Blue LED inhibits the growth of Porphyromonas gingivalis by suppressing the expression of genes associated with DNA replication and cell division

Effects of various light-emitting diode wavelengths on periodontopathic bacteria and gingival fibroblasts: An in vitro study

BACKGROUND

In recent years, light has been used for bacterial control of periodontal diseases. This in vitro study evaluated the effects of light-emitting diode (LED) irradiation at different wavelengths on both Porphyromonas gingivalis and human gingival fibroblasts (HGF-1).

METHODS

P. gingivalis suspension was irradiated with LEDs of 365, 405, 450, 470, 565, and 625 nm at 50, 100, 150, and 200 mW/cm2 for 3 min (radiant exposure: 9, 18, 27, 36 J/cm2, respectively). Treated samples were anaerobically cultured on agar plates, and the number of colony-forming units (CFUs) was determined. Reactive oxygen species (ROS) levels were measured after LED irradiation. The viability and damage of HGF-1 were measured through WST-8 and lactate dehydrogenase assays, respectively. Gene expression in P. gingivalis was evaluated through quantitative polymerase chain reaction.

RESULTS

The greatest reduction in P. gingivalis CFUs was observed on irradiation at 365 nm with 150 mW/cm2 for 3 min (27 J/cm2), followed by 450 and 470 nm under the same conditions. While 365-nm irradiation significantly decreased the viability of HGF-1 cells, the cytotoxic effects of 450- and 470-nm irradiation were comparatively low and not significant. Further, 450-nm irradiation indicated increased ROS production and downregulated the genes related to gingipain and fimbriae. The 565- and 625-nm wavelength groups exhibited no antibacterial effects; rather, they significantly activated HGF-1 proliferation.

CONCLUSIONS

The 450- and 470-nm blue LEDs showed high antibacterial activity with low cytotoxicity to host cells, suggesting promising bacterial control in periodontal therapy. Additionally, blue LEDs may attenuate the pathogenesis of P. gingivalis.

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.

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.

Photoinactivation and Photoablation of Porphyromonas gingivalis

Several types of phototherapy target human pathogens and Porphyromonas gingivitis (Pg) in particular. The various approaches can be organized into five different treatment modes sorted by different power densities, interaction times, effective wavelengths and mechanisms of action. Mode 1: antimicrobial ultraviolet (aUV); mode 2: antimicrobial blue light (aBL); mode 3: antimicrobial selective photothermolysis (aSP); mode 4: antimicrobial vaporization; mode 5: antimicrobial photodynamic therapy (aPDT). This report reviews the literature to identify for each mode (a) the putative molecular mechanism of action; (b) the effective wavelength range and penetration depth; (c) selectivity; (d) in vitro outcomes; and (e) clinical trial/study outcomes as these elements apply to Porphyromonas gingivalis (Pg). The characteristics of each mode influence how each is translated into the clinic.

Response of genes related to iron and porphyrin transport in Porphyromonas gingivalis to blue light

BACKGROUND

Antimicrobial blue light (aBL) kills a variety of bacteria, including Porphyromonas gingivalis. However, little is known about the transcriptomic response of P. gingivalis to aBL therapy. This study was designed to evaluate the selective cytotoxicity of aBL against P. gingivalis over human cells and to further investigate the genetic response of P. gingivalis to aBL at the transcriptome level.

METHODS

Colony forming unit (CFU) testing, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) were used to investigate the antimicrobial effectiveness of blue light against P. gingivalis. The temperatures of the irradiated targets were measured to prevent overheating. Multiple fluorescent probes were used to quantify reactive oxygen species (ROS) generation after blue-light irradiation. RNA sequencing (RNA-seq) was used to investigate the changes in global gene expression. Following the screening of target genes, real-time quantitative polymerase chain reaction (RT-qPCR) was performed to confirm the regulation of gene expression.

RESULTS

A 405 nm aBL at 100 mW/cm² significantly killed P. gingivalis within 5 min while sparing human gingival fibroblasts (HGFs). No obvious temperature changes were detected in the irradiated surface under our experimental conditions. RNA-seq showed that the transcription of multiple genes was regulated, and RT-qPCR revealed that the expression levels of the genes RgpA and RgpB, which may promote heme uptake, as well as the genes Ftn and FetB, which are related to iron homeostasis, were significantly upregulated. The expression levels of the FeoB-2 and HmuR genes, which are related to hydroxyl radical scavenging, were significantly downregulated.

CONCLUSIONS

aBL strengthens the heme uptake and iron export gene pathways while reducing the ROS scavenging pathways in P. gingivalis, thus improving the accumulation of endogenous photosensitizers and enhancing oxidative damage to P. gingivalis.

Joint toxicity mechanisms of binary emerging PFAS mixture on algae (Chlorella pyrenoidosa) at environmental concentration

Since traditional Per- and polyfluoroalkyl substances (PFAS) were banned in 2009 due to their bioaccumulation, persistence and biological toxicity, the emerging PFAS have been widely used as their substitutes and entered the aquatic environment in the form of mixtures. However, the joint toxicity mechanisms of these emerging PFAS mixtures to aquatic organisms remain largely unknown. Then, based on the testing of growth inhibition, cytotoxicity, photosynthesis and oxidative stress, and the toxicity mechanism of PFAS mixture (Perfluorobutane sulfonate and Perfluorobutane sulfonamide) to algae was explored using the Gene set enrichment analysis (GSEA). The results revealed that all three emerging PFAS treatments had a certain growth inhibitory effect on Chlorella pyrenoidosa (C. pyrenoidosa), but the toxicity of PFAS mixture was stronger than that of individual PFAS and showed a significant synergistic effect at environmental concentration. The joint toxicity mechanisms of binary PFAS mixture to C. pyrenoidosa were related to the damage of photosynthetic system, obstruction of ROS metabolism, and inhibition of DNA replication. Our findings are conductive to adding knowledge in understanding the joint toxicity mechanisms and provide a basis for assessing the environmental risk of emerging PFAS.

Apoptotic mechanism activated by blue light and cisplatinum in cutaneous squamous cell carcinoma cells

New approaches are being studied for the treatment of skin cancer. It has been reported that light combined with cisplatinum may be effective against skin cancer. In the present study, the effects of specific light radiations and cisplatinum on A431 cutaneous squamous cell carcinoma (cSCC) and HaCaT non-tumorigenic cell lines were investigated. Both cell lines were exposed to blue and red light sources for 3 days prior to cisplatinum treatment. Viability, apoptosis, cell cycle progression and apoptotic-related protein expression levels were investigated. The present results highlighted that combined treatment with blue light and cisplatinum was more effective in reducing cell viability compared with single treatments. Specifically, an increase in the apoptotic rate was observed when the cells were treated with blue light and cisplatinum, as compared to treatment with blue light or cisplatinum alone. Combined treatment with blue light and cisplatinum also caused cell cycle arrest at the S phase. Treatment with cisplatinum following light exposure induced the expression of apoptotic proteins in the A431 and HaCaT cell lines, which tended to follow different apoptotic mechanisms. On the whole, these data indicate that blue light combined with cisplatinum may be a promising treatment for cSCC.

Effect of low power lasers on prokaryotic and eukaryotic cells under different stress condition: a review of the literature

Radiations emitted by low power radiation sources have been applied for therapeutic proposals due to their capacity of inactivating bacteria and cancer cells in photodynamic therapy and stimulating tissue cells in photobiomodulation. Exposure to these radiations could increase cell proliferation in bacterial cultures under stressful conditions. Cells in infected or not infected tissue injuries are also under stressful conditions and photobiomodulation-induced regenerative effect on tissue injuries could be related to effects on stressed cells. The understanding of the effects on cells under stressful conditions could render therapies based on photobiomodulation more efficient as well as expand them. Thus, the objective of this review was to update the studies reporting photobiomodulation on prokaryotic and eukaryotic cells under stress conditions. Exposure to radiations emitted by low power radiation sources could induce adaptive responses enabling cells to survive in stressful conditions, such as those experienced by bacteria in their host and by eukaryotic cells in injured tissues. Adaptive responses could be the basis for clinical photobiomodulation applications, either considering their contraindication for treatment of infected injuries or indication for treatment of injuries, inflammatory process resolution, or tissue regeneration.

The Effectiveness of Photobiomudulation Therapy (PBMT) in COVID-19 Infection

Introduction: Currently, the COVID-19 pandemic is an important health challenge worldwide. Due to the cytokine storm, the mortality rate in acute respiratory distress syndrome (ARDS) is high, but until now no therapy for these patients was approved. The aim of this review was to discuss the possible anti-inflammatory effect of photobiomodulation therapy (PBMT) on ARSD patients and present the potential role of low-level laser therapy (LLLT) in the improvement of respiratory symptoms associated with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Methods: Studies about PBMT in inflammation and ARSD patients were examined. A primary search with reviewing English-language citations between 2005 and 2020 using the keywords COVID-19, ADRS, cytokine storm, low-level laser therapy, anti-inflammatory, and photobiomodulation was performed. The initial search yielded 818 articles; however, 60 articles were selected and discussed in the present study. Results: The results of the selected studies showed the usefulness of PBMT in the treatment of inflammation and ARSD in patients with COVID-19 infection. This therapy is non-invasive and safe to modulate the immune responses in ARSD patients. Conclusion: PBMT can potentially reduce the viral load and bacterial super-infections in patients with COVID-19 infection and control the inflammatory response. Therefore, the use of PBMT could be an efficient strategy for preventing severe and critical illness in SARS-COV2 infection.

The effect of antimicrobial photodynamic therapy using yellow-green LED and rose bengal on Porphyromonas gingivalis

INTRODUCTION

This study aimed to investigate the effects of a new antimicrobial photodynamic therapy (aPDT) system using yellow-green light-emitting diode (YGL) and rose bengal (RB) on Porphyromonas gingivalis (Pg) in vitro.

MATERIALS AND METHODS

Pg suspension mixed with RB was irradiated with YGL (565 nm) or blue light-emitting diode (BL, 470 nm) at 428 mW/cm² in comparison with chlorhexidine (CHG) treatment. The cells were cultured anaerobically on agar plates, and the number of colony-forming units (CFU) was determined. The treated suspension was anaerobically incubated, and the cell density (OD_600nm) was monitored for 24 h. Also, the viability of treated human gingival fibroblast (HGF-1) was measured using WST-8 assay. Pg morphology was observed with a scanning electron microscope. The RNA integrity number of aPDT-treated Pg was determined and gene expressions were evaluated by quantitative real-time polymerase chain reaction.

RESULTS

RB + YGL (aPDT) demonstrated a significantly higher reduction of CFU, compared to RB + BL (aPDT) and CHG, furthermore the OD value rapidly decreased. Morphological changes of Pg with RB + YGL were more severe than with CHG. Although RB + YGL reduced HGF-1 viability, aPDT's impact was significantly lower than CHG's. With RB + YGL treatment, RIN values decreased; furthermore, gene expressions associated with DNA replication and cell division were remarkably decreased after 12 h.

CONCLUSION

The results of this study demonstrated that a novel aPDT system using RB + YGL may have potential as a new technical modality for bacterial elimination in periodontal therapy.

Assessment of safety and efficacy of antimicrobial photodynamic therapy for peri-implant disease

BACKGROUND

There is no reliable treatment procedure for peri-implant disease, despite the rise in its incidence. This study sought to evaluate the short-term safety and efficacy of antimicrobial photodynamic therapy (a-PDT) on peri-implantitis by assessing the volume of pus discharge after a-PDT.

METHODS

Patients with pus discharge from a peri-implant pocket were recruited from December 1st, 2019 to April 30th, 2020. The enrolled implants were randomly assigned to one of two groups, the irrigation and a-PDT groups. Their peri-implant pocket was irrigated with normal saline in the irrigation group, and a saline irrigation and subsequent a-PDT with toluidine blue (TB) was performed in the a-PDT group. The safety and efficacy of a-PDT were assessed 7 days after treatment.

RESULTS

Twenty-five implants in 21 patients (irrigation group; 13 implants, a-PDT group; 12 implants) were registered. No complication was observed after a-PDT. Pus discharge was decreased in 7 of 12 implants (58.3 %) in the a-PDT group, and in 2 of 13 implants (15.4 %) in the irrigation group. According to Fisher's exact test, a-PDT resulted in a statistically significant decrease in pus discharge compared to irrigation alone (p = 0.0414).

CONCLUSIONS

a-PDT was confirmed to be a safe treatment for peri-implantitis, and the short-term efficacy of a-PDT with TB on peri-implantitis was clarified. Nevertheless, its efficacy remains restricted, and a new combination therapy of a-PDT and decontamination procedures is expected to be developed in future.

Antimicrobial effect of photodynamic therapy using sinoporphyrin sodium and 390-400 nm light-emitting diode on Porphyromonas gingivalis in vitro

This study aims to investigate the effect of antimicrobial photodynamic therapy (a-PDT) using a novel combination of sinoporphyrin sodium (DVDMS) and light-emitting diode (LED) with a wavelength of 390-400 nm on Porphyromonas gingivalis in vitro. Absorption spectrum of DVDMS was determined by spectrometer for selecting suitable wavelength light source. The uptake of DVDMS by P. gingivalis was evaluated according to fluorescence intensity detected by a spectrometer. Then effects of DVDMS alone, 390-400 nm LED alone, and photodynamic therapy produced by 10, 20, 40, and 80 μg/mL DVDMS and 390-400 nm LED on the suspension of P. gingivalis were evaluated by counting the number of colony forming units (CFU) after incubation. In the experiment, the LED illumination time was 30, 60, 90, 120, 180, 240, and 360 s, respectively, and the corresponding energy density was 1, 2, 3, 4, 6, 8, and 12 J/cm², respectively. According to the absorption spectrum of DVDMS, the 390-400-nm light emitted by the LED was selected as the light source. The fluorescence intensity of DVDMS on P. gingivalis increased significantly at 5 min, and with the extension of time, it decreased at 30 min. DVDMS alone did not produce a significant toxicity on P. gingivalis compared with PBS (p = 0.979). While 390-400 nm LED alone had a certain bactericidal effect on P. gingivalis, the bactericidal effect was more obvious as the light dose increased (p < 0.001). The effect of a-PDT produced by 20, 40, and 80 μg/mL DVDMS and 390-400 nm LED were significantly better than that of 390-400 nm LED alone (p < 0.05). Both DVDMS concentration and light dose could enchance the bactericidal effect. The strongest photo-killing effect was generated by 80 μg/mL DVDMS with 360 s illumination (energy density is 12 J/cm²), and the log reduction of bacteria was 5.69 ± 1.70. a-PDT using the combination of DVDMS with 390-400 nm LED shows promise as a new treatment modality for pathogens elimination in periodontal therapy.

Staphylococcus aureus growth delay after exposure to low fluencies of blue light (470 nm)

Antibiotic resistance is one of the greatest challenges to treat bacterial infections worldwide, leading to increase in medical expenses, prolonged hospital stay and increased mortality. The use of blue light has been suggested as an innovative alternative to overcome this problem. In this study we analyzed the antibacterial effect of blue light using low emission parameters on Staphylococcus aureus cultures. In vitro bacterial cultures were used in two experimental approaches. The first approach included single or fractionated blue light application provided by LED emitters (470 nm), with the following fluencies: 16.29, 27.16 and 54.32 J/cm2. For the second approach a power LED (470 nm) was used to deliver 54.32 J/cm2 fractionated in 3 applications. Our results demonstrated that bacterial cultures exposed to fractionated blue light radiation exhibited significantly smaller sizes colonies than the control group after 24 h incubation, however the affected bacteria were able to adapt and continue to proliferate after prolonged incubation time. We could conclude that the hypothetical clinical use of low fluencies of blue light as an antibacterial treatment is risky, since its action is not definitive and proves to be ineffective at least for the strain used in this study.

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.

Susceptibility of oral bacteria to antibacterial photodynamic therapy

Effective methods for managing the oral microbiome are necessary to ensure not only the oral but also the systemic health of a human body. The purpose of this study was to determine the sensitivity of four photosensitizers (PSs) to blue light in six representative oral bacterial species that cause intraoral diseases. The following six strains were investigated: Actinomyces israelii, Enterococcus faecium, Fusobacterium nucleatum, Lactobacillus gasseri, Streptococcus mutans, Veillonella parvula. PS stock solutions (1 mg/ml) were prepared by dissolving curcumin and protoporphyrin-IX in dimethyl sulfoxide, and resazurin and riboflavin in distilled water. The inoculation of 20 ml of a bacterial suspension cultured for 24 hours was mixed with 1,980 ml of each test solution, and then a light source was placed in front of the mixture. The irradiation wavelength was 405 nm and its applied energy was 25.3 J. The independent-samples t-test and one-way analysis of variance within groups were performed to compare the antibacterial effects in the four PSs. The antibacterial susceptibility when using different PSs and visible blue-light irradiation differed between the bacterial strains. Antibacterial photodynamic therapy that includes light exposure and PSs can be used to control the oral bacteria strains related to oral disease.

The Effects of Ultraviolet Light-Emitting Diodes with Different Wavelengths on Periodontopathic Bacteria In Vitro

Objective: The aim of this study was to examine effects of recently developed ultraviolet light-emitting diodes (UV LEDs) wavelengths on in vitro growth and gene expression of cultural periodontopathic bacteria, and on viability of experimental gingival fibroblasts. Materials and methods: Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Streptococcus oralis were irradiated by UV LEDs (265, 285, 310, 365, and 448 nm) at 600 mJ/cm² and grown anaerobically in vitro. The colony forming units were counted after 1 week. Cell morphology was observed using a scanning electron microscope (SEM). Quantitative real-time polymerase chain reaction was performed to investigate gene expression changes by 310 nm irradiation. Viability of the irradiated human gingival fibroblasts was evaluated using WST-8 assay. Results: Both 265 and 285 nm resulted in the complete death of bacteria and fibroblasts, whereas 310 nm caused partial killing and suppression of bacterial growth and much less damage to the fibroblasts in vitro. Both 365 and 448 nm resulted in no significant change. SEM showed that P. gingivalis cells gradually degraded from day 2 or 3 and were severely destructed on day 5 for 265, 285, and 310 nm. The 310 nm irradiation transiently suppressed the transcripts of SOS response- and cell division-relative genes. Conclusions: Both 265 and 285 nm may induce powerful bactericidal effects and severe fibroblast phototoxicity, and 310 nm may induce partial killing or growth suppression of bacterial cells with much less fibroblast phototoxicity. UV lights may have potential for bacterial suppression, with situations dependent on wavelength, in periodontal and peri-implant therapy.

Nanoparticles having amphiphilic silane containing Chlorin e6 with strong anti-biofilm activity against periodontitis-related pathogens

OBJECTIVES

The objectives of this study were to: (1) develop the multifunctional nanoparticles containing Chlorin e6 (Ce6), Coumarin 6 (C6) and Fe₃O₄ nanoparticles (NPs); and (2) investigate the inhibitory effects of the nanoparticles via antibacterial photodynamic therapy (aPDT) against three species of periodontitis-related pathogens for the first time.

MATERIALS AND METHODS

Ce6 and C6 were co-loaded into the Fe₃O₄-silane core-shell structure to form multifunctional nanoparticles (denoted "Fe₃O₄-silane@Ce6/C6 MNPs"). The physical and chemical properties of nanoparticles were characterized. Biofilm properties of Streptococcus sanguinis, Porphyromonas gingivalis and Fusobacterium nucleatum were tested. Colony-forming units (CFU), live/dead assay, and metabolic activity of biofilms were determined to evaluate the aPDT function mediated by the Fe₃O₄-silane@Ce6/C6 MNPs. Fluorescence imaging and the targeted antibacterial effects were also investigated.

RESULTS

Fe₃O₄-silane@Ce6/C6 MNPs showed superparamagnetic properties, chemical stability and water-solubility, with no cytotoxicity. Fe₃O₄ NPs did not compromise the emission peaks of C6 and Ce6. The Fe₃O₄-silane@Ce6/C6-mediated aPDT had much greater reduction in biofilms than the control groups (p < 0.05). Biofilm CFU was reduced by about 4-5 orders of magnitude via Fe₃O₄-silane@Ce6/C6-mediated aPDT. The co-loading of Ce6 and C6 enabled the real-time aPDT monitoring by ratio emissions with the same wavelength. Fe₃O₄ with magnetic field enabled the targeting of infection sites by killing bacteria via magnetic field.

CONCLUSION

The multifunctional nanoparticles exerted strong anti-biofilm activity against periodontitis-related pathogens, with excellent biocompatibility, real-time monitoring, and magnetically-targeting capacities. The multifunctional nanoparticles have great potential in antibacterial applications to inhibit the occurrence and progression of periodontitis.

Remediation of adult black dental stains by phototherapy

Introduction and aims

This study investigates the effects of the application of antimicrobial phototherapy on black-stained tooth surfaces. Key variables were area, color and time taken to reappearance of black stain following dental prophylaxis with and without antimicrobial phototherapy. Differences in bacterial composition of black stain (specifically Aggregatibacter actinomycetemcomitans, Tannerella forsythia, and Porphyromonas gingivalis) were analyzed.

Material and methods

The phototherapy device used was GLO™ Science LLC, New York, America, emitting light at 475 nm and a power of 3 W. Light was applied in 2 cycles of 8 min on 31 volunteers. Microbial identification was carried out on DNA extracted from black plaque. This study is registered with ClinicalTrials.gov, number NCT03309748.

Results

Following antimicrobial phototherapy, 64.5% of patients displayed reduced pigmentation area. Plaque color was lighter in 48.4% of subjects. Pigmentation area and depth of color returned to normal levels during the course of the study. Colonization by the three bacterial species decreased, although the changes were not statistically significant. We report a key novel finding showing elevated levels of colonization by Tannerella forsythia (83.9%) in adult black stain.

Conclusions

Application of phototherapy results in a reduction in area, color and bacterial colonization of black plaque in adults. The changes were not found to be statistically significant, perhaps owing to the low illumination power of the home-whitening device. For the first time, we document the elevated presence of Tannerella forsythia in adult black stain. We also demonstrate the potential application of a commercially available home-whitening device for black plaque treatment.

Photodynamic Inactivation of Porphyromonas gingivalis utilizing Radachlorin and Toluidine Blue O as Photosensitizers: An In Vitro Study

Introduction:Porphyromonas gingivalis is one of the major pathogens in the development and progression of periodontal disease. Antimicrobial photodynamic therapy (aPDT) is a new approach which is sorted in non-invasive phototherapy for bacterial elimination. This in vitro study was conducted to compare photodynamic inactivation using Radachlorin and Toluidine blue O (TBO) as photosensitizers on P. gingivalis. Methods: Bacterial suspensions (200 µL) of P. gingivalis were exposed to either TBO with concentration of 0.1 mg/mL associated with portable light-emitting diode (LED) device (peak wavelength: 630 nm, output intensity: 2.000 mW/cm2, tip diameter: 6.2 mm) or 0.1% Radachlorin® and laser irradiation (InGaAlP, Peak wavelength: 662±0.1% nm, output power: 2.5 W, energy density: 6 J/cm2, fiber diameter: 2 mm). Those in control groups were subjected to laser irradiation or LED alone, Radachlorin® or TBO alone, and one group received neither photosensitizer nor light irradiation. Then counting of colony forming units (CFU) was performed to determine the bactericidal effects in each subgroup. Results: LED-based aPDT reduced the colony count of P. gingivalis more than that of TBO (P<0.001) or LED group (P=0.957). Also, laser-based aPDT had a great reduction in colony count of P. gingivalis in comparison with Radachlorin® (P<0.001) or laser irradiation alone (P=0.28). In addition, the colony count reduction of laser-based aPDT was significantly more than LED-based aPDT (P<0.05). Conclusion: Considering the results of this study, the viability of P. gingivalis was more affected by the combination of laser and Radachlorin® 0.1% in comparison with LED and TBO 0.1.

Antimicrobial blue light inactivation of pathogenic microbes: State of the art

As an innovative non-antibiotic approach, antimicrobial blue light in the spectrum of 400-470nm has demonstrated its intrinsic antimicrobial properties resulting from the presence of endogenous photosensitizing chromophores in pathogenic microbes and, subsequently, its promise as a counteracter of antibiotic resistance. Since we published our last review of antimicrobial blue light in 2012, there have been a substantial number of new studies reported in this area. Here we provide an updated overview of the findings from the new studies over the past 5 years, including the efficacy of antimicrobial blue light inactivation of different microbes, its mechanism of action, synergism of antimicrobial blue light with other angents, its effect on host cells and tissues, the potential development of resistance to antimicrobial blue light by microbes, and a novel interstitial delivery approach of antimicrobial blue light. The potential new applications of antimicrobial blue light are also discussed.

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.

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.

Antimicrobial photodynamic therapy and dental plaque: a systematic review of the literature

Background. The aim of this study was to perform a systematic review of the literature on the efficacy of antimicrobial photodynamic therapy (PDTa) on cariogenic dental biofilm. Types of Studies Reviewed. Studies in vivo, in vitro, and in situ were included. Articles that did not address PDTa, those that did not involve cariogenic biofilm, those that used microorganisms in the plankton phase, and reviews were excluded. Data extraction and quality assessments were performed independently by two raters using a scale. Results. Two hundred forty articles were retrieved; only seventeen of them met the eligibility criteria and were analyzed in the present review. Considerable variability was found regarding the methodologies and application protocols for antimicrobial PDTa. Two articles reported unfavorable results. Practical Implications. The present systematic review does not allow drawing any concrete conclusions regarding the efficacy of antimicrobial PDTa, although this method seems to be a promising option.

Wavelength and bacterial density influence the bactericidal effect of blue light on methicillin-resistant Staphylococcus aureus (MRSA)

OBJECTIVE

The purpose of this study was to investigate the effect of wavelength and methicillin-resistant Staphylococcus aureus (MRSA) density on the bactericidal effect of 405 and 470 nm light.

BACKGROUND DATA

It is recognized that 405 and 470 nm light-emitting diode (LED) light kill MRSA in standard 5 × 10(6) colony-forming units (CFU)/mL cultures; however, the effect of bacterial density on the bactericidal effect of each wavelength is not known.

METHODS

In three experiments, we cultured and plated US300 MRSA at four densities. Then, we irradiated each plate once with either wavelength at 0, 1, 3, 45, 50, 55, 60, and 220 J/cm(2).

RESULTS

Irradiation with either wavelength reduced bacterial colonies at each density (p<0.05). More bacteria were cleared as density increased; however, the proportion of colonies cleared, inversely decreased as density increased--the maximum being 100%, 96%, and 78% for 3 × 10(6), 5 × 10(6), and 7 × 10(6) CFU/mL cultures, respectively. Both wavelengths had similar effects on the sparser 3 × 10(6) and 5 × 10(6) CFU/mL cultures, but in the denser 7 × 10(6) CFU/mL culture, 405 nm light cleared more bacteria at each fluence (p<0.001). To determine the effect of beam penetration, denser 8 × 10(6) and 12 × 10(6) CFU/mL culture plates were irradiated either from the top, the bottom, or both directions. More colonies were eradicated from plates irradiated from top and bottom, than from plates irradiated from top or bottom at the same sum total fluences (p<0.001).

CONCLUSIONS

The bactericidal effect of LED blue light is limited more by light penetration of bacterial layers than by bacterial density per se.

Antimicrobial effect of photodynamic therapy using high-power blue light-emitting diode and red-dye agent on Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Antimicrobial photodynamic therapy (a-PDT) using a combination of red-colored laser/light-emitting diode (LED) and blue dye has been employed for periodontal therapy and the antimicrobial effect seems promising. Blue light, which has favorable wavelength properties, would be more effective as a light source for a-PDT because blue light itself possesses an antimicrobial effect. This study aimed to investigate the effect of a-PDT using a novel combination of high-power blue LED and red-dye agent on Porphyromonas gingivalis in vitro.

MATERIAL AND METHODS

Porphyromonas gingivalis ATCC 33277 suspension was irradiated with blue LED (BL) (425-470 nm) or red LED (RL) (625-635 nm) at 30-90 J/cm(2) , or was mixed with erythrosine (ER), phloxine B (PB) or rose bengal (RB) with or without BL irradiation (30 J/cm(2) ). RL (30 J/cm(2) ) in combination with toluidine blue was employed as positive control. All the suspensions of P. gingivalis were serially diluted, plated and incubated anaerobically, and the numbers of colony-forming units (CFUs) were counted on day 7.

RESULTS

BL irradiation at 60 and 90 J/cm(2) demonstrated a significant reduction in the numbers of CFUs. ER, PB and RB solutions at 160 μg/mL showed almost no or only a minimal reduction in the numbers of CFUs. BL at 30 J/cm(2) combined with ER, PB or RB at 160 μg/mL resulted in a log reduction of 0.9, 1.0 and 7.1, respectively, in the numbers of CFUs; 30 J/cm(2) BL with RB at 1.6, 16 and 160 μg/mL demonstrated a log reduction of 6.3, 8.0 and 5.5, respectively; and a log reduction of 5.2 was obtained after 30 J/cm(2) RL with 16 μg/mL TB.

CONCLUSION

Within the limits of this study, BL was found to have an antimicrobial/growth-inhibiting effect on P. gingivalis, and a-PDT using a combination of BL and RB shows promise as a new technical modality for bacterial elimination in periodontal therapy.