Antibacterial photodynamic therapy with curcumin and Curcuma xanthorrhiza extract against Streptococcus mutans

Polydopamine-curcumin coating of titanium for remarkable antibacterial activity via synergistic photodynamic and photothermal properties

Combined photothermal therapy (PTT) and photodynamic therapy (PDT) has emerged as a novel and effective antibacterial strategy. In order to endow titanium (Ti) with antibacterial properties, the Ti-PDA-Cur composite was prepared using the excellent adhesion properties of polydopamine (PDA) to load curcumin (Cur) on the surface of Ti. The Ti-PDA-Cur coating can produce singlet oxygen (1O2) and heat under 405 + 808 nm light irradiation, which can effectively kill Staphylococcus aureus and Escherichia coli. Moreover, the cytotoxicity and hemolysis rate of Ti-PDA-Cur were low, indicating its good biocompatibility. Therefore, this study provided a new strategy for the development of new Ti implants.

Photoinactivation Effects of Curcumin, Nano-curcumin, and Erythrosine on Planktonic and Biofilm Cultures of Streptococcus mutans

Introduction: This in vitro study was conducted to assess the phototoxic effects of curcumin, nano-curcumin, and erythrosine on the viability of Streptococcus mutans (S. mutans) in suspension and biofilm forms. Methods: Various concentrations of curcumin (1.5 g/L, 3 g/L), nano-curcumin (3 g/L), and erythrosine (100 μM/L, 250 μM/L) were examined for their impact on planktonic and biofilm cultures of S. mutans, either individually or in conjunction with light irradiation (photodynamic therapy or PDT). A blue light-emitting diode (LED) with a central wavelength of 450 nm served as the light source. The results were compared to 0.12% chlorhexidine digluconate (CHX) as the positive control, and a solution containing neither a photosensitizer (PS) nor a light source as the negative control group. The dependent variable was the number of viable microorganisms per experiment (CFU/mL). Results: Antimicrobial PDT caused a significant reduction in the viability of S. mutans in both planktonic and biofilm forms, compared to the negative control group (P<0.05). The highest cell killing was observed in PDT groups with curcumin 3 g/L or erythrosine 250 μmol/L, although the difference with PDT groups using curcumin 1.5 g/L or erythrosine 100 μmol/L was not significant (P>0.05). Antimicrobial treatments were more effective against planktonic S. mutans than the biofilm form. Conclusion: PDT with either curcumin 1.5 g/L or erythrosine 100 μmol/L may be suggested as an alternative to CHX to inactivate the bacteria in dental plaque or deep cavities. Nano-curcumin, at the selected concentration, exhibited lower efficacy in killing S. mutans compared to Curcumin or erythrosine.

Application of Natural Medicinal Plants Active Ingredients in Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is the most common malignant cancer of the head and neck, with high morbidity and mortality, ranking as the sixth most common cancer in the world. The treatment of OSCC is mainly radiotherapy, chemotherapy and surgery, however, the prognosis of patients is still poor and the recurrence rate is high. This paper reviews the range of effects of natural medicinal plant active ingredients (NMPAIs) on OSCC cancer, including the types of NMPAIs, anti-cancer mechanisms, involved signaling pathways, and clinical trials. The NMPAIs include terpenoids, phenols, flavonoids, glycosides, alkaloids, coumarins, and volatile oils. These active ingredients inhibit proliferation, induce apoptosis and autophagy, inhibit migration and invasion of OSCC cells, and regulate cancer immunity to exert anti-cancer effects. The mechanism involves signaling pathways such as mitogen-activated protein kinase, phosphatidylinositol 3 kinase/protein kinase B, nuclear factor kappa B, miR-22/WNT1/β-catenin and Nrf2/Keap1. Clinically, NMPAIs can inhibit the growth of OSCC, and the combined drug is more effective. Natural medicinal plants are promising candidates for the treatment of OSCC.

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

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

The effect of photodynamic therapy in controlling the oral biofilm: A comprehensive overview

Several resistance mechanisms are involved in dental caries, including oral biofilms. An accumulation of bacteria on the surface of teeth is called plaque. Periodontitis and gingivitis are caused by dental plaque. In this review article, we aimed to review the studies associated with the application of photodynamic therapy (PDT) to prevent and treat various microbial biofilm-caused oral diseases in recent decades. There are several studies published in PubMed that have described antimicrobial photodynamic therapy (APDT) effects on microorganisms. Several in vitro and in vivo studies have demonstrated the potential of APDT for treating endodontic, periodontal, and mucosal infections caused by bacteria as biofilms. Reactive oxygen species (ROS) are activated in the presence of oxygen by integrating a nontoxic photosensitizer (PS) with appropriate wavelength visible light. By causing irreversible damage to microorganisms, ROS induces some biological and photochemical events. Testing several wavelengths has been conducted to identify potential PS for APDT. A standard protocol is not yet available, and the current review summarizes findings from dental studies on APDT.

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

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

Polyphenolic natural products as photosensitizers for antimicrobial photodynamic therapy: recent advances and future prospects

Antimicrobial photodynamic therapy (aPDT) has become a potent contender in the fight against microbial infections, especially in the context of the rising antibiotic resistance crisis. Recently, there has been significant interest in polyphenolic natural products as potential photosensitizers (PSs) in aPDT, given their unique chemical structures and inherent antimicrobial properties. Polyphenolic natural products, abundant and readily obtainable from natural sources, are generally regarded as safe and highly compatible with the human body. This comprehensive review focuses on the latest developments and future implications of using natural polyphenols as PSs in aPDT. Paramount polyphenolic compounds, including curcumin, hypericin, quercetin, hypocrellin, celastrol, riboflavin, resveratrol, gallic acid, and aloe emodin, are elaborated upon with respect to their structural characteristics, absorption properties, and antimicrobial effects. Furthermore, the aPDT mechanism, specifically its targeted action on microbial cells and biofilms, is also discussed. Polyphenolic natural products demonstrate immense potential as PSs in aPDT, representing a promising alternate approach to counteract antibiotic-resistant bacteria and biofilm-related infections.

Anti-biofilm activity of a novel nanoemulsion containing Curcuma xanthorrhiza oil

OBJECTIVES

We aimed to solubilize Curcuma xanthorrhiza oil (CXO) using nanoemulsification and evaluate its inhibitory effects against biofilm formation.

METHODS

The components of CXO were evaluated through high-performance liquid chromatography (HPLC) analysis. Healthy human saliva was inoculated onto hydroxyapatite discs to form microcosm biofilms for four days and treated six times with each antimicrobial agent: distilled water (DW), CXO emulsion (EM), CXO nanoemulsion (NE), and positive controls (Listerine and chlorhexidine). Biofilm fluorescence imaging was performed using quantitative light-induced fluorescence, and cell viability and dry-weight measurements were obtained. We compared the bacterial cell and extracellular polysaccharide (EPS) biovolume and thickness using confocal laser scanning microscopy (CLSM).

RESULTS

HPLC analysis revealed that CXO was composed of approximately 47% xanthorrhizol. Compared with DW, NE exhibited significantly lower red fluorescence intensity and area (42% and 37%, p < 0.001 and p < 0.001, respectively), and reduced total and aciduric bacterial cell viability (7.3% and 3.9%, p < 0.001, p = 0.01, respectively). Furthermore, the bacterial cell and EPS biovolume and thickness in NE decreased by 40-80% compared to DW, similar to chlorhexidine. Conversely, EM showed a significant difference only in cell viability against total bacteria when compared with DW (p = 0.003), with EPS biovolume and thickness exhibiting higher values than DW.

CONCLUSIONS

Nanoemulsification successfully solubilized CXO and demonstrated superior anti-biofilm effects compared to the emulsion form.

CLINICAL SIGNIFICANCE

These findings suggest the potential use of NE as a novel antimicrobial agent for preventing oral diseases.

Dual Action of Curcumin as an Anti- and Pro-Oxidant from a Biophysical Perspective

Curcumin, a natural polyphenol widely used as a spice, colorant and food additive, has been shown to have therapeutic effects against different disorders, mostly due to its anti-oxidant properties. Curcumin also reduces the efficiency of melanin synthesis and affects cell membranes. However, curcumin can act as a pro-oxidant when blue light is applied, since upon illumination it can generate singlet oxygen. Our review aims to describe this dual role of curcumin from a biophysical perspective, bearing in mind its concentration, bioavailability-enhancing modifications and membrane interactions, as well as environmental conditions such as light. In low concentrations and without irradiation, curcumin shows positive effects and can be recommended as a beneficial food supplement. On the other hand, when used in excess or irradiated, curcumin can be toxic. Therefore, numerous attempts have been undertaken to test curcumin as a potential photosensitizer in photodynamic therapy (PDT). At that point, we underline that curcumin-based PDT is limited to the treatment of superficial tumors or skin and oral infections due to the weak penetration of blue light. Additionally, we conclude that an increase in curcumin bioavailability through the using nanocarriers, and therefore its concentration, as well as its topical use if skin is exposed to light, may be dangerous.

The Effect of Different Output Powers of Blue Diode Laser along with Curcumin and Riboflavin against Streptococcus mutans around Orthodontic Brackets: An In Vitro Study

OBJECTIVES

The aim of the present study was to determine the effects of antimicrobial photodynamic therapy (aPDT) using the blue diode laser (BDL) with different output powers and the photosensitizers riboflavin and curcumin on reducing the number of Streptococcus mutans around orthodontic brackets.

MATERIALS AND METHODS

A total of 36 orthodontic brackets were contaminated with S. mutans and randomly assigned to 12 groups as follows: control, riboflavin alone, riboflavin + BDL with an output power of 200, 300, 400, or 500 mW, and curcumin alone, curcumin + BDL with an output power of 200, 300, 400, or 500 mW, and 0.2% chlorhexidine (CHX-positive control). Orthodontic brackets were irradiated with a BDL (wavelength 445 nm) at a power density of 0.4-1.0 W/cm2 for 30 s. All orthodontic brackets were examined under a stereomicroscope at 10× magnification. Mean colony-forming units (CFUs)/mL were measured before and after treatment. A one-way analysis of variance with Tukey's post hoc test was performed to compare CFU/mL between groups.

RESULTS

CHX and curcumin plus BDL with an output power of 500 mW had the highest reduction in S. mutans colony numbers (p < 0.001). The curcumin groups were more effective than the riboflavin groups. Riboflavin alone and riboflavin + BDL with an output power of 200 mW showed no significant difference from the control group (p = 0.99 and 0.74, respectively).

CONCLUSION

Our results suggest that aPDT using curcumin as a photosensitizer plus BDL with an output power of 500 mW and a power density of 1.0 W/cm2 at a wavelength of 445 nm can effectively reduce colonies of S. mutans around stainless steel brackets.

Photodynamic Therapy, Probiotics, Acetic Acid, and Essential Oil in the Treatment of Chronic Wounds Infected with Pseudomonas aeruginosa

As a prevalent medical problem that burdens millions of patients across the world, chronic wounds pose a challenge to the healthcare system. These wounds, often existing as a comorbidity, are vulnerable to infections. Consequently, infections hinder the healing process and complicate clinical management and treatment. While antibiotic drugs remain a popular treatment for infected chronic wounds, the recent rise of antibiotic-resistant strains has hastened the need for alternative treatments. Future impacts of chronic wounds are likely to increase with aging populations and growing obesity rates. With the need for more effective novel treatments, promising research into various wound therapies has seen an increased demand. This review summarizes photodynamic therapy, probiotics, acetic acid, and essential oil studies as developing antibiotic-free treatments for chronic wounds infected with Pseudomonas aeruginosa. Clinicians may find this review informative by gaining a better understanding of the state of current research into various antibiotic-free treatments. Furthermore. this review provides clinical significance, as clinicians may seek to implement photodynamic therapy, probiotics, acetic acid, or essential oils into their own practice.

Efficacy of ozonated water as a PS in photodynamic therapy: A tool for dental caries management? An in vitro study

Background

The most prevalent noncommunicable disease in the world is dental caries; and when it is not adequately treated, it is usually associated with tooth loss or severe dental lesions. In fact, expensive care or tooth extraction may be necessary due to the negative effects dental caries have on general health. This is due to its frequent pain and secondary bacterial infections. The aim of this study was to investigate the activity of ozonated water as such and in combination with appropriate light radiation so as to perform a photodynamic treatment (PDT) against the cariogenic bacterium Streptococcus mutans.

Design and methods

This work has been performed in vitro by using an S. mutans strain mainly structured in a biofilm status, reproducing the natural condition of the tooth infection. The ozone was tested at three different concentrations by using a commercial device able to generate different O3 formulations in water. The PDT treatment requires an appropriate light wavelength, evaluated in this work through the UV-Vis adsorption spectrum of the ozonated water.

Results

The obtained results suggested an effective and synergic property of O3 and light at 460-470 nm against this microorganism. The most antibiofilm activity was observed using a concentration of ozone of 0.06 mg/L alone as well as with PDT treatment.

Conclusions

The results are encouraging for additional research and in vitro/in vivo fresh experimental investigations to perform an exhaustive antimicrobial treatment protocol against the S. mutans tooth infection.

The Role of Singlet Oxygen in Photoreactivity and Phototoxicity of Curcumin

Curcumin is a plant-derived yellow-orange compound widely used as a spice, dye and food additive. It is also believed to have therapeutic effects against different disorders. On the other hand, there are data showing its phototoxicity against bacteria, fungi and various mammalian cells. Since the mechanism of its phototoxic action is not fully understood, we investigated here the phototoxic potential of curcumin in liposomal model membranes and in HaCaT cells. First, detection of singlet oxygen (¹ O₂ ) luminescence proved that curcumin generates ¹ O₂ upon blue light irradiation in organic solvent and in liposomes. Then, HPLC-EC(Hg) measurements revealed that liposomal and cellular cholesterol is oxidized by ¹ O₂ photogenerated by curcumin. Enrichment of liposome membranes with curcumin significantly increased the oxygen photo-consumption rate compared to the control liposomes as determined by EPR oximetry. Cytotoxicity measurements, mitochondrial membrane potential analyses and protein hydroperoxides detection confirmed strong phototoxic effects of curcumin in irradiated HaCaT cells. These data show that since curcumin is advertised as a valuable dietary supplement, or a component of cosmetics for topical use, caution should be recommended especially when skin is exposed to light.

Effectiveness of curcumin-based antimicrobial photodynamic therapy against Staphylococcus aureus

PURPOSE

This study investigated the effectiveness of curcumin-based antimicrobial photodynamic therapy (aPDT) against Staphylococcus aureus (S. aureus), the causative agent of ventilator-associated pneumonia.

METHODS

Curcumin was added to S. aureus culture medium at concentrations of 25, 2.5, and 0.25 µM. After 60 min (20-25°C), each culture was irradiated for 1 and 3 min, and viable bacteria were counted. Curcumin (25 µM) was also added to a bacterial suspension with D-mannitol and sodium azide; microbial counts were determined after irradiation for 3 min.

RESULTS

S. aureus was significantly reduced in the 1-min (P = 0.043) and 3-min (P = 0.011) irradiation groups in comparison to the 0-min irradiation group with 25 µM curcumin. No significant differences were observed between the curcumin alone group and the curcumin plus D-mannitol or sodium azide group.

CONCLUSION

The findings of this study indicate that prolonged exposure (≥1 min) of S. aureus to LED in 25 μM curcumin solution induces cell wall injury. Curcumin-based aPDT as an adjunct to conventional oral care, employing existing dentistry equipment, offers a promising approach that does not rely on antimicrobial drugs or allows the emergence of resistant bacterial strains. This suggests its potential role in future strategies aimed at preventing ventilator-associated pneumonia.

Effect of nanomicelle curcumin-based photodynamic therapy on the dynamics of white spot lesions and virulence of Streptococcus mutans in patients undergoing fixed orthodontic treatment: A randomized double-blind clinical trial

BACKGROUND/PURPOSE

The formation of white spot lesions (WSLs) around fixed orthodontic appliances is a major complication during treatment. The current double-blind, randomized clinical trial (RCT) study aims to investigate the varying effects of nanomicelle curcumin-based photodynamic therapy (NMCur-aPDT) on microbial count and virulence of Streptococcus mutans as well as the number and dynamics of WSLs.

MATERIALS AND METHODS

Double-blind prospective RCT, comprised of 48 patients with fixed orthodontic appliances, were recruited for the current study. The patients were divided into four groups according to the type of the treatment (NMCur, LED, NMCur-aPDT or VITIS® anti-caries mouthwash), using block randomization. Antimicrobial and anti-virulence activities of the treatments against isolated S. mutans were assessed via colony counting and quantitative real-time polymerase chain reaction (qRT-PCR), respectively. The visual inspection using the International Caries Detection and Assessment System (ICDAS II) score and laser fluorescence (LF) detection using a DIAGNOdent device were used for the detection and assessment of the dynamics of WSLs, respectively, on the labial surface in four areas (i.e., gingival, incisal, mesial, and distal) of the upper and lower anterior teeth at 30-, 60-, 90-, and 120-days follow-up after bonding of the lower and upper arches.

RESULTS

The antimicrobial properties of NMCur, VITIS®, and NMCur-aPDT were time-dependent so the highest reduction in S. mutans population was observed following NMCur-aPDT (99.98%) on day 120 of the study. The gtfB gene expression levels in S. mutans isolates from the NMCur-aPDT group on days 60, 90, and 120 decreased by 2.07-, 2.32-, and 3.01-fold more than in S. mutans isolates from the VITIS® group, respectively (all P < 0.05), while NMCur and LED treatments could not significantly reduce gtfB gene expression up to 120 days of follow-up (P > 0.05). In patients who were treated with LED, an increase in the mean number of WSLs per patient (mean increase, 1.8; P < 0.05) was found, while in NMCur-aPDT and VITIS® groups, not only no increases were observed, but the mean number of WSLs per patient decreased (mean reductions, 0.5 and 0.9, respectively; not significant). LED treatment caused significant increases (P < 0.05) in the mean LF values at 90-and 120-days of follow-up in comparison with the baseline (mean increases, 5.1 and 6.5, respectively) while, in NMCur-aPDT, VITIS®, and NMCur groups 11.8-, 7.1-, and 4.4-reductions in the mean LF values were observed, respectively (all, P < 0.05).

CONCLUSIONS

The antimicrobial and anti-virulence activities of NMCur-aPDT against S. mutans were higher than the other treatment groups. In patients who were treated with NMCur-aPDT, the mean number and LF values of WSLs per patient were significantly lower than the other groups in 90-and 120-days of follow-up.

Antibacterial activity of curcumin and its essential nanoformulations against some clinically important bacterial pathogens: A comprehensive review

Multidrug-resistant bacterial infections can kill 700,000 individuals globally each year and is considered among the top 10 global health threats faced by humanity as the arsenal of antibiotics is becoming dry and alternate antibacterial molecule is in demand. Nanoparticles of curcumin exhibit appreciable broad-spectrum antibacterial activity using unique and novel mechanisms and thus the process deserves to be reviewed and further researched to clearly understand the mechanisms. Based on the antibiotic resistance, infection, and virulence potential, a list of clinically important bacteria was prepared after extensive literature survey and all recent reports on the antibacterial activity of curcumin and its nanoformulations as well as their mechanism of antibacterial action have been reviewed. Curcumin, nanocurcumin, and its nanocomposites with improved aqueous solubility and bioavailability are very potential, reliable, safe, and sustainable antibacterial molecule against clinically important bacterial species that uses multitarget mechanism such as inactivation of antioxidant enzyme, reactive oxygen species-mediated cellular damage, and inhibition of acyl-homoserine-lactone synthase necessary for quorum sensing and biofilm formation, thereby bypassing the mechanisms of bacterial antibiotic resistance. Nanoformulations of curcumin can thus be considered as a potential and sustainable antibacterial drug candidate to address the issue of antibiotic resistance.

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

BACKGROUND

Drug-resistant bacterial infections have received much attention in recent years. Antimicrobial photodynamic therapy (aPDT) is an effective antimicrobial strategy. This study aimed to evaluate the therapeutic effect of methylene blue (MB)-mediated aPDT against subgingival multidrug-resistant (MDR) bacterial infections in intensive care unit (ICU) patients.

METHODS

Eighty-three patients who were hospitalized in the ICU of the Second Affiliated Hospital of Nanchang University from July 2019 to June 2021 were selected. The intraoral partitioned control test was conducted. Teeth that met the criteria were selected from different quadrants of the same patient, randomly divided into three groups, namely, A, B, and C, and treated with aPDT, chlorhexidine gargle, or normal saline. The counts of MDR bacteria in the gingival crevicular fluid were assessed in the different groups at different time points before and after treatment.

RESULTS

The MDR bacterial count decreased immediately after aPDT and was significantly different from that in the chlorhexidine gargle rinse group and the normal saline rinse group (P<0.05). There was no significant difference among the three groups at 6, 12, and 24 hours after treatment (P>0.05).

CONCLUSION

aPDT can be used to treat subgingival MDR bacterial infections, but the long-term effects of treatment need to be further studied.

Comparative effects of SWEEPS technique and antimicrobial photodynamic therapy by using curcumin and nano-curcumin on Enterococcus faecalis biofilm in root canal treatment

OBJECTIVES

This study aimed to compare the antimicrobial effects of the shock wave enhanced emission photoacoustic streaming (SWEEPS) technique and Antimicrobial photodynamic therapy (aPDT) with curcumin and nano-curcumin photosensitizers on Enterococcus faecalis (E. faecalis) biofilm in root canals of extracted teeth.

MATERIALS AND METHODS

This experimental study was conducted on extracted single-rooted human teeth. The teeth were decoronated at the cementoenamel junction, the root canals were instrumented with BioRace system, and their apices were sealed. Smear layer was removed, and the teeth were autoclave-sterilized. E. faecalis strains were cultured in sterile brain heart infusion (BHI) and a bacterial suspension with 0.5 McFarland standard concentration was prepared. The root canals were inoculated with the bacterial suspension and incubated at 37 °C for 4 weeks. The teeth were then divided into 12 groups (curcumin, nano-curcumin, curcumin + LED, nano-curcumin + LED, curcumin + SWEEPS, nano-curcumin + SWEEPS, curcumin + LED + SWEEPS, nano-curcumin + LED + SWEEPS, SWEEPS, positive control and negative control). The number of colony forming units (CFUs) was counted and analyzed by one-way ANOVA and Tukey's test.

RESULTS

A significant difference was noted in colony count among the groups (P<0.001). LED alone had the lowest and nano-curcumin + LED + SWEEPS had the highest root canal cleaning efficacy. SWEEPS along with curcumin, nano-curcumin, and LED significantly decreased the bacterial count compared with other groups (P<0.05).

CONCLUSION

Application of the SWEEPS technique with curcumin and nano-curcumin as photosensitizer activated by LED in aPDT improved the reduction of E. faecalis in root canals.

Effect of Chitosan and Amphiphilic Polymers on the Photosensitizing and Spectral Properties of Rose Bengal

The influence of chitosan (CS) and amphiphilic polymers (AP: pluronic F108 and polyvinylpyrrolidone (PVP)) on the photocatalytic activity of rose bengal (RB) in a model reaction of tryptophan photo-oxidation in phosphate-buffered saline (PBS) was studied. It was shown that in the presence of CS, the effective rate constant k_eff of tryptophan photo-oxidation catalyzed by RB in PBS solution decreases by a factor of two. This is due to the ionic interaction of the RB with the chitosan. Rose bengal in a slightly acidic environment (pH 4.5) passes into a neutral lactone form, which sharply reduces the photosensitizing properties of the dye. It was demonstrated that the introduction of AP into a solution containing RB and CS prevents direct interaction between RB and CS. This is evidenced by the presence of photocatalytic activity of the dye in the RB-AP-CS systems, as well as bathochromic shifts of the main absorption bands of the dye, and an increase in the optical density and luminescence intensity of the RB when AP is introduced into a buffer solution containing RB and chitosan. The presence of RB-CS and RB-AP interaction in aqueous and PBS media is confirmed by the increase in the degree of fluorescence anisotropy (r) of these binary systems. In an aqueous solution, the value of r for the RB-F108-CS system decreases by a factor of 3.5 (compared to the value of r for the RB-CS system), which is associated with the localization of the dye in pluronic micelles. In PBS, the fluorescence anisotropy is practically the same for all systems, which is related to the stability of the dye structure in this medium. The presence of interaction between RB and AP in aqueous solutions was confirmed by the proton NMR method. In addition, the formation of RB-F108 macromolecular complexes, which form associates during solution concentration (in particular, during evaporation), was shown by AFM. Such RB-AP-CS systems may be promising for practical application in the treatment of local foci of infections by aPDT.

The Potential Application of Natural Photosensitizers Used in Antimicrobial Photodynamic Therapy against Oral Infections

Oral health problems and the emergence of antimicrobial resistance among pathogenic bacterial strains have become major global challenges and are essential elements that negatively affect general well-being. Antimicrobial photodynamic therapy (APDT) is based on a light source and oxygen that activates a nontoxic photosensitizer, resulting in microbial destruction. Synthetic and natural products can be used to help the APDT against oral microorganisms. The undesirable consequences of conventional photosensitizers, including toxicity, and cost encourage researchers to explore new promising photosensitizers based on natural compounds such as curcumin, chlorella, chlorophyllin, phycocyanin, 5-aminolevulinic acid, and riboflavin. In this review, we summarize in vitro studies describing the potential use of APDT therapy conjugated with some natural products against selected microorganisms that are considered to be responsible for oral infections.

Applications of Antimicrobial Photodynamic Therapy against Bacterial Biofilms

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

Exploring the use of a Ruthenium complex incorporated into a methacrylate-based dental material for antimicrobial photodynamic therapy

OBJECTIVES

To evaluate the effects of a blue light photosensitizer (PS), Ruthenium II complex (Ru), on the chemical, physical, mechanical, and antimicrobial properties of experimental dental resin blends.

METHODS

The experimental resin (BisEMA, TEEGDMA, HPMA, ethanol, and photoinitiator) was loaded with Ru at 0.00%, 0.07%, 0.14%, 0.28%, 0.56%, 1.12%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% w/w. Samples were evaluated for the degree of conversion (DC) after 30 and 60 s curing-time (n = 6). Selected formulations (0.00%, 0.28%, 0.56%, 1.12%) were further tested for shear bond strength (SBS) (n = 15); flexural strength (FS) (n = 12); and antimicrobial properties (CFUs), in dark and light conditions. These latter tests were performed on specimens stored for 24-h or 2-month in 37°C water. Water sorption (WS) and solubility (SL) tests were also performed (n = 12). Data were analyzed either by a one- or two-factor general linear model (α = 0.05).

RESULTS

Overall, Ru concentration above 1.2% resulted in reduced DC. In SBS results, only the 1.12%Ru resin blend samples had statistically lower values compared to the 0.00%Ru resin blend at 24-h storage (p = 0.004). In addition, no differences in SBS were detected among the experimental groups after 2-month storage in water. Meanwhile, FS increased for all experimental groups under similar aging conditions (p < 0.001). Antimicrobial properties were improved upon inclusion of Ru and application of light (p < 0.001 for both) at 24-h and 2-month storage. Lastly, no detectable changes in WS or SL were observed for the Ru-added resins compared to the 0.00%Ru resin blend. However, the 0.28% Ru blend presented significantly higher WS compared to the 0.56% Ru blend (p = 0.007).

CONCLUSIONS

Stable SBS, improved FS, and sustained antimicrobial properties after aging gives significant credence to our approach of adding the Ruthenium II complex into dental adhesive resin blends intended for an aPDT approach.

Dental-Plaque Decontamination around Dental Brackets Using Antimicrobial Photodynamic Therapy: An In Vitro Study

Background: In orthodontic therapy, the enamel around brackets is very susceptible to bacterial-plaque retention, which represents a risk factor for dental tissues. The aim of this study was to evaluate the effect of methylene blue and a chlorophyllin–phycocyanin mixture, used with and without light activation, in contrast with a 2% chlorhexidine solution, on Streptococcus mutans colonies. Methods: Twenty caries-free human extracted teeth were randomized into five groups. A Streptococcus mutans suspension was inoculated on teeth in groups B, C, D, and E (A was the positive-control group). Bacterial colonies from groups C, D, and E (B was the negative-control group) were subjected to photosensitizers and 2% chlorhexidine solution. For groups C and D, a combined therapy consisting of photosensitizer and light activation was performed. The Streptococcus mutans colonies were counted, and smears were examined with an optical microscope. Two methods of statistical analysis, unidirectional analysis of variance and the Tukey–Kramer test, were used to evaluate the results. Results: A statistically significant reduction in bacterial colonies was detected after the combined therapy was applied for groups C and D, but the most marked bacterial reduction was observed for group D, where a laser-activated chlorophyll–phycocyanin mixture was used. Conclusions: Photodynamic therapy in combination with methylene blue or chlorophyllin–phycocyanin mixture sensitizers induces a statistically significant decrease in the number of bacterial colonies.

Recent Advances in Photodynamic Therapy against Fungal Keratitis

Fungal keratitis is a serious clinical infection on the cornea caused by fungi and is one of the leading causes of blindness in Asian countries. The treatment options are currently limited to a few antifungal agents. With the increasing incidence of drug-resistant infections, many patients fail to respond to antibiotics. Riboflavin-mediated corneal crosslinking (similar to photodynamic therapy (PDT)) for corneal ectasia was approved in the US in the early 2000s. Current evidence suggests that PDT could have the potential to inhibit fungal biofilm formation and overcome drug resistance by using riboflavin and rose bengal as photosensitizers. However, only a few clinical trials have been initiated in anti-fungal keratitis PDT treatment. Moreover, the removal of the corneal epithelium and repeated application of riboflavin and rose bengal are required to improve drug penetration before and during PDT. Thus, an improvement in trans-corneal drug delivery is mandatory for a successful and efficient treatment. In this article, we review the studies published to date using PDT against fungal keratitis and aim to enhance the understanding and awareness of this research area. The potential of modifying photosensitizers using nanotechnology to improve the efficacy of PDT on fungal keratitis is also briefly reviewed.

Antimicrobial Effect of Phytochemicals from Edible Plants

Current strategies of combating bacterial infections are limited and involve the use of antibiotics and preservatives. Each of these agents has generally inadequate efficacy and a number of serious adverse effects. Thus, there is an urgent need for new antimicrobial drugs and food preservatives with higher efficacy and lower toxicity. Edible plants have been used in medicine since ancient times and are well known for their successful antimicrobial activity. Often photosensitizers are present in many edible plants; they could be a promising source for a new generation of drugs and food preservatives. The use of photodynamic therapy allows enhancement of antimicrobial properties in plant photosensitizers. The purpose of this review is to present the verified data on the antimicrobial activities of photodynamic phytochemicals in edible species of the world’s flora, including the various mechanisms of their actions.

New Perspectives on Old and New Therapies of Staphylococcal Skin Infections: The Role of Biofilm Targeting in Wound Healing

Among the most common complications of both chronic wound and surgical sites are staphylococcal skin infections, which slow down the wound healing process due to various virulence factors, including the ability to produce biofilms. Furthermore, staphylococcal skin infections are often caused by methicillin-resistant Staphylococcus aureus (MRSA) and become a therapeutic challenge. The aim of this narrative review is to collect the latest evidence on old and new anti-staphylococcal therapies, assessing their anti-biofilm properties and their effect on skin wound healing. We considered antibiotics, quorum sensing inhibitors, antimicrobial peptides, topical dressings, and antimicrobial photo-dynamic therapy. According to our review of the literature, targeting of biofilm is an important therapeutic choice in acute and chronic infected skin wounds both to overcome antibiotic resistance and to achieve better wound healing.

pH and light-responsive polycaprolactone/curcumin@zif-8 composite films with enhanced antibacterial activity

Food packaging materials, especially biodegradable polymer composites incorporated with natural antimicrobial agents with excellent antibacterial activities, are in high demand and attracted immense attention. Herein, a polycaprolactone/curcumin@zeolitic imidazolate framework-8 (PCL/Cur@ZIF-8) composite film with enhanced antibacterial activity was developed. Curcumin, a natural photosensitizer, was loaded in the highly porous nanocrystals ZIF-8 to improve its poor water solubility and stability. The integral structure of Cur@ZIF-8 was maintained well in the PCL matrix even at the highest loading of 35% (w/w), and all composite films had good light transmittance at 420-430 nm. The PCL/Cur@ZIF-8 composite films responded to the acidic growth environment of bacteria by releasing zinc ions and curcumin molecules. Furthermore, upon blue light irradiation (420-430 nm, 2.2 mW/cm² ), curcumin molecules generated singlet oxygen. With the synergistic effects of zinc ions and singlet oxygen, the composite films exhibited a 99.9% reduction of Escherichia coli and Staphylococcus aureus strains when the amount of Cur@ZIF-8 loading was more than 15% (w/w), as well as a strong anti-adhesion effect on bacteria. Moreover, bacterial resuscitation tests indicated that the composite films exhibited 99.9% reduction in the adhered bacteria population through treatment with photodynamic sterilization. This is the first study presenting that the incorporated curcumin ZIF-8 nanoparticles in the matrix of polymer are pH and light responsive for anti-adhesion of bacteria, which is of great potential application as antibacterial packaging material for the food industry. PRACTICAL APPLICATION: A novel, biodegradable, pH, and light-responsive composite film was developed for antibacterial activity. Natural photosensitizer curcumin was encapsulated in ZIF-8 nanocrystals (Cur@ZIF-8) as the antimicrobial agent. With the synergistic effects of Zn²⁺ and singlet oxygen, the composite film exhibited a 99.9% reduction of Escherichia coli and Staphylococcus aureus strains, and a strong anti-adhesion property toward bacteria. This composite film is of great potential application as an antibacterial packaging material that enhances the shelf life of fruits, meat, and so on.

Photo-enhanced antibacterial activity of polydopamine-curcumin nanocomposites with excellent photodynamic and photothermal abilities

Background and objective Photodynamic therapy (PDT) and photothermal therapy (PTT) have gradually become options for select anti-tumor and antibacterial treatment . The combination of PDT and PTT show great research value, which may greatly improve the curative effect. The aim of the present study was to prepare a compound system of polydopamine and curcumin (PDA-Cur nanocomposites) with excellent antibacterial effect towards Gram-positive and Gram-negative bacteria. Methods Dopamine hydrochloride was oxidized and self polymerized in alkaline condition to form PDA-Cur nanocomposites. The structure and morphology of PDA-Cur were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser scattering microscopy (LSM), ultraviolet spectrophotometer (UV-vis), infrared spectroscopy (IR) and fluorescence emission spectrometer. Using 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), 1,3-diphenylbenzofuran (DPBF) and 2',7'-Dichlorodihydrofluorescein diacetate (DCFH-DA) were used to detect the production of reactive oxygen species (ROS). The thermal stability of PDA-Cur nanocomposites was investigated by temperature rising test. The antibacterial effect of PDA-Cur was determined by plate counting technique using Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) as models. In addition, the stability and antibacterial mechanism of PDA-Cur were investigated. Finally, the biocompatibility was evaluated by cytotoxicity and hemolysis tests. Results The compound system of polydopamine and curcumin was successfully prepared, which showed improved stability compared with Cur. The consumption of DPBF by the singlet oxygen produced by PDA-Cur was as high as 80%. In the heating test, the highest temperature increased to 59 °C, which contributed to the photodynamic and photothermal inactivation of bacteria. PDA-Cur nanocomposites showed good antibacterial activity against S. aureus and E. coli. Under 405 nm light, the bactericidal rate of PDA-Cur against S. aureus can reach 100% at a low concentration of 10^-4 nM, and that against E. coli was 100% at 1 nM. Under 405 + 808 nm light, the bactericidal rate of PDA-Cur against E. coli enhanced to 100% at 0.1 nM. In addition, PDA-Cur had low cytotoxicity and negligible hemolytic activity, showing good biocompatibility. Conclusion PDA-Cur nanocomposites had good photodynamic effect, photo thermal conversion ability and biocompatibility. Compared with free Cur, the antibacterial activity of PDA-Cur was significantly improved, and the antibacterial effect with combined light was stronger than that of free Cur. Therefore, the construction of PDA-Cur nanocomposites have confirmed that the combination of PDT and PTT can greatly improve the antibacterial effect and reach bactericidal effect at low concentration, which provides a strategy for the design of next generation antimicrobial agents.

Antibacterial Photodynamic Inactivation of Fagopyrin F from Tartary Buckwheat (Fagopyrum tataricum) Flower against Streptococcus mutans and Its Biofilm

The objective of this study was to determine reactive oxygen species (ROS) produced by fagopyrin F-rich fraction (FFF) separated from Tartary buckwheat flower extract exposed to lights and to investigate its antibacterial photodynamic inactivation (PDI) against Streptococcus mutans and its biofilm. ROS producing mechanisms involving FFF with light exposure were determined using a spectrophotometer and a fluorometer. S. mutans and its biofilm inactivation after PDI treatment of FFF using blue light (BL; 450 nm) were determined by plate count method and crystal violet assay, respectively. The biofilm destruction by ROS produced from FFF after exposure to BL was visualized using confocal laser scanning microscopy (CLSM) and field emission scanning electron microscope (FE-SEM). BL among 3 light sources produced type 1 ROS the most when applying FFF as a photosensitizer. FFF exposed to BL (5 and 10 J/cm2) significantly more inhibited S. mutans viability and biofilm formation than FFF without the light exposure (p < 0.05). In the PDI of FFF exposed to BL (10 J/cm2), an apparent destruction of S. mutans and its biofilm were observed by the CLSM and FE-SEM. Antibacterial PDI effect of FFF was determined for the first time in this study.

Natural Photosensitizers in Antimicrobial Photodynamic Therapy

Health problems and reduced treatment effectiveness due to antimicrobial resistance have become important global problems and are important factors that negatively affect life expectancy. Antimicrobial photodynamic therapy (APDT) is constantly evolving and can minimize this antimicrobial resistance problem. Reactive oxygen species produced when nontoxic photosensitizers are exposed to light are the main functional components of APDT responsible for microbial destruction; therefore, APDT has a broad spectrum of target pathogens, such as bacteria, fungi, and viruses. Various photosensitizers, including natural extracts, compounds, and their synthetic derivatives, are being investigated. The main limitations, such as weak antimicrobial activity against Gram-negative bacteria, solubility, specificity, and cost, encourage the exploration of new photosensitizer candidates. Many additional methods, such as cell surface engineering, cotreatment with membrane-damaging agents, nanotechnology, computational simulation, and sonodynamic therapy, are also being investigated to develop novel APDT methods with improved properties. In this review, we summarize APDT research, focusing on natural photosensitizers used in in vitro and in vivo experimental models. In addition, we describe the limitations observed for natural photosensitizers and the methods developed to counter those limitations with emerging technologies.

Curcumin in Osteosarcoma Therapy: Combining With Immunotherapy, Chemotherapeutics, Bone Tissue Engineering Materials and Potential Synergism With Photodynamic Therapy

Osteosarcoma is a dominating malignant bone tumor with high mortality due to pulmonary metastases. Furthermore, because of the cancer cell erosion and surgery resection, osteosarcoma always causes bone defects, which means dysfunction and disfigurement are seldom inevitable. Although various advanced treatments (e.g. chemotherapy, immunotherapy, radiotherapy) are coming up, the 5-year survival rate for osteosarcoma with metastases is still dismal. In line with this, the more potent treatments for osteosarcoma are in high demand. Curcumin, a perennial herb, has been reportedly applied in the therapy of various types of tumors via different mechanisms. In vitro, it has also been reported that curcumin can inhibit the proliferation of osteosarcoma cell lines and can be used to repair bone defects. This seems curcumin is a promising candidate in osteosarcoma treatment. However, due to its congenital property like hydrophobicity, and low bioavailability, affecting its anticancer effect, clinical applications of curcumin are highly limited. To enhance its performance in cancer therapies, some synergist approaches with curcumin have emerged. The present review presents some prospective ones (i.e. combinations with immunotherapy, chemotherapeutics, bone tissue engineering, and biomaterials) applied in osteosarcoma treatment. Additionally, with the advancements of photodynamic therapy in cancer therapy, this review also prospects the combination of curcumin with photodynamic therapy in osteosarcoma treatment.

Curcumin-Loaded Micelles Dispersed in Ureasil-Polyether Materials for a Novel Sustained-Release Formulation

Vulvovaginal candidiasis (VVC) is a vulvar/vaginal infection that affects approximately 75% of women worldwide. The current treatment consists of antimicrobials with hepatotoxic properties and high drug interaction probabilities. Therefore, this study aimed to develop a new treatment to VVC based on micelles containing curcumin (CUR) dispersed in a ureasil-polyether (U-PEO) hybrid. The physical-chemical characterization was carried out in order to observe size, shape, crystallinity degree and particle dispersion in the formulation and was performed by dynamic light scattering (DLS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and through in vitro release study. The results of DLS and SEM exhibited micelles with 35 nm, and encapsulation efficiency (EE) results demonstrated 100% of EE to CUR dispersed in the U-PEO, which was confirmed by the DRX. The release results showed that CUR loaded in U-PEO is 70% released after 10 days, which demonstrates the potential application of this material in different pharmaceutical forms (ovules and rings), and the possibility of multidose based on a single application, suggesting a higher rate of adherence.

Antibacterial and Antimicrobial Effects of Xanthorrhizol in the Prevention of Dental Caries: A Systematic Review

Background

Xanthorrhizol is one of the numerous phytochemicals whose pharmacological benefits have been explored for its antibacterial and antimicrobial effects. In light of the role bacteria play for initiating tooth decay, this present systematic review assessed xanthorrhizol’s effect against dental caries.

Methods

The electronic databases including Pubmed, Scopus and Embase were searched up to September 2020, Studies examining the antibacterial and antimicrobial effects of xanthorrhizol in the prevention and treatment of dental caries.

Results

Eleven studies met the criteria for final inclusion. Findings from these studies showed that xanthorrhizol showed significant inhibition of notable caries causing bacteria including Streptococcus mutans, Streptococcus sanguinis, Enterococcus faecalis and Bacillus cereus. Furthermore, there was no reported toxicity. However, it could not selectively target the growth of cariogenic bacteria.

Conclusion

So far, studies exploring the use of xanthorrhizol as a potential drug for the prevention and treatment of dental caries have shown promising outcomes. However, more work needs to be done especially in areas such as optimal dose or concentration, in addition, in vitro, in vivo and clinical studies and selective targeting of cariogenic bacteria has been performed.

Synergistic effect of hypocrellin B and curcumin on photodynamic inactivation of Staphylococcus aureus

Antimicrobial photodynamic inactivation (aPDI) serves as a new approach to control the growth of foodborne bacteria. It remains elusive if the photodynamic efficacy of hypocrellin B (HB) can be potentiated by joint action with curcumin. In this study, we measured the survival rate of Staphylococcus aureus strains under the varying photodynamic conditions. According to our data, a maximum of 5–6 log₁₀ decrease of bacterial survival can be achieved under the tested conditions (500 nM, 9 J cm^‒2). Regarding the bactericidal mechanisms, HB‐based aPDI disrupted the membrane integrity of staphylococcal cells, probably owing to the stimulated reactive oxygen species (ROS). In addition, aPDI disrupted the enzymatic activities of bacterial antioxidant proteins and caused the leakage of multiple intracellular substances. The HB‐mediated photodynamic efficacy was potentiated by the addition of curcumin with a sublethal dose. This dual‐photon synergy arose from unique aPDI conditions (100 nM each and 9 J cm^‒2). The synergistic action might be accounted for by the increased type I/type II ratio of ROS, as evidenced by the effect of different quenchers. Finally, the joint use of photosensitizers reduced the microbial contamination of the tested apple while maintaining its quality. In summary, photodynamic inactivation based on dual photons showed synergistic activity in controlling the growth of Staphylococcal aureus, which provided a novel approach to maintain food safety.

Targeted Photodynamic Treatment of Bacterial Biofilms Using Curcumin Encapsulated in Cells and Cell Wall Particles

Efficient inactivation and removal of pathogenic biofilms in food and biomedical environments remain a significant challenge for food safety applications and medical facilities. This research aims to develop food-grade microcarriers for the targeted delivery of a photosensitizer, curcumin, and photodynamic inactivation of a model pathogenic bacterial biofilm. The microcarriers evaluated in this study include alive yeast cell carriers, deactivated yeast cell carriers, and yeast cell wall particles. The microcarriers were evaluated based on the encapsulation yield of a model photosensitizer (curcumin), binding of the microcarriers to biofilms, and inactivation of the bacteria in the biofilms. The results illustrate that the combination of binding affinity, encapsulation yield, and the intracellular composition of the microcarriers influenced the overall inactivation of bacteria in the biofilms. All of the selected compositions achieved more than 93% inactivation of the bacteria in the biofilm using the photodynamic treatment, and the yeast cell wall particles with curcumin achieved over 99% inactivation of the bacteria in the biofilm matrix. In addition, all of the selected compositions demonstrated significant potential to remove the biofilm from the plastic surface, suggesting the role of binding affinity of the microcarriers in removal of the biofilm from surfaces. Overall, this study developed biomaterial formulations for targeted photodynamic inactivation and potential removal of biofilms.

Screening of antimicrobial synergism between phenolic acids derivatives and UV-A light radiation

The objective of this study was to investigate synergistic antibacterial activity based on a combination of UV-A light and three classes of food grade compounds: benzoic acid derivatives, cinnamic acid derivatives, and gallates. By using Escherichia coli O157:H7 as the model strain, it was observed that three cinnamic acid derivatives (ferulic acid, coumaric acid, and caffeic acid) and one benzoic acid derivative (2,5-dihydroxybenzoic acid) presented strong synergistic antibacterial activity with UV-A light radiation, where 1 mM levels of these compounds plus with 15 min of UV-A light (total light dose of 6.1 cm^-2) led to more than 7-log CFU mL^-1 of bacterial inactivation. In contrast, synergistic antibacterial activity between UV-A light and most benzoic acid derivatives (benzoic acid, gallic acid, vanillic acid, and 2,5-dimethoxybenzoic acid) were only observed after higher concentrations of these compounds were applied (10 mM). Lastly, from the three gallates tested (methyl gallate, ethyl gallate, and propyl gallate), only propyl gallate showed strong antibacterial synergism with UV-A light, where 10 mM of propyl gallate plus 15 min of UV-A light led to approximately 6.5-log of bacterial reduction. Presence of antioxidant compounds mitigated the light-mediated antibacterial activity of gallic acid, 2,5-dihydroxybenzoic acid, and propyl gallate. Similarly, the light-mediated antibacterial activity of these compounds was significantly (P < 0.05) reduced against metabolic-inhibited bacterial cells (sodium azide pretreatment). On the other hand, the antibacterial synergism between ferulic acid and UV-A light was not affected by the presence of antioxidants or the metabolic state of the bacterial cells. Due to the increasing concerns of antimicrobial resistant (AMR) pathogens, the study also investigated the proposed synergistic treatment on AMR Salmonella. Combinations of 1 mM of ferulic acid or 1 mM of 2,5-dihydroxybenzoic acid with UV-A light radiation was able to inactivate more than 6-log of a multi-drug resistant Salmonella Typhimurium strain.

Role of Photoactive Phytocompounds in Photodynamic Therapy of Cancer

Cancer is one of the greatest life-threatening diseases conventionally treated using chemo- and radio-therapy. Photodynamic therapy (PDT) is a promising approach to eradicate different types of cancers. PDT requires the administration of photosensitisers (PSs) and photoactivation using a specific wavelength of light in the presence of molecular oxygen. This photoactivation exerts an anticancer effect via apoptosis, necrosis, and autophagy of cancer cells. Recently, various natural compounds that exhibit photosensitising potentials have been identified. Photoactive substances derived from medicinal plants have been found to be safe in comparison with synthetic compounds. Many articles have focused on PDT mechanisms and types of PSs, but limited attention has been paid to the phototoxic activities of phytocompounds. The reduced toxicity and side effects of natural compounds inspire the researchers to identify and use plant extracts or phytocompounds as a potent natural PS candidate for PDT. This review focusses on the importance of common photoactive groups (furanocoumarins, polyacetylenes, thiophenes, curcumins, alkaloids, and anthraquinones), their phototoxic effects, anticancer activity and use as a potent PS for an effective PDT outcome in the treatment of various cancers.

Antimicrobial activity of Curcuma xanthorrhiza nanoemulsions on Streptococcus mutans biofilms

In this study, an optimal nanoemulsion formulation for Curcuma xanthorrhiza oil (Xan) was investigated using different sonication times. The antimicrobial effects of the nanoemulsion, the original emulsion, distilled water (DW), and Listerine, on Streptococcus mutans biofilms were compared. The optimum ultrasonic time, determined in terms of droplet size and stability, was found to be 10 min. Cell viability was the lowest on exposure to the nanoemulsion, and significantly different compared with exposure to DW or Listerine. The emulsion's effect was similar to that of the nanoemulsion, but was non-uniform with a high interquartile range. Confocal microscope analysis revealed that the live/dead cell ratio in the nanoemulsion was 50% and 40% less than those in DW and Listerine, respectively. Biofilm treated with the nanoemulsion was thinner than biofilms exposed to the other treatments. Xan nanoemulsions exhibited stable and strong antimicrobial effects due to nano-sized particles, highlighting their potential use in oral health treatment.

[Research progress on the regulation of phenolic compounds of traditional Chinese herbs on oral microbes]

Phenolic compounds are widely found in natural Chinese medicinal plants and have excellent pharmacological properties, such as antioxidation and anti-inflammation. They are the main pharmacological components of many medicinal Chinese herbs. Oral microbiota, especially its composition and metabolism, is highly related to the balance of oral microecology and plays a key role in the occurrence and development of oral diseases. Recent studies have shown that phenolic compounds of traditional Chinese herbs can prevent and treat oral diseases, such as caries, periodontal disease, and oral mucosal infection, by regulating the composition, metabolites, and virulence of oral microorganisms. This review will summarize and discuss the regulation of phenolic compounds on oral microbes.

Total mouth photodynamic therapy mediated by blue led and curcumin in individuals with AIDS

OBJECTIVES

To test the effectiveness of an efficient therapeutic protocol for the total mouth antimicrobial photodynamic therapy (aPDT) mediated by 450 nm blue LED associated with curcumin in individuals with AIDS.

METHODS

Patients were selected by exclusion criteria and randomly distributed in groups to test the effectiveness of antimicrobial aPDT with curcumin 0.75 mg/mL associated with the blue LED (67 mW/cm², 20.1 J/cm²). Before and after the treatments, samples were collected from the saliva being processed in duplicate in selective culture media. The colonies were counted and the results obtained in log10 CFU/mL were statistically tested (T-paired statistical test, 5%).

RESULTS

The log10 CFU/mL of Streptococcus spp., Staphylococcus spp., and total count of microorganisms showed statistically significant (p = 0.023; p = 0.001 and p = 0.017, respectively) reduction after treatment in patients with aPDT.

CONCLUSION

aPDT was effective in reducing Streptococcusspp. in addition to reducing Staphylococcusspp., enterobacteria and the total count of microorganisms when considering the numbers of TCD4 and TCD8 lymphocytes. The aPDT in the studied protocol was able to control clinically important intraoral microorganisms for AIDS patients, both those with TCD4 lymphocytes above or below 25% of normal and those with TCD8 lymphocytes above 25% of normal.

Identification of carbonylated proteins in a bactericidal process induced by curcumin with blue light irradiation on imipenem-resistant Acinetobacter baumannii

RATIONALE

Antimicrobial photodynamic treatment is potentially an alternative to antibiotics and is also effective against viruses, fungi and some cancers. Our previous studies have shown that blue light combined with curcumin, a chemical from the turmeric plant, exerted effective antimicrobial activity via photodynamic treatment. The study reported in this paper investigates which target proteins are affected after the treatment.

METHODS

We treated imipenem-resistant Acinetobacter baumannii with blue light and curcumin and used protein carbonylation as a marker for oxidative damage. After treatment, the bacterial proteins were extracted and the protein carbonyls marked using dinitrophenylhydrazide. After enzyme digestion, we used liquid chromatography/nano-electrospray ionization (LC/nano-ESI) ion trap mass spectrometry to identify bacterial peptides from a customized database. The functional enrichment analyses of the identified proteins were performed using gene ontology annotation and the STRING protein-protein interaction network.

RESULTS

The application of curcumin with blue light showed good antibacterial activity against imipenem-resistant A. baumannii. Using a shotgun proteomics approach, the carbonylated proteins in A. baumannii caused by the photolytic curcumin were identified. The results showed that the proteins related to membrane structures, translation and response to oxidative stress were preferentially modified.

CONCLUSIONS

The photolytic curcumin treatment could be a potential alternative to antibiotics for bacterial infection. In this study, the shotgun proteomics strategy allows us to explore the possible bactericidal mechanisms under this oxidative stress. The result provides a reference for future studies on the enhancement of the action of photolytic curcumin.

Effect of Photodynamic Therapy on Microorganisms Responsible for Dental Caries: A Systematic Review and Meta-Analysis

The aim of this study was to perform a systematic review of the literature followed by a meta-analysis about the efficacy of photodynamic therapy (PDT) on the microorganisms responsible for dental caries. The research question and the keywords were constructed according to the PICO strategy. The article search was done in Embase, Lilacs, Scielo, Medline, Scopus, Cochrane Library, Web of Science, Science Direct, and Pubmed databases. Randomized clinical trials and in vitro studies were selected in the review. The study was conducted according the PRISMA guideline for systematic review. A total of 34 articles were included in the qualitative analysis and four articles were divided into two subgroups to perform the meta-analysis. Few studies have achieved an effective microbial reduction in microorganisms associated with the pathogenesis of dental caries. The results highlight that there is no consensus about the study protocols for PDT against cariogenic microorganisms, although the results showed the PDT could be a good alternative for the treatment of dental caries.

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 photoactivity of natural products - An overlooked potential of phytomedicines?

BACKGROUND

Photoactivity, though known for centuries, is only recently shifting back into focus as a treatment option against cancer and microbial infections. The external factor light is the ingenious key-component of this therapy: Since light activates the drug locally, a high level of selectivity is reached and side effects are avoided. The first reported photoactive medicines were plant extracts. Synthetic entities (so-called photosensitizers PSs), however, paved the route towards the clinical approval of the so-called photodynamic therapy (PDT), and thus natural PSs took a backseat in the past.

HYPOTHESIS

Many isolated bioactive phytochemicals hold a hidden photoactive potential, which is overlooked due to the reduced common awareness of photoactivity.

METHODS

A systematic review of reported natural PSs and their supposed medicinal application was conducted by employing PubMed, Scifinder, and Web of Science. The identified photoactive natural products were compiled including information about their natural sources, their photoyield, and their pharmacological application. Furthermore, the common chemical scaffolds of natural PS are shown to enable the reader to recognize potentially overlooked natural PSs.

RESULTS

The literature review revealed over 100 natural PS, excluding porphyrins. The PSs were classified according to their scaffold. Thereby it was shown that some PS-scaffolds were analyzed in a detailed way, while other classes were only scarcely investigated, which leaves space for future discoveries. In addition, the literature revealed that many PSs are phytoalexins, thus the selection of the starting material significantly matters in order to find new PSs.

CONCLUSION

Photoactive principles are ubiquitous and can be found in various plant extracts. With the increasing availability of light-irradiation setups for the identification of photoactive natural products, we anticipate the discovery of many new natural PSs in the near future. With the accumulation of chemically diverse PSs, PDT itself might finally reach its clinical breakthrough as a promising alternative treatment against multi-resistant microbes and cancer types.