Application Of Antimicrobial Photodynamic Therapy Research Articles

Applications of Antimicrobial Photodynamic Therapy in Aquaculture: Effect on Fish Pathogenic Bacteria

Increased infectious diseases and the reduced effectiveness of antibiotics due to antimicrobial resistance pose global challenges affecting the aquaculture industry. As bacteria increasingly develop antibiotic resistance, research scientists are shifting their focus to technologies such as antimicrobial photodynamic therapy (aPDT), which show potential for treating and controlling fish infections without promoting the development of resistant bacteria. Various photosensitizers (PSs), both natural and synthetic, are under investigation for their application in aPDT within the aquaculture industry. This shift is crucial for the sustainability of the aquaculture industry, which plays a significant role in achieving several of the United Nations (UN) Sustainable Development Goals (SDGs). This review highlights the application of aPDT against fish pathogens in the industry and the types of PSs utilized. It also explores the potential application of this technique for treating and controlling fish infections, along with the advantages and limitations of its use in aquaculture production systems. Finally, a conclusion and future perspectives are provided.

Oxygen Availability on the Application of Antimicrobial Photodynamic Therapy against Multi-Species Biofilms.

Methylene blue (MB)- or Curcumin (Cur)-based photodynamic therapy (PDT) has been used as an adjunctive treatment for periodontitis. Its actual clinical efficacy is still in question because the lack of oxygen in a deep periodontal pocket might reduce the PDT efficacy. We aim to investigate the effect of oxygen on PDT efficacy and to examine if the addition of hydrogen peroxide (HP) could improve PDT performance anaerobically. To this end, we cultured 48 h saliva-derived multi-species biofilms and treated the biofilms with 25 µM MB or 40 µM Cur, HP (0.001%, 0.01% and 0.1%), light (L-450 nm or L-660 nm), or combinations thereof under ambient air or strictly anaerobic conditions. MB- and Cur-PDTs significantly reduced biofilm viability in air but not under anaerobic conditions. HP at 0.1% significantly enhanced the killing efficacies of both MB- and Cur-PDTs anaerobically. The killing efficacy of Cur-PDT combined with 0.1% HP was higher anaerobically than in air. However, this was not the case for MB-PDT combined with 0.1% HP. In conclusion, this study demonstrated that the biofilm killing efficacies of MB- and Cur-PDTs diminished when there was no oxygen. HP at 0.1% can enhance the efficacy of PDT performed anaerobically, but the level of enhancement is photosensitizer-dependent.

Knowledge and application of antimicrobial photodynamic therapy among restorative dentist in Saudi Arabia

BackgroundThe aim was to identify the restorative dentist, knowledge and application of Antimicrobial photodynamic therapy (aPDT) in dental practice; and to provide an overview of the potential challenges faced by restorative dentists (RD) in Saudi Arabia. MethodsA 15-item cross sectional study questionnaire was distributed through online portal to assess the knowledge, and practice of RD towards aPDT and its practice. The questionnaire consisted of 3 sections, exploring the demographics of participants, knowledge, application and perception of aPDT using yes/no response and Likert scale. Response means, frequencies, and chi-square tests to compare subgroups based on gender, education level, and practice experience. ResultsOut of 500 participants, 375 completed the survey forms (75% response rate). The majority was male (68%) with a mean age of 46 years. Respondents demonstrated a moderate level of knowledge (60.5%). Only 33% expressed confidence in aPDT as a standalone treatment, while 67% showed limited referrals to specialists. However, 88.5% expressed interest in receiving training and attending workshops for aPDT therapy. Education and experience significantly influenced overall knowledge question responses (p = 0.031). ConclusionMajority of restorative dentists demonstrated a moderate understanding of the role of aPDT in dentistry. More than two thirds of respondents (77%) believed that aPDT is an effective adjuvant therapy. Increased experience (> 10 years) and education (Post-graduates) showed higher application of aPDT. The study reveals the potential for incorporating aPDT knowledge into restorative dental practices, particularly among general dentists

Antimicrobial Photodynamic Therapy for the Remote Eradication of Bacteria.

The emergence of multi-drug resistant bacteria strains has been an uphill battle in modern healthcare worldwide, due to the increasing difficulty of killing them. The evolving pathogenicity of bacteria has led to researchers searching for more effective antimicrobial therapeutics to successfully eliminate them without undesirable consequences to the human body. In recent years, antimicrobial photodynamic therapy (APDT), an obsolete technique for cancer treatments, has been reported to eradicate bacteria and biofilm-related infections. The principle of antimicrobial photodynamic therapy solely relies on the photosensitizers (PSs) generating reactive oxygen species, in the presence of oxygen and light, to destroy pathogens. Thus, it can target a broad spectrum of microorganisms, owing to the indirect interaction between PSs and the bacteria, resulting in the less likelihood for the development of drug resistant bacteria strains. This review will focus on the recent progress of APDT in the last five years and some future perspectives of APDT. The mechanism of APDT against bacteria and biofilms, various PSs used for APDT, and some common multidrug-resistant bacteria strains will be briefly introduced. The reported in vivo applications of APDT in the several types of bacterial infections that includes periodontitis, wound infections, keratitis, endophthalmitis and tuberculosis in the last five years will be summarized in detail.

Clinical applications of antimicrobial photodynamic therapy in dentistry.

Given the emergence of resistant bacterial strains and novel microorganisms that globally threaten human life, moving toward new treatment modalities for microbial infections has become a priority more than ever. Antimicrobial photodynamic therapy (aPDT) has been introduced as a promising and non-invasive local and adjuvant treatment in several oral infectious diseases. Its efficacy for elimination of bacterial, fungal, and viral infections and key pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Candida albicans, and Enterococcus faecalis have been investigated by many invitro and clinical studies. Researchers have also investigated methods of increasing the efficacy of such treatment modalities by amazing developments in the production of natural, nano based, and targeted photosensitizers. As clinical studies have an important role in paving the way towards evidence-based applications in oral infection treatment by this method, the current review aimed to provide an overall view of potential clinical applications in this field and summarize the data of available randomized controlled clinical studies conducted on the applications of aPDT in dentistry and investigate its future horizons in the dental practice. Four databases including PubMed (Medline), Web of Science, Scopus and Embase were searched up to September 2022 to retrieve related clinical studies. There are several clinical studies reporting aPDT as an effective adjunctive treatment modality capable of reducing pathogenic bacterial loads in periodontal and peri-implant, and persistent endodontic infections. Clinical evidence also reveals a therapeutic potential for aPDT in prevention and reduction of cariogenic organisms and treatment of infections with fungal or viral origins, however, the number of randomized clinical studies in these groups are much less. Altogether, various photosensitizers have been used and it is still not possible to recommend specific irradiation parameters due to heterogenicity among studies. Reaching effective clinical protocols and parameters of this treatment is difficult and requires further high quality randomized controlled trials focusing on specific PS and irradiation parameters that have shown to have clinical efficacy and are able to reduce pathogenic bacterial loads with sufficient follow-up periods.

Application of Antimicrobial Photodynamic Therapy for Inactivation of Acinetobacter baumannii Biofilms.

Acinetobacter baumannii is a dangerous hospital pathogen primarily due to its ability to form biofilms on different abiotic and biotic surfaces. The present study investigated the effect of riboflavin- and chlorophyllin-based antimicrobial photodynamic therapy, performed with near-ultraviolet or blue light on the viability of bacterial cells in biofilms and their structural stability, also determining the extent of photoinduced generation of intracellular reactive oxygen species as well as the ability of A. baumannii to form biofilms after the treatment. The efficacy of antimicrobial photodynamic therapy was compared with that of light alone and the role of the photosensitizer type on the photosensitization mechanism was demonstrated. We found that the antibacterial effect of riboflavin-based antimicrobial photodynamic therapy depends on the ability of photoactivated riboflavin to generate intracellular reactive oxygen species but does not depend on the concentration of riboflavin and pre-incubation time before irradiation. Moreover, our results suggest a clear interconnection between the inactivation efficiency of chlorophyllin-based antimicrobial photodynamic therapy and the sensitivity of A. baumannii biofilms to used light. In summary, all the analyzed results suggest that riboflavin-based antimicrobial photodynamic therapy and chlorophyllin-based antimicrobial photodynamic therapy have the potential to be applied as an antibacterial treatment against A. baumannii biofilms or as a preventive measure against biofilm formation.

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

BackgroundDrug-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. MethodsEighty-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. ResultsThe 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). ConclusionaPDT can be used to treat subgingival MDR bacterial infections, but the long-term effects of treatment need to be further studied.

Photodynamic potential of hexadecafluoro zinc phthalocyanine in nanostructured lipid carriers: physicochemical characterization, drug delivery and antimicrobial effect against Candida albicans.

This study aims to develop and characterize NCL loaded with ZnF16Pc (Pc) for application in antimicrobial photodynamic therapy. For the development of the NLC, the fusion-emulsification technique followed by sonication was applied. NLC and Pc-NLC were characterized in terms of mean diameter (Dm.n), polydispersity index (PdI), zeta potential (ZP), encapsulation efficiency (%EE), transmission electron microscopy (TEM), differential scanning (DSC), photobleaching and singlet oxygen generation in cellular systems (SOSG), and in vitro release assays performed by the beaker method, using dialysis membranes. Cell viability was performed by colony forming units (CFU/mL). The mean size of NLC and Pc-NLC was 158 nm ± 1.49 to 161.80 nm and showed PdI < 0.3 and ZP between -17.8 and -19.9, and stable during storage time (90 days). The TEM presented spherical particles, the Pc-NLC promoted the encapsulation of 75.57% ± 0.58. DSC analysis confirmed that there was no incompatibility between Pc and NLC. The analysis of the photodegradation profile proved to be photostable after encapsulation and this corroborates the data obtained by SOSG. In vitro release showed controlled and prolonged release. PDT Pc-NLC exhibited greater antifungal effect against C. albicans (3 log10 reduction) than Pc-NLC without light (1 log10 reduction). NLC can be an alternative to the application of Pc and improve the effect during PDT treatment.

The Application of Antimicrobial Photodynamic Therapy (aPDT) in the Treatment of Peri-Implantitis

Background This literature review evaluates the mechanisms and efficacy of different types of antimicrobial photodynamic therapy (aPDT) for treating peri-implantitis by reviewing existing experimental studies to provide guidance for the clinical application of antibacterial photodynamic therapy (aPDT) in oral implants. Materials and Methods From February 2001 to February 2021, we have collected 152 randomized controlled trials of aPDT for peri-implantitis by searching the experimental studies and clinical trials published in PubMed, Embase, Web of Science, and Google Scholar databases via online search. After screening the retrieved literature, we finally selected 10 statistically significant literature for evaluation and review. Results Compared with the traditional nonsurgical treatment of peri-implantitis, the aPDT was superior to the traditional mechanical irrigation treatment group in terms of periodontal indexes PD, BOP, PLI, and postoperative effect, and the difference was statistically significant (P < 0.05). Furthermore, the combination of the aPDT and other treatments shows the synergistic antibacterial effect, signifying better clinical effect in many aspects (P < 0.05). In these 10 papers, by comparing the probe depth (PD), bleeding on probing (BOP), synosteosis, and periodontal pathogenic bacteria detection, etc., obtained after treating peri-implantitis by application of the antimicrobial photodynamic therapy, and using the SPSS data analysis software for statistical data processing, we found that the antimicrobial photodynamic therapy combined with other periodontal treatments has a more prominent postoperative effect. Meanwhile, the antibacterial photodynamic therapy with targeted action of photosensitizer has strong specificity to some bacteria, while the synthetic photosensitize for antibacterial photodynamic therapy can show good inactivation effect on broad-spectrum periodontal anaerobes without side effect. Conclusion The experimental studies and clinical data of antibacterial photodynamic therapy for treating peri-implantitis show a good postoperative treatment effect. In addition, it did not develop resistance due to the use of antibiotic drugs. Owing to multiple advantages from combining antibacterial photodynamic therapy and other treatments, it is applicable for clinical treatment.

Protocol for the clinical practice of photodynamic therapy in endodontics: assessment of guideline quality using the AGREE II instrument

BackgroundThe choice of parameters in Photodynamic Therapy for endodontic treatment, such as wavelength, energy, application time, and number of sessions can vary based on the characteristics of the procedure and the patient. Providing information supported by scientific evidence in an accessible way to clinicians who are unfamiliar with the literature is necessary. Thus, this study aimed to synthesize a clinical protocol for the use of photodynamic therapy in endodontics in permanent teeth. MethodsProtocols with high methodological quality were identified using a literature search and the Appraisal of Guidelines Research and Evaluation Instrument (AGREE II), a validated tool for assessing quality. The recommendations of these studies were synthesized and submitted to a group of experts for evaluation and adaptation, and consensus was assessed using the Delphi methodology. ResultsThe analysis of the literature on the application of antimicrobial photodynamic therapy in endodontics showed that clinical trials with good levels of evidence and clinical recommendations have been reported previously, with two studies identified as having a clinical recommendation level of A1A and an evidence level of A. ConclusionThe written protocol was considered to be satisfactory and as having appropriate content validity during the second round of evaluation by the experts. The studies included in this research were predominantly explanatory in nature, highlighting the need for pragmatic designs to increase the degree of clinical applicability.

Applications of Antimicrobial Photodynamic Therapy against Bacterial Biofilms.

Antimicrobial photodynamic therapy and allied photodynamic antimicrobial chemotherapy have shown remarkable activity against bacterial pathogens in both planktonic and biofilm forms. There has been little or no resistance development against antimicrobial photodynamic therapy. Furthermore, recent developments in therapies that involve antimicrobial photodynamic therapy in combination with photothermal hyperthermia therapy, magnetic hyperthermia therapy, antibiotic chemotherapy and cold atmospheric pressure plasma therapy have shown additive and synergistic enhancement of its efficacy. This paper reviews applications of antimicrobial photodynamic therapy and non-invasive combination therapies often used with it, including sonodynamic therapy and nanozyme enhanced photodynamic therapy. The antimicrobial and antibiofilm mechanisms are discussed. This review proposes that these technologies have a great potential to overcome the bacterial resistance associated with bacterial biofilm formation.

Application of Antimicrobial Photodynamic Therapy in Periodontal Treatment

Application of Antimicrobial Photodynamic Therapy in Periodontal Treatment

Antimicrobial photodynamic therapy (aPDT) with curcumin controls intradermal infection by Staphylococcus aureus in mice with type 1 diabetes mellitus: a pilot study.

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the main pathogens that cause infections in diabetic individuals. In this paper, we report the outcomes of our investigation on the intradermal application of antimicrobial photodynamic therapy (PDT) with curcumin in an infection induced by MRSA ATCC 43300 strain in the ear of mice with Type 1 Diabetes Mellitus (T1DM). A solution containing 100μg of curcumin was photoactivated ex vivo with a LED light (450nm) delivering a fluency of 13.5J/cm3. This solution was administered in the ear intradermally, at the same inoculum site as the MRSA ATCC 43300 strain (PDT Group). This study also included the use of two control groups (both infected): One was treated with saline and the other was treated with non-photoactivated curcumin. The animals were euthanized 24h after these treatments and samples of draining lymph node and treated ear were collected for examination. The PDT group showed lower bacterial load in the draining lymph node when compared to the saline and curcumin groups (p-value <0.05) 24h after treatment. In addition to bacterial load, the PDT group presented a higher concentration of nitrates and nitrites in the draining lymph node when compared to the saline and curcumin groups (p-value <0.001). Examining the infectious site, despite apparently having similar inflammatory cell recruitment compared with the control groups, the PDT group showed a profile with less intense activity in the myeloperoxidase expression when compared to the saline group (p-value <0.001). Additionally, the detected concentration of cytokines such as IL-1β, IL-12, and IL-10 was significantly lower in the PDT group when compared to the saline group (p-value <0.01; p-value <0.05; p-value <0.05, respectively), thus presenting a less intense inflammatory response during infection resolution. Our pilot study showed for the first time the therapeutic potential of PDT using curcumin when administered intradermally in the treatment of infections caused by S. aureus in mice with T1DM.

Diamond Nanoparticles-Porphyrin mTHPP Conjugate as Photosensitizing Platform: Cytotoxicity and Antibacterial Activity.

Conjugation of photosensitizers (PS) with nanoparticles has been largely used as a strategy to stabilize PS in the biological medium resulting in photosensitizing nanoparticles of enhanced photoactivity. Herein, (Meso-5, 10, 15, 20-tetrakis (3-hydroxyphenyl) phorphyryn (mTHPP) was conjugated with diamond nanoparticles (ND) by covalent bond. Nanoconjugate ND-mTHPP showed suitable stability in aqueous suspension with 58 nm of hydrodynamic diameter and Zeta potential of −23 mV. The antibacterial activity of ND-mTHPP was evaluated against Escherichia coli for different incubation times (0–24 h). The optimal activity was observed after 2 h of incubation and irradiation (660 nm; 51 J/cm2) performed right after the addition of ND-mTHPP (100 μg/mL) to the bacterial suspension. The inhibitory activity was 56% whereas ampicillin at the same conditions provided only 14% of bacterial growth inhibition. SEM images showed agglomerate of ND-mTHPP adsorbed on the bacterial cell wall, suggesting that the antimicrobial activity of ND-mTHPP was afforded by inducing membrane damage. Cytotoxicity against murine embryonic fibroblast cells (MEF) was also evaluated and ND-mTHPP was shown to be noncytotoxic since viability of cells cultured for 24 h in the presence of the nanoconjugate (100 μg/mL) was 78%. Considering the enhanced antibacterial activity and the absence of cytotoxic effect, it is possible to consider the ND-mTHPP nanoconjugate as promising platform for application in antimicrobial photodynamic therapy (aPDT).

Effects of Antibiotics Versus Repeated Applications of Photodynamic Therapy as an Adjunctive Treatment for Periodontitis: A Systematic Review and Meta-Analysis

Objective: Although multiple applications of antimicrobial photodynamic therapy (aPDT) and antibiotics (AB) have been proved to have a biomodulatory effect, no systematic review has exclusively compared the effectiveness as an adjunct to scaling and root planning (SRP). This study sought to systematically compare the clinical efficacy of repeated antimicrobial photodynamic therapy (RaPDT) with that of the systemic administered AB as an alternative approach to SRP in treating periodontitis. Methods: In this systematic review, two independent reviewers searched PubMed, Embase, and CENTRAL databases. The primary outcomes assessed were bleeding on probing (BOP), probing pocket depth (PPD), and clinical attachment level (CAL). Results: Five randomized clinical trials were included after screening 457 records. Results revealed that when patients from all studies were categorized based on their baseline CAL, AB demonstrated significant benefits over RaPDT in the improvement of PPD [weighted mean differences (WMD) = -0.36, 95% confidence interval (CI) = -0.71 to -0.02, p < 0.05] in the patients with severe periodontitis (CAL baseline ≥5 mm) 3-month postoperatively, and CAL (WMD = -0.57, 95% CI = -1.11 to -0.04, p < 0.05) at 6-month observation. Nevertheless, AB failed to show significant benefits over RaPDT, when CAL baseline <5 mm in terms of clinical parameters. Conclusions: RaPDT may represent an alternative approach to SRP in treating slight-to-moderate periodontitis cases (CAL <5 mm), whereas AB remain a main therapy for treating severe periodontitis (CAL ≥5 mm).

New poly(acrylamide) nanoparticles in the development of third generation photosensitizers

There are promising data on the use of poly(acrylamide) nanoparticles (PAA-NPs) in the development of third generation photosensitizers for application in antimicrobial photodynamic therapy. These nanoparticle delivery systems are suitable for biological applications and have potential for drug delivery due to their biocompatibility, chemical flexibility, easy preparation and low cost.The objective of this work was to obtain new PAA-NPs for the vehiculization of the monobrominated derivatives of Azure B (AzBBr) and Neutral Red (NRBr). These two dyes were found to have promising properties as photosensitizers. However, the use of nanotechnology was required to overcome difficulties in solubility, aggregation and stability in order to optimize their photodynamic efficiency.The combination of different monomers and crosslinkers allowed us to develop two new PAA-NPs. These systems were loaded with AzBBr and NRBr and characterized according to their morphology, size, polydispersity index and zeta potential. The new third generation photosensitizers showed better photochemical reactivity, chemical stability and photodynamic efficacy against Gram-positive and Gram-negative bacteria than the free photosensitizers.The use of this vehiculization strategy improved the properties of the second generation photosensitizers (AzBBr and NRBr) studied. This improvement in their properties makes them good candidates for potential phototherapeutic applications against numerous pathologies.

Thionine in the design of new photosensitizers: Bromination and vehiculization in polymeric nanoparticles

To face the challenges of optimizing the properties of the photosensitizers currently used in the photodynamic inactivation of various microorganisms, we propose the bromination of thionine and the use of polymeric nanoparticles for the entrapment of halogenated derivative. Within this framework, the dibrominated derivative of thionine was synthesized and characterized. This new compound showed a high chemical and photochemical stability. In addition, bromination decreased the ionization constant and increased the aggregation of this photosensitizer in an aqueous medium. For this reason, the new compound showed a lower quantum yield of singlet oxygen production. However, the dibrominated thionine showed greater cell damage after photodynamic treatment. In order to prevent or decrease the aggregation of the photosensitizer in an aqueous medium, it was vehiculized in different polymeric polyacrylamide nanoparticles. In general, the vehiculization of the photosensitizers (PSs) in nanosized systems increased the production of singlet oxygen and enhanced their phototoxic activity against the microorganisms evaluated (methicillin-sensitive Staphylococcus aureus and methicillin-resistant Staphylococcus aureus). The nanoparticle formed with the monomer 2 hydroxyethyl methacrylate (HEMA) showed the best photodynamic efficacy. The results obtained clearly suggest that polyacrylamide nanoparticles loaded with photosensitizers of the thiazine family have great potential for further application in antimicrobial photodynamic therapy.

Nanomedicine Fight against Antibacterial Resistance: An Overview of the Recent Pharmaceutical Innovations.

Based on the recent reports of World Health Organization, increased antibiotic resistance prevalence among bacteria represents the greatest challenge to human health. In addition, the poor solubility, stability, and side effects that lead to inefficiency of the current antibacterial therapy prompted the researchers to explore new innovative strategies to overcome such resilient microbes. Hence, novel antibiotic delivery systems are in high demand. Nanotechnology has attracted considerable interest due to their favored physicochemical properties, drug targeting efficiency, enhanced uptake, and biodistribution. The present review focuses on the recent applications of organic (liposomes, lipid-based nanoparticles, polymeric micelles, and polymeric nanoparticles), and inorganic (silver, silica, magnetic, zinc oxide (ZnO), cobalt, selenium, and cadmium) nanosystems in the domain of antibacterial delivery. We provide a concise description of the characteristics of each system that render it suitable as an antibacterial delivery agent. We also highlight the recent promising innovations used to overcome antibacterial resistance, including the use of lipid polymer nanoparticles, nonlamellar liquid crystalline nanoparticles, anti-microbial oligonucleotides, smart responsive materials, cationic peptides, and natural compounds. We further discuss the applications of antimicrobial photodynamic therapy, combination drug therapy, nano antibiotic strategy, and phage therapy, and their impact on evading antibacterial resistance. Finally, we report on the formulations that made their way towards clinical application.

Application of Antimicrobial Photodynamic Therapy with Indocyanine Green Encapsulated Nanoparticles and Diode Laser to Endodontic Treatment

Application of Antimicrobial Photodynamic Therapy with Indocyanine Green Encapsulated Nanoparticles and Diode Laser to Endodontic Treatment

Antimicrobial Photoinactivation Using Visible Light Plus Water-Filtered Infrared-A (VIS\u2009+\u2009wIRA) and Hypericum Perforatum Modifies In Situ Oral Biofilms

Due to increasing antibiotic resistance, the application of antimicrobial photodynamic therapy (aPDT) is gaining increasing popularity in dentistry. The aim of this study was to investigate the antimicrobial effects of aPDT using visible light (VIS) and water-filtered infrared-A (wIRA) in combination with a Hypericum perforatum extract on in situ oral biofilms. The chemical composition of H. perforatum extract was analyzed using ultra-high-performance liquid chromatography coupled with high resolution mass spectrometry (UPLC-HRMS). To obtain initial and mature oral biofilms in situ, intraoral devices with fixed bovine enamel slabs (BES) were carried by six healthy volunteers for two hours and three days, respectively. The ex situ exposure of biofilms to VIS + wIRA (200 mWcm−2) and H. perforatum (32 mg ml−1, non-rinsed or rinsed prior to aPDT after 2-min preincubation) lasted for five minutes. Biofilm treatment with 0.2% chlorhexidine gluconate solution (CHX) served as a positive control, while untreated biofilms served as a negative control. The colony-forming units (CFU) of the aPDT-treated biofilms were quantified, and the surviving microorganisms were identified using MALDI-TOF biochemical tests as well as 16 S rDNA-sequencing. We could show that the H. perforatum extract had significant photoactivation potential at a concentration of 32 mg ml−1. When aPDT was carried out in the presence of H. perforatum, all biofilms (100%) were completely eradicated (p = 0.0001). When H. perforatum was rinsed off prior to aPDT, more than 92% of the initial viable bacterial count and 13% of the mature oral biofilm were killed. Overall, the microbial composition in initial and mature biofilms was substantially altered after aPDT, inducing a shift in the synthesis of the microbial community. In conclusion, H. perforatum-mediated aPDT using VIS + wIRA interferes with oral biofilms, resulting in their elimination or the substantial alteration of microbial diversity and richness. The present results support the evaluation of H. perforatum-mediated aPDT for the adjunctive treatment of biofilm-associated oral diseases.