regulated genes.

Methods

Cytotoxicity and intracellular reactive oxygen species (ROS) generation were assessed following synthesis and confirmation of N-QCT. Subsequently, the minimum biofilm inhibitory concentration (MBIC) of N-QCT against S. mutans and anti-biofilm effects of aPDT were assessed using colorimetric assay and plate counting. Molecular modeling and docking analysis were performed to confirm the connection of QCT to CSP. The metabolic activity of S. mutans and the expression level of various genes involved in QS were evaluated by flow cytometry and reverse transcription quantitative real-time PCR, respectively.

Results

Successful synthesis of non-toxic N-QCT was confirmed through several characterization tests. The MBIC value of N-QCT against S. mutans was 128 μg/mL. Similar to the crystal violet staining, the results log₁₀ CFU/mL showed a significant degradation of preformed biofilms in the group treated with aPDT compared to the control group (P < 0.05). Following aPDT, metabolic activity of S. mutans also decreased by 85.7% (1/2 × MBIC of N-QCT) and 77.3% (1/4 × MBIC of N-QCT), as compared to the control values (P < 0.05). In silico analysis showed that the QCT molecule was located in the site formed by polypeptide helices of CSP. The relative expression levels of the virulence genes were significantly decreased in the presence of N-QCT-mediated aPDT (P < 0.05).

Conclusions

The combination of N-QCT with blue laser as a QQ-strategy leads to maximum ROS generation, disrupts the microbial biofilm of S. mutans, reduces metabolic activity, and downregulates the expression of genes involved in the QS pathway by targeting genes of the QS signaling system of S. mutans.

Photodynamic therapy and photobiomodulation therapy in zoledronic acid-induced osteonecrosis in rats

BACKGROUND

This study investigated the effect of antimicrobial photodynamic therapy (PDT), using methylene blue (MBO) and photobiomodulation therapy (PT), on the alveolar bone of rats submitted to bisphosphonate-induced osteonecrosis of the maxillaries (OMB) model using zoledronic acid (ZA).

METHODS

Sixty rats divided into six groups were used: SALINE, PDT, ZA, ZA+PDT, ZA+PT, and ZA+MBO. Three weekly administrations (Days 0, 7, and 14) of ZA 0.20 mg/kg or saline solution were performed. After one month (Day 42), the exodontia of the left lower first molars were performed. An additional dose of ZA was administered at Day 49. PDT was performed on days 42, 45, 49, and 54. One month after exodontia (Day 70), the animals were euthanized to obtain samples for imaging and microscopic analysis. ANOVA/Bonferroni tests were used for statistical analysis.

RESULTS

The ZA+PDT group showed a significantly lower percentage of apoptotic osteocytes than the ZA group (p<0.001). The ZA+MBO, ZA+PT, and PDT groups significantly reduced the number of mononuclear cells compared to the ZA group (p<0.001). The ZA+PT and ZA+PDT groups showed a significant reduction in the number of CD 68+ (p<0.001) and CD3+ (p=0.002) cells compared to the ZA group. The number of cells expressing INF-y had a significant reduction in the groups co-treated with PT and PDT compared to the ZA group (p<0.001).

CONCLUSIONS

We conclude that PDT and PT attenuated the severity of OMB and the inflammatory process due to a reduction of macrophages, T lymphocytes, and cytokines that stimulate the activity of these cells.

Photodynamic Therapy (PDT) in Prosthodontics: Disinfection of Human Teeth Exposed to Streptococcus mutans and the Effect on the Adhesion of Full Ceramic Veneers, Crowns, and Inlays: An In Vitro Study

The use of PDT in prosthodontics as a disinfection protocol can eradicate bacteria from tooth surfaces by causing the death of the microorganisms to which the photosensitizer binds, absorbing the energy of laser light during irradiation. The aim of the study was to investigate the capacity of PDT to increase the bond strength of full ceramic restorations. In this study, 45 extracted human teeth were prepared for veneers, crowns, and inlays and contaminated with Streptococcus mutans. Tooth surfaces decontamination was performed using a diode laser and methylene blue as a photosensitizer. The disinfection effect and the impact on tensile bond strength were evaluated by scanning electron microscopy (SEM) and pull-out tests of the cemented ceramic prosthesis. Results show that the number of bacteria was reduced from colonized prepared tooth surfaces, and the bond strength was increased when PDT was used. In conclusion, the present study indicates that using PDT as a protocol before the final adhesive cementation of ceramic restorations could be a promising approach, with outstanding advantages over conventional methods.

Photoactive electrospun cellulose acetate/polyethylene oxide/methylene blue and trilayered cellulose acetate/polyethylene oxide/silk fibroin/ciprofloxacin nanofibers for chronic wound healing

This study aimed to synthesize cellulose acetate (CA)-based electrospun nanofibers as drug delivery dressings for chronic wound healing. For the first time, CA was blended with polyethylene oxide (PEO) using acetone and formic acid. Methylene blue (MB) was incorporated into monolayered random CA/PEO nanofibers. They had a diameter of 400-600 nm, were hydrophilic, and generated reactive oxygen species upon irradiation. Thus, they mediated antimicrobial photodynamic inactivation (aPDI) against isolated biofilm-forming Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Bacterial survival, biofilm mass, and produced pyocyanin of the treated groups declined by 90%, 80%, and 3 folds, respectively. On the other hand, ciprofloxacin (Cipro) was loaded into an innovative trilayered aligned nanofiber consisting of CA/PEO surrounding a blank layer of silk fibroin. Cipro and MB release followed the Korsmeyer-Peppas model. An infected diabetic wound mouse model was established and treated with either MB-aPDI or Cipro. A combined therapy group of MB-aPDI followed by Cipro was included. The combined therapy showed significantly better results than monotherapies delineated by elevation in re-epithelization, collagen deposition, CD34, and TGF-β expression, along with a decline in CD95+ cells. This study deduced that drug-loaded CA electrospun nanofibers might be exploited in multimodal chronic wound healing.

Antimicrobial photodynamic therapy mediated by methylene blue coupled to β-cyclodextrin reduces early colonizing microorganisms from the oral biofilm

OBJECTIVE

To test the effect of antimicrobial photodynamic therapy (A-PDT) on the oral biofilm formed with early colonizing microorganisms, using the photosensitizer methylene blue coupled with β-cyclodextrin nanoparticles and red light sources laser or LED (λ =660 nm).

METHODS

The groups were divided into (n = 3, in triplicate): C (negative control, 0.9 % NaCl), CX (positive control, 0.2 % chlorhexidine), P (Photosensitizer/Nanoparticle), L (Laser), LED (light-emitting diode), LP (Laser + Photosensitizer/Nanoparticle) and LEDP (LED + Photosensitizer/Nanoparticle). A multispecies biofilm composed ofS. gordonii, S. oralis, S. mitis, and S. sanguinis was grown in microplates containing BHI supplemented with 1% sucrose (w/v) for 24 h. Light irradiations were applied with a laser at 9 J for 90 s (320 J/cm²), or with LED, at 8.1 J for 90 s (8.1 J/cm²). The microbial reduction was assessed by counting viable biofilm microorganisms in selective culture media, before and after the treatments. Data normality was assessed by the Shapiro-Wilk test, and the results were submitted to Kruskal-Wallis analysis, followed by Dunn's test, with a significance level of 5%.

RESULTS

The groups LP and LEDP were able to significantly reduce the biofilm microorganism counts by as much as 4 log₁₀ times compared to the negative control group (p < 0.05) and did not statistically differ from the positive control group (CX) (p > 0.05).

CONCLUSION

The A-PDT mediated by encapsulated β-cyclodextrin methylene blue irradiated by Laser or LED was effective in the microbial reduction of multispecies biofilm composed of early colonizing microorganisms.

Impact of riboflavin mediated photodynamic disinfection around fixed orthodontic system infected with oral bacteria

PURPOSE

The aim of this laboratory study was to investigate the amount of bacterial destruction through riboflavin mediated photodynamic therapy (PDT) around fixed orthodontic devices by using the two strains of bacteria Streptococcus mutans and Streptococcus sanguinis.

MATERIALS AND METHODS

A total of 80 metallic brackets were divided into four groups consisting of 20 brackets each. Group-I: riboflavin + LED irradiation; Group-II: riboflavin alone; Group-III: immersion in 0.2 % chlorhexidine gluconate solution and Group-IV: not submitted to any treatment. All metallic brackets were immersed in the standard bacterial solutions and incubated at 48 h. All samples were subjected to MTT assay for microbial cell viability testing after treatment. After 24 h of incubation, biofilms adhered on the mesh of metallic brackets after treatment were assessed by confocal laser microscopy. The total CFU/mL was estimated, and the results were log-transformed (log₁₀) and analyzed using one-way analysis of variance and Tukey-Kramer test. P-value was set to <0.05 that indicated statistical significance.

RESULTS

The samples from group-IV showed the highest amount of relative biofilm viability compared to any other group while group-I (PDT) showed the least viability of the two bacterial strains studied (p < 0.05). Group-I showed no significant difference when compared with group-III (chlorhexidine) (p > 0.05). The biofilms on the samples from group-II and group-IV were largely viable indicating thick green staining across the mesh of the brackets. Among the group-III samples, there were predominantly dead cells as compared to the live cell staining. A considerable amount of red staining was observed with noticeable less green staining in group-I samples.

CONCLUSION

This laboratory investigation revealed that riboflavin mediated PDT significantly reduced the amounts of S. mutans and S. sanguinis around the orthodontic brackets.

High-rate microbial selenate reduction in an up-flow anaerobic fluidized bed reactor (FBR)

Wastewater contaminated with high concentrations of selenium oxyanions requires treatment prior to discharge. Biological fluidized bed reactors (FBRs) can be an option for removing selenium oxyanions from wastewater by converting them into elemental selenium, which can be separated from the treated effluent. In this study, a lab-scale FBR was constructed with granular activated carbon as biofilm carrier and inoculated with a consortium of selenate reducing bacteria enriched from environmental samples. The FBR was loaded with an influent containing ethanol (10 mM) and selenate (10 mM) as the microbial electron donor and acceptor, respectively. The performance of the FBR in reducing selenate was evaluated under various hydraulic retention times (HRTs) (120 h, 72 h, 48 h, 24 h, 12 h, 6 h, 3 h, 1 h and 20 min). After process acclimatization, selenate was completely removed with no notable selenite produced when the HRT was stepwise decreased from 120 h to 6 h. However, decreasing the HRT to 3 h resulted in selenite accumulation (0.17 ± 0.023 mM) in the effluent although selenate removal efficiency remained at 99.8 ± 0.20%. At 1 h HRT, the FBR removed 90.8 ± 1.4% of the selenate at a rate of 9.6 ± 0.15 mM h^-1, which is the highest selenate reduction rate reported in the literature so far. However, 1 h HRT resulted in notable selenite accumulation (up to 2.4 ± 0.27 mM). Further decreasing the HRT to 20 min resulted in a notable decline in selenate reduction. Selenate reduction recovered from the "shock loading" after the HRT was increased back to 3 h. However, selenite still accumulated until the FBR was operated in batch mode for 6 days. This study affirmed that FBR is a promising treatment option for selenate-rich wastewater, and the process can be efficiently operated at low HRTs.

Efficacy of antimicrobial photodynamic therapy with Rose Bengal and blue light against cariogenic bacteria

OBJECTIVE

We evaluated the effect of antimicrobial photodynamic therapy (a-PDT) with Rose Bengal and blue light LED on bacteria that initiate and promote dental caries.

DESIGN

Colony forming units of Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinis, and Lactobacillus salivarius under planktonic and biofilm conditions were counted after a-PDT treatment using Rose Bengal and blue light LED. In addition, cariogenic bacteria from saliva and dental plaques from ten volunteers were used for evaluation of a-PDT treatment.

RESULTS

We found that a-PDT using Rose Bengal at > 10 μg/mL had antimicrobial effects on oral Gram-positive S. mutans, S. sobrinus, S. sanguinis, and L. salivarius under both planktonic and biofilm conditions. The effect was also observed for cariogenic bacteria that formed biofilms containing water-insoluble glucans, through which the bacteria are firmly attached to the tooth surface. Moreover, a-PDT led to a marked reduction in cariogenic bacteria in saliva and dental plaques.

CONCLUSION

a-PDT could be a useful approach for controlling dental caries in dental surgery.

Photodynamic antimicrobial chemotherapy using indocyanine green in experimentally induced intraoral ulcers in rats

BACKGROUND

Photodynamic antimicrobial chemotherapy (PACT) is a promising modality for eradication of microorganisms from the wound. This study aimed to investigate the effectiveness of PACT using indocyanine green (ICG) for reduction of bacterial load of oral ulcers in rats and its impact on the healing process.

METHODS

In this experimental study, 50 adult male Sprague Dawley rats were recruited. Oral ulcers were surgically made on the left cheek mucosa, and animals were randomly assigned into five groups (n = 10). Wound site in groups 1, 2, and 3 was irrigated with the sterile saline (0.9%), chlorhexidine (CHX; 0.2%), and ICG solutions (1 mg/mL), respectively. Group 4 was exposed to laser irradiation using 810 nm diode laser on continuous-wave mode for 30 seconds (fluence: 55 J/cm² , power: 300 mW, spot size: 4.5 mm). In group 5, PACT was performed using topical application of ICG followed by laser irradiation in the same way as the previous group. Bacterial load of oral ulcers was assessed before and after each treatment modality. Besides, rats were sacrificed on the 5th day post ulceration and histological features of healing were evaluated.

RESULTS

Bacterial load was significantly reduced merely in the PACT-ICG-treated group by one log (P < .0001). Animals in the PACT-ICG-treated group also showed an accelerated healing in comparison with others on the 5th day of an experiment.

CONCLUSION

Photodynamic antimicrobial chemotherapy using topical application of ICG has a potential to reduce the bacterial load of oral ulcers and accelerate wound repair. Therefore, it can be considered as an alternative to currently available modalities for wound management.

The Impact of Photosensitizer Selection on Bactericidal Efficacy Of PDT against Cariogenic Biofilms: A Systematic Review and Meta-Analysis

BACKGROUND

There are investigations on multiple photosensitizers for modulation of caries-related biofilms using PDT. However, much controversy remains about recommended parameters mostly on the selection of an efficient photosensitizer.

OBJECTIVE

The study performed a systematic review to identify the answer to the following question: What photosensitizers present high bactericidal efficacy against cariogenic biofilms?

METHODS

Systematic review with meta-analyses were carried out for English language articles from October to December 2019 (PRISMA standards) using MEDLINE, Scopus, Biomed Central, EMBASE, LILACS, and Web of Science. Information on study design, biofilm model, photosensitizer, light source, energy delivery, the incubation time for photosensitizer, and bacterial reduction outcomes were recorded. We performed two meta-analyses to compare bacterial reduction, data was expressed by (1) base 10 Logarithm values and (2) Log reduction RESULTS: After the eligibility criteria were applied (PEDro scale), the selected studies showed that toluidine Blue Ortho (TBO) and methylene blue (MBO) (5-min incubation time and 5-min irradiation) demonstrated better bacterial reduction outcomes. For the data expressed by Log TBO, MBO, curcumin, and Photogem® presented a significant bacterial decrease in comparison to the control (p = 0.042). For the data represented by Log reduction, the bacterial reduction toward S.mutans was not significant for any photosensitizer (p = 0.679).

CONCLUSION

The lack of methodological standardization among the studies still hinders the establishment of photosensitizer and bactericidal efficiency. TBO, MBO, curcumin, and photogem generate greater PDT-based bacterial reduction on caries-related bacteria.. Further clinical studies are necessary in order to obtain conclusive results.

Does pre-irradiation time influence the efficacy of antimicrobial photodynamic therapy?

Antimicrobial photodynamic therapy (aPDT) has emerged as a promising antimicrobial treatment to control microorganisms including those involved in oral diseases, especially dental caries. Hence, the aim of this study was to evaluate the influence of aPDT - pre-irradiation time (PIT), at different periods, on antimicrobial rate of Streptococcus mutans (S. mutans). A standard suspension of S. mutans UA159 was prepared and submitted at sensitization of 0.005 % methylene blue (MB) for 0, 1, 3 and 5 min (G1 - G4 groups, respectively) and irradiated with a red laser (660 nm; 321 J/cm²; 9 J; 90 s) afterward. A control group using PBS instead of MB was performed as well (G5). The number of colony-forming units (CFU)/mL was recorded, transformed into log₁₀ and analyzed by ANOVA and Tukey's test at a cutoff value at 0.05. Overall, the aPDT groups tested achieved a bacterial reduction > 1-log₁₀ when compared to G5 (p < 0.05) with no statistical difference among the different PIT tested. The need of PIT before aPDT application deserves attention, since its time reduction implies on shorter clinical approaches without compromising the photodynamic antibacterial efficacy in the in vitro parameters employed.

Antimicrobial photodynamic therapy against metronidazole-resistant dental plaque bactéria

The antimicrobial photodynamic therapy (aPDT) has stood out as an alternative and promising method of disinfection and has been exploited for the treatment of oral bacteria. In this study, we evaluate in vitro the action of aPDT, mediated by methylene blue, chlorin-e6, and curcumin against clinical subgingival plaques that were resistant to metronidazole. The sensitivity profile of the samples to metronidazole was analyzed by the agar dilution method. Cell viability in the planktonic and biofilm phase was assessed by CFU / mL. The composition of the biofilm was evaluated by the checkboard DNA-DNA Hibrydization technique. Photosensitizers internalization was qualitatively assessed by confocal fluorescence microscopy (CLSM). The aPDT mediated by the three photosensitizers tested was able to reduce the totality of the planktonic microbial load and partially reduce the biofilm samples. The analysis performed by CLSM showed that the photosensitizers used in the application of aPDT were able to permeate the interior of the biofilm. The aPDT has been shown to be useful in a supportive and effective approach to the treatment of periodontal disease.

Comparison of photodynamic therapy with methylene blue associated with ceftriaxone in gram-negative bacteria; an in vitro study

The resistance of microorganisms increases the need for new antimicrobial therapies. The aim of this study was to evaluate the in vitro action of photodynamic therapy and its combination with ceftriaxone in third generation cephalosporin resistant gram-negative bacteria. Clinical strains of Klebsiella pneumoniae, Enterobacter aerogenes and Escherichia coli were obtained, incubated with MB for 15 min combined or not with ceftriaxone and irradiated with fluence of 10 and 25 J/cm². MB internalization was evaluated by confocal microscopy. Cell viability was assessed by counting colony forming units and bacterian metabolism by the resazurin test. MB has been observed within cells, although not in all bacteria. PDT-MB alone and combined with Ceftriaxone reduced bacterial growth by approximately 1 log at 10 J/cm² of fluence and 4 logs by 25 J/cm², with a significant difference from the control group. The reduction in bacterial growth between the treated groups was similar, without significant difference between them. The Resazurin test showed lower bacterial metabolic activity in the treated groups, but it did not allow to observe difference between fluences. It was concluded with this study that the internalization of MB was not observed in all cells of K. pneumoniae, E. aerogenes and E. coli strains. There was less bacterial metabolic activity in the treated groups, with no variation between different fluences. PDT-MB 25 J/cm² alone and combined with Ceftriaxone showed antimicrobial action, but the PDT-MB/Ceftriaxone combination had no potentiating effect.

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.

The feasibility of using Saffron to reduce the photosensitivity reaction of selected photosensitizers using red blood cells and staphylococcusAureus bacteria as targets

BACKGROUND

The photosensitivity reaction which appears after a Photodynamic therapy treatment session is a challenge that needs further investigation. The goal of this research is to evaluate the possibility of using saffron to reduce or control this photosensitivity reaction and to present mathematical modeling of the cell survival curves and their dependency on saffron concentration.

METHODS

Red blood cells (RBC) and Staphylococcus aureus Bacteria (STB) were used as targets in this study. The Photosensitivity of Rose Bengali, Methylene Blue, and Photofrin independently and incorporated with saffron was investigated for continued irradiation at different Saffron concentrations. Gompertz's function was used to fit the survival curve parameters. The 50% cell survival rate was fit to an empirical formula based on Saffron concentrations.

RESULTS

Saffron inhibits the photosensitivity reaction of the three photosensitizers and causes a significant increase in the 50% survival rate time (t₅₀) for RBC`s and STB. Saffron didn't show phototoxicity when incubated alone with RBC`s and STB. The survival curve parameters of the RBCs and STB showed a good fit to the Gompertz function. Saffron concentration is related to the RBC`s t₅₀ based on power dependency of 0.56, 0.38 and 0.31 for Photofrin, Methylene Blue and Rose Bengali respectively and 0.1 on STB for Rose Bengali.

CONCLUSION

Saffron can efficiently be used to reduce the photosensitivity reaction of Photosensitizers after a PDT treatment session. Gompertz function was found to be an appropriate mathematical model for survival rate curves. The t₅₀ and the saffron concentration are well related through a power dependence empirical formula.

Oral microbiological control by photodynamic action in orthodontic patients

BACKGROUND

Orthodontics involves diagnosis and treatment of dental and skeletal malocclusions. Orthodontic apparatus may repair these malocclusions but may also impair oral hygiene making patients prone to develop both periodontal diseases and caries. Antimicrobial agents may be used to prevent this.To avoid increased antimicrobial resistance to available drugs, A-PDT (Antimicrobial Photodynamic Therapy) appears as a viable alternative.

OBJECTIVE

This work aimed to evaluate the efficacy of A-PDT on reducing the number of colony forming units (CFU) through the use of phenothiazine compound (methylene blue+ toluidine blue) as a photosensitizer, associated with red LED (λ640±5ηm) irradiation in orthodontic patients.

METHODOLOGY

Twenty-one patients consented to participate in the study. Three biofilm collections were performed around the brackets and gums of the inferior central incisors; first before any intervention (Control); second after 5min of pre-irradiation and the last one immediately after AmPDT. Subsequently, a microbiological routine for microorganism growth period were performed and CFU counting after a 24h done.

RESULTS

The data showed that the AmPDT was able to reduce CFU count around 90% when compared to Control group (p=0.007) and also between the A-PDT and Photosensitizer groups (p=0.010). However, there were no differences between the Control and Photosensitizer groups.

CONCLUSION

A-PDT associated with the use of phenothiazine compounds and red LED was able to significantly reduce the number of CFUs in orthodontic patients.

Effect of Photodynamic Therapy on Microorganisms Responsible for Dental Caries: A Systematic Review and Meta-Analysis

The aim of this study was to perform a systematic review of the literature followed by a meta-analysis about the efficacy of photodynamic therapy (PDT) on the microorganisms responsible for dental caries. The research question and the keywords were constructed according to the PICO strategy. The article search was done in Embase, Lilacs, Scielo, Medline, Scopus, Cochrane Library, Web of Science, Science Direct, and Pubmed databases. Randomized clinical trials and in vitro studies were selected in the review. The study was conducted according the PRISMA guideline for systematic review. A total of 34 articles were included in the qualitative analysis and four articles were divided into two subgroups to perform the meta-analysis. Few studies have achieved an effective microbial reduction in microorganisms associated with the pathogenesis of dental caries. The results highlight that there is no consensus about the study protocols for PDT against cariogenic microorganisms, although the results showed the PDT could be a good alternative for the treatment of dental caries.

Antimicrobial efficacy of methylene blue-mediated photodynamic therapy on titanium alloy surfaces in vitro

Bacterial elimination using antimicrobial photodynamic therapy (aPDT) has been considered an alternative therapeutic modality in peri-implantitis treatment. The present in vitro study evaluated the dose-dependent and pH-dependent bactericidal effects of methylene blue (MB)-mediated aPDT at eliminating Gram-negative (P. gingivalis and A. actinomycetemcomitans) and Gram-positive (S. mutans) bacteria on sandblasting, large-grit and acid-etching (SLA)-pretreated titanium alloy. The effects of different MB concentrations (50, 100, and 200 μg/mL), the pH of the MB (4, 7, and 10), and irradiation time (0, 30, and 60 s) on the bacterial viability and residual lipopolysaccharide (LPS) levels were examined. The variations in the pH of the MB solution after aPDT for 60 s on the uncontaminated and contaminated specimens were also detected. The experimental results indicated that MB-mediated PDT could effectively kill the majority of bacteria on the titanium alloy surfaces of biofilm-contaminated implants compared with the MB alone. Of note, aPDT exhibited better antibacterial efficacy with increase in the MB concentration and irradiation time. While treated in an acidic solution on the biofilm-contaminated specimens, aPDT caused the pH to increase. By contrast, the initially high alkaline pH decreased to a value of about pH 8.5 after aPDT. Intriguingly, the neutral pH had minor changes, independent of the MB concentration and bacterial species. As expected, aPDT with higher MB concentration at higher pH environment significantly lowered the LPS concentration of A. actinomycetemcomitans and P. gingivalis. On the basis of the data, the aPDT with 200 μg/mL MB at pH 10 for 60 s of irradiation time might be an effectively treatment to eliminate bacteria and LPS adherent to titanium surface, however, the use of the multispecies biofilm model and the evaluation of in vitro osteogenesis needed to be further evaluated.

Assessment of Chitosan-Based Hydrogel and Photodynamic Inactivation against Propionibacterium acnes

Chitosan (CH) is a biopolymer that exhibits a number of interesting properties such as anti-inflammatory and antibacterial activity and is also a promising platform for the incorporation of photosensitizing agents. This study aimed to evaluate the efficacy of antimicrobial activity of chitosan hydrogel formulation alone and in combination with the methylene blue (MB) associated with antimicrobial photodynamic therapy (aPDT) against planktonic and biofilm phase of Propionibacterium acnes. Suspensions were sensitized with 12.5, 25.0, 37.5, 50.0 μg/mL of MB for 10 min and biofilms to 75, 100 and 150 μg/mL for 30 min then exposed to red light (660 nm) at 90 J/cm² and 150 J/cm² respectively. After treatments, survival fractions were calculated by counting the number of colony-forming units. The lethal effect of aPDT associated with CH hydrogel in planktonic phase was achieved with 12.5 µg/mL MB and 1.9 log10 biofilm reduction using 75 µg/mL MB. Rheological studies showed that formulations exhibited pseudoplastic non-Newtonian behavior without thixotropy. Bioadhesion test evidenced that the formulations are highly adhesive to skin and the incorporation of MB did not influence the bioadhesive force of the formulations.