Effect Of Photodynamic Treatment Research Articles

SARS-CoV-2 surrogate bacteriophage φ6 cross-contamination between fruits and gloves, survival on discarded gloves and inactivation by photodynamic treatment

This study assessed the SARS-CoV-2 surrogate bacteriophage φ6 cross-contamination between high-density polyethylene or polyvinyl chloride gloves and fruits (tomato and cucumber) using different inoculum levels (6.0 and 4.0 log PFU/sample). Bacteriophage φ6 survival on contaminated gloves was assessed over 9 days at 25 °C. The effectiveness of photodynamic treatment using curcumin as a photosensitizer to inactivate φ6 on fruits was determined. The fruit type and the glove material influenced the φ6 transfer. Longer contact times resulted in greater φ6 transfer. The highest φ6 transfer occurred from tomato to HDPE glove (0.8% or −1.1 log % transfer) after 30 s of contact at the higher inoculum level. Bacteriophage φ6 was detected on cross-contaminated HDPE gloves for up to 6 days. Bacteriophage φ6 survived better on vinyl gloves cross-contaminated by cucumber vs. tomato (detected up to 6 vs 3 days). Photodynamic inactivation of φ6 was time-dependent and varied with the tested fruit but was not influenced by viral starting concentration. Photodynamic treatment decreased the φ6 titer by 3.0 and 2.2 log PFU/sample in tomato and cucumber, respectively. Transmission electronic microscopy showed that photodynamic treatment changed the structure of the φ6 capsid. These findings may help in the management of SARS-CoV-2 contamination risks in fruit handling. They may also help in the establishment of effective measures to manage cross-contamination risk.

Evaluation of chlorophyll-loaded mesoporous silica nanoparticles for photodynamic therapy on cancer cell lines

Chlorophyll (Chl) is a promising natural photosensitizer (PS) in photodynamic treatment (PDT). Mesoporous silica nanoparticles (MSNs) were chosen to increase the effectiveness of PDT. This study aimed to evaluate the synergistic efficacy of chlorophyll-loaded mesoporous silica nanoparticles (Chl-MSNs) with photodynamic therapy (PDT) and to investigate their potential toxicity in HepG2, MDA-MB-231, and HSF cell lines. Chl-MSNs were prepared via the physical adsorption method. TEM, DLS, and zeta potential examined morphology, size, and surface characteristics. MSNs and Chl-MSNs were characterized using the same techniques. HPLC was used to assess the encapsulation efficiency. At pH 7.4, an in vitro release experiment of Chl-MSNs was performed. Chl, MSNs, and Chl-MSNs were applied to the three cell lines at different concentrations and subjected to red (650 nm) and blue (450–500 nm) lasers. MSNs and Chl-MSNs’ sizes were 90.338 ± 38.49 nm and 123.84 ± 15.67 nm, respectively, as obtained by TEM; the hydrodynamic diameter for MSNs (93.69 ± 20.53 nm) and Chl-MSNs (212.95 ± 19.76 nm); and their zeta potential values are − 16.7 ± 2.19 mV and − 18.84 ± 1.40 mV. The encapsulation efficiency of Chl-MSNs was 70%. Chl-MSNs displayed no toxicity in dark conditions but showed excellent photostability under blue and red light exposure. Furthermore, using Chl over Chl-MSNs has a higher PDT efficiency than the tested cell lines. Chl-MSNs have the potential to be an effective delivery system. PDT proved to be an essential technique for cancer treatment. Blue laser is recommended over red laser with Chl and MSNs for destroying cancer cells.Graphical

Curcumin-mediated photodynamic treatment extends the shelf life of salmon (Salmo salar) sashimi during chilled storage: Comparisons of preservation effects with five natural preservatives

The impact of curcumin-mediated photodynamic treatment (PDT) on the microbiological, physicochemical and sensory qualities of salmon sashimi has not been explored. Herein, this study aimed to evaluate the effects of PDT on the shelf-life quality of ready-to-eat salmon fillets during chilled storage (4 °C) in comparison with five widely investigated natural extracts, including cinnamic aldehyde, rosmarinic acid, chlorogenic acid, dihydromyricetin and nisin. From a microbial perspective, PDT exhibited outstanding bacterial inhibition, the results of total viable counts, total coliform bacteria, psychrotrophic bacteria, Pseudomonas spp., Enterobacteriaceae family, and H2S-producing bacteria were notably inactivated (p < 0.05) to meet the acceptable limits by PDT in comparison with those of the control group and natural origin groups, which could extend the shelf-life of salmon fillets from<6 days to 10 days. In the alteration of physicochemical indicators, PDT and natural extracts were able to maintain the pH value and retard lipid oxidation in salmon fillets, while apparently slowing the accumulation (p < 0.05) of total volatile basic nitrogen and biogenic amines, especially the allergen histamine, which contrary to with the variation trend of spoilage microbiota. In parallel, PDT worked effectively (p < 0.05) on the breakdown of adenosine triphosphate and adenosine diphosphate to maintain salmon fillet freshness. Additionally, the physical indicators of texture profile and color did not have obvious changes (p < 0.05) after treated by PDT during the shelf life. Besides, the sensory scores of salmon samples were also significantly improved. In general, PDT not only has a positive effect on organoleptic indicators but is also a potential antimicrobial strategy for improving the quality of salmon sashimi.

Identification of Blood Transport Proteins to Carry Temoporfin: A Domino Approach from Virtual Screening to Synthesis and In Vitro PDT Testing.

Temoporfin (mTHPC) is one of the most promising photosensitizers used in photodynamic therapy (PDT). Despite its clinical use, the lipophilic character of mTHPC still hampers the full exploitation of its potential. Low solubility in water, high tendency to aggregate, and low biocompatibility are the main limitations because they cause poor stability in physiological environments, dark toxicity, and ultimately reduce the generation of reactive oxygen species (ROS). Applying a reverse docking approach, here, we identified a number of blood transport proteins able to bind and disperse monomolecularly mTHPC, namely apohemoglobin, apomyoglobin, hemopexin, and afamin. We validated the computational results synthesizing the mTHPC-apomyoglobin complex (mTHPC@apoMb) and demonstrated that the protein monodisperses mTHPC in a physiological environment. The mTHPC@apoMb complex preserves the imaging properties of the molecule and improves its ability to produce ROS via both type I and type II mechanisms. The effectiveness of photodynamic treatment using the mTHPC@apoMb complex was then demonstrated in vitro. Blood transport proteins can be used as molecular "Trojan horses" in cancer cells by conferring mTHPC (i) water solubility, (ii) monodispersity, and (iii) biocompatibility, ultimately bypassing the current limitations of mTHPC.

Effects of curcumin‐based photodynamic treatment combined with low‐temperature storage on shelf life and purine content of Litopenaeus vannamei

In this study, the effects of photodynamic treatment on the shelf life and purine content of Litopenaeus vannamei under low-temperature storage conditions were investigated. Indicators of shelf life were detected to evaluate the shelf life, and the change of purine content during storage detected by HPLC. The results showed that compared with cold storage, the shelf life of shrimp was extended from 3 days to 8 days with the treatment of microcrystalline storage. Moreover, the shelf life of shrimp was extended to 12 days when stored with the photodynamic treatment combined with microcrystalline storage (PDT + MT). The content of hypoxanthine decreased significantly after 24 h storage, which may be related to the inhibition of 5′-NT, PNP, ADA, and XOD activities. This study provided scientific support for the popularization and application of photodynamic technology in the storage of shrimp. Novelty impact statement Photodynamic technology is helpful to prolong the shelf life of shrimp during low-temperature. Photodynamic combined with low-temperature can affect purine content by affecting purine metabolism enzymes.

Photoacoustic Effect of Near-Infrared Absorbing Organic Molecules via Click Chemistry.

Near-infrared dyes were developed to be contrast agents due to their ability to improve the productivity of photoacoustic (PA) imaging and photothermal therapy (PTT) treatments. During the article, we described in detail the PA and PT effects of a category of organic molecules. F4-TCNQ could potentially cause a red-shift in the peak PA intensity. The results show that the PTT intensity of the near-infrared dyes with phenyl groups were higher than near-infrared dyes with thiophene groups. We also investigated the photodynamic treatment effect of C1b to demonstrate that these dyes are highly desirable in biochemistry. The high photoacoustic intensity of the organic molecules and the good yield of reactive oxygen species could indicate that these dyes have good potential for a wide range of imaging applications. Finally, we embedded the dye (C1b) in a liposomal hydrophobic phospholipid bilayer (C1b⊂L) to facilitate the application of hydrophobic dyes in biomedical applications, which can be absorbed by cells with good compatible and high stability for the imaging of cellular PA.

Photobiomodulation and Antimicrobial Photodynamic Influence of a 650 nm Wavelength on Staphylocoagulase and Viability of Staphylococcus aurous

Introduction: Staphylococcus aureus is one of the critical pathological bacteria. This bacterium had developed a variety of genetic mutations that made it resistant to drugs and more harmful to humans. In addition, all attempts to design a specific vaccine against S. aureus have failed. Therefore, this experiment was designed as a trial for vaccine production, by using a photodynamic treatment (PDT) through partial biological inhibition. The PDT of bacteria mainly focused on reducing the activity of staphylocoagulase (SC), which has a protective feature for bacteria. This study aimed to examine the photodynamic effect of combining a specific wavelength of a laser and a certain dilution photosensitizer, methylene blue (MB) dye. The possible PDT effect on the inhibition of pathogenic enzymatic activity was predicted. This study also aimed to evaluate the inhibitory effect of PDT on the total bacterial account (viability) simultaneously with SC assay. Methods: A 650nm wavelength diode laser was used with 100 mW output power and 2 minutes of exposure time. Dye dilutions were 50, 100, 150 and 200 μg/mL. The viability of bacteria after and before laser treatment was calculated using single plate-serial dilution spotting methods. The activity of SC was detected by using human plasma for 4 hours incubation of crude-substrate interaction. Results: The results revealed a significant decrease in enzyme activity and colony-forming units (CFU) after irradiating bacterial suspension with 150 g/mL MB, as well as a decline in CFU. However, irradiation with a laser alone showed a significant increase in SC activity and CFU for the same exposure time. Conclusion: Besides reducing the production of SC activity, PDT significantly inhibited the viability of S. aureus. The application of MB photosensitizer at a concentration of 150 g/mL in combination with a laser wavelength of 650 nm resulted in a complete decrease in the SC activity value as well as the viability of bacteria.

Drug delivery system with dual imaging and dual response control drug release functions for chemo-photodynamic synergistic therapy

Traditional treatment of cancers such as chemotherapy still causes many side effects after the treatment even nowadays, therefore combination therapies by using drug delivery systems are valued by more and more scientists. However, loading multiple drugs in the nanoparticles for drug delivery system may cause insufficient drugs or functional groups, which might let the nanomaterial have fewer functions. Therefore, making the mesoporous silica nanoparticles (MSNs) have photodynamic therapy function by “doping “ lanthanide ions into the material structure, can evade this problem. Moreover, with the doping of lanthanide metals, the MSNs can have not only dual imaging functions of both magnetic resonance imaging and fluorescence, but also achieve photodynamic function. To feature the material with more function, chemotherapeutic drug-doxorubicin was loaded into the pores of MSNs and then bonded hyaluronic acid which is the active target and a gatekeeper, on the surface of MSNs. Finally, an all-in-one drug delivery system” Hyaluronidase and pH-responsive mesoporous silica nanoparticles with dual-imaging activity for chemo-photodynamic therapy” is synthesized. The first part in this experiment was to confirm the physical properties of the lanthanides dopped MSN and its photodynamic treatment effect. The second part was to confirm that each organic molecule had been successfully bonded to the surface of the MSN and achieve pH and Hyaluronidase response drug release effect, The last part was to prove that the drug delivery system had a significant anticancer effect through cell experiments.

Min Oscillations as Real-time Reporter of Sublethal Effects in Photodynamic Treatment of Bacteria.

The Min protein system is a cell division regulator in Escherichia coli. Under normal growth conditions, MinD is associated with the membrane and undergoes pole-to-pole oscillations. The period of these oscillations has been previously proposed as a reporter for the bacterial physiological state at the single-cell level and has been used to monitor the response to sublethal challenges from antibiotics, temperature, or mechanical fatigue. Using real-time single-cell fluorescence imaging, we explore here the effect of photodynamic treatment on MinD oscillations. Irradiation of bacteria in the presence of the photosensitizer methylene blue disrupts the MinD oscillation pattern depending on its concentration. In contrast to antibiotics, which slow down the oscillation, photodynamic treatment results in an abrupt interruption, reflecting divergent physiological mechanisms leading to bacterial death. We show that MinD oscillations are sensitive to mild photodynamic effects that are overlooked by traditional methods, expanding the toolbox for mechanistic studies in antimicrobial photodynamic therapy.

Effects of curcumin-mediated photodynamic treatment on lipid degradation of oysters during refrigerated storage.

Oyster's lipid degradation leads to a decrease in edible and nutritional value. Curcumin-mediated photodynamic treatment (PDT) is an innovative non-thermal technology, although evaluation of the oyster's lipid degradation has been scarce. In the present study, we investigated peroxide value, thiobarbituric acid reactive substance, triacylglycerol and free fatty acids to evaluate the effect of curcumin-mediated PDT on lipid degradation of oysters during refrigerated storage. The results showed that curcumin-mediated PDT could delay oyster's lipid degradation. Next, the activities of enzymes were detected to determine the mechanisms behind the effects of curcumin-mediated PDT. It was revealed that the activities of lipase, phospholipase A2 (PLA2 ), phospholipase C (PLC), phospholipase D (PLD) and lipoxygenase (LOX) were significantly inhibited after curcumin-mediated PDT (P < 0.05). Furthermore, 16 s rRNA analysis established that the relative abundances of Pseudoalteromonas and Psychrilyobacter were reduced by 51.58% and 43.82%, respectively, after curcumin-mediated PDT. Curcumin-mediated PDT could delay oyster's lipid degradation by inhibiting the activities of lipase, PLA2 , PLC, PLD and LOX, as well as by changing the oyster's microbial composition, reducing the relative abundance of Pseudoalteromonas and Psychrilyobacter. © 2021 Society of Chemical Industry.

Photodynamic Therapy for Advanced Gastric Cancer: A Case Report

Background and Study Aims: To observe the efficacy of photodynamic therapy in patients with advanced gastric cancer and analyze the reasons affecting the efficacy. Methods: In this paper, a patient with advanced gastric cancer in our hospital was selected.HoPorfin is used as a photosensitizer and photodynamic therapy was performed 48 hours and 72 hours later. Results: One month after the photodynamic treatment, the patient came to our hospital to reexamine the gastroscope. Through the comparison of gastroscopy before and after the photodynamic treatment, the gastric cancer lesion of the patient after the photodynamic treatment was not significantly smaller than before, and the effect of photodynamic treatment was not ideal. Conclusion: The four reasons for the unsatisfactory effect: individual differences of patients, photosensitizer, light source and oxygen.

Impact of Blue LED Illumination and Natural Photosensitizer on Bacterial Pathogens, Enzyme Activity and Quality Attributes of Fresh-Cut Pineapple Slices

Fresh-cut fruits are susceptible for microbial contamination during handling and storage. Hence, there is a need for minimal processing of such foods using non-thermal technology that can inactivate both bacterial pathogens and undesirable enzymes while retaining the quality. In this regard, synergistic effect of light emitting diode (LED) based blue light (BL) and natural exogenous photosensitizer- curcumin (PS) on the inactivation of bacterial pathogens (Escherichia coli, Staphylococcus aureus), and enzymes (polyphenol oxidase, peroxidase, bromelain) of fresh-cut pineapple slices were evaluated. The effect of photodynamic treatment (PS+BL) on quality attributes like color, phenolics, flavonoids, ascorbic acid content and antioxidant activity was also investigated. The PS+BL treatment at optimized conditions resulted in 3 and 4 log reduction of E. coli and S. aureus, respectively. PS(100 μM)+BL treatment led to partial inactivation of polyphenol oxidase (33.5%) and peroxidase (25.7%), synergistically, but preserved desired enzyme bromelain. The PS+BL didn’t show any significant (p<0.05) consequence on color, phenolics, flavonoids and antioxidant activity, while it affected the ascorbic acid content negatively (reduced by ~30%). The current investigation showed that the photodynamic inactivation of E. coli and S. aureus using LED-based photosensitization in fresh-cut fruit slices could be used as a potential method for microbial control although some phytochemical losses.

A few-layer graphene/chlorin e6 hybrid nanomaterial and its application in photodynamic therapy against Candida albicans.

The global emergence of multidrug resistance of fungal infections and the decline in the discovery of new antibiotics are increasingly prevalent causes of hospital-acquired infections, among other major challenges in the global health care sector. There is an urgent need to develop noninvasive, nontoxic, and new antinosocomial approaches that work more effectively and faster than current antibiotics. In this work, we report on a biocompatible hybrid nanomaterial composed of few-layer graphene and chlorin e6 (FLG-Ce6) for the photodynamic treatment (PDT) of Candida albicans. We show that the FLG-Ce6 hybrid nanomaterial displays enhanced reactive oxygen species (ROS) generation compared with Ce6. The enhancement is up to 5-fold when irradiated for 15 min at 632 nm with a red light-emitting diode (LED). The viability of C. albicans in the presence of FLG-Ce6 was measured 48 h after photoactivation. An antifungal effect was observed only when the culture/FLG-Ce6 hybrid was exposed to the light source. C. albicans is rendered completely unviable after exposure to ROS generated by the excited FLG-Ce6 hybrid nanomaterial. An increased PDT effect was observed with the FLG-Ce6 hybrid nanomaterial by a significant reduction in the viability of C. albicans, by up to 95%. This is a marked improvement compared to Ce6 without FLG, which reduces the viability of C. albicans to only 10%. The antifungal action of the hybrid nanomaterial can be activated by a synergistic mechanism of energy transfer of the absorbed light from Ce6 to FLG. The novel FLG-Ce6 hybrid nanomaterial in combination with the red LED light irradiation can be used in the development of a wide range of antinosocomial devices and coatings.

Impact of Molar Furcations on Photodynamic Therapy Outcomes: A 6-Month Split-Mouth Randomized Clinical Trial.

The effectiveness of adjunctive photodynamic treatment (PDT) to non-surgical periodontal therapy has been shown to depend on initial periodontal status. As molar furcation involvement impairs healing response to non-surgical periodontal therapy, the aim of this study was to evaluate the impact of furcation involvement on PDT outcomes. Thirty-six patients suffering from severe chronic periodontitis were included in a 6-month split-mouth randomized clinical trial. PDT applications used the toluidine blue O and a light-emitting diode (LED) with a red spectrum. Repeated PDT applications were performed in addition to non-surgical periodontal treatment at baseline and at 3-months. Pocket probing depth (PPD), plaque index, bleeding on probing, and clinical attachment level were recorded at baseline, and again at 3- and 6-months. Furcation sites of molars were compared to other sites of molars and non-molars. Multilevel analysis showed no PDT effect in molar furcation sites while an additional significant reduction (odds ratio = 0.67) of pockets with PPD > 5 mm in other sites at 3-months was measured. PPD reduction appeared delayed in molar furcation sites treated with PDT. There is no additional apparent benefit to use PDT in molar furcation sites for the reduction of pockets with PPD > 5 mm contrary to other sites.

Effect of Photodynamic Treatment on Skin Microbiome. Single Center Study

Effect of Photodynamic Treatment on Skin Microbiome. Single Center Study

Impact of tooth-related factors on photodynamic therapy effectiveness during active periodontal therapy: A 6-months split-mouth randomized clinical trial.

The persistence of periodontal pockets > 5 mm after periodontal treatments increases the risk of periodontitis recurrence and the need of periodontal surgery. This study evaluated the impact of tooth-related factors on the effectiveness of adjunctive photodynamic treatment (PDT) in the reduction of pockets > 5 mm during active periodontal treatment. Thirty-six patients suffering from severe chronic periodontitis were evaluated in a 6-months split-mouth randomized clinical trial. Each quadrant was assigned to test (scaling and root planing (SRP) + PDT) or control (SRP alone) group. PDT was conducted using the toluidine blue O and a light-emitting diode (LED) with a red spectrum. PDT applications were performed immediately after SRP, 7 days later and at 3 months. Plaque index (PI), bleeding on probing (BOP), periodontal pocket depth (PPD), and clinical attachment level (CAL) were recorded at baseline, 3 and 6 months. Multilevel analysis showed a significant reduction of pockets > 5 mm in test group in comparison with control group at 3 (OR = 0.69) and 6 months (OR = 0.77). This effect was mainly observed at 6 months in initially deep sites (PPD > 6 mm) with BOP (OR = 0.57). At sites exhibiting PI > 1 no PDT effect was observed. A more moderate PDT effect was observed on mean PPD and BOP reductions at 3 months only. Repeated applications of PDT significantly improved SRP outcomes, reducing by more than 40% residual pockets > 5 mm in initially deep and bleeding on probing periodontal sites. PDT effect was negatively influenced by dental plaque accumulation.

Effects of curcumin-based photodynamic treatment on the storage quality of fresh-cut apples

Photodynamic treatment (PDT) is an innovative technology with non-thermal and environmentally sound merits, but the evaluation on the storage qualities of fresh produce was scarce. In this study, the effects of curcumin-based PDT on the quality of fresh-cut ‘Fuji’ apple slices during storage at 4 °C were investigated. The impacts on the survival of Escherichia coli, color and weight loss were examined under different curcumin concentrations, illumination time or incubation time. Curcumin-based photodynamic inactivation of E. coli on the surface of apple slices reached 0.95 log. Curcumin-based PDT was proven to prevent browning and weight loss. Additionally, PDT significantly reduced the activity of polyphenol oxidase and peroxidases to 48% and 51%, respectively. Moreover, there were few negative changes in total phenolic, ascorbic acid content and anti-oxidant activity of the treated apples. These results indicated that curcumin-based PDT was a viable and promising non-thermal technology to preserve the quality of fresh produce.

Photodynamic opening of the blood‐brain barrier and pathways of brain clearing

A new application of the photodynamic treatment (PDT) is presented for the opening of blood-brain barrier (BBB) and the brain clearing activation that is associated with it, including the use of gold nanoparticles as emerging photosensitizer carriers in PDT. The obtained results clearly demonstrate 2 pathways for the brain clearing: (1) using PDT-opening of BBB and intravenous injection of FITC-dextran we showed a clearance of this tracer via the meningeal lymphatic system in the subdural space; (2) using optical coherence tomography and intraparenchymal injection of gold nanorods, we observed their clearance through the exit gate of cerebral spinal fluid from the brain into the deep cervical lymph node, where the gold nanorods were accumulated. These data contribute to a better understanding of the cerebrovascular effects of PDT and shed light on mechanisms, underlying brain clearing after PDT-related opening of BBB, including clearance from nanoparticles as drug carriers.

The effects of photodynamic treatment with new methylene blue N on the Candida albicans proteome.

Candida albicans is a human pathogenic fungus mainly affecting immunocompromised patients. Resistance to the commonly used fungicides can lead to poor treatment of mucosal infections which, in turn, can result in life-threatening systemic candidiasis. In this scenario, antimicrobial photodynamic treatment (PDT) has emerged as an effective alternative to treat superficial and localized fungal infections. Microbial death in PDT is a consequence of the oxidation of many cellular biomolecules, including proteins. Here, we report a combination of two-dimensional electrophoresis and tandem mass spectrometry to study the protein damage resulting from treating C. albicans with PDT with new methylene blue N and red light. Two-dimensional gels of treated cells showed an increase in acidic spots in a fluence-dependent manner. Amino acid analysis revealed a decrease in the histidine content after PDT, which is one plausible explanation for the observed acidic shift. However, some protein spots remained unchanged. Protein identification by mass spectrometry revealed that both modified and unmodified proteins could be localized to the cytoplasm, ruling out subcellular location as the only explanation for damage selectivity. Therefore, we hypothesize that protein modification by PDT is a consequence of both photosensitizer binding affinity and the degree of exposure of the photooxidizable residues on the protein surface.

Minimizing Concentration of Sodium Hypochlorite in Root Canal Irrigation by Combination of Ultrasonic Irrigation with Photodynamic Treatment.

Concentration of sodium hypochlorite (NaOCl) is positively correlated with its effectiveness in root canal disinfection but negatively correlated with its biocompatibility. The objective of this invitro study was to compare the bactericidal effects among ultrasonic irrigation with different concentration of NaOCl alone or together with photodynamic treatment (PDT) against Enterococcus faecalis (E.faecalis) in infected root canals. One hundred and twenty bovine root canals contaminated with E.faecalis were randomly distributed into 12 groups treated with different disinfection methods: PDT, ultrasonic irrigation with NaOCl at different concentrations (0.5%, 1.0%, 2.0%, 2.5% and 5.25%), and ultrasonic irrigation with NaOCl at different concentrations plus PDT. Data of microorganism load were collected before and after disinfection and analyzed by one-way ANOVA and LSD tests. Significantly enhanced antibacterial effects were noticed in groups treated by PDT plus 2.0% or 2.5% NaOCl irrigation (P<0.05). No statistical differences existed in bactericidal efficacy among groups of PDT plus ultrasonic irrigation with 2.0%, 2.5% or 5.25% NaOCl, and ultrasonic irrigation with 5.25% NaOCl alone (P>0.05). Our study confirmed the feasibility to reduce the concentration of NaOCl to a safer level while maintaining its antibacterial efficiency through synergistic effect of PDT with NaOCl ultrasonic irrigation.