Reduced methicillin-resistant Staphylococcus aureus biofilm formation in bone cavities by photodynamic therapy

Enhancing the efficacy of antimicrobial photodynamic therapy through curcumin modifications

Curcumin serves as a photosensitizer (PS) in the context of microbial inactivation when subjected to light exposure, to produce reactive oxygen species, which exhibit efficacy in eradicating microorganisms. This remarkable property underscores the growing potential of antimicrobial photodynamic therapy (aPDT) in the ongoing fight against bacterial infections. Considering this, we investigate the efficacy of various in vitro curcumin formulations within a PDT protocol designed to target Staphylococcus aureus. Specifically, we conduct a comparative analysis involving synthetic curcumin (Cur-Syn) and curcumin derivatives modified with chlorine (Cl), selenium (Se), and iodine (I) (Cur-Cl, Cur-Se, Cur-I). To assess the impact of aPDT, we subject S. aureus to incubation with curcumin, followed by irradiation at 450 nm with energy doses of 3.75, 7.5, and 15 J/cm2. Our investigation encompasses an evaluation of PS uptake and photobleaching across the various curcumin variants. Notably, all three modifications (Cur-Cl, Cur-Se, Cur-I) induce a significant reduction in bacterial viability, approximately achieving a 3-log reduction. Interestingly, the uptake kinetics of Cur-Syn and Cur-Se exhibit similarities, reaching saturation after 20 min. Our findings suggest that modifications to curcumin have a discernible impact on the photodynamic properties of the PS molecule.

Natural compounds in the fight against Staphylococcus aureus biofilms: a review of antibiofilm strategies

Staphylococcus aureus is an important pathogen due to its ability to form strong biofilms and antibiotic resistance. Biofilms play an important role in bacterial survival against the host immune system and antibiotics. Natural compounds (NCs) have diverse bioactive properties with a low probability of resistance, making them promising candidates for biofilm control. NC such as curcumin, cinnamaldehyde, carvacrol, eugenol, thymol, citral, linalool, 1,8-cineole, pinene, cymene, terpineol, quercetin, and limonene have been widely utilized for the inhibition and destruction of S. aureus biofilms. NCs influence biofilm formation through several procedures. Some of the antibiofilm mechanisms of NCs are direct bactericidal effect, disrupting the quorum sensing system, preventing bacteria from aggregation and attachment to surfaces, reducing the microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), interfering with sortase A enzyme, and altering the expression of biofilm-associated genes such as icaADBC, agr, and sarA. Furthermore, these compounds affect extracellular polymeric substances (EPS) and their components, such as polysaccharide intercellular adhesin (PIA) and eDNA. However, some disadvantages, such as low water solubility and bioavailability, limit their clinical usage. Therefore, scientists have considered using nanotechnology and drug platforms to improve NC's efficacy. Some NC, such as thymol and curcumin, can also enhance photodynamic therapy against S. aurous biofilm community. This article evaluates the anti-biofilm potential of NC, their mechanisms of action against S. aureus biofilms, and various aspects of their application.

Impact of PVC microplastics in photodynamic inactivation of Staphylococcus aureus and MRSA

Photodynamic processes have found widespread application in therapies. These processes involve photosensitizers (PSs) that, when excited by specific light wavelengths and in the presence of molecular oxygen, generate reactive oxygen species (ROS), that target cells leading to inactivation. Photodynamic action has gained notable attention in environmental applications, particularly against pathogens and antibiotic-resistant bacteria (ARB) that pose a significant challenge to public health. However, environmental matrices frequently encompass additional contaminants and interferents, including microplastics (MPs), which are pollutants of current concern. Their presence in water and effluents has been extensively documented, highlighting their impact on conventional treatment methods, but this information remains scarce in the context of photodynamic inactivation (PDI) setups. Here, we described the effects of polyvinyl chloride (PVC) microparticles in PDI targeting Staphylococcus aureus and its methicillin-resistant strain (MRSA), using curcumin as a PS under blue light. The presence of PVC microparticles does not hinder ROS formation; however, depending on its concentration, it can impact bacterial inactivation. Our results underscore that PDI remains a potent method for reducing bacterial concentrations in water and wastewater containing ARB, even in highly contaminated scenarios with MPs.

Photodynamic Inactivation of Foodborne Bacteria: Screening of 32 Potential Photosensitizers

The development of novel antimicrobial technologies for the food industry represents an important strategy to improve food safety. Antimicrobial photodynamic disinfection (aPDD) is a method that can inactivate microbes without the use of harsh chemicals. aPDD involves the administration of a non-toxic, light-sensitive substance, known as a photosensitizer, followed by exposure to visible light at a specific wavelength. The objective of this study was to screen the antimicrobial photodynamic efficacy of 32 food-safe pigments tested as candidate photosensitizers (PSs) against pathogenic and food-spoilage bacterial suspensions as well as biofilms grown on relevant food contact surfaces. This screening evaluated the minimum bactericidal concentration (MBC), minimum biofilm eradication concentration (MBEC), and colony forming unit (CFU) reduction against Salmonella enterica, methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas fragi, and Brochothrix thermosphacta. Based on multiple characteristics, including solubility and the ability to reduce the biofilms by at least 3 log10 CFU/sample, 4 out of the 32 PSs were selected for further optimization against S. enterica and MRSA, including sunset yellow, curcumin, riboflavin-5'-phosphate (R-5-P), and erythrosin B. Optimized factors included the PS concentration, irradiance, and time of light exposure. Finally, 0.1% w/v R-5-P, irradiated with a 445 nm LED at 55.5 J/cm2, yielded a "max kill" (upwards of 3 to 7 log10 CFU/sample) against S. enterica and MRSA biofilms grown on metallic food contact surfaces, proving its potential for industrial applications. Overall, the aPDD method shows substantial promise as an alternative to existing disinfection technologies used in the food processing industry.

The effects of antimicrobial photodynamic therapy (aPDT) with nanotechnology-applied curcumin and 450nm blue led irradiation on multi-species biofilms in root canals

This study aimed to evaluate the effectiveness of antimicrobial photodynamic therapy (aPDT) utilizing nanotechnology-applied curcumin activated by blue LED (450 nm) on the elimination of microorganisms arranged in multispecies biofilms inside the root canals of extracted human teeth. Forty single-rooted human teeth were used; these were randomized into four experimental groups, each comprising 10 teeth: control group, no treatment; photosensitizer (PS) group, nanotechnology-applied curcumin alone; light group, blue LED used separately; and aPDT group, nanotechnology-applied curcumin activated by blue LED. To carry out the tests, the interiors of the root canals were inoculated with species of Candida albicans (ATCC 90029), Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 25922), and methicillin-resistant Staphylococcus aureus (MRSA) (ATCC 43300), using a multispecies biofilm. After the incubation period, the canals were treated according to the experimental groups, with no treatment given in the control group. Studied inasmuch as the antimicrobial effectiveness of aPDT was concerned, it was observed that the greatest reduction in microbial counts using aPDTs was achieved against MRSA (mean reduction = 2.48 Log10 CFU/mL), followed by Escherichia coli (mean reduction = 1.72), and Enterococcus faecalis (mean reduction = 1.65); a reduction greater than 1.5 Log10 CFU/mL showed relevant effectiveness of aPDT against these microorganisms. Of note, aPDT has also shown considerable effectiveness against Candida albicans (mean reduction = 0.71), with a statistical difference in the reduction between the groups. aPDT was effective in reducing all microorganisms examined. The average reduction was greater than 1.5 Log10 in all microorganisms except for Candida albicans. HIGHLIGHTS: • aPDT was a viable treatment for root canals; • Nanotechnological curcumin aPDT was effective in reducing multispecies biofilm microorganisms; • aPDT technique showed efficacy under the worst microbiological conditions , such as mature multispecies biofilm; • Nanotechnological curcumin aPDT was able to reduce Gram positive, negative bacterial and yeasts in root canals.

Photonics-based treatments: Mechanisms and applications in oral infectious diseases

Infectious diseases remain a serious global challenge threatening human health. Oral infectious diseases, a major neglected global problem, not only affect people's lifestyles but also have an intimate association with systemic diseases. Antibiotic therapy is a common treatment. However, the emergence of new resistance problems hindered and enhanced the complication of the treatment. Currently, antimicrobial photodynamic therapy (aPDT) has long been the topic of intense interest due to the advantage of being minimally invasive, low toxicity, and high selectivity. aPDT is also becoming increasingly popular and applied in treating oral diseases such as tooth caries, pulpitis, periodontal diseases, peri-implantitis, and oral candidiasis. Photothermal therapy (PTT), another phototherapy, also plays an important role in resisting resistant bacterial and biofilm infections. In this mini-review, we summarize the latest advances in photonics-based treatments of oral infectious diseases. The whole review is divided into three main parts. The first part focuses on photonics-based antibacterial strategies and mechanisms. The second part presents applications for photonics-based treatments of oral infectious diseases. The last part discusses present problems in current materials and future perspectives.

Antibacterial intraosseous implant surface coating that responds to changes in the bacterial microenvironment

Bone implant-associated infection is one of the most challenging problems encountered by orthopedic surgeons. There is considerable interest in the development of drug-loaded antibacterial coatings for the surfaces of metal implants. However, it is difficult to achieve the stable local release of an effective drug dose for many antibacterial coatings. In the present study, analyses of the thickness and water contact angle of multiple layers confirmed the successful assembly of multilamellar membrane structures. Measurement of the zone of bacterial inhibition indicated gradual degradation of the (montmorillonite [MMT]/hyaluronic acid [HA])₁₀ multilamellar film structure with concentration-dependent degradation during incubation with hyaluronidase solution and Staphylococcus aureus. In vivo results resembled the in vitro results. Overall, the findings confirm that the (MMT/HA-rifampicin)₁₀ multilamellar film structure exhibits good antibacterial properties and excellent biocompatibility. Further studies of the clinical potential of the antibacterial coating prepared in this experiment are warranted.

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.

Antimicrobial curcumin-mediated photodynamic inactivation of bacteria in natural bovine casing

BACKGROUND

Outbreaks related to food contamination by resistant microorganisms is a worldwide concern that, motivates industries and research institutions to search for affordable solutions. Among the solutions that have been proposed, Photodynamic Inactivation (PDI) of microorganisms has gained prominence, among other aspects, because it is easy to apply and does not generate microbial resistance.

METHODS

In this study, we used the association between curcumin solubilized with Tween and light in the photodynamic inactivation process, using light-emitting diodes with a wavelength of 430 nm for decontamination S. Typhimurium and K. pneumoniae from bovine casings used as wrappers for meat products. The result was verified by counting and comparing the number of colony-forming units of the treatment concerning the negative control.

RESULTS

The solubilizer, Tween 80, used does not change the optical absorption of curcumin. An optical fluence of 150J/cm² induces a microbial log reduction of 3.8±0.2 and 2.7±0.1 for S. Typhimurium, and K. pneumoniae contaminated guts, respectively. For the 200μM concentration of curcumin, the PDI provided a microbial log reduction of 3.16±0.03 for S. Typhimurium. For K. pneumoniae, the minimal inhibitory concentration of curcumin occurs up to 12.5μM, causing an microbial log reduction of 2.08±0.03.

CONCLUSION

Both curcumin and tween are already used as additives in food production and do not pose health risks at the concentrations used. Furthermore, in the case of the material studied, the addition of curcumin favors the organoleptic quality associated with the color of the food, unlike the green or blue photossensitizers. The results pave the way for possible application of curcumin in finished meat products.

Comparative randomized trial study about the efficacy of photobiomodulation and curcumin antimicrobial photodynamic therapy as a coadjuvant treatment of oral mucositis in oncologic patients: antimicrobial, analgesic, and degree alteration effect

INTRODUCTION

As conventional treatments currently available for mucositis are not considerably effective, there is a need to implement an adjuvant protocol for the treatment of oral mucositis in patients undergoing radiotherapy and chemotherapy.

PURPOSE

To evaluate the effect of photobiomodulation (PBM) and antimicrobial photodynamic therapy (aPDT) mediated by curcumin and blue LED as an adjunct treatment of oral mucositis for oncology patients using chemotherapy and/or radiotherapy.

METHODS

Clinical, randomized study, in a single location, in an oncology service of a general hospital, with a total of 30 patients (over 18 years old) with stable oral mucosa lesions in the process of chemotherapy and/or radiotherapy. The patients were divided into 3 groups: control group (treated with nystatin), PBM group (treated with low-level laser therapy), and the aPDT group (treated with 450-nm blue LED and curcumin photosensitizer).

RESULTS

The results showed, by means of intra-group comparisons, that the two experimental treatments promoted yeast reduction of the genus Candida in the last two evaluations (21 days and 30 days), but not in the first two evaluations (7 days and 14 days). The intra-group comparisons showed that the control and aPDT group showed a significant difference in the degree of mucositis over the four evaluations performed, with the results pointing out that the mucositis worsened in the control group from the 14th day, while reduced in the aPDT group from the 21st day of treatment.

CONCLUSION

A reduction in the degree of mucositis and pain score was observed in the PBM and aPDT groups, with the aPDT group standing out when presenting early clinical improvement in relation to the PBM group and the control group, thus emphasizing its effectiveness within the desired aspects. Regarding the antimicrobial effect, aPDT showed a greater reduction of yeasts of the genus Candida in the tested parameters.

4Antimicrobial photodynamic therapy with curcumin on methicillin-resistant Staphylococcus aureus biofilm

Healthcare-Associated Infections (HAI) affect approximately 1.5 million individuals worldwide. Among the causes of HAIs in Latin America, Staphylococcus aureus presents a severe danger due to its rapid spread and ease of developing antibiotic resistance. Upon acquiring methicillin resistance, it receives the classification Methicillin-Resistant Staphylococcus aureus (MRSA), responsible for 40 to 60% of HAIs. The increase in resistant microorganisms led to the search for alternative methods, such as antimicrobial Photodynamic Therapy (aPDT), forming Reactive Oxygen Species (ROS), leading bacterial cells to death. The objective of this work was to evaluate in vitro the antimicrobial action of PDT with curcumin in MRSA biofilm. The strains were induced to form biofilm and incubated with curcumin for 20 minutes, irradiated with LED (Light Emitting Diode) 450 nm, at 110 mW/cm2, 50 J/cm2 for 455 seconds, subsequently counting the Colony Forming Units, Scanning Electron Microscopy (SEM) micrographs, Confocal Microscopy images, Resazurin dye test, ROS quantification to assess the effect of PDT on biofilm. The results show that PDT with curcumin reduced the biofilm growth of the MRSA strain. In addition, confocal microscopy showed that curcumin was internalized by S. aureus in the cells at the concentration used, and when isolated, curcumin and the irradiation parameter did not show cytotoxicity. The study demonstrated that the PDT in the established parameters reduced the growth of the MRSA strain biofilm, making it a relevant alternative possibility for the inactivation of this strain.

Optical clearing of tissues: Issues of antimicrobial phototherapy and drug delivery

This review presents principles and novelties in the field of tissue optical clearing (TOC) technology, as well as application for optical monitoring of drug delivery and effective antimicrobial phototherapy. TOC is based on altering the optical properties of tissue through the introduction of immersion optical cleaning agents (OCA), which impregnate the tissue of interest. We also analyze various methods and kinetics of delivery of photodynamic agents, nanoantibiotics and their mixtures with OCAs into the tissue depth in the context of antimicrobial and antifungal phototherapy. In vitro and in vivo studies of antimicrobial phototherapies, such as photodynamic, photothermal plasmonic and photocatalytic, are summarized, and the prospects of a new TOC technology for effective killing of pathogens are discussed.

Photodynamic treatment of pathogens

The current viral pandemic has highlighted the compelling need for effective and versatile treatments, that can be quickly tuned to tackle new threats, and are robust against mutations. Development of such treatments is made even more urgent in view of the decreasing effectiveness of current antibiotics, that makes microbial infections the next emerging global threat. Photodynamic effect is one such method. It relies on physical processes proceeding from excited states of particular organic molecules, called photosensitizers, generated upon absorption of visible or near infrared light. The excited states of these molecules, tailored to undergo efficient intersystem crossing, interact with molecular oxygen and generate short lived reactive oxygen species (ROS), mostly singlet oxygen. These species are highly cytotoxic through non-specific oxidation reactions and constitute the basis of the treatment. In spite of the apparent simplicity of the principle, the method still has to face important challenges. For instance, the short lifetime of ROS means that the photosensitizer must reach the target within a few tens nanometers, which requires proper molecular engineering at the nanoscale level. Photoactive nanostructures thus engineered should ideally comprise a functionality that turns the system into a theranostic means, for instance, through introduction of fluorophores suitable for nanoscopy. We discuss the principles of the method and the current molecular strategies that have been and still are being explored in antimicrobial and antiviral photodynamic treatment.

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.

Derivatives of Natural Chlorophylls as Agents for Antimicrobial Photodynamic Therapy

The rapid growth of drug-resistant bacteria all over the world has given rise to a major research challenge, namely a search for alternative treatments to which bacteria will be unable to develop resistance. Photodynamic therapy is an approach of this kind. It involves the use of photosensitizers in combination with visible light at a certain wavelength to excite the former and generate reactive oxygen species. Various synthetic heterocyclic compounds are used as photosensitizers. Of these, derivatives of natural chlorophylls have a special place due to their properties. This review deals with the use of such compounds in antimicrobial PDT.

Photodynamic therapy for treatment of Staphylococcus aureus infections

BACKGROUND

Staphylococcus aureus is a Gram-positive spherical bacterium that commonly causes various infections which can range from superficial to life-threatening. Hospital strains of S. aureus are often resistant to antibiotics, which has made their treatment difficult in recent decades. Other therapeutic alternatives have been postulated to overcome the drawbacks of antibiotic multi-resistance. Of these, photodynamic therapy (PDT) is a promising approach to address the notable shortage of new active antibiotics against multidrug-resistant S. aureus. PDT combines the use of a photosensitizer agent, light, and oxygen to eradicate pathogenic microorganisms. Through a systematic analysis of published results, this work aims to verify the usefulness of applying PDT in treating multidrug-resistant S.aureus infections.

METHODS

This review was based on a bibliographic search in various databases and the analysis of relevant publications.

RESULTS

There is currently a large body of evidence demonstrating the efficacy of photodynamic therapy in eliminating S.aureus strains. Both biofilm-producing strains, as well as multidrug-resistant strains.

CONCLUSION

We conclude that there is sufficient scientific evidence that PDT is a useful adjunct to traditional antibiotic therapy for treating S. aureus infections. Clinical application through appropriate trials should be introduced to further define optimal treatment protocols, safety and efficay.

Microbial Composition of Oral Biofilms after Visible Light and Water-Filtered Infrared a Radiation (VIS+wIRA) in Combination with Indocyanine Green (ICG) as Photosensitizer

In view of increasing antibiotic resistance, antimicrobial photodynamic therapy (aPDT) is an alternative treatment method used to eradicate the microbial community of oral biofilms that can be responsible for different oral infections. In order to investigate changes in the microbial composition after application of aPDT with visible light and water-filtered infrared A (VIS+wIRA) in combination with indocyanine green (ICG), oral microorganisms of the initial and mature biofilm were evaluated by mass spectrometry (MALDI-TOF-MS). To determine surviving microorganisms using MALDI-TOF-MS, an in situ biofilm was irradiated with VIS+wIRA for five minutes in the presence of ICG (300 and 450 µg/mL, respectively). Treatment with chlorhexidine (0.2%) served as positive control. Identified microorganisms of the initial biofilm treated with ICG showed a clear reduction in diversity. The microbial composition of the mature oral biofilm also showed changes after the implementation of aPDT, which mainly resulted in a shift in the percentage of bacterial species. The resulting destruction of the microbial balance within the oral biofilm by aPDT using VIS+wIRA and ICG can be seen as an advantageous supplementary approach in the adjunctive treatment of periodontitis and peri-implantitis.

Contemporary approaches and future perspectives of antibacterial photodynamic therapy (aPDT) against methicillin-resistant Staphylococcus aureus (MRSA): A systematic review

The high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) causing skin and soft tissue infections in both the community and healthcare settings challenges the limited options of effective antibiotics and motivates the search for alternative therapeutic solutions, such as antibacterial photodynamic therapy (aPDT). While many publications have described the promising anti-bacterial activities of PDT in vitro, its applications in vivo and in the clinic have been very limited. This limited availability may in part be due to variabilities in the selected photosensitizing agents (PS), the variable testing conditions used to examine anti-bacterial activities and their effectiveness in treating MRSA infections. We thus sought to systematically review and examine the evidence from existing studies on aPDT associated with MRSA and to critically appraise its current state of development and areas to be addressed in future studies. In 2018, we developed and registered a review protocol in the International Prospective Register of Systematic Reviews (PROSPERO) with registration No: CRD42018086736. Three bibliographical databases were consulted (PUBMED, MEDLINE, and EMBASE), and a total of 113 studies were included in this systematic review based on our eligibility criteria. Many variables, such as the use of a wide range of solvents, pre-irradiation times, irradiation times, light sources and light doses, have been used in the methods reported by researchers, which significantly affect the inter-study comparability and results. On another note, new approaches of linking immunoglobulin G (IgG), antibodies, efflux pump inhibitors, and bacteriophages with photosensitizers (PSs) and the incorporation of PSs into nano-scale delivery systems exert a direct effect on improving aPDT. Enhanced activities have also been achieved by optimizing the physicochemical properties of the PSs, such as the introduction of highly lipophilic, poly-cationic and site-specific modifications of the compounds. However, few in vivo studies (n = 17) have been conducted to translate aPDT into preclinical studies. We anticipate that further standardization of the experimental conditions and assessing the efficacy in vivo would allow this technology to be further applied in preclinical trials, so that aPDT would develop to become a sustainable, alternative therapeutic option against MRSA infection in the future.

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.

Antimicrobial photodynamic therapy effectiveness against susceptible and methicillin-resistant Staphylococcus aureus biofilms

BACKGROUND

Staphylococcus aureus have a great ability to become rapidly resistant to conventional antimicrobial therapies. This study evaluated the efficacy of antimicrobial photodynamic therapy (aPDT) mediated by Curcumin (Cur) and light-emitting diode (LED) in the inactivation of biofilms of methicillin susceptible and resistant S. aureus (MSSA and MRSA, respectively).

METHODS

Biofilms were treated with Cur (20, 40 or 80 μM) and illuminated with LED source (455 ± 3 nm; 5.28 J/cm²) (aPDT groups), or treated either with Cur or LED only. Other samples were not exposed to Cur or LED (negative control). The biofilms viability after all experimental conditions were evaluated by counting the number of colonies (CFU/mL) and XTT assay. Additional samples were also evaluated by LIVE/DEAD® staining using confocal laser scanning microscopy (CLSM). Data were analyzed by ANOVAs followed by the Games-Howell post hoc test (α = 0.05).

RESULTS

For both strains, all aPDT groups significantly reduced both CFU/mL and metabolic activity of biofilms compared to the negative control (p < 0.001). The results were enhanced when 80 μM of Cur was used. CLSM images showed that both bacteria biofilms submitted to aPDT had a large number of red-stained colonies, especially at aPDT80. In general, MRSA biofilms tended to be less susceptible to aPDT than MSSA biofilms.

CONCLUSIONS

It can be concluded that aPDT mediated by Cur and LED was an efficient method to inactivate 48 -h biofilms of both S. aureus strains.

High-power light-emitting diode array design and assembly for practical photodynamic therapy research

SIGNIFICANCE

Commercial lasers, lamps, and light-emitting diode (LED) light sources have stimulated the clinical translation of photodynamic therapy (PDT). Yet, the continued exploration of new photosensitizers (PSs) for PDT often requires separate activation wavelengths for each agent being investigated. Customized light sources for such research frequently come at significant financial or technical cost, especially when compounded over many agents and wavelengths.

AIM

LEDs offer potential as a cost-effective tool for new PS and multi-PS photodynamic research. A low-cost-per-wavelength tool leveraging high-power LEDs to facilitate efficient and versatile research is needed to further accelerate research in the field.

APPROACH

We developed and validated a high-power LED array system for benchtop PDT with a modular design for efficient switching between wavelengths that overcome many challenges in light source design. We describe the assembly of a low-cost LED module plus the supporting infrastructure, software, and protocols to streamline typical in vitro PDT experimentation.

RESULTS

The LED array system is stable at intensities in excess of 100  mW  /  cm2 with 2.3% variation across the illumination field, competitive with other custom and commercial devices. To demonstrate efficacy and versatility, a primary ovarian cancer cell line was treated with two widely used PSs, aminolevulinic acid and verteporfin, using the LED modules at a clinically relevant 50  J  /  cm2 light dose that induced over 90% cell death for each treatment.

CONCLUSIONS

Our work provides the community with a tool for new PS and multi-PS benchtop photodynamic research that, unlike most commercial light sources, affords the user a low barrier to entry and low-cost-per-wavelength with the goal of illuminating new insights at the forefront of PDT.

Inactivation of oral biofilms using visible light and water-filtered infrared A radiation and indocyanine green

Aim: To investigate the antimicrobial photodynamic therapy (aPDT) of visible light and water-filtered infrared A radiation in combination with indocyanine green (ICG) on planktonic oral microorganisms as well as on oral biofilm. Methods: The irradiation was conducted for 5 min in combination with ICG. Treatment with chlorhexidine served as a positive control. The number of colony forming units and bacterial vitality were quantified. Results: All tested bacterial strains and salivary bacteria were killed at a level of 3log_10. The colony forming units of the initial mature oral biofilms were strongly reduced. The high bactericidal effect of aPDT was confirmed by live/dead staining. Conclusion: The aPDT using visible light and water-filtered infrared A radiation and ICG has the potential to treat periodontitis and peri-implantitis.

Chitosan-Based Drug Delivery Systems for Optimization of Photodynamic Therapy: a Review

Drug delivery systems (DDS) can be designed to enrich the pharmacological and therapeutic properties of several drugs. Many of the initial obstacles that impeded the clinical applications of conventional DDS have been overcome with nanotechnology-based DDS, especially those formed by chitosan (CS). CS is a linear polysaccharide obtained by the deacetylation of chitin, which has potential properties such as biocompatibility, hydrophilicity, biodegradability, non-toxicity, high bioavailability, simplicity of modification, aqueous solubility, and excellent chemical resistance. Furthermore, CS can prepare several DDS as films, gels, nanoparticles, and microparticles to improve delivery of drugs, such as photosensitizers (PS). Thus, CS-based DDS are broadly investigated for photodynamic therapy (PDT) of cancer and fungal and bacterial diseases. In PDT, a PS is activated by light of a specific wavelength, which provokes selective damage to the target tissue and its surrounding vasculature, but most PS have low water solubility and cutaneous photosensitivity impairing the clinical use of PDT. Based on this, the application of nanotechnology using chitosan-based DDS in PDT may offer great possibilities in the treatment of diseases. Therefore, this review presents numerous applications of chitosan-based DDS in order to improve the PDT for cancer and fungal and bacterial diseases.

Photodynamic inactivation of S. aureus with a water-soluble curcumin salt and an application to cheese decontamination

In this study, the optimal parameters for the photodynamic inactivation (PDI) of Staphylococcus aureus in bacterial suspensions and in cheese were assessed using a water-soluble curcumin salt as the photosensitizer (PS).