Antimicrobial photodynamic therapy suppresses dental plaque formation in healthy adults: a randomized controlled clinical trial

Polphylipoprotein-induced autophagy mechanism with high performance in photodynamic therapy

Polphylipoprotein (PLP) is a recently developed nanoparticle with high biocompatibility and tumor selectivity, and which has demonstrated unprecedentedly high performance photosensitizer in photodynamic therapy (PDT) and photodynamic diagnosis. On the basis of these discoveries, PLP is anticipated to have a very high potential for PDT. However, the mechanism by which PLP kills cancer cells effectively has not been sufficiently clarified. To comprehensively understand the PLP-induced PDT processes, we conduct multifaceted experiments using both normal cells and cancer cells originating from the same sources, namely, RGM1, a rat gastric epithelial cell line, and RGK1, a rat gastric mucosa-derived cancer-like mutant. We reveal that PLP enables highly effective cancer treatment through PDT by employing a unique mechanism that utilizes the process of autophagy. The dynamics of PLP-accumulated phagosomes immediately after light irradiation are found to be completely different between normal cells and cancer cells, and it becomes clear that this difference results in the manifestation of the characteristic effect of PDT when using PLP. Since PLP is originally developed as a drug delivery agent, this study also suggests the potential for intracellular drug delivery processes through PLP-induced autophagy.

Application of Different Wavelengths of LED Lights in Antimicrobial Photodynamic Therapy for the Treatment of Periodontal Disease

Therapeutic light has been increasingly used in clinical dentistry for surgical ablation, disinfection, bio-stimulation, reduction in inflammation, and promotion of wound healing. Photodynamic therapy (PDT), a type of phototherapy, has been used to selectively destroy tumor cells. Antimicrobial PDT (a-PDT) is used to inactivate causative bacteria in infectious oral diseases, such as periodontitis. Several studies have reported that this minimally invasive technique has favorable therapeutic outcomes with a low probability of adverse effects. PDT is based on the photochemical reaction between light, a photosensitizer, and oxygen, which affects its efficacy. Low-power lasers have been predominantly used in phototherapy for periodontal treatments, while light-emitting diodes (LEDs) have received considerable attention as a novel light source in recent years. LEDs can emit broad wavelengths of light, from infrared to ultraviolet, and the lower directivity of LED light appears to be suitable for plaque control over large and complex surfaces. In addition, LED devices are small, lightweight, and less expensive than lasers. Although limited evidence exists on LED-based a-PDT for periodontitis, a-PDT using red or blue LED light could be effective in attenuating bacteria associated with periodontal diseases. LEDs have the potential to provide a new direction for light therapy in periodontics.

Effectiveness of Photodynamic Therapy as Antiseptic Measure for Oral Cavity and Pharynx: A Systematic Review

BACKGROUND

The complex traditional treatment of inflammation diseases in oral cavity includes the prescription of antibiotic and antiseptic therapy. This systematic review aims to evaluate the effect of photodynamic therapy as a part of management of inflammatory diseases in oral cavity; Methods: The study is presented in accordance with the preferred reporting points for systematic reviews and meta-analyses (PRISMA). This systematic review was conducted using electronic databases such as Medline PubMed, Scopus and the Cochrane Central Register of Controlled Trials. All the studies in this systematic review, were randomized, the risk of bias 2 (ROB 2) were assessed; Results: Considering the inclusion and exclusion criteria, we included 10 randomized clinical trials, published up to 2023 investigating the application of photodynamic therapy as a part of management of inflammatory diseases in oral cavity. The diode laser was used in the oral cavity in the zone of inflammatory process (gingivitis, mucositis, periimplantitis, marginal periodontitis, abscess, periostitis, osteomyelitis etc.) in nine studies or in the zone before surgical procedures in one study; Conclusion: Based on the results of clinical studies, it can be stated that photodynamic therapy shows good results for operations performed in the oral cavity and pharynx.

Nanotechnology for Dentistry: Prospects and Applications

In the XXI century, application of nanostructures in oral medicine has become common. In oral medicine, using nanostructures for the treatment of dental caries constitutes a great challenge. There are extensive studies on the implementation of nanomaterials to dental composites in order to improve their properties, e.g., their adhesive strength. Moreover, nanostructures are helpful in dental implant applications as well as in maxillofacial surgery for accelerated healing, promoting osseointegration, and others. Dental personal care products are an important part of oral medicine where nanomaterials are increasingly used, e.g., toothpaste for hypersensitivity. Nowadays, nanoparticles such as macrocycles are used in different formulations for early cancer diagnosis in the oral area. Cancer of the oral cavity-human squamous carcinoma-is the sixth leading cause of death. Detection in the early stage offers the best chance at total cure. Along with diagnosis, macrocycles are used for photodynamic mechanism-based treatments, which possess many advantages, such as protecting healthy tissues and producing good cosmetic results. Application of nanostructures in medicine carries potential risks, like long-term influence of toxicity on body, which need to be studied further. The introduction and development of nanotechnologies and nanomaterials are no longer part of a hypothetical future, but an increasingly important element of today's medicine.

Smart dental materials for antimicrobial applications

Smart biomaterials can sense and react to physiological or external environmental stimuli (e.g., mechanical, chemical, electrical, or magnetic signals). The last decades have seen exponential growth in the use and development of smart dental biomaterials for antimicrobial applications in dentistry. These biomaterial systems offer improved efficacy and controllable bio-functionalities to prevent infections and extend the longevity of dental devices. This review article presents the current state-of-the-art of design, evaluation, advantages, and limitations of bioactive and stimuli-responsive and autonomous dental materials for antimicrobial applications. First, the importance and classification of smart biomaterials are discussed. Second, the categories of bioresponsive antibacterial dental materials are systematically itemized based on different stimuli, including pH, enzymes, light, magnetic field, and vibrations. For each category, their antimicrobial mechanism, applications, and examples are discussed. Finally, we examined the limitations and obstacles required to develop clinically relevant applications of these appealing technologies.

Effects of blue-light LED toothbrush on reducing dental plaque and gingival inflammation in orthodontic patients with fixed appliances: a crossover randomized controlled trial

BACKGROUND

Patients with fixed orthodontic appliances have higher plaque accumulation and gingival inflammation. Our aim was to compare the effectiveness of a light emitting diode (LED) toothbrush with a manual toothbrush in reducing dental plaque and gingival inflammation in orthodontic patients with fixed appliances, and to investigate the effect of the LED toothbrush on Streptococcus mutans (S. mutans) biofilm in vitro.

METHODS

Twenty-four orthodontic patients were recruited and randomly assigned into 2 groups: (1) started with manual and (2) started with LED toothbrushes. After a 28-day usage and 28-day wash-out period, the patients switched to the other intervention. The plaque and gingival indices were determined at baseline and 28 days after each intervention. The patients' compliance and satisfaction scores were collected using questionnaires. For the in vitro experiments, S. mutans biofilm was divided into 5 groups (n = 6) with 15-, 30-, 60-, or 120-sec LED exposure, and without LED exposure as a control group.

RESULTS

There was no significant difference in the gingival index between the manual and LED toothbrush groups. The manual toothbrush was significantly more effective in reducing the plaque index in the proximal area on the bracket side (P = 0.031). However, no significant difference was found between the two groups in other areas around the brackets or on the non-bracket side. After LED exposure in vitro, the percentages of bacterial viability after LED exposure for 15-120 s were significantly lower compared with the control (P = 0.006).

CONCLUSION

Clinically, the LED toothbrush was not more effective in reducing dental plaque or gingival inflammation than the manual toothbrush in orthodontic patients with fixed appliances. However, the blue light from the LED toothbrush significantly reduced the number of S. mutans in biofilm when it was exposed to the light for at least 15 s in vitro.

CLINICAL TRIAL REGISTRATION

Thai Clinical Trials Registry (TCTR20210510004). Registered 10/05/2021.

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.

Reactive Oxygen Species Enlightened Therapeutic Strategy for Oral and Maxillofacial Diseases-Art of Destruction and Reconstruction

Reactive oxygen species (ROS) are byproducts of cell metabolism produced by living cells and signal mediators in biological processes. As unstable and highly reactive oxygen-derived molecules, excessive ROS production and defective oxidant clearance, or both, are associated with the pathogenesis of several conditions. Among them, ROS are widely involved in oral and maxillofacial diseases, such as periodontitis, as well as other infectious diseases or chronic inflammation, temporomandibular joint disorders, oral mucosal lesions, trigeminal neuralgia, muscle fatigue, and oral cancer. The purpose of this paper is to outline how ROS contribute to the pathophysiology of oral and maxillofacial regions, with an emphasis on oral infectious diseases represented by periodontitis and mucosal diseases represented by oral ulcers and how to effectively utilize and eliminate ROS in these pathological processes, as well as to review recent research on the potential targets and interventions of cutting-edge antioxidant materials. The PubMed, Web of Science, and Embase databases were searched using the MesH terms "oral and maxillofacial diseases", "reactive oxygen species", and "antioxidant materials". Irrelevant, obsolete, imprecise, and repetitive articles were excluded through screening of titles, abstracts, and eventually full content. The full-text data of the selected articles are, therefore, summarized using selection criteria. While there are various emerging biomaterials used as drugs themselves or delivery systems, more attention was paid to antioxidant drugs with broad application prospects and rigorous prophase animal experimental results.

Cell-Level Analysis Visualizing Photodynamic Therapy with Porphylipoprotein and Talaporphyrin Sodium

We revealed the difference in the mechanism of photodynamic therapy (PDT) between two photosensitizers: porphylipoprotein (PLP), which has recently attracted attention for its potential to be highly effective in treating cancer, and talaporphyrin sodium (NPe6). (1) NPe6 accumulates in lysosomes, whereas PLP is incorporated into phagosomes formed by PLP injection. (2) PDT causes NPe6 to generate reactive oxygen species, thereby producing actin filaments and stress fibers. In the case of PLP, however, reactive oxygen species generated by PDT remain in the phagosomes until the phagosomal membrane is destroyed, which delays the initiation of RhoA activation and RhoA*/ROCK generation. (4) After the disruption of the phagosomal membrane, however, the outflow of various reactive oxygen species accelerates the production of actin filaments and stress fibers, and blebbing occurs earlier than in the case of NPe6. (5) PLP increases the elastic modulus of cells without RhoA activity in the early stage. This is because phagosomes are involved in polymerizing actin filaments and pseudopodia formation. Considering the high selectivity and uptake of PLP into cancer cells, a larger effect with PDT can be expected by skillfully combining the newly discovered characteristics, such as the appearance of a strong effect at an early stage.

Randomized and Controlled Clinical Studies on Antibacterial Photodynamic Therapy: An Overview

The emergence of drug-resistant bacteria is considered a critical public health problem. The need to establish alternative approaches to countering resistant microorganisms is unquestionable in overcoming this problem. Among emerging alternatives, antimicrobial photodynamic therapy (aPDT) has become promising to control infectious diseases. aPDT is based on the activation of a photosensitizer (PS) by a particular wavelength of light followed by generation of the reactive oxygen. These interactions result in the production of reactive oxygen species, which are lethal to bacteria. Several types of research have shown that aPDT has been successfully studied in in vitro, in vivo, and randomized clinical trials (RCT). Considering the lack of reviews of RCTs studies with aPDT applied in bacteria in the literature, we performed a systematic review of aPDT randomized clinical trials for the treatment of bacteria-related diseases. According to the literature published from 2008 to 2022, the RCT study of aPDT was mostly performed for periodontal disease, followed by halitosis, dental infection, peri-implantitis, oral decontamination, and skin ulcers. A variety of PSs, light sources, and protocols were efficiently used, and the treatment did not cause any side effects for the individuals.

Enhanced antimicrobial activity through the combination of antimicrobial photodynamic therapy and low-frequency ultrasonic irradiation

The rapid increase of antibiotic resistance in pathogenic microorganisms has become one of the most severe threats to human health. Antimicrobial photodynamic therapy (aPDT), a light-based regimen, has offered a compelling nonpharmacological alternative to conventional antibiotics. The activity of aPDT is based on cytotoxic effect of reactive oxygen species (ROS), which are generated through the photosensitized reaction between photon, oxygen and photosensitizer. However, limited by the penetration of light and photosensitizers in human tissues and/or the infiltration of oxygen and photosensitizers in biofilms, the eradication of deeply located or biofilm-associated infections by aPDT remains challenging. Ultrasound irradiation bears a deeper penetration in human tissues than light and, sequentially, can promote drug delivery through cavitation effect. As such, the combination of ultrasound and aPDT represents a potent antimicrobial strategy. In this review, we summarized the recent progresses in the area of the combination therapy using ultrasound and aPDT, and discussed the potential mechanisms underlying enhanced antimicrobial effect by this combination therapy. The future research directions are also highlighted.

Selective photodynamic inactivation of Helicobacter pylori by a cationic benzylidene cyclopentanone photosensitizer - an in vitro and ex vivo study

The rise in the antibiotic resistance rate of Helicobacter pylori has led to an increasing eradication failure of this carcinogenic bacterial pathogen worldwide. This underlines the need for alternative antibacterial strategies against H. pylori infection. Antimicrobial photodynamic therapy (aPDT) is a promising non-pharmacological antibacterial technology. In this study, the selective killing activities of three benzylidene cyclopentanone (BCP) photosensitizers (Y1, P1 and P3) towards H. pylori over normal human gastric epithelial GES-1 cells were evaluated and the ex vivo photodynamic inactivation effect was preliminarily assessed on twelve H. Pylor-infected mice. Results showed that under the irradiation of 24 J/cm² 532 nm laser, Y1, P1 and P3 at 2.5 μM induced a 3-log₁₀ reduction of H. pylori CFU (99.9% killing). Confocal images showed that P3, unlike Y1 and P1, could not be uptaken by GES-1 cells. P3 at 2.5 to 20 μM showed not significant (p > 0.05) phototoxicity to GES-1 cells, nevertheless, Y1 and P1 under the same concentrations exhibited remarkable phototoxicity to GES-1 cells. In the co-culture of H. pylori and GES-1 cells, P3 at 2.5 μM led to a complete eradication of H. pylori under the irradiation of 24 J/cm² 532 nm laser. While for the GES-1 cells, no significant (p > 0.05) phototoxicity was observed under the same aPDT dosage. The ex vivo experiments showed that P3 mediated aPDT resulted in 82.4% to 100% reduction of H. pylori CFU without damaging the gastric mucosa. To sum up, P3 is a promising anti-H. pylori photosensitizer with the ability to selectively photo-inactivate H. pylori while sparing normal gastric tissues.

Indocyanine Green-Assisted and LED-Light-Activated Antibacterial Photodynamic Therapy Reduces Dental Plaque

Aim: This study aimed to determine the feasibility and first efficacy of indocyanine green (ICG)-assisted antimicrobial photodynamictherapy (aPDT) as activated using LED light to the dental plaque. Methods: Fifteen healthy adults were assigned to this four-day randomized study. After rinsing with ICG, 100 J/cm² of 810 nm LED light was applied to the aPDT-treatment area. Plaque area and gingival crevicular fluid (GCF) matrix metalloproteinase-8 (MMP-8) were measured, and plaque bacteriomes before and after the study were analyzed using 16S rRNA sequencing. Results: aPDT administration was preformed successfully and plaque-specifically with the combination of ICG and the applicator. Total plaque area and endpoint MMP-8 levels were reduced on the aPDT-treatment side. aPDT reduced Streptococcus, Acinetobacteria, Capnocytophaga, and Rothia bacteria species in plaques. Conclusion: ICG-assisted aPDT reduces plaque forming bacteria and exerts anti-inflammatory and anti-proteolytic effects.

Antibacterial Photodynamic Treatment of Porphyromonas gingivalis with Toluidine Blue O and a NonLaser Red Light Source Enhanced by Dihydroartemisinin

In vitro experiments confirmed that antibacterial photodynamic treatment (aPDT) inactivates periodontal pathogens. However, more effective sterilization is needed in the complex oral environment. This study tested whether dihydroartemisinin (DHA) enhanced the photokilling effect of aPDT on Porphyromonas gingivalis (P. gingivalis) in planktonic and biofilm states. aPDT combining toluidine blue O (TBO) with 630 nm red light was performed on bacterial suspensions and biofilms in vitro with different final concentrations of DHA (10, 20 and 40 μg mL^-1 ). The sensitization mechanism was preliminarily investigated by uptake experiments. The above experiments were repeated with different incubation times (30, 60, 120 s). Porphyromonas gingivalis biofilms exhibited significantly higher resistance to aPDT than P. gingivalis in suspension under the same experimental parameters. DHA alone had no cytotoxic effect on P. gingivalis with or without light irradiation. In either bacterial suspensions or biofilms, DHA concentration-dependently enhanced the photokilling effect of aPDT and increased TBO uptake by P. gingivalis. Prolonged incubation time enhanced the photokilling efficiency of aPDT until cellular TBO uptake reached saturation. DHA can enhance aPDT activity against P. gingivalis in planktonic and biofilm states. DHA also accelerated TBO uptake, reducing incubation time.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

CONCLUSION

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

Biogenic Silver Nanoparticles Decorated with Methylene Blue Potentiated the Photodynamic Inactivation of Pseudomonas aeruginosa and Staphylococcus aureus

The persistence of multidrug resistance among microorganisms has directed a mandate towards a hunt for the development of alternative therapeutic modalities. In this context, antimicrobial photodynamic therapy (aPDT) is sprouted as a novel strategy to mitigate biofilms and planktonic cells of pathogens. Nanoparticles (NPs) are reported with unique intrinsic and antimicrobial properties. Therefore, silver NPs (AgNPs) were investigated in this study to determine their ability to potentiate the aPDT of photosensitizer against Staphylococcus aureus and Pseudomonas aeruginosa. Biologically synthesized AgNPs were surface coated with methylene blue (MB) and studied for their aPDT against planktonic cells and biofilms of bacteria. The nano-conjugates (MB-AgNPs) were characterized for their size, shape and coated materials. MB-AgNPs showed significant phototoxicity against both forms of test bacteria and no toxicity was observed in the dark. Moreover, activity of MB-AgNPs was comparatively higher than that of the free MB, which concludes that MB-AgNPs could be an excellent alternative to combat antibiotic resistant bacteria.

Applications of Light-Emitting Diodes (LEDs) in Food Processing and Water Treatment

Light-emitting diode (LED) technology is an emerging nonthermal food processing technique that utilizes light energy with wavelengths ranging from 200 to 780 nm. Inactivation of bacteria, viruses, and fungi in water by LED treatment has been studied extensively. LED technology has also shown antimicrobial efficacy in food systems. This review provides an overview of recent studies of LED decontamination of water and food. LEDs produce an antibacterial effect by photodynamic inactivation due to photosensitization of light absorbing compounds in the presence of oxygen and DNA damage; however, such inactivation is dependent on the wavelength of light energy used. Commercial applications of LED treatment include air ventilation systems in office spaces, curing, medical applications, water treatment, and algaculture. As low penetration depth and high-intensity usage can challenge optimal LED treatment, optimization studies are required to select the right light wavelength for the application and to standardize measurements of light energy dosage.

Antimicrobial photodynamic therapy efficacy against specific pathogenic periodontitis bacterial species

BACKGROUND

To determine the safety and efficacy of antimicrobial photodynamic therapy (aPDT) combination of 0.33 mM Toluidine Blue O (TBO) with 60 mW/cm² LED irradiation for 5 min that we had established, this study investigated the cytotoxic effect of aPDT combination on mammalian oral cells (gingival fibroblast and periodontal ligament cells) and compared the antimicrobial efficacy of antibiotics (the combination of amoxicillin (AMX) and metronidazole (MTZ)) against representative periodontitis pathogenic bacteria (Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans) versus our aPDT combination.

RESULT

aPDT combination did not show any detectable effect on the viability of Streptococcus sanguinis or Streptococcus mitis, the most common resident species in the oral flora. However, it significantly reduced CFU values of P. gingivalis, F. nucleatum, and A. actinomycetemcomitans. The cytotoxicity of the present aPDT combination to mammalian oral cells was comparable to that of standard antiseptics used in oral cavity. In antimicrobial efficacy test, the present aPDT combination showed equivalent bactericidal rate compared to the combination of AMX + MTZ, the most widely used antibiotics in the periodontitis treatment. The bactericidal ability of the AMX + MTZ combination was effective against all five bacteria tested regardless of the bacterial species, whereas the bactericidal ability of the aPDT combination was effective only against P. gingivalis, F. nucleatum, and A. actinomycetemcomitans, the representative periodontitis pathogenic bacterial species.

CONCLUSION

The present study demonstrated the safety and efficacy of the present aPDT combination in periodontitis treatment. TBO-mediated aPDT with LED irradiation has the potential to serve as a safe single or adjunctive antimicrobial procedure for nonsurgical periodontal treatment without damaging adjacent normal oral tissue or resident flora.

Exposure of Streptococcus mutans and Streptococcus sanguinis to blue light in an oral biofilm model

The potential anti-cariogenic effect of blue light was evaluated using an oral biofilm model. Two species, Streptococcus mutans and Streptococcus sanguinis, were cultivated ex vivo on bovine enamel blocks for 24 h, either separately or mixed together, then exposed to blue light (wavelengths 400-500 nm) using 112 J/cm². Twenty four or 48 h after exposure to light the biofilm structure and biomass were characterized and quantified using SEM and qPCR, respectively. Bacterial viability was analyzed by CLSM using live/dead bacterial staining. Gene expression was examined by RT-qPCR. After exposure to light, S. mutans biomass in mono-species biofilm was increased mainly by dead bacteria, relative to control. However, the bacterial biomass of S. mutans when grown in mixed biofilm and of S. sanguinis in mono-species biofilm was reduced after light exposure, with no significant change in viability when compared to control. Furthermore, when grown separately, an upregulation of gene expression related to biofilm formation of S. mutans, and downregulation of similar genes of S. sanguinis, were measured 24 h after exposure to blue light. However, in mixed biofilm, a downregulation of those genes in both species was observed, although not significant in S. mutans. In conclusion, blue light seems to effectively alter the bacterial biomass by reducing the viability and virulence characteristics in both bacterial species and may promote the anti-cariogenic balance between them, when grown in a mixed biofilm. Therefore, exposure of oral biofilm to blue light has the potential to serve as a complementary approach in preventive dentistry.

Anti-Oral Pathogens of Tecoma stans (L.) and Cassia javanica (L.) Flower Volatile Oils in Comparison with Chlorhexidine in Accordance with Their Folk Medicinal Uses

Background and Objectives: Teeth decay and plaque are complicated problems created by oral pathogens. Tecoma stans (L.) and Cassia javanica (L.) are two ornamental evergreen plants widely distributed in Egypt. These plants are traditionally used for oral hygienic purposes. This study aims to elucidate the volatile oil constituents obtained from the flowers of these plants and evaluate the antimicrobial activity of these volatile oils against specific oral pathogens in comparison to chlorhexidine. Materials and Methods: The flowers obtained from both plants were extracted by n-hexane. GC-MS spectrometry was used to identify the constituents. Minimum inhibitory concentrations (MICs) were measured using tetrazolium salt (2,3-bis[2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide) (XTT). Results: GC-MS analysis revealed the presence of 32 and 29 compounds, representing 100% of the volatile constituents of Tecoma stans and Cassia javanica, respectively. The GC-MS analysis showed more than 60% of the volatile oil constituents are represented in both plants with different proportions. Chlorhexidine exerted stronger activity than tested plants against all microorganisms. Cassia javanica flower extract was more active against all tested microorganisms than Tecoma stans. Of note was the effect on Streptococcus mutans, which was inhibited by 100% at 12.5 and 25 µg/mL of Cassia javanica and Tecoma stans, respectively. The growth of Lactobacillus acidophilus was also completely inhibited by 25 µg/mL of the Cassia javanica extract. MIC90 and MIC were also calculated, which revealed the superiority of Cassia javanica over Tecoma stans against all tested oral pathogens. Conclusion: Cassia javanica flower volatile oils showed a potential anti-oral pathogen activity at relatively low concentrations. Also, Cassia javanica and Tecoma stans demonstrated a strong activity against tooth decay's notorious bacteria Streptococcus mutans. Both plants can be potential substituents to chlorhexidine. Formulating the constituents of these plants in toothpastes and mouthwashes as anti-oral pathogen preparations can be an interesting future plan.

Bactericidal effects of hematoporphyrin monomethyl ether-mediated blue-light photodynamic therapy against Staphylococcus aureus

The implementation of photodynamic therapy (PDT) usually uses red light as the excitation source to obtain a deeper penetration depth. However, for some superficial infectious diseases, using red-light PDT may damage the normal tissues underneath. If we choose a shorter wavelength light, then the effect of PDT can be limited to the superficial region. This study assessed the effect of blue-light PDT against Staphylococcus aureus. The absorption of hematoporphyrin monomethyl ether (HMME) by S. aureus was investigated using fluorescence spectroscopy. The bactericidal effects of HMME, light alone, and PDT using blue light (405 nm) on S. aureus were studied. The results indicate that the HMME uptake by S. aureus rapidly reached a certain value, then steadily increased with time in the range of 0-80 min, and thenreached a plateau at 80 min before a slow decline afterward. Without light irradiation, less than 2 μg ml^-1 HMME showed no bactericidal effect on S. aureus. Without HMME, blue-light at a power density of 20 mW cm^-2 had no significant bactericidal effect for 0.5 min to 10 min. When 2 μg ml^-1 of HMME was combined with blue-light (20 mW cm^-2), the bactericidal effect showed a reduction of 3 log₁₀ with the extension of irradiation time. These results demonstrated that bacteria have the ability to absorb HMME, and HMME-mediated blue-light PDT can effectively kill the bacteria, which laid the foundation for blue-light PDT as a non-invasive treatment for superficial infectious diseases.

Confocal fluorescence imaging to evaluate the effect of antimicrobial photodynamic therapy depth on P. gingivalis and T. denticola biofilms

BACKGROUND

Porphyromonas gingivalis and Treponema denticola are both principally implicated in the incidence of both periodontal disease and peri-implantitis. Recent studies have demonstrated that these bacteria exhibit symbiotic growth in vitro and a synergistic virulence in co-infection of animal models. Found at varying depths throughout the biofilm, these bacteria present a significant challenge to traditional antimicrobial treatment modalities. Antimicrobial photodynamic therapy (aPDT) has yielded high success against bacterial biofilms, namely those found in the oral cavity. Data on the use of aPDT against these particular periodontal pathogens is, however, scarce. Here, we studied the qualitative killing efficacy and depth of drug and laser penetration into defined P. gingivalis and T. denticola biofilms.

METHODS

P. gingivalis and T. denticola were incubated under anaerobic (10%CO2, 10%H2, 80%N2) conditions for two days in diluted TSB with PBS (TYGVS for T. denticola maintenance) to elicit biofilm growth on coverslip-modified polystyrene dishes. Treated biofilms were exposed to a purpurin-based sensitizer (25 μg/mL in DMSO) for 30 min, and then aPDT was carried out using a diode laser at 664 nm. Light doses of 15 and 45 J/cm2 were used. All biofilms were then exposed to Filmtracer™ LIVE/DEAD® Biofilm Viability Kit (Cat No. L10316). Qualitative analysis was performed using a Zeiss LSM 510 Meta NLO Confocal Microscope with attached Zeiss Axioimager Z1 and Axiovert 200 M for visual data collection, and images were processed using the ZEN Digital Imaging for Light Microscopy software suite. Analysis was performed in 2 × 3 stacks to assess the entire depth of both the biofilm and presumed drug/laser penetration.

RESULTS

Initial planktonic studies confirmed that the bacteria in question were present in the grown cultures and susceptible to aPDT exposure. Biofilm control groups were found to have significant levels of surviving bacterial colonies. Both treatment groups featured complete bacterial kill throughout the entirety of the biofilm (average: 23.17 μm; range: 18.13-27.20 μm).

CONCLUSIONS

The efficacy of the purpurin-based PS and aPDT is demonstrated to be effective at both high and low light doses. Bacterial kill was fully efficacious at each visualized biofilm layer (1.01 μm/z-level). This study serves as a proof of concept for future studies that must consider appropriate treatment parameters, including the amount of applied PS, and laser dose. These findings indicate that aPDT is a method that can be used to eliminate microorganisms associated with biofilms implicated in the etiology of peri-implantitis and periodontitis at large.

Efficacy of photodynamic therapy against Streptococcus mutans biofilm: Role of singlet oxygen

In photodynamic therapy (PDT), killing is entirely based on the ROS generation and among different types of ROS generated during PDT, singlet oxygen is considered as the most potential as illustrated in many studies and therefore it is predominantly responsible for photodamage and cytotoxic reactions. The aim of this study was to check whether singlet oxygen (Type II photochemistry) is more potential than free radicals (Type I photochemistry) against Streptococcus mutans biofilm. We have taken two phenothiazinium dyes i.e. toluidine blue O (TBO) and new methylene blue (NMB). TBO was found to have better antibacterial as well as antibiofilm effect than NMB. Antibacterial effect was evaluated by colony forming unit while antibiofilm action by crystal violet and congo red binding assays. We have also evaluated the disruption of preformed biofilm by biofilm reduction assay, confocal laser electron and scanning electron microscopy. More singlet oxygen production was detected in case of TBO than NMB while more Free radical (HO) was produced by NMB than TBO. TBO showed better antibacterial as well as antibiofilm effect than NMB so; we conclude that potency of a photosensitizer is correlated with the capability to produce singlet oxygen.

Enhanced photodynamic therapy using light fractionation against Streptococcus mutans biofilm: type I and type II mechanism

AIM

The objective of the study was to look the efficacy of fractionated light against Streptococcus mutans biofilm.

MATERIALS & METHODS

Antibiofilm assays (crystal violet, congo red), electron microscopic, confocal and spectroscopic studies were performed to check the effect of fractionated light.

RESULTS

6-6.5 log₁₀ reduction of planktonic and 3.6-4.2 log₁₀ reduction in biofilm were observed after irradiation with fractionated as compared with continuous light. Increased permeability to propidium iodide and leakage of cellular constituent validate the greater antibiofilm effect of fractionated light. Spectroscopic studies confirmed the relative contribution of type I and type II photochemistry.

CONCLUSION

Phenothiazinium dyes have a potential against bacterial biofilm in combination with light fractionation and it offers new opportunities to explore its clinical implication.

Antimicrobial photodynamic activity and cytocompatibility of Au25(Capt)18 clusters photoexcited by blue LED light irradiation

Antimicrobial photodynamic therapy (aPDT) has beneficial effects in dental treatment. We applied captopril-protected gold (Au₂₅(Capt)₁₈) clusters as a novel photosensitizer for aPDT. Photoexcited Au clusters under light irradiation generated singlet oxygen (¹O₂). Accordingly, the antimicrobial and cytotoxic effects of Au₂₅(Capt)₁₈ clusters under dental blue light-emitting diode (LED) irradiation were evaluated. ¹O₂ generation of Au₂₅(Capt)₁₈ clusters under blue LED irradiation (420–460 nm) was detected by a methotrexate (MTX) probe. The antimicrobial effects of photoexcited Au clusters (0, 5, 50, and 500 μg/mL) on oral bacterial cells, such as Streptococcus mutans, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis, were assessed by morphological observations and bacterial growth experiments. Cytotoxicity testing of Au clusters and blue LED irradiation was then performed against NIH3T3 and MC3T3-E1 cells. In addition, the biological performance of Au clusters (500 μg/mL) was compared to an organic dye photosensitizer, methylene blue (MB; 10 and 100 μg/mL). We confirmed the ¹O₂ generation ability of Au₂₅(Capt)₁₈ clusters through the fluorescence spectra of oxidized MTX. Successful application of photoexcited Au clusters to aPDT was demonstrated by dose-dependent decreases in the turbidity of oral bacterial cells. Morphological observation revealed that application of Au clusters stimulated destruction of bacterial cell walls and inhibited biofilm formation. Aggregation of Au clusters around bacterial cells was fluorescently observed. However, photoexcited Au clusters did not negatively affect the adhesion, spreading, and proliferation of mammalian cells, particularly at lower doses. In addition, application of Au clusters demonstrated significantly better cytocompatibility compared to MB. We found that a combination of Au₂₅(Capt)₁₈ clusters and blue LED irradiation exhibited good antimicrobial effects through ¹O₂ generation and biosafe characteristics, which is desirable for aPDT in dentistry.

The impact of antimicrobial photodynamic therapy on peri-implant disease: What mechanisms are involved in this novel treatment?

According to the American Academy of Implant Dentistry, 3 million Americans have dental implants, and this number is growing by 500,000 each year. Proportionally, the number of biological complications is also increasing. Among them, peri-implant disease is considered the most common cause of implant loss after osseointegration. In this context, microorganisms residing on the surfaces of implants and their prosthetic components are considered to be the primary etiologic factor for peri-implantitis. Some research groups have proposed combining surgical and non-surgical therapies with systemic antibiotics. The major problem associated with the use of antibiotics to treat peri-implantitis is that microorganisms replicate very quickly. Moreover, inappropriate prescription of antibiotics is not only associated with potential resistance but also and most importantly with the development of superinfections that are difficult to eradicate. Although antimicrobial photodynamic therapy (aPDT) was discovered several years ago, aPDT has only recently emerged as a possible alternative therapy against different oral pathogens causing peri-implantitis. The mechanism of action of aPDT is based on a combination of a photosensitizer drug and light of a specific wavelength in the presence of oxygen. The reaction between light and oxygen produces toxic forms of oxygen species that can kill microbial cells. This mechanism is crucial to the efficacy of aPDT. To help us understand conflicting data, it is necessary to know all the particularities of the etiology of peri-implantitis and the aPDT compounds. We believe that this review will draw attention to new insights regarding the impact of aPDT on peri-implant disease.

Effect of fiber insertion depth on antibacterial efficacy of photodynamic therapy against Enterococcus faecalis in rootcanals

OBJECTIVES

This in vitro study evaluated the effect of fiber insertion depth on antimicrobial efficacy of antimicrobial photodynamic therapy (aPDT) using a photosensitizer (PS; toluidine blue) and a red light-emitting diode (LED) in root canals infected with Enterococcus faecalis.

MATERIALS AND METHODS

Single-rooted extracted teeth were prepared with nickel-titanium-instruments, sterilized, contaminated with E. faecalis, and incubated for 72 h. Roots were randomly divided into four experimental groups: PS only, LED only, aPDT with LED in the apical third, aPDT with LED in the coronal third, as well as into infection and sterile controls (each n = 10). Samples were taken by collecting standardized dentine shavings from the root canal walls. After serial dilution and culturing on blood agar, colony-forming units (CFU) were counted.

RESULTS

Both aPDT groups showed a CFU reduction of 1-2 log₁₀ steps compared with the infection control, whereas the effect of fiber insertion depth was negligible (<0.5 log₁₀ steps). CFU reduction of approximately 0.5 log₁₀ steps for PS alone was detected compared with the infection control, but PS alone was less effective than both aPDT groups. No antibacterial effect was detected for LED alone.

CONCLUSIONS

aPDT reduced E. faecalis within the root canal, whereas fiber insertion depth had a negligible influence on antimicrobial effectiveness of aPDT.

CLINICAL RELEVANCE

The insertion depth of the light-emitting diode may not influence the antibacterial efficacy of photodynamic therapy against E. faecalis in straight root canals.

Antibiofilm action of a toluidine blue O-silver nanoparticle conjugate on Streptococcus mutans: a mechanism of type I photodynamic therapy

The objective of this study was to evaluate the anti-biofilm efficacy of photodynamic therapy by conjugating a photosensitizer (TBO) with silver nanoparticles (AgNP). Streptococcus mutans was exposed to laser light (630 nm) for 70 s (9.1 J cm(-2)) in the presence of a toluidine blue O-silver nanoparticle conjugate (TBO-AgNP). The results showed a reduction in the viability of bacterial cells by 4 log10. The crystal violet assay, confocal laser scanning microscopy and scanning electron microscopy revealed that the TBO-AgNP conjugates inhibited biofilm formation, increased the uptake of propidium iodide and leakage of the cellular constituents, respectively. Fluorescence spectroscopic studies confirmed the generation of OH(•) as a major reactive oxygen species, indicating type I phototoxicity. Both the conjugates down-regulated the expression of biofilm related genes compared to TBO alone. Hence TBO-AgNP conjugates were found to be more phototoxic against S. mutans biofilm than TBO alone.

Effect of antimicrobial photodynamic therapy using rose bengal and blue light-emitting diode on Porphyromonas gingivalis in vitro: Influence of oxygen during treatment

Aims: A combination of rose bengal (RB) and blue LED (BL) has emerged as a new technical modality for antimicrobial photodynamic therapy (a-PDT). The purpose of this study was to clarify the influence of oxygen on the antimicrobial effect of RB + BL treatment on Porphyromonas gingivalis in vitro.Materials and Methods:P. gingivalis cells were treated with RB, BL (450-470 nm; 1 W/cm², 5 s), or RB + BL under anaerobic/aerobic conditions. Cells were incubated anaerobically, and the cell density (OD_{600 nm}) was measured after 6-48 h. Additionally, cells were cultured anaerobically on blood agar plates for 9 days, and the resulting colonies were observed. Bacterial growth within 1 h of aerobic RB + BL treatment was examined, and RNA degradation due to anaerobic/aerobic RB + BL treatment was measured after 3 h of culture. Results: Under anaerobic conditions, RB + BL significantly suppressed bacterial growth after 18 h; however, the growth after 48 h and the number of colonies after 9 days were similar to those of the untreated control. RNA degradation in the anaerobic-treatment group was not significantly different from that in the control. Under aerobic conditions, RB + BL immediately affected bacterial growth and completely inhibited growth for up to 48 h. Few colonies were detected even after 9 days of culture, and RNA was completely degraded. Conclusions: Unlike the bacteriostatic effect of anaerobic treatment, aerobic RB + BL treatment may have a bactericidal action via a-PDT effect, resulting in the destruction of RNA and bacterial cells within a short period.

Biofilms and human health

A biofilm can be defined as a surface-attached (sessile) community of microorganisms embedded and growing in a self-produced matrix of extracellular polymeric substances. These biofilm communities can be found in medical, industrial and natural environments, and can also be engineered in vitro for various biotechnological applications. Biofilms play a significant role in the transmission and persistence of human disease especially for diseases associated with inert surfaces, including medical devices for internal or external use. Biofilm infections on implants or in-dwelling devices are difficult to eradicate because of their much better protection against macrophages and antibiotics, compared to free living cells, leading to severe clinical complications often with lethal outcome. Recent developments in nanotechnology have provided novel approaches to preventing and dispersing biofilm related infections and potentially providing a novel method for fighting infections that is nondrug related.