The application of antimicrobial photodynamic therapy (aPDT) in dentistry: a critical review

Antimicrobial photodynamic effect of the photosensitizer riboflavin, alone and in combination with colistin, against pandrug-resistant Pseudomonas aeruginosa clinical isolates

INTRODUCTION

Development of multi-, extensively-, and pandrug-resistant (MDR, XDR, and PDR) strains of Pseudomonas aeruginosa remains a major problem in medical care. The present study evaluated the effect of antimicrobial photodynamic therapy (aPDT) as a monotherapy and in combination with colistin against P. aeruginosa isolates.

METHODS

Two P. aeruginosa isolates recovered from patients with respiratory tract infections were examined in this study. Minimum inhibitory concentration (MIC) of colistin was determined by the colistin broth disk elution (CBDE) and the reference broth microdilution (rBMD) methods. aPDT was performed using the photosensitizer (Ps) riboflavin at several concentrations and a light-emitting diode (LED) emitting blue light for different irradiation times with or without colistin at 1/2 × MIC concentration.

RESULTS

Both PA1 and PA2 isolates were identified as colistin-resistant P. aeruginosa with a MIC ≥4 μg/mL by the CBDE and MICs of 512 μg/mL and 256 μg/mL, respectively, by the rBMD. In aPDT, neither riboflavin nor LED light alone had antibacterial effects. The values of colony forming units per milliliter (CFU/mL) in both isolates were significantly reduced by LED + Ps treatments in a time-dependent manner (LED irradiation time) and dose-dependent manner (Ps concentration). In comparison with control, treatment with Ps (50 μM) + LED (120 s) and Ps (100 μM) + LED (120 s) resulted in 0.27 log10 CFU/mL and 0.43 log10 CFU/mL reductions in PA1, and 0.28 log10 CFU/mL and 0.34 log10 CFU/mL reductions in PA2, respectively, (P < 0.01). The best results were obtained after the combination of aPDT followed by colistin, which increased bacterial reduction, resulting in a 0.41-0.7 log10 CFU/mL reduction for PA1 and 0.35-0.83 log10 CFU/mL reduction for PA2 (P = 0.001).

CONCLUSIONS

This study suggests the potential implications of aPDT in combination with antibiotics, such as colistin for treatment of difficult-to-treat P. aeruginosa infections.

Molecular docking and antimicrobial activities of photoexcited inhibitors in antimicrobial photodynamic therapy against Enterococcus faecalis biofilms in endodontic infections

Antimicrobial photodynamic therapy (aPDT) is a promising approach to combat antibiotic resistance in endodontic infections. It eliminates residual bacteria from the root canal space and reduces the need for antibiotics. To enhance its effectiveness, an in silico and in vitro study was performed to investigate the potential of targeted aPDT using natural photosensitizers, Kojic acid and Parietin. This approach aims to inhibit the biofilm formation of Enterococcus faecalis, a frequent cause of endodontic infections, by targeting the Ace and Esp proteins. After determining the physicochemical characteristics of Ace and Esp proteins and model quality assessment, the molecular dynamic simulation was performed to recognize the structural variations. The stability and physical movement of the protein-ligand complexes were evaluated. In silico molecular docking was conducted, followed by ADME/Tox profiling, pharmacokinetics characteristics, and assessment of drug-likeness properties of the natural photosensitizers. The study also investigated the changes in the expression of genes (esp and ace) involved in E. faecalis biofilm formation. The results showed that both Kojic acid and Parietin complied with Lipinski's rule of five and exhibited drug-like properties. In silico analysis indicated stable complexes between Ace and Esp proteins and the natural photosensitizers. The molecular docking studies demonstrated good binding affinity. Additionally, the expression of the ace and esp genes was significantly downregulated in aPDT using Kojic acid and Parietin with blue light compared to the control group. This investigation concluded that Kojic acid and Parietin with drug-likeness could efficiently interact with Ace and Esp proteins with a strong binding affinity. Hence, natural photosensitizers-mediated aPDT can be considered a promising adjunctive treatment against endodontic infections.

Nanomaterials: innovative approaches for addressing key objectives in periodontitis treatment

Periodontitis is a chronic inflammatory disease primarily caused by dental plaque, which is a significant global public health concern due to its high prevalence and severe impact on oral, and even systemic diseases. The current therapeutic plan focuses on three objectives: pathogenic bacteria inhibition, inflammation control, and osteogenic differentiation induction. Existing treatments still have plenty of drawbacks, thus, there is a pressing need for novel methods to achieve more effective treatment effects. Nanomaterials, as emerging materials, have been proven to exert their inherent biological properties or serve as stable drug delivery platforms, which may offer innovative solutions in periodontitis treatment. Nanomaterials utilized in periodontitis treatment fall into two categories, organic and inorganic nanomaterials. Organic nanomaterials are known for their biocompatibility and their potential to promote tissue regeneration and cell functions, including natural and synthetic polymers. Inorganic nanomaterials, such as metal, oxides, and mesoporous silica nanoparticles, exhibit unique physicochemical properties that make them suitable as antibacterial agents and drug delivery platforms. The inorganic nanosurface provides terrain induction for cell migration and osteogenic regeneration at defect sites by introducing different surface morphologies. Inorganic nanomaterials also play a role in antibacterial photodynamic therapy (aPDT) for eliminating pathogenic bacteria in the oral cavity. In this review, we will introduce multiple forms and applications of nanomaterials in periodontitis treatment and focus on their roles in addressing the key therapeutic objectives, to emphasize their promising future in achieving more effective and patient-friendly approaches toward periodontal tissue regeneration and overall health.

What is the potential of antibacterial, antiviral and antifungal photodynamic therapy in dentistry?

DESIGN

A review of the principal clinical applications of antimicrobial photodynamic therapy (aPDT) in dentistry.

AIM

To provide an overview of clinical applications and future perspectives of aPDT in dentistry.

METHODS

A comprehensive search was conducted on PubMed, Web of Science, Scopus, and Embase up to September 2022, where only data from randomized clinical trials were included. In vitro studies, animal studies, literature reviews, and duplicate articles were excluded from the review. Out of a total of 1042 references initially identified, only 89 studies were included in the review. Six main oral conditions for which aPDT has been used were identified: periodontal and peri-implant diseases, endodontics, bacterial plaque, caries, and fungal and viral infections.

RESULTS

The review suggests that aPDT can be used as an effective complementary treatment for reducing pathogenic microorganisms in bacterial plaque; carious lesions; and periodontal, peri-implant, endodontic, fungal, and viral infections.

CONCLUSIONS

Despite the efficacy of aPDT against different types of microorganisms, there are no specific irradiation parameters for its respective photosensitizers due to the significant heterogeneity of clinical trials. Therefore, more studies are needed to determine irradiation protocols and development of new photosensitizers to improve the safety and efficacy of aPDT.

Photosensitizer-Amplified Antimicrobial Materials for Broad-Spectrum Ablation of Resistant Pathogens in Ocular Infections

The emergence of multidrug resistant (MDR) pathogens and the scarcity of new potent antibiotics and antifungals are one of the biggest threats to human health. Antimicrobial photodynamic therapy (aPDT) combines light and photosensitizers to kill drug-resistant pathogens; however, there are limited materials that can effectively ablate different classes of infective pathogens. In the present work, a new class of benzodiazole-paired materials is designed as highly potent PDT agents with broad-spectrum antimicrobial activity upon illumination with nontoxic light. The results mechanistically demonstrate that the energy transfer and electron transfer between nonphotosensitive and photosensitive benzodiazole moieties embedded within pathogen-binding peptide sequences result in increased singlet oxygen generation and enhanced phototoxicity. Chemical optimization renders PEP3 as a novel PDT agent with remarkable activity against MDR bacteria and fungi as well as pathogens at different stages of development (e.g., biofilms, spores, and fungal hyphae), which also prove effective in an ex vivo porcine model of microbial keratitis. The chemical modularity of this strategy and its general compatibility with peptide-based targeting agents will accelerate the design of highly photosensitive materials for antimicrobial PDT.

Role of Photodynamic Therapy in Osteonecrosis and Osteoradionecrosis of the Jaws: A Systematic Review

Aim

Photodynamic therapy (PDT) is a minimally invasive treatment modality that has been used clinically for early stage and inoperable cancers. Successful use of this atraumatic therapy in osteoradionecrosis (ORN) and osteonecrosis of the jaws (ONJ) has been documented in the literature. The aim of this review was to systematically evaluate the role of photodynamic therapy in ORN and ONJ.

Methods

Two independent reviewers conducted an elaborate search in PubMed, Google Scholar and Cochrane's CENTRAL database for studies published on PDT as stand-alone or adjuvant therapy in ORN/ONJ until June 2022. The present study was based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Demographic data, type and stage of necrosis of the jaws, site, PDT protocol, time to heal and follow-up were evaluated. Eighteen articles were included totally based on the inclusion and exclusion criteria for final analysis.

Results

A total of 94 patients were included in the present review out of which 36 were males and 58 were females. Five studies reported the use of PDT as an adjuvant therapy in ORN. Thirteen studies reported successful outcomes with PDT in ONJ. Complete epithelialization was achieved with PDT ± other adjuvants in 86/94 (91.48%) patients. The time taken for regression of the lesion ranged between 4 days and 12 months with PDT in the present study.

Conclusion

The reviewed studies demonstrate the effectiveness of PDT, as an adjuvant therapy, in managing various stages of ORN and ONJ.

CLINICAL EFFICACY OF PHOTODYNAMIC THERAPY IN MANAGEMENT OF ORAL POTENTIALLY MALIGNANT DISORDERS: A SYSTEMATIC REVIEW AND META-ANALYSIS

OBJECTIVES

Despite phototherapy (in the form of photodynamic therapy (PDT)-mediated oxidative stress) being utilized in the management of oral potentially malignant disorders (OPMDs), the evidence of certainty remains unclear. Hence, this systematic review and meta-analysis (PROSPERO # CRD42021218748) is aimed to evaluate the clinical efficacy of PDT-induced oxidative stress in OPMDs METHODS: PubMed, Embase, Web of Science, Scopus, and Cochrane Library databases were searched without restriction of language or year of publication. In addition, gray literature was searched and a manual search was performed. Two independent reviewers screened all the studies, assessing data extraction, risk of bias and certainty of evidence. A narrative synthesis was carried out. For the meta-analysis, random effects were considered to determine the prevalence of a total and a partial remission (PR) of oral potentially malignant disorders (OPMDs). The certainty of evidence was explored using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Twenty-three studies were included in the qualitative and quantitative syntheses. A total of 880 patients were included (564 males; 218 females) with an age range between 24 and 89-years-old. The results showed the prevalence of the total and partial remissions respectively for the following OPMLs: actinic cheilitis (AC): 69.9% and 2.4%; oral leukoplakia (OL): 44% and 36.9%; oral verrucous hyperplasia (OVH): 98.5%; oral erythroleukoplakia (OEL): 92.1% and 7.9%. The prevalence of no remission of OL was 18.8%.

CONCLUSIONS

PDT demonstrated significant results in clinical remission of OPMDs and most of the eligible studies have shown a total or a partial remission of the included lesions, but at a low or a very low certainty of evidence. Hence, further clinical studies with robust methodology are warranted to offer further validated data. Also, further evidence is required to understand further the mechanism of PDT-induced oxidative stress.

Bacterial resistance to antimicrobial photodynamic therapy: A critical update

Bacterial antibiotic resistance is one of the most significant challenges for public health. The increase in bacterial resistance, mainly due to microorganisms harmful to health, and the need to search for alternative treatments to contain infections that cannot be treated by conventional antibiotic therapy has been aroused. An alternative widely studied in recent decades is antimicrobial photodynamic therapy (aPDT), a treatment that can eliminate microorganisms through oxidative stress. Although this therapy has shown satisfactory results in infection control, it is still controversial in the scientific community whether bacteria manage to develop resistance after successive applications of aPDT. Thus, this work provides an overview of the articles that performed successive aPDT applications in models using bacteria published since 2010, focusing on sublethal dose cycles, highlighting the main PSs tested, and addressing the possible mechanisms for developing tolerance or resistance to aPDT, such as efflux pumps, biofilm formation, OxyR and SoxRS systems, catalase and superoxide dismutase enzymes and quorum sensing.

Photodynamic therapy repairs medication-related osteonecrosis of the jaw by reducing NF-kB protein in rats

OBJECTIVE

To evaluate whether antimicrobial photodynamic therapy (aPDT) repairs bisphosphonate-related osteonecrosis of the jaw (BRONJ) modulated by the reduction of NF-kB protein in a murine model.

METHODOLOGY

Male Wistar rats (N=30) were divided into the following groups (n=6/group): negative control (NC); experimental osteonecrosis (ONE); ONE + photosensitizer (PS); ONE + photobiomodulation (PBM); and ONE + aPDT. Over 8 weeks, ONE was induced by zoledronic acid 250 µg/kg injections, except in the NC group, which received sterile 0.9% saline, followed by extraction of the lower left first molar. Red light laser irradiation (wavelength ~660 nm, power 50 mW, energy of 2 J, energy dose of 66.67 J/cm2 for 40 s) was performed once a week for 4 weeks. Methylene blue 0.3% was used as PS. The animals were euthanized and examined macroscopically for the presence of exposed bone and epithelial repair and microscopically by histochemical (hematoxylin-eosin and Masson's trichrome staining) and immunohistochemical (anti-NF-kB) methods. Macroscopic and histomorphometric data were analyzed by one-way ANOVA and Tukey's post-test (p<0.05).

RESULTS

Mucosal repair, viable osteocytes, and NF-kB immunostaining were observed in the NC, ONE+PS, ONE+PBM, and ONE+aPDT groups. The ONE group showed no mucosal repair, showing empty lacunae and multifocal immunostaining for NF-kB. The ONE+PBM and ONE+aPDT groups had greater deposition of extracellular matrix and less necrotic bone tissue (p<0.05).

CONCLUSION

PBM and aPDT treatments for BRONJ were effective for bone and epithelial repair, in addition to reducing inflammation mediated by the decrease of NF-kB protein in the irradiated regions.

Synergistic antimicrobial photodynamic therapy using gated mesoporous silica nanoparticles containing curcumin and polymyxin B

Photodynamic Therapy is a therapy based on combining a non-toxic compound, known as photosensitizer (PS), and irradiation with light of the appropriate wavelength to excite the PS molecule. The photon absorption by the PS leads to reactive oxygen species generation and a subsequent oxidative burst that causes cell damage and death. In this work, we report an antimicrobial nanodevice that uses the activity of curcumin (Cur) as a PS for antimicrobial Photodynamic Therapy (aPDT), based on mesoporous silica nanoparticles in which the action of the classical antibiotic PMB is synergistically combined with the aPDT properties of curcumin to combat bacteria. The synergistic effect of the designed gated device in combination with irradiation with blue LED light (470 nm) is evaluated against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus epidermidis. The results show that the nanodevice exhibits a noteworthy antibacterial activity against these microorganisms, a much more significant effect than free Cur and PMB at equivalent concentrations. Thus, 0.1 µg/mL of MSNs-Cur-PMB eliminates a bacterial concentration of about 105 CFU/mL of E. coli, while 1 µg/mL of MSNs-Cur-PMB is required for P. aeruginosa and S. epidermidis. In addition, antibiofilm activity against the selected bacteria was also tested. We found that 0.1 mg/mL of MSNs-Cur-PMB inhibited 99 % biofilm formation for E. coli, and 1 mg/mL of MSNs-Cur-PMB achieved 90 % and 100 % inhibition of biofilm formation for S. epidermidis and P. aeruginosa, respectively.

Application of photosensitive dental materials as a novel antimicrobial option in dentistry: A literature review

The formation of dental plaque is well-known for its role in causing various oral infections, such as tooth decay, inflammation of the dental pulp, gum disease, and infections of the oral mucosa like peri-implantitis and denture stomatitis. These infections primarily affect the local area of the mouth, but if not treated, they can potentially lead to life-threatening conditions. Traditional methods of mechanical and chemical antimicrobial treatment have limitations in fully eliminating microorganisms and preventing the formation of biofilms. Additionally, these methods can contribute to the development of drug-resistant microorganisms and disrupt the natural balance of oral bacteria. Antimicrobial photodynamic therapy (aPDT) is a technique that utilizes low-power lasers with specific wavelengths in combination with a photosensitizing agent called photosensitizer to kill microorganisms. By inducing damage through reactive oxygen species (ROS), aPDT offers a new approach to addressing dental plaque and associated microbial biofilms, aiming to improve oral health outcomes. Recently, photosensitizers have been incorporated into dental materials to create photosensitive dental materials. This article aimed to review the use of photosensitive dental materials for aPDT as an innovative antimicrobial option in dentistry, with the goal of enhancing oral health.

An update on alternative therapy for Escherichia coli causing urinary tract infections; a narrative review

BACKGROUND

Urinary tract infections (UTIs) are the most common type of nosocomial infection and severe health issues because of the difficulties and frequent recurrence. Today, alternative methods such as sonodynamic therapy (SDT), photodynamic therapy (PDT) and herbal materials use for treating infections like UTI in many countries.

METHOD

We conducted searches of the biomedical databases (Google Scholar, Scopus, PubMed, and Web of sciences) to identify related studies from 2008 to 2023.

RESULT

SDT aims to use ultrasound to activate a sonosensitizer, which causes a biological effect by raising reactive oxygen species (ROS). When bacteria are exposed to ROS, several important effects occur: oxidative damage, DNA damage, protein dysfunction etc. SDT with herbal medicine significantly reduced the number of colony-forming units and bactericidal activity for Klebsiella pneumonia and E. coli. PDT is a promising treatment for cancer and microbial infections, combining a photosensitiser, light and tissue molecular oxygen. It involves a photosensitizer, light source, and oxygen, with variations affecting microbial binding and bactericidal activity. Factors affecting antibacterial properties include plant type, growing conditions, harvesting, and processing. This review highlights the recent advancements in sonodynamic, photodynamic, herbal, and bio-material-based approaches in the treatment of E. coli infections.

CONCLUSIONS

These alternative therapies offer exciting prospects for addressing UTIs, especially in cases where traditional antibiotic treatments may be less effective. Further research and clinical studies are warranted to fully explore the potential of these innovative treatment modalities in combating UTIs and improving patient outcomes.

Clinical and Radiographic Outcomes of Adjunctive Phototherapy Versus Antibiotic Therapy Against Peri-Implant Diseases: A Systematic Review and Meta-Analysis

Background: Peri-implantitis, an inflammatory condition in implant tissues, requires bacterial eradication and implant surface decontamination, with aPDT as a helpful surgical adjunct. Objective:This project was designed to investigate the effect of antibiotic therapy versus aPDT, as adjuncts to conventional mechanical debridement (MD), on the peri-implant clinical and/or radiographic parameters among patients with peri-implant diseases. Methods: A comprehensive search was conducted across electronic databases, including PubMed, Scopus, and Web of Science, up to and including April 2023, without any restriction on the language and year of publication, focusing the following research question: "Does adjunctive aPDT improve the peri-implant clinical and/or radiographic parameters in treating peri-implant diseases compared to antibiotic therapy?" Statistical analysis was performed on peri-implant clinical [plaque index (PI), probing depth (PD), and bleeding on probing (BOP)] and radiographic parameters [marginal bone loss (MBL)]. The study included six randomized controlled trials and one clinical (nonrandomized) study. Results: The systematic review findings indicate that the application of aPDT as an adjunct to MD is equally effective as adjunctive antibiotic therapy in improving peri-implant clinical parameters and radiographic parameters in patients with peri-implant diseases. Only two studies were classified as having a low risk of bias (RoB), two were assessed as having an unclear RoB, and the remaining three studies were determined to have a high RoB. However, the meta-analysis results revealed no statistically significant difference in peri-implant PI, PD, and MBL scores between patients treated with adjunct aPDT or adjunct antibiotic therapy. Notably, there was a statistically significant difference favoring adjunct aPDT in peri-implant BOP values compared to the control group. Conclusions: Despite the limited number of included studies and the significant heterogeneity among them, the findings suggest that aPDT yields comparable peri-implant clinical and radiographic outcomes to adjunctive antibiotic therapy, as adjuncts to MD, for the potential treatment of peri-implant diseases.

Synthesis and characterization of novel BODIPYs and their antioxidant, antimicrobial, photodynamic antimicrobial, antibiofilm and DNA interaction activities

In the current study, we synthesized and characterized new BODIPY derivatives (1-4) having pyridine or thienyl-pyridine substituents at meso- position and 4-dibenzothienyl or benzo[b]thien-2-yl moieties at 2-,6- positions. We investigated fluorescence properties and the ability to form singlet oxygen. In addition, various biological activities of BODIPYs such as DPPH scavenging, DNA binding/cleavage ability, cell viability inhibition, antimicrobial activity, antimicrobial photodynamic therapy (aPDT) and biofilm inhibition properties were performed. BODIPY derivatives BDPY-3 (3) and BDPY-4 (4) have high fluorescence quantum yields as 0.50 and 0.61 and 1 O2 quantum yields were calculated as 0.83 for BDPY-1 (1), 0.12 for BDPY-2 (2), 0.11 for BDPY-3 and 0.23 for BDPY-4. BODIPY derivatives BDPY-2, BDPY-3 and BDPY-4 displayed 92.54 ± 5.41%, 94.20 ± 5.50%, and 95.03 ± 5.54% antioxidant ability, respectively. BODIPY compounds showed excellent DNA chemical nuclease activity. BDPY-2, BDPY-3 and BDPY-4 also exhibited 100% APDT activity against E. coli at all tested concentrations. In addition to these, they demonstrated a highly effective biofilm inhibition activity against Staphyloccous aureus and Pseudomans aeruginosa. BDPY-4 showed the most effective antioxidant and DNA cleavage activity, while BDPY-3 exhibited the most effective antimicrobial and antibiofilm activity.

The Impact of Hydrogen Peroxide (H2O2) Fumigation on Bacterial Levels in Dental Office Environments: A Randomized Clinical Trial Investigation

BACKGROUND

Fumigation with hydrogen peroxide has proven to be a highly effective approach to maintaining biological safety within dental offices. The main purpose of this research was to investigate the efficacy of hydrogen peroxide (H2O2) fumigation in reducing bacterial levels in dental office environments.

METHODS

The study involved 30 participants diagnosed with moderate caries decay (ICDAS 3 and 4) in their mandibular molars. Sixty Petri dishes (two per patient) with Columbia Agar and 5% Sheep Blood were opened at the beginning of the caries treatment. After the completion of caries treatment and tooth restoration, 30 plates (G1 group) were closed. Following this, a 20 min fumigation procedure with 6% hydrogen peroxide biosanitizer using a compressed air device was conducted. After the fumigation, the remaining plates were closed (G2 group). The total number of bacteria CFUs (colony-forming units) in the dental office air was determined using the Koch sedimentation method.

RESULTS

The total bacterial colony (TBC) level, measured in cfu/m3, demonstrated a significant decrease in the number of bacteria following room environment fumigation (163.1 ± 145.7; G2 group) compared to non-fumigated samples (817.2 ± 208.2; G1 group) (p < 0.001). The predominant bacteria observed in the microbiological plates before fumigation were Micrococcus and Bacillus species, found in 80% (24/30) and 60% (18/30) of the plates, respectively. Application of H2O2 room fumigation resulted in a significant reduction in bacterial numbers: 79.2% (5/30) for Micrococcus species (p < 0.001), 83.3% (3/30) for Bacillus species (p < 0.001), and 100% (0/30) for Staphylococcus arlettae (p < 0.05).

CONCLUSION

Fumigation with 6% H2O2 is an effective method for reducing bacterial counts in a dental office environment.

A Systematic Evaluation of Curcumin Concentrations and Blue Light Parameters towards Antimicrobial Photodynamic Therapy against Cariogenic Microorganisms

Dental caries is a highly preventable and costly disease. Unfortunately, the current management strategies are inadequate at reducing the incidence and new minimally invasive strategies are needed. In this study, a systematic evaluation of specific light parameters and aqueous curcumin concentrations for antimicrobial photodynamic therapy (aPDT) was conducted. Aqueous solutions of curcumin were first prepared and evaluated for their light absorbance after applying different ~56 mW/cm2 blue light treatments in a continuous application mode. Next, these same light treatments as well as different application modes were applied to the curcumin solutions and the molar absorptivity coefficient, reactive oxygen species (ROS) release, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) for Streptococcus mutans and the MIC and minimum fungicidal concentration (MFC) for Candida albicans were measured. After up to 1 min of light treatment, the molar absorptivity of curcumin when added to culture media was lower than that for water only; however, at higher energy levels, this difference was not apparent. There was a noted dependence on both ROS type and cariogenic microorganism species on the sensitivity to both blue light treatment and application mode. In conclusion, this study provides new information towards improving the agonistic potential of aPDT associated with curcumin against cariogenic microorganisms.

Does aPDT reduce bacterial load in endodontic infected teeth? A systematic review and meta-analysis

This systematic review investigated whether antimicrobial photodynamic therapy (aPDT) after chemomechanical root canal disinfection (CD) yields a greater microbial load reduction than only CD. An electronic literature search was conducted on four databases up to November 2022, with no language or publication date restrictions. Randomized and non-randomized clinical trials were included if participants had a primary endodontic infection in permanent teeth, and if microbial loads before and after using aPDT were compared. Two researchers independently screened titles and abstracts to determine study eligibility. Assessments included risk of bias and methodological quality. This review was registered in PROSPERO (CRD42020181783). Eight studies were included in the qualitative analysis, and six were eligible for meta-analysis. In the random effects model, aPDT significantly improved the results of root canal disinfection when compared with standard protocols for cleaning and shaping (p = 0.04, 95% CI -1.72, -0.05). Subgroup analysis suggested that aPDT has a better effect on reducing the load of anaerobic microorganisms (p = 0.003, 95% CI -3.36, -0.69). The use of aPDT as an adjunct to chemomechanical disinfection promotes additional reduction of the microbial load and, therefore, seems to improve the results of root canal treatments in permanent teeth with a primary endodontic infection. However, certainty of evidence should be improved.

In Vitro Comparative Evaluation of the Efficacy of Antimicrobial Photodynamic Therapy, Chlorhexidine, Sodium Fluoride, and Hydrogen Peroxide for Acrylic Resin Disinfection

Introduction: Plaque accumulation on the surface of removable orthodontic appliances could lead to dental caries, periodontitis, and fungal infections. This study evaluated the effectiveness of antimicrobial photodynamic therapy (aPDT), chlorhexidine (CHX), sodium fluoride (NaF), and hydrogen peroxide (H2O2) for the disinfection of acrylic resin. Methods: In this in vitro experimental study, 100 acrylic resin specimens were randomly divided into five groups (n=20 each): Enterococcus faecalis, Streptococcus mutans, Streptococcus salivarius, Streptococcus sanguinis, and Lactobacillus acidophilus. Each group was immersed separately in 5 mL of microbial suspension. They were then incubated until biofilm formation on their surface. Of each microorganism, one biofilm sample in phosphate-buffered saline was considered as negative control, and other biofilm samples (n=80) were subjected to aPDT with curcumin, 0.12% CHX (positive control), 1% H2O2, and 0.2% NaF. Finally, the number of colonies was counted. Data were analyzed by the Kruskal-Wallis and Mann-Whitney tests, two-way ANOVA, and Bonferroni adjustment at a significance level of 0.05. Results: The interaction effect of the treatment modality and type of microorganism was significant on the microbial count (effect size: 0.91, P<0.05). Maximum bacterial proliferation was noted in the following combinations: NaF/E. faecalis, H2O2/E. faecalis, and H2O2/S. salivarius. Microorganisms had no or insignificant growth and proliferation in the aPDT and CHX groups. Conclusion: The results supported the optimal antimicrobial efficacy of PDT which was comparable to that of CHX. aPDT showed superior antimicrobial efficacy to NaF and H2O2 for the disinfection of acrylic resin.

Antimicrobial photodynamic therapy in the treatment of oral erythematous candidiasis: a controlled and randomized clinical trial

OBJECTIVE

To analyze the clinical and microbiological efficacy of antimicrobial photodynamic therapy (aPDT) in patients with erythematous candidiasis (EC).

METHODS

This study was a controlled and randomized clinical trial in patients diagnosed with EC, who were allocated into a control group (CG) and experimental group (EG) treated with nystatin oral suspension and aPDT with methylene blue 0.1%, respectively. A clinical index was used to classify the EC lesions from mild to severe and assess the treatment efficacy. Microbiological samples were collected before and after aPDT session and analyzed by counting colony-forming units (CFUs) of Candida and Staphylococcus sp.

RESULTS

A total of 41 patients (CG (n = 18); EG (n = 23)) were analyzed in our research. Of these, 16 (94.1%) of the CG and 16 (84.2%) of the EG exhibited complete remission of the lesions. Regarding the degree of the lesion, it was observed that the severe lesions were more difficult to present remission, while all the mild and moderate lesions showed complete regression (p = 0.001). The microbiological analysis showed that Candida albicans and Staphylococcus sp. were the most prevalent microorganisms, and the aPDT group showed a decrease in CFUs of these microorganisms after the first aPDT session (p < 0.05).

CONCLUSIONS

aPDT proved to be a clinically and microbiologically effective therapy for treating EC.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov; Set 12th, 2019; No. RBR-8w8599.

CLINICAL RELEVANCE

aPDT is a promising alternative treatment since it presents satisfactory results and does not cause damage to oral tissues or develop resistance to the treatment.

Antimicrobial photodynamic therapy for the treatment of oral infections: A systematic review

Oral infection is a common clinical symptom. While antibiotics are widely employed as the primary treatment for oral diseases, the emergence of drug-resistant bacteria has necessitated the exploration of alternative therapeutic approaches. One such modality is antimicrobial photodynamic therapy (aPDT), which utilizes light and photosensitizers. Indeed, aPDT has been used alone or in combination with other treatment options dealing with periodontal disease for the elimination of biofilms from bacterial community to achieve bone formation and/or tissue regeneration. In this review article, in addition to factors affecting the efficacy of aPDT, various photosensitizers, the latest technology and perspectives on aPDT are discussed in detail. More importantly, the article emphasizes the novel design and clinical applications of photosensitizers, as well as the synergistic effects of chemical and biomolecules with aPDT to achieve the complete eradication of biofilms and even enhance the biological performance of tissues surrounding the treated oral area.

Blue Light-Emitting Diode Irradiation Without a Photosensitizer Alters Oral Microbiome Composition of Ligature-Induced Periodontitis in Mice

Objective: This study investigated the suppressive effects of blue light-emitting diode (LED) irradiation on bone resorption and changes in the oral microbiome of mice with ligature-induced periodontitis. Background: Wavelength of blue light has antimicrobial effects; however, whether blue LED irradiation alone inhibits the progression of periodontitis remains unclear. Methods: Nine-week-old male mice ligated ligature around the right maxillary second molar was divided into ligation alone (Li) and ligation with blue LED irradiation (LiBL) groups. The LiBL group underwent blue LED (wavelength, 455 nm) irradiation four times in a week at 150 mW/cm2 without a photosensitizer on the gingival tissue around the ligated tooth at a distance of 5 mm for 5 min. The total energy density per day was 45 J/cm2. Bone resorption was evaluated using micro-computed tomography at 8 days. Differences in the oral microbiome composition of the collected ligatures between the Li and LiBL groups were analyzed using next-generation sequencing based on the 16S rRNA gene from the ligatures. Results: Blue LED irradiation did not suppress bone resorption caused by ligature-induced periodontitis. However, in the LiBL group, the α-diversity, number of observed features, and Chao1 were significantly decreased. The relative abundances in phylum Myxococcota and Bacteroidota were underrepresented, and the genera Staphylococcus, Lactococcus, and Lactobacillus were significantly overrepresented by blue LED exposure. Metagenomic function prediction indicated an increase in the downregulated pathways related to microbial energy metabolism after irradiation. The co-occurrence network was altered to a simpler structure in the LiBL group, and the number of core genera decreased. Conclusions: Blue LED irradiation altered the composition and network of the oral microbiome of ligature-induced periodontitis in mice.

Antimicrobial Resistance: Is There a 'Light' at the End of the Tunnel?

In recent years, with the increases in microorganisms that express a multitude of antimicrobial resistance (AMR) mechanisms, the threat of antimicrobial resistance in the global population has reached critical levels. The introduction of the COVID-19 pandemic has further contributed to the influx of infections caused by multidrug-resistant organisms (MDROs), which has placed significant pressure on healthcare systems. For over a century, the potential for light-based approaches targeted at combatting both cancer and infectious diseases has been proposed. They offer effective killing of microbial pathogens, regardless of AMR status, and have not typically been associated with high propensities of resistance development. To that end, the goal of this review is to describe the different mechanisms that drive AMR, including intrinsic, phenotypic, and acquired resistance mechanisms. Additionally, the different light-based approaches, including antimicrobial photodynamic therapy (aPDT), antimicrobial blue light (aBL), and ultraviolet (UV) light, will be discussed as potential alternatives or adjunct therapies with conventional antimicrobials. Lastly, we will evaluate the feasibility and requirements associated with integration of light-based approaches into the clinical pipeline.

Do Antimicrobial Photodynamic Therapy and Low-Level Laser Therapy Influence Oral Health-Related Quality of Life After Molar Extraction?

PURPOSE

Most individuals experience significant deterioration in their oral health-related quality of life (OHRQoL) in the first few days after tooth extraction. This study aimed to evaluate the impact of antimicrobial photodynamic therapy (aPDT) and low-level laser therapy (LLLT) protocols on OHRQoL after extraction of lower molars.

METHODS

The investigators designed a double-blind, randomized controlled clinical trial study. Patients with indications for lower molar extraction were included in the study and randomized into four groups: control group, antimicrobial photodynamic therapy group, LLLT group (LLLT.G), and aPDT and LLLT group (aPDT + LLLT.G).The Oral Health Impact Profile (OHIP-14) questionnaire was used through an interview with the participants before the extraction (T0 - baseline) and on the 7th (T1) and 30th (T2) days after extraction. Other variables were age, sex, ethnicity, decayed-missing-filled teeth (DMFT) and tooth types. Appropriate univariate and bivariate statistics were computed, and statistical significance was set at a value P < .05.

RESULTS

The sample was composed of 40 patients with a mean age of 41.25 ± 13.97 and 25 (62.5%) were women. The mean OHIP-14 scores were significantly different in the intervals at T0 versus T1 and T0 versus T2 for all domains (P < .001), demonstrating a positive impact on the OHRQoL. The total scores indicated a significant improvement in the OHRQoL in the aPDT (7.10, standard deviation 4.18, P = .043), LLLT (6.40, SD 5.87, P = .025), and aPDT + LLLT (5.30, SD 3.59, P = .012) groups compared to that in the control group (12.90, SD 6.64) at T1. Patients undergoing extraction of lower mandibular molars with aPDT + LLLT had the lowest mean OHIP-14 total score at T1 (5.30) and T2 (0.70).

CONCLUSION

The aPDT and LLLT protocols had a positive impact on the participants' OHRQoL. These procedures can be applied in everyday surgical practice.

Lysosome-Targeting Aggregation-Induced Emission Nanoparticle Enables Adoptive Macrophage Transfer-Based Precise Therapy of Bacterial Infections

Traditional antibacterial procedures are getting inefficient due to the emergence of antimicrobial resistance, which makes alternative treatments in urgent demand. However, the selectivity toward infectious bacteria is still challenging. Herein, by taking advantage of the self-directed capture of infectious bacteria by macrophages, we developed a strategy to realize precise in vivo antibacterial photodynamic therapy (APDT) through adoptive photosensitizer-loaded macrophage transfer. TTD with strong reactive oxygen species (ROS) production and bright fluorescence was first synthesized and was subsequently formulated into TTD nanoparticles for lysosome targeting. TTD-loaded macrophages (TLMs) were constructed by direct incubation of TTD nanoparticles with macrophages, in which the TTD was localized in the lysosomes to meet the captured bacteria in the phagolysosomes. The TLMs could precisely capture and eradicate bacteria while being activated toward the proinflammatory and antibacterial M1 phenotype upon light illumination. More importantly, after subcutaneous injection, TLMs could effectively inhibit bacteria in the infected tissue through APDT, leading to good tissue recovery from severe bacterial infection. Overall, the engineered cell-based therapeutic approach shows great potential in the treatment of severe bacterial infectious diseases.

Efficacy of adjunct photodynamic therapy on Candida growth and oral health quality of life in denture stomatitis patients with type 2 diabetes mellitus wearing implant-retained overdentures: a randomized clinical study

AIM

The aim of the present clinical trial was to study the efficacy of combined miconazole and PDT in the improvement of quality of life and levels of Candida species in chronic hyperglycemic patients with denture stomatitis (DS).

METHODS

One hundred patients were randomly divided into five groups; 20 each in the miconazole, PDT, miconazole+ PDT, CHX and distilled water groups. Methylene blue mediated irradiation was conducted using 600nm diode laser with power, energy density and radiance as 100 mW, 3527 mW/cm2 and 9 J, respectively. Patients were advised to apply 2.5 ml of 2% topical miconazole four times a day. The existence of Candida spp. was detected by means of microbiological culture technique. Candida colony counts from the palates and dentures surfaces, quantified as colony forming unit (CFU)/mL were evaluated at baseline, end of 14 days, 28 days and 60 days. Oral health related quality of life was assessed with the help of a questionnaire.

RESULTS

The quality of life showed significant improvement in the group where combination treatment was executed. The overall CFU/mL values were greater in the dentures in comparison to those from the palates of the patients of all the five groups. During all time periods of the study, the CFU/mL values obtained from combination treatment group showed significant differences. Candida albicans was the most predominant yeast.

CONCLUSION

This study showed the effectiveness of methylene blue- PDT in combination with miconazole in improving oral health related quality of life and significantly reducing Candida CFU counts to resolve palatal inflammation in diabetic individuals with implant-supported complete dentures.

Coping with the ESKAPE pathogens: Evolving strategies, challenges and future prospects

Globally, the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are the major cause of nosocomial infections. These pathogens are multidrug resistant, and their negative impacts have brought serious health challenges and economic burden on many countries worldwide. Thus, this narrative review exploits different emerging alternative therapeutic strategies including combination antibiotics, antimicrobial peptides ((AMPs), bacteriophage and photodynamic therapies used in the treatment of the ESKAPE pathogens, their merits, limitations, and future prospects. Our findings indicate that ESKAPE pathogens exhibit resistance to drug using different mechanisms including drug inactivation by irreversible enzyme cleavage, drug-binding site alteration, diminution in permeability of drug or drug efflux increment to reduce accumulation of drug as well as biofilms production. However, the scientific community has shown significant interest in using these novel strategies with numerous benefits although they have some limitations including but not limited to instability and toxicity of the therapeutic agents, or the host developing immune response against the therapeutic agents. Thus, comprehension of resistance mechanisms of these pathogens is necessary to further develop or modify these approaches in order to overcome these health challenges including the barriers of bacterial resistance.

An Explorative Review on Advanced Approaches to Overcome Bacterial Resistance by Curbing Bacterial Biofilm Formation

The continuous emergence of multidrug-resistant pathogens evoked the development of innovative approaches targeting virulence factors unique to their pathogenic cascade. These approaches aimed to explore anti-virulence or anti-infective therapies. There are evident concerns regarding the bacterial ability to create a superstructure, the biofilm. Biofilm formation is a crucial virulence factor causing difficult-to-treat, localized, and systemic infections. The microenvironments of bacterial biofilm reduce the efficacy of antibiotics and evade the host's immunity. Producing a biofilm is not limited to a specific group of bacteria; however, Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus biofilms are exemplary models. This review discusses biofilm formation as a virulence factor and the link to antimicrobial resistance. In addition, it explores insights into innovative multi-targeted approaches and their physiological mechanisms to combat biofilms, including natural compounds, phages, antimicrobial photodynamic therapy (aPDT), CRISPR-Cas gene editing, and nano-mediated techniques.

Methylene Blue/Carbon Dots Composite with Photothermal and Photodynamic Properties: Synthesis, Characterization, and Antibacterial Application

Photodynamic therapy and photothermal therapy provide new ways to combat antibiotic resistance. In this research, methylene blue (MB) as an effective photosensitizer was conjugated with carbon quantum dots (CQDs), the composite product not only possessed good antibacterial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) due to excellent singlet oxygen (¹ O₂ ) production rate and light heat transfer performance, but also showed good biocompatibility. Combined with 808 nm and 660 nm laser irradiation, the minimum bactericidal concentration of CQDs-MB towards S. aureus and E. coli was 5 μm. Therefore, this study provides a potential candidate material based on CQDs for clinical applications.

Phototherapies for erythema multiforme secondary to viral infections: A case report of a child

INTRODUCTION

Erythema multiforme (EM) is a reactive mucocutaneous disorder typically initiated by viral infections. Although the management of EM differs according to the clinical course and trigger factor, it is not clear whether antiviral suppressive therapies may be useful in cases related to such infections. Moreover, the treatment is most often based on supportive care directed towards only the symptoms.

AIM

To present a clinical case of a child in which antimicrobial photodynamic therapy (aPDT) and photobiomodulation therapy (PBMT) were used for orofacial manifestations of EM secondary to viral infections.

CASE REPORT

A Brazilian 1-year-old boy was admitted to an ICU due to a severe Influenza A H3N2 infection, pneumonia with pleural effusion, and sepsis. About 10 days later, it was noted bleeding lip lesions covered by crusts and bleeding tongue lesions, diagnosed as EM secondary to both H3N2 and herpes simplex virus infections, confirmed by serology tests. A combination of an aPDT session and six PBMT sessions was proposed and resulted in almost complete resolution of the lesion on the 7th day.

CONCLUSION

Given the complexity of the present case, the combination of phototherapies seems to be a promising tool for treating acute orofacial mucosal lesions of viruses-induced EM. More studies, however, are needed to reach a definite conclusion.

Mechanical and antibacterial efficacy of photo-sonodynamic therapy via methylene blue-loaded nanoparticles over dental implants for treating peri-implantitis

AIM

This study aimed to evaluate the mechanical (i.e., flexural modulus [FM], flexural strength [FS], and surface roughness [R_a]) and antibacterial efficacy of photo-sonodynamic therapy via methylene blue-loaded poly(D,L-lactide-co-glycolide) nanoparticles (MB-loaded PLGA NPs) over dental implants for potential treatment of peri-implantitis.

METHODS

PLGA NPs were synthesized via a solvent displacement method. After the synthesis and confirmation of MB-loaded PLGA NPs via physical (Scanning Electron Microscope [SEM]) and chemical characterization (Fourier transform infrared spectroscopy [FTIR]), the mature dental biofilm of Porphyromonas gingivalis was produced over the surfaces of dental implants. Then, the bacterial viability assessment of the following five study groups was performed: group-I (diode laser treatment); group-II (PDT/MB-loaded PLGA NPs treatment; group-III (ultrasound treatment); group-IV (ultrasound/PLGA NPs-MB treatment); and group-V: control group included the samples without any treatment. Finally, the FS, FM, and R_a of the samples was assessed.

RESULTS

Under the SEM, the NPs were spherical homogeneous particles having round morphology ranging approximately 100 nm in size without aggregation. The FTIR spectra of PLGA NPs and MB-loaded PLGA NPs demonstrated absorption peaks at approximately 1000 cm^-1 to 1200 cm^-1 and around 1500 cm^-1 to 1750 cm^-1. The greatest level of P. gingivalis killing was exhibited by ultrasound/MB-loaded PLGA-NPs-treated samples. The FS was statistically significantly greater for control group samples than any other group (i.e., 100.28 MPa; p<0.05). The FM and R_a ranged between 3.31 and 3.58 GPa and between 0.18 and 0.20 µm without any statistically significant difference between the control and experimental groups (p>0.05), respectively.

CONCLUSION

Within the limitations of this study, the application of photo-sonodynamic therapy via MB-loaded PLGA NPs demonstrated the greatest antibacterial activity against P. gingivalis without deteriorating the surfaces and compromising the mechanical properties of dental implants.

Antimicrobial photodynamic therapy as an adjunctive treatment to ultrasound for the dentin caries-like lesion removal

OBJECTIVE

To evaluate in vitro the efficacy of ultrasound device to remove caries-like dentin and the curcumin-mediated antimicrobial photodynamic therapy (aPDT) to decontaminate the affected dentin.

METHODS

Bovine dentin specimens (n = 173) of 4 × 4 × 2 mm were first submitted to Knoop surface microhardness to standardize the specimens (29 ± 3 KHN). Artificial caries lesion was induced by Streptococcus mutans strain by biological model for 7 days. Infected dentin was removed (1 min) with the following techniques: dentin excavator, bur at low-speed rotation and ultrasound device. After that, aPDT application was performed using blue LED under 460 nm. Polarized light microscopy (PLM), removal rate (n = 10), cross-sectional microhardness (n = 10), colony forming units per milliliter (CFU) (n = 9) and confocal laser microscopy (CM) (n = 2) were performed. ANOVA with Welch correction, post-hoc Games-Howell and two-way ANOVA followed by Tukey's post-hoc tests were used.

RESULTS

PLM confirmed the caries lesion formation with a depth of ∼147.9 µm. Groups treated with ultrasound showed lower removal rate (p = 0.001). Regardless of the treatment, the microhardness values increased as function of depth (p ≤ 0.05). Carbide bur showed the highest microhardness value, followed by ultrasound and excavator. CFU and CM showed a significant reduction in S. mutans after aPDT application.

CONCLUSION

Ultrasound was efficient, since it removed infected dentin, preserving the affected dentin and aPDT can be used as a complementary therapy to decontaminate the affected dentin.

CLINICAL SIGNIFICANCE

Ultrasound device may help the clinician to remove dentin caries-like lesions since it is a conservative technique and provided the removal of infected dentin, preserving the affected dentin. aPDT application may be used as a complimentary technique to promote antibacterial effect and possibly minimize the risk of secondary caries.

Effectiveness of antimicrobial photodynamic therapy mediated by butyl toluidine blue in preventing medication-related osteonecrosis of the jaws in rats

BACKGROUND

Medication-related osteonecrosis of the jaws (MRONJ) is difficult to treat, therefore, prevention would be the ideal clinical approach. This study evaluated the effectiveness of antimicrobial photodynamic therapy (aPDT), mediated by butyl toluidine blue (BuTB) in the prevention of MRONJ-like lesions after tooth extraction in rats.

METHODS

Twenty-eight senescent female rats were distributed in groups: VEH and VEH-aPDT, treated with vehicle, ZOL and ZOL-aPDT, treated with 100 µg/Kg of zoledronate, both treatments every three days over seven weeks. After three weeks from the commencement of treatment, the mandibular first molar was extracted. For the VEH and ZOL groups, no local treatment was performed, while with the VEH-aPDT and ZOL-aPDT groups, photodynamic treatment was carried out at 0, 2, and 4 days after extraction. For aPDT, 500μl of BuTB solution was deposited on the dental extraction site (0.5 mg/ml; 60 s), followed by irradiation with low-level laser (InGaAIP; 660 nm; 35 mW; 74.2 J/cm²; 60 s). After 28 postoperative days, euthanasia was performed. The hemimandibles were processed to: (1) histological analysis of tissue repair; (2) histometric analysis of the percentage of newly formed bone tissue (PNFBT) and percentage of non-vital bone tissue (PNVBT); (3) immunohistochemical analysis for tartrate-resistant acid phosphatase (TRAP).

RESULTS

The ZOL and ZOL-aPDT groups showed less TRAP-positive cells when compared with VEH and VEH-aPDT. The ZOL group demonstrated great compromise in the tissue repair process, consistent with MRONJ-like lesions. VEH, VEH-aPDT and ZOL-aPDT presented a favorable tissue repair process. PNFBT in the ZOL group was lower than in the VEH, VEH-aPDT and ZOL-aPDT groups, whereas PNVBT in the ZOL group was higher than in the VEH, VEH-aPDT and ZOL-aPDT groups.

CONCLUSION

aPDT mediated by BuTB prevented the occurrence of MRONJ-like lesions after tooth extraction in rats.

State-of-the-Art on the Sulfate Radical-Advanced Oxidation Coupled with Nanomaterials: Biological and Environmental Applications

Sulfate radicals (SO₄^-·) play important biological roles in biomedical and environmental engineering, such as antimicrobial, antitumor, and disinfection. Compared with other common free radicals, it has the advantages of a longer half-life and higher oxidation potential, which could bring unexpected effects. These properties have prompted researchers to make great contributions to biology and environmental engineering by exploiting their properties. Peroxymonosulfate (PMS) and peroxydisulfate (PDS) are the main raw materials for SO₄^-· formation. Due to the remarkable progress in nanotechnology, a large number of nanomaterials have been explored that can efficiently activate PMS/PDS, which have been used to generate SO₄^-· for biological applications. Based on the superior properties and application potential of SO₄^-·, it is of great significance to review its chemical mechanism, biological effect, and application field. Therefore, in this review, we summarize the latest design of nanomaterials that can effectually activate PMS/PDS to create SO₄^-·, including metal-based nanomaterials, metal-free nanomaterials, and nanocomposites. Furthermore, we discuss the underlying mechanism of the activation of PMS/PDS using these nanomaterials and the application of SO₄^-· in the fields of environmental remediation and biomedicine, liberating the application potential of SO₄^-·. Finally, this review provides the existing problems and prospects of nanomaterials being used to generate SO₄^-· in the future, providing new ideas and possibilities for the development of biomedicine and environmental remediation.

Investigation of bactericidal effect of a mid-infrared free electron laser on Escherichia coli

The rapid increase in the number of bacteria that are resistant to many commonly used antimicrobial agents and their global spread have become a major problem worldwide. In particular, for periodontal disease, which is a localized infection, there is a growing need for treatment methods that do not primarily involve antimicrobial agents, and antimicrobial photodynamic therapy (aPDT) is attracting attention. In this study, the bactericidal effects of a mid-infrared free electron laser (MIR-FEL) on E. coli were investigated as a basic study to examine the applicability of MIR-FELs, which can selectively excite molecular vibrations due to their wavelength tunability, to aPDT. The optimal irradiation wavelengths to be examined in this study were determined from the infrared spectrum of the bacteria, which was obtained using Fourier transform infrared spectroscopy. Five irradiation wavelengths (6.62, 6.88, 7.14, 8.09 and 9.26 µm) were selected from the FT-IR spectrum, and we found that the bactericidal effects at a wavelength of 6.62 µm were markedly stronger than those observed at the other wavelengths. At this wavelength corresponding to the Amide II band, the bacterial survival rate decreased significantly as the irradiation time increased. On the contrary, irradiation of a neodymium-doped yttrium aluminum garnet (Nd: YAG) laser at 1.06 µm exhibited no distinct bactericidal effect. No morphological changes were observed after MIR-FEL irradiation, suggesting that a bacterial organelle molecule may be the target of MIR-FEL irradiation, but the exact target was not identified. Furthermore, the temperature change induced in the culture medium by the laser irradiation was ± 1.5 °C at room temperature. These results suggest that the bactericidal effects of MIR-FEL are derived from photochemical reactions involving infrared photons, since E. coli is usually killed by heating it to 75 °C for 1 min or longer.

Enzymatic Dispersion of Biofilms: An Emerging Biocatalytic Avenue to Combat Biofilm-Mediated Microbial Infections

Drug resistance by pathogenic microbes has emerged as a matter of great concern to mankind. Microorganisms such as bacteria and fungi employ multiple defense mechanisms against drugs and the host immune system. A major line of microbial defense is the biofilm, which comprises extracellular polymeric substances that are produced by the population of microorganisms. Around 80% of chronic bacterial infections are associated with biofilms. The presence of biofilms can increase the necessity of doses of certain antibiotics up to 1000-fold to combat infection. Thus, there is an urgent need for strategies to eradicate biofilms. Although a few physicochemical methods have been developed to prevent and treat biofilms, these methods have poor efficacy and biocompatibility. In this review, we discuss the existing strategies to combat biofilms and their challenges. Subsequently, we spotlight the potential of enzymes, in particular, polysaccharide degrading enzymes, for biofilm dispersion, which might lead to facile antimicrobial treatment of biofilm-associated infections.

Comparison Between Two Antimicrobial Photodynamic Therapy Protocols for Oral Candidiasis in Patients Undergoing Treatment for Head and Neck Cancer: A two-arm, single-blind clinical trial

PURPOSE

This study aimed to compare the efficacy of Antimicrobial Photodynamic Therapy (aPDT) with 300 µmol/L of methylene blue and 8 µmol/L of curcumin on oral candidiasis patients with HNSCC undergoing treatment.

METHODS

A two-arm, single-blind clinical trial was performed. Following verification for eligibility (n = 447), 108 patients were included in the study. The study consisted of a group that received aPDT with methylene blue (n = 57) and another that received aPDT with curcumin (n = 51). The patients rinsed their mouths with an aqueous solution of 300 µmol/L of methylene blue and 8 µmol/L of curcumin in four sessions, and then the lesion was scraped for the subsequent RT-qPCR. The primary outcome was that no cure was presented for oral candidiasis after treatment. The secondary result was reducing the number of sites affected by oral candidiasis.

RESULTS

There was no difference in treatment failure evaluated by the necessity of drug prescription or Candida sp DNA quantification. However, clinically the methylene blue protocol reduced the number of infected anatomical sites compared to the curcumin protocol.

CONCLUSION

Methylene Blue aPDT reduced the number of infected anatomical sites compared to curcumin.

Photodynamic therapy and combinatory treatments for the control of biofilm-associated infections

The advent of antimicrobial resistance has added considerable impact to infectious diseases both in the number of infections and healthcare costs. Furthermore, the relentless emergence of multidrug-resistant bacteria, particularly in the biofilm state, has made mandatory the discovery of new alternative antimicrobial therapies that are capable to eradicate resistant bacteria and impair the development of new forms of resistance. Amongst the therapeutic strategies for treating biofilms, antimicrobial photodynamic therapy (aPDT) has shown great potential in inactivating several clinically relevant micro-organisms, including antibiotic-resistant 'priority bacteria' declared by the WHO as critical pathogens. Its antimicrobial effect is centred on the basis that harmless low-intensity light stimulates a non-toxic dye named photosensitizer, triggering the production of reactive oxygen species upon photostimulation. In addition, combination therapies of aPDT with other antimicrobial agents (e.g. antibiotics) have also drawn considerable attention, as it is a multi-target strategy. Therefore, the present review highlights the recent advances of aPDT against biofilms, also covering progress on combination therapy.

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.

Photobiomodulation (PBMT) and antimicrobial photodynamic therapy (aPDT) in oral manifestations of patients infected by Sars-CoV-2: systematic review and meta-analysis

BACKGROUND

In 2019, a viral and respiratory pathology called COVID-19 emerged in Wuhan, China, and spread to other continents. Its main symptoms include fever, cough, dyspnea, myalgia, anorexia and respiratory distress in the most severe cases, which can lead to death. Furthermore, manifestations in the oral cavity such as ageusia and dysgeusia, as well as lesions in other regions of the oral cavity, can be observed.

MAIN BODY

This systematic review and meta-analysis aimed to critically assess the clinical evidence on the use of photobiomodulation (PBMT) and antimicrobial photodynamic therapy (aPDT) for the treatment of oral lesions in patients infected with Sars-Cov-2. The literature extracted from electronic databases such as PubMed, Medline, CINAHL, and Google Scholar was screened for eligibility, and relevant articles were included. The review is limited to manuscripts published in English, Spanish and Portuguese language between December 2019 and October 2021. A total of 5 articles with 11 cases retracting PBMT and aPDT as therapeutic strategies for the regression of oral lesions and painful symptoms. The results show favoring the associated use of PBMT with aPDT (P = 0.004), and the isolated use of PBMT with the result of significant "P = 0.005" and good confidence interval (7.18, 39.20) in ulcerative lesions, herpetic, aphthous, erythematous, petechiae and necrotic areas.

CONCLUSIONS

PBMT and aPDT could be effective in the treatment of oral lesions of patients infected with Sars-Cov-2 in a short period of time; however, more long-term randomized clinical trials studies are needed to define the therapeutic strategy.

Antimicrobial Behavior and Cytotoxicity of Indocyanine Green in Combination with Visible Light and Water-Filtered Infrared A Radiation against Periodontal Bacteria and Subgingival Biofilm

The widespread increase of antibiotic resistance highlights the need for alternative treatments such as antimicrobial photodynamic therapy (aPDT). This study aimed to evaluate the antimicrobial behavior and cytotoxicity of aPDT with indocyanine green (ICG) in combination with visible light (Vis) and water-filtered infrared A (wIRA). Representative periodontal bacteria (Parvimonas micra, Atopobium riame, Slackia exigua, Actinomyces naeslundii, Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Prevotella nigrescens) and subgingival in situ biofilms from periodontal patients were treated with aPDT for 5 min. ICG was used at different concentrations (50–500 µg/mL) and the number of viable cells was determined in colony forming units (CFU). Untreated negative controls and 0.2% chlorhexidine as a positive control were also prepared. The cytotoxicity test on human keratinocytes in vitro was analyzed with the AlamarBlue assay after 5, 10, and 20 min, with four ICG concentrations, and at two temperatures (room temperature and 37 °C). The tested periodontal pathogens treated with aPDT were eliminated in a range between 1.2 and 6.7 log₁₀ CFU, except for A. naeslundii, which was killed at a lower range. The subgingival biofilm treated with aPDT expressed significant differences to the untreated controls except for at 300 µg/mL ICG concentration. The cytotoxicity was directly related to the concentration of ICG and irradiation time. These observations raise questions concerning the use of this specific aPDT as an adjuvant to periodontal treatments due to its possible toxicity towards human gingival cells.

Synergistic Effect of Combination of a Temoporfin-Based Photodynamic Therapy with Potassium Iodide or Antibacterial Agents on Oral Disease Pathogens In Vitro

5, 10, 15, 20-Tetrakis(3-hydroxyphenyl)chlorin (temoporfin) is a photosensitizer used in photodynamic therapy for oral cancer and periodontal disease treatment. This study determined the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of temoporfin. Additionally, the combination of potassium iodide (KI) or antimicrobial agents in oral pathogens under hypoxic or normoxic conditions were determined. We also evaluated the biofilm removal effect and detected the expressions of the antibiotic resistance-related genes and biofilm formation-related genes of methicillin-resistant staphylococcus aureus (MRSA). The results provided reveal that the combination of the temoporfin and KI had a synergistic effect of reducing the MICs and MBCs of Lactobacillus acidophilus and Lactobacillus paracasei under normoxic and hypoxic conditions due to increasing H₂O₂ production. Temoporfin increased the biofilm removal of Aggregatibacter actinomycetemcomitans, Enterococcus faecalis, and Staphylococcus aureus under normoxic condition, and it reduced the antibiotic resistance-related genes expression of MRSA. The combination of temoporfin with ampicillin or chlorhexidine significantly enhanced the bactericidal effect on MRSA. This study provides a potential application of temoporfin on the clinical side against oral pathogens and the prevention of oral diseases.

Recent advances in nanoparticle-based targeting tactics for antibacterial photodynamic therapy

Abstract

The rise of antibacterial drug resistance means treatment options are becoming increasingly limited. We must find ways to tackle these hard-to-treat drug-resistant and biofilm infections. With the lack of new antibacterial drugs (such as antibiotics) reaching the clinics, research has switched focus to exploring alternative strategies. One such strategy is antibacterial photodynamic therapy (aPDT), a system that relies on light, oxygen, and a non-toxic dye (photosensitiser) to generate cytotoxic reactive oxygen species. This technique has already been shown capable of handling both drug-resistant and biofilm infections but has limited clinical approval to date, which is in part due to the low bioavailability and selectivity of hydrophobic photosensitisers. Nanotechnology-based techniques have the potential to address the limitations of current aPDT, as already well-documented in anti-cancer PDT. Here, we review recent advances in nanoparticle-based targeting tactics for aPDT.

Graphical Abstract

Comparing deep eutectic solvents and cyclodextrin complexes as curcumin vehicles for blue-light antimicrobial photodynamic therapy approaches

Curcumin (Cur), a polyphenolic compound derived from Curcuma longa L., has garnered the attention of the scientific community due to its remarkable biological properties such as its potential as a photosensitizing agent for photodynamic therapy (PDT). However, due to its low solubility in aqueous media and instability at physiological and alkaline pH, Cur has struggled to find relevant clinical application. To tackle these shortcomings, two distinct Cur-based formulations based on either complexation with methyl-β-cyclodextrin (MβCD), MβCDC-Cur, or dissolution in a choline chloride (ChCl): glycerol (Gly) deep eutectic solvent (DES), DES-Cur, were produced, physio-chemically characterized and compared regarding their potential as phototherapeutic agents for blue-light antimicrobial photodynamic therapy (aPDT) approaches. Both MβCD-Cur and DES-Cur were able to greatly enhance Cur solubility profile when compared to Cur powder. However, MβCD-Cur appears to hinder some of Cur's basal biological properties and possessed greater basal cytotoxicity towards L929 murine fibroblast cell line. Furthermore, MβCD-Cur was less photo-responsive when exposed to light which may hamper its application in blue-light aPDT approaches. In contrast, DES-Cur showed good biological properties and high photoresponsivity, displaying relevant phototoxicity against bacterial pathogens (≥ 99.9% bacterial reduction) while being better tolerated by L929 murine cells. Overall, this study found DES to be the more effective vehicle for Cur in terms of phototherapeutic potential which will serve as basis to develop novel platforms and approaches for blue-light aPDT targeting localized superficial infections.

Photodynamic Therapy Using 5-Aminolevulinic Acid (Ala) for the Treatment of Chronic Periodontitis: A Prospective Case Series

Aim: The objective of this study was to compare the efficacy of supportive periodontal therapy (i.e., scaling and root planning, SRP) alone versus ALADENT medical device used in association with SRP in the treatment of chronic periodontitis in adult patients. Materials and Methods: A total of 20 patients with a diagnosis of chronic periodontitis (40 localized chronic periodontitis sites) aged between 35 and 55 were selected. None of these patients previously received any surgical or non-surgical periodontal therapy, and they presented radiographic evidence of moderate bone loss. Two non-adjacent sites in different quadrants were identified and observed in each patient, analyzing treatment effectiveness (split-mouth design). Clinical pocket depth, clinical attachment loss, and bleeding on probing were evaluated at time 0 and after 6 months, while microbial analysis (MA) was conducted at baseline and after 15 days. Significant differences were calculated using SPSS program and paired simple statistic t-test. Results: Total bacteria loadings had a statistically significant reduction before and after treatment with SRP (left site) (total average decrease of 27%). The sites treated with SRP plus ALADENT (right) showed a significantly reduced total bacterial loading compared to the untreated sites (right) (total average decrease of 75%). Mean values of CAL/PD and percentages data of BOP, recorded after SRP + ALADENT therapy, showed a higher reduction (CAL = 2.42, PD = 2.87 mm, 90% of sites with no bleeding) than those obtained after SRP treatment (CAL = 4.08 mm, PD = 4.73 mm, 70% of sites with no bleeding). Conclusion: The treatment of moderate and severe chronic periodontitis should include, beside SRP, the use of ALADENT medical device, which has been proved to be a useful adjuvant therapy.

Theranostic nanoplatforms of emodin-chitosan with blue laser light on enhancing the anti-biofilm activity of photodynamic therapy against Streptococcus mutans biofilms on the enamel surface

Background

Combining photosensitizer and light irradiation, named antimicrobial photodynamic therapy (aPDT) is an adjuvant therapy for eliminating microbial biofilms. This ex vivo study evaluates the effect of anti-biofilm activity of aPDT based on emodin-chitosan nanoparticles (Emo-CS-NPs) plus blue laser light against Streptococcus mutans biofilm on the enamel surface.

Materials

After determination of the fractional inhibitory concentration index of Emo and CS by checkerboard array assay, Emo-CS-NPs were synthesized and characterized. Following treatment of pre-formed S. mutans biofilms on the enamel slabs, cellular uptake of Emo-CS-NPs and intracellular reactive oxygen species (ROS) production were determined. The anti-biofilm and anti-metabolic activities of aPDT were investigated. Eventually, lactic acid production capacity, concentrations of S. mutans extracellular DNA (eDNA) levels, and expression of the gene involved in the biofilm formation (gtfB) were evaluated.

Results

The maximum uptake of Emo-CS-NPs occurs in an incubation time of 5 min. When irradiated, Emo-CS-NPs were photoactivated, generating ROS, and led to a decrease in the cell viability and metabolic activity of S. mutans significantly (P < 0.05). S. mutans eDNA and lactic acid production outcomes indicated that Emo-CS-NPs-mediated aPDT led to a significant reduction of eDNA levels (48%) and lactic acid production (72.4%) compared to the control group (P < 0.05). In addition, gtfB mRNA expression in S. mutans was downregulated (7.8-fold) after aPDT in comparison with the control group (P < 0.05).

Conclusions

Our data support that, aPDT using Emo-CS-NPs revealed the highest cellular uptake and ROS generation. Emo-CS-NPs based aPDT could inhibit significantly biofilm formation and reduce effectively virulence potency of S. mutans; thus, it could be an adjuvant therapy against dental caries.

Evaluation of antimicrobial photodynamic therapy with acidic methylene blue for the treatment of experimental periodontitis

OBJECTIVE

To investigate the security and effectiveness of antimicrobial photodynamic therapy (aPDT) with a citric acid-based methylene blue (MB) on the periodontal repair following the treatment of ligature-induced experimental periodontitis (EP) in rats.

MATERIAL AND METHODS

Were used 120 male rats, randomly divided into 4 experimental groups (n = 30): no treatment (NT), SRP alone (SRP), SRP plus aPDT using conventional MB pH 7.0 (aPDT-pH7), SRP plus aPDT using acidic MB pH 1.0 (aPDT-pH1). EP was induced at day 0 by the placement of a ligature around the mandibular left first molars. Ten animals per group/period were euthanized at 14, 22 and 37 days. Histopathological, histometric (percentage of bone in the furcation [PBF]) and immunohistochemical (for tartrate-resistant acid phosphatase [TRAP] and osteocalcin [OCN]) analyses were performed. Data were statistically analyzed.

RESULTS

aPDT-pH1 showed the highest PBF as compared with the other treatments. Collectively, tissues' reaction to both dyes were controlled and healthy for the periodontium. Both aPDT protocols reduced the extent and intensity of the local inflammatory response, reduced the alveolar bone resorption, and promoted a better structural arrangement of the connective tissue as compared with SRP. TRAP expression was downregulated while OCN expression was upregulated by aPDT as compared with SRP alone.

CONCLUSION

Our data implicate that the novel MB pH 1.0 is as safe as the conventional MB for use in aPDT and raises its additional benefit of increasing the amount of alveolar bone in the furcation.

Inhibitory effect of 405-nm blue LED light on the growth of Candida albicans and Streptococcus mutans dual-species biofilms on denture base resin

We investigated whether irradiation with 405-nm blue LED light could inhibit the growth of not only single- but dual-species biofilms formed by Candida albicans and Streptococcus mutans on denture base resin and cause the alteration in gene expression related to adhesion and biofilm formation. C. albicans and S. mutans single-/dual-species biofilms were formed on the denture base specimens. The biofilms were irradiated with 405-nm blue LED light (power density output: 280 mW/cm²) for 0 (control) and 40 min. Dual-species biofilms were analyzed using CFU assay and fluorescence microscopy, and single-/dual-species biofilms were analyzed using alamarBlue assays and gene expression analysis. To assess the inhibitory effect of irradiation on dual-species biofilms, specimens after irradiation were aerobically incubated for 12 h. After incubation, the inhibition of growth was assessed using CFU assays and fluorescence microscopy. Data were analyzed using the Mann-Whitney U or Student's t test (p < 0.05). Irradiation produced a significant inhibitory effect on biofilms. Fluorescence microscopy revealed that almost all C. albicans and S. mutans cells were killed by irradiation, and there was no notable difference in biofilm thickness immediately after irradiation and after irradiation and incubation for 12 h. alamarBlue assays indicated the growth of the biofilms was inhibited for 12-13 h. The expression of genes associated with adhesion and biofilm formation-als1 in C. albicans and ftf, gtfC, and gtfB in S. mutans-significantly reduced by irradiation. Irradiation with 405-nm blue LED light effectively inhibited the growth of C. albicans and S. mutans dual-species biofilms for 12 h.