Methylene blue mediated antimicrobial photodynamic therapy in clinical human studies: The state of the art

Catalase Deactivation Increases Dermatophyte Sensitivity to ROS Sources

As the leading cause of fungal skin infections around the globe, dermatophytes are responsible for a multitude of skin ailments, ranging from athlete's foot to ringworm. Due to the combination of its growing prevalence and antifungal misuse, antifungal-resistant dermatophyte strains like Trichophyton indotineae have begun to emerge, posing a significant global health risk. The emergence of these resistant dermatophytes highlights a critical need to identify alternative methods of treating dermatophyte infections. In our study, we utilized a 405 nm LED to establish that blue light can effectively inactivate catalase within a variety of both susceptible and resistant dermatophytes. Through this catalase inactivation process, light-treated dermatophytes were found to exhibit increased sensitivity to reactive oxygen species (ROS)-producing agents, improving the performance of antimicrobial agents such as H2O2 and amphotericin B. Our findings further demonstrate that light-induced catalase inactivation can inhibit the formation and polarized growth of hyphae from dermatophytes, suppressing biomass formation. Thus, by increasing ROS sensitization and inhibiting hyphal development, catalase-deactivating blue light offers a potential non-invasive and non-drug-reliant method of managing dermatophyte infections, opening new avenues for the potential treatment of these common infections in conjunction with existing treatments.

Highly Efficient Quenching of Singlet Oxygen by DNA Origami Nanostructures

DNA origami nanostructures (DONs) are able to scavenge reactive oxygen species (ROS) and their scavenging efficiency toward ROS radicals was shown to be comparable to that of genomic DNA. Herein, we demonstrate that DONs are highly efficient singlet oxygen quenchers outperforming double-stranded (ds) DNA by several orders of magnitude. To this end, a ROS mixture rich in singlet oxygen is generated by light irradiation of the photosensitizer methylene blue and its cytotoxic effect on Escherichia coli cells is quantified in the presence and absence of DONs. DONs are found to be vastly superior to dsDNA in protecting the bacteria from ROS-induced damage and even surpass established ROS scavengers. At a concentration of 15 nM, DONs are about 50 000 times more efficient ROS scavengers than dsDNA at an equivalent concentration. This is attributed to the dominant role of singlet oxygen, which has a long diffusion length and reacts specifically with guanine. The dense packing of the available guanines into the small volume of the DON increases the overall quenching probability compared to a linear dsDNA with the same number of base pairs. DONs thus have great potential to alleviate oxidative stress caused by singlet oxygen in diverse therapeutic settings.

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.

Adjuvant effect of antimicrobial photodynamic therapy (aPDT) in the treatment of diabetic foot ulcers: A case series

This study aimed to evaluate the clinical evolution of patients with diabetic foot ulcer treated with antimicrobial photodynamic therapy (aPDT) using the Bates-Jensen (BJ) scale. A total of 21 patients were monitored, with an average age of 58 years. Patients underwent the standard treatment protocol of the institution, supplemented with aPDT utilizing 0.01% methylene blue (MB) and laser irradiation (660 nm, 100 mW, 6 J per point). Following aPDT, the lesions were protected with hydrofiber dressings containing silver. The Bates-Jensen Scale was employed at pre-treatment and post-aPDT sessions to assess lesion progression. The results demonstrated a significant difference between pre- and post-treatment values in the overall BJ score. The use of MB in aPDT proved to be an effective, safe, well-tolerated treatment with high patient adherence and the potential for implementation in the care of diabetic foot conditions.

Exploring the synergistic effects of amoxicillin and methylene blue on unsaturated lipid structures: A study of Langmuir monolayers and giant unilamellar vesicles

The potentially toxic effects of emerging pollutant mixtures often deviate from the individual compound effects, presenting additive, synergistic, or agonistic interactions. This study delves into the complex world of emerging pollutants' mixtures, with a particular focus on their potential impact on unsaturated lipid DOPC (1,2-dioleoyl-sn-glycerol-3-phosphocholine) structured as both monolayers and bilayers, which are valuable tools for mimicking cell membranes. Specifically, we examine the effects of two common types of pollutants: antibiotics (amoxicillin) and dyes (methylene blue). Utilizing Langmuir monolayers, our research reveals a synergistic effect within the pollutant mixture, as evidenced by pressure-area isotherms and polarization-modulated infrared reflection absorption spectroscopy. We identify the specific chemical interactions contributing to this synergistic effect. Furthermore, through contrast phase microscopy experiments on giant unilamellar vesicles (bilayer system), we find that the individual pollutants and the mixture exhibit similar molecular effects on the bilayer, revealing that the molecular size is a key factor in the bilayer-mixture of pollutant interaction. This highlights the importance of considering molecular size in the interactions with bilayer systems. In summary, our research dissects the critical factors of chemical interactions and molecular size concerning the effects of pollutants on DOPC, serving as simplified models of cell membranes. This study underscores the significance of comprehending the molecular effects of emerging pollutants on human health and the development of models for exploring their intricate interactions with cell membranes.

Potential of photodynamic therapy in the management of infectious oral diseases

Photodynamic therapy (PDT) can take place in the presence of three elements: Light with an appropriate wavelength; a photosensitizer; and the presence of oxygen. This type of treatment is very effective overall against bacterial, viral and mycotic cells. In the last 10 years many papers have been published on PDT with different types of photosensitizers (e.g., methylene blue, toluidine blue, indocyanine green, curcumin-based photosensitizers), different wavelengths (e.g., 460 nm, 630 nm, 660 nm, 810 nm) and various parameters (e.g., power of the light, time of illumination, number of sessions). In the scientific literature all types of PDT seem very effective, even if it is difficult to find a standard protocol for each oral pathology. PDT could be an interesting way to treat some dangerous oral infections refractory to common pharmacological therapies, such as candidiasis from multidrug-resistant Candida spp.

Safety and Feasibility of Photodynamic Therapy for Percutaneous Image-guided Abdominopelvic Abscess Drainage: Phase 1 Trial

Background Standard-of-care abscess management includes image-guided percutaneous drainage and antibiotics; however, cure rates vary, and concern for antibiotic-resistant bacteria is growing. Photodynamic therapy (PDT), which uses light-activated dyes to generate cytotoxic reactive oxygen species, could complement the standard of care by sterilizing the abscess at the time of drainage. Purpose To evaluate safety and feasibility of PDT with methylene blue (hereafter, MB-PDT) at the time of percutaneous abscess drainage. Materials and Methods This prospective, open-label, dose-escalation, first-in-humans, registered phase 1 clinical study of MB-PDT included participants who underwent percutaneous abdominal or pelvic abscess drainage with CT or US guidance from January 2015 to March 2020 and September 2022 to September 2023. Following drainage, MB-PDT was performed with laser illumination at a fluence rate of 20 mW/cm2, with fluence groups of 6, 12, 18, 24, 30, and 36 J/cm2 (n = 3 each). The primary outcome was safety, indicated by absence of fat embolism, MB escape, abscess wall damage, and need for surgery to remove optical fibers. Preliminary efficacy end points included the time to drainage catheter removal, drainage catheter output volume, and clinical symptom and fever duration. Relationships between fluence and outcomes were analyzed with Spearman correlation and linear regression analyses, and ordinary one-way analysis of variance was used for group comparisons. Results MB-PDT was safe and feasible in all 18 participants (mean age, 60.1 years ± 18.3 [SD]; 10 female), with no negative safety outcomes observed for any participant. No study-related adverse events were encountered, and the procedure did not increase reported pain (P = .1). Clinical symptom and fever duration was shorter in participants receiving higher fluences (30 and 36 J/cm2 vs 6 J/cm2) (P = .03). The presence of antibiotic-resistant bacteria was not predictive of clinical symptom and fever duration (β = 0.13, P = .37). Conclusion MB-PDT was a safe and feasible adjunct to image-guided percutaneous abscess drainage. Clinical measures indicated a dose-dependent response to PDT. ClinicalTrials.gov registration no.: NCT02240498 © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Johnston and Goldberg in this issue.

Antimicrobial photodynamic therapy for the management of gingivitis and white spot lesions in fixed orthodontic patients: A systematic review

AIM

We conducted this review to evaluate the safety and efficacy of antimicrobial photodynamic therapy (aPDT) for the management of gingivitis and white spot lesions (WSLs) in fixed orthodontic patients.

METHODS

The PubMed/MEDLINE, Cochrane Library, Scopus, and Google Scholar databases were searched for randomized controlled trials and clinical trials assessing the clinical effectiveness of aPDT for the management of gingivitis and WSLs in fixed orthodontic patients without time limitation. Primary outcomes were the changes in clinical parameters such as DIAGNOdent, plaque index (PI), bleeding on probing (BOP), and gingival index (GI). Secondary outcomes included measurements of microbial and inflammatory factors, such as cytokine levels (tumor necrosis factor alpha [TNF-α], interleukin-1 beta [IL-1β], and interleukin-6 [IL-6]), and bacterial counts.

RESULTS

Our search yielded a total of 12 studies that met the inclusion criteria. Among the 11 studies that evaluated gingivitis, the majority employed a diode laser (670nm, 150 mW, 22J/cm2, 60seconds) as the light source and methylene blue at a concentration of 0.0005% (applied for 3minutes) as the photosensitizer in a single treatment session. The included studies reported positive effects of aPDT on gingivitis management, with more improvements observed in PI, BOP, and GI following aPDT treatment. Additionally, aPDT was found to reduce the counts of periopathogens such as Porphyromonas gingivalis, as well as inflammatory factors (TNF-α, IL-1β, and IL-6). Two studies demonstrated that aPDT, particularly when administered in multiple sessions, effectively controlled the extent of WSLs during orthodontic treatment and yielded favorable outcomes that persisted for several months after treatment.

CONCLUSION

Based on the available evidence, aPDT appears to be a safe and effective treatment option for managing WSLs and gingivitis in patients with fixed orthodontic appliances. However, further high-quality RCTs are necessary to investigate the impact of potential confounding factors on the efficacy of aPDT.

In vitro photoinactivation effectiveness of a portable LED device aimed for intranasal photodisinfection and a photosensitizer formulation comprising methylene blue and potassium iodide against bacterial, fungal, and viral respiratory pathogens

Antimicrobial photodynamic therapy (aPDT) can be a viable option for management of intranasal infections. However, there are light delivery, fluence, and photosensitizer-related challenges. We report in vitro effectiveness of an easily fabricated, low-cost, portable, LED device and a formulation comprising methylene blue (MB) and potassium iodide (KI) for photoinactivation of pathogens of the nasal cavity, namely, methicillin-resistant Staphylococcus aureus, antibiotic-resistant Klebsiella pneumoniae, multi-antibiotic-resistant Pseudomonas aeruginosa, Candida spp., and SARS-CoV-2.In a 96-well plate, microbial suspensions incubated with 0.005% MB alone or MB and KI formulation were exposed to different red light (~ 660 ± 25 nm) fluence using the LED device fitted to each well. Survival loss in bacteria and fungi was quantified using colony-forming unit assay, and SARS-CoV-2 photodamage was assessed by RT-PCR.The results suggest that KI addition to MB leads to KI concentration-dependent potentiation (up to ~ 5 log10) of photoinactivation in bacteria and fungi. aPDT in the presence of 25 or 50 mM KI shows the following photoinactivation trend; Gm + ve bacteria  > Gm - ve bacteria > fungi  > virus. aPDT in the presence of 100 mM KI, using 3- or 5-min red light exposure, results in complete eradication of bacteria or fungi, respectively. For SARS-CoV-2, aPDT using MB-KI leads to a ~ 6.5 increase in cycle threshold value.The results demonstrate the photoinactivation effectiveness of the device and MB-KI formulation, which may be helpful in designing of an optimized protocol for future intranasal photoinactivation studies in clinical settings.

The Use of Photoactive Polymeric Nanoparticles and Nanofibers to Generate a Photodynamic-Mediated Antimicrobial Effect, with a Special Emphasis on Chronic Wounds

This review is concerned with chronic wounds, with an emphasis on biofilm and its complicated management process. The basics of antimicrobial photodynamic therapy (PDT) and its underlying mechanisms for microbial eradication are presented. Intrinsically active nanocarriers (polydopamine NPs, chitosan NPs, and polymeric micelles) that can further potentiate the antimicrobial photodynamic effect are discussed. This review also delves into the role of photoactive electrospun nanofibers, either in their eluting or non-eluting mode of action, in microbial eradication and accelerating the healing of wounds. Synergic strategies to augment the PDT-mediated effect of photoactive nanofibers are reviewed.

Antimicrobial photodynamic therapy for managing the peri-implant mucositis and peri-implantitis: A systematic review of randomized clinical trials

BACKGROUND

The presence of peri‑implant inflammation including peri‑implant mucositis and peri‑implantitis, is a crucial factor that impacts the long-term stability and success of dental implants. This review aimed to evaluate the safety and effectiveness of antimicrobial photodynamic therapy (aPDT) as an adjuvant therapy option for managing peri‑implant mucositis and peri‑implantitis.

METHODS

We systematically searched the PubMed/MEDLINE, Cochrane Library, Scopus, and Google Scholar databases (no time limitation). The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the quality of the studies was assessed using the Cochrane Collaboration tool.

RESULTS

Of 322 eligible articles, 14 studies were included in this review. The heterogeneity and poor quality of the articles reviewed prevented a meta-analysis. The reviewed articles used a light source (60 s, 1 session) with a wavelength of 635 to 810 nm for optimal tissue penetration. These studies showed improved clinical parameters such as probing depth, bleeding on probing (BOP), and plaque index after aPDT treatment. However, in smokers, BOP increased after aPDT. Compared to conventional therapy, aPDT had a longer-term antimicrobial effect and reduced periopathogens like Porphyromonas gingivalis, as well as inflammatory factors such as Interleukin (IL)-1β, IL-6, and Tumor necrosis factor alpha (TNF-α). No undesired side effects were reported in the studies.

CONCLUSION

Although the reviewed articles had limitations, aPDT showed effectiveness in improving peri‑implant mucositis and peri‑implantitis. It is recommended as an adjunctive strategy for managing peri‑implant diseases, but further high-quality research is needed for efficacy and long-term outcomes.

Evaluation of antimicrobial photodynamic action of a pluronic and pectin based film loaded with methylene blue against methicillin resistantStaphylococcus aureus

Antimicrobial wound dressings play a crucial role in treatment of wound infections. However, existing commercial options fall short due to antibiotic resistance and the limited spectrum of activity of newly emerging antimicrobials against bacteria that are frequently encountered in wound infections. Antimicrobial photodynamic therapy (aPDT) is very promising alternative therapeutic approach against antibiotic resistant microbes such as methicillin resistantStaphylococcus aureus (MRSA). However, delivery of the photosensitizer (PS) homogeneously to the wound site is a challenge. Though polymeric wound dressings based on synthetic and biopolymers are being explored for aPDT, there is paucity of data regarding theirin vivoefficacy. Moreover, there are no studies on use of PS loaded, pluoronic (PL) and pectin (PC) based films for aPDT. We report development of a polymeric film for potential use in aPDT. The film was prepared using PL and PC via solvent casting approach and impregnated with methylene blue (MB) for photodynamic inactivation of MRSAin vitroandin vivo. Atomic force microscopic imaging of the films yielded vivid pictures of surface topography, with rough surfaces, pores, and furrows. The PL:PC ratio (2:3) was optimized that would result in an intact film but exhibit rapid release of MB in time scale suitable for aPDT. The film showed good antibacterial activity against planktonic suspension, biofilm of MRSA upon exposure to red light. Investigations on MRSA infected excisional wounds of mice reveal that topical application of MB loaded film for 30 min followed by red light exposure for 5 min (fluence; ∼30 J cm-2) or 10 min (fluence; ∼60 J cm-2) reduces ∼80% or ∼92% of bioburden, respectively. Importantly, the film elicits no significant cytotoxicity against keratinocytes and human adipose derived mesenchymal stem cells. Taken together, our data demonstrate that PS-loaded PL-PC based films are a promising new tool for treatment of MRSA infected wounds.

Investigating Photoactive Antimicrobials as Alternatives (or Adjuncts) to Traditional Therapy

Photodynamic therapy (PDT) is an established therapy used for the treatment of cutaneous skin cancers and other non-infective ailments. There has been recent interest in the opportunity to use aPDT (antimicrobial PDT) to treat skin and soft tissue infections. PDT utilizes photosensitizers that infiltrate all cells and "sensitize" them to a given wavelength of light. The photosensitizer is simply highly absorbent to a given wavelength of light and when excited will produce, in the presence of oxygen, damaging oxygen radicals and singlet oxygen. Bacterial cells are comparatively poor at combatting oxidative stress when compared with human cells therefore a degree of selective toxicity can be achieved with aPDT.In this chapter, we outline methodologies for testing aPDT in vitro using standard lab equipment.

Photodynamic Action of Curcumin and Methylene Blue against Bacteria and SARS-CoV-2-A Review

Coronavirus disease 19 (COVID-19) has occurred for more than four years, and the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing COVID-19 is a strain of coronavirus, which presents high rates of morbidity around the world. Up to the present date, there are no therapeutics that can avert this form of illness, and photodynamic therapy (PDT) may be an alternative approach against SARS-CoV-2. Curcumin and methylene blue have been approved and used in clinical practices as a photosensitizer in PDT for a long time with their anti-viral properties and for disinfection through photo-inactivated SARS-CoV-2. Previously, curcumin and methylene blue with antibacterial properties have been used against Gram-positive bacteria, Staphylococcus aureus (S. aureus), and Gram-negative bacteria, Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), and Pseudomonas aeruginosa (P. aeruginosa).

METHODS

To conduct a literature review, nine electronic databases were researched, such as WanFang Data, PubMed, Science Direct, Scopus, Web of Science, Springer Link, SciFinder, and China National Knowledge Infrastructure (CNKI), without any regard to language constraints. In vitro and in vivo studies were included that evaluated the effect of PDT mediated via curcumin or methylene blue to combat bacteria and SARS-CoV-2. All eligible studies were analyzed and summarized in this review.

RESULTS

Curcumin and methylene blue inhibited the replication of SARS-CoV-2. The reactive oxygen species (ROS) are generated during the treatment of PDT with curcumin and methylene blue to prevent the attachment of SARS-CoV-2 on the ACE2 receptor and damage to the nucleic acids either DNA or RNA. It also modulates pro-inflammatory cytokines and attenuates the clotting effects of the host response.

CONCLUSION

The photodynamic action of curcumin and methylene blue provides a possible approach against bacteria and SARS-CoV-2 infection because they act as non-toxic photosensitizers in PDT with an antibacterial effect, anti-viral properties, and disinfection functions.

Utility of devices for onychomycosis: a review

Onychomycosis is difficult to treat due to long treatment durations, poor efficacy rates of treatments, high relapse rates, and safety issues when using systemic antifungal agents. Device-based treatments are targeted to specific regions of the nail, have favorable safely profiles, and do not interfere with systemic agents. They may be an effective alternative therapy for onychomycosis especially with increasing reports of squalene epoxidase gene mutations and potential resistance to terbinafine therapy. In this review, we discuss four devices used as antifungal treatments and three devices used as penetration enhancers for topical agents. Lasers, photodynamic therapy, microwaves, and non-thermal plasma have the capacity to inactivate fungal pathogens demonstrated through in vivo studies. Efficacy rates for these devices, however, remain relatively low pointing toward the need to further optimize device or usage parameters. Ultrasound, nail drilling, and iontophoresis aid in improving the permeability of topical agents through the nail and have been investigated as adjunctive therapies. Due to the paucity in clinical data, their efficacy in treating onychomycosis has not yet been established. While the results of clinical studies point toward the potential utility of devices for onychomycosis, further large-scale randomized clinical trials following regulatory guidelines are required to confirm current results.

Adjunctive phototherapies for oral manifestation of HIV-related histoplasmosis and leishmaniasis: An unusual case report

BACKGROUND

Secondary infections of leishmaniasis and histoplasmosis in patients with advanced HIV are still a concern in low- and middle-income countries. The most common drugs for the treatment of both infections may be problematic mainly due to their toxicity.

AIM AND CASE REPORT

The present study aimed to report a case in which a concurrent oral manifestation of leishmaniasis and histoplasmosis in a hospitalized patient with HIV was managed with a combination of photobiomodulation therapy (PBMT) and antimicrobial photodynamic therapy (aPDT) as an adjuvant treatment. In addition to the use of conventional systemic oral drugs, a single aPDT session followed by two PBMT sessions was proposed, which resulted in complete wound healing within four days.

CONCLUSION

Given the complexity of the current case, PBMT in combination with aPDT may be considered as an effective adjuvant option for managing oral infectious lesions of histoplasmosis and leishmaniasis in immunocompromised patients.

Photodynamic therapy is a safe and feasible adjunct to percutaneous drainage of deep tissue abscesses: Results of a first in humans Phase 1 clinical trial

Background

Standard of care for abscess management includes image-guided percutaneous drainage and antibiotics. However, cure rates vary between patients and there is growing concern for antibiotic-resistant bacteria. Photodynamic therapy (PDT), which utilizes light-activated dyes to generate cytotoxic reactive species, could complement the standard of care by sterilizing the abscess at time of drainage.

Purpose

The goal of this study was to perform a first in humans Phase 1 clinical study evaluating safety and feasibility of PDT with methylene blue (MB) at the time of percutaneous abscess drainage. This was accomplished through an open-label dose escalation study, with duration of light delivery escalated from 5-30 minutes.

Materials and Methods

We performed MB-PDT in 18 subjects undergoing percutaneous abscess drainage. Following standard of care drainage, 1 mg/mL MB was delivered for 10 minutes. MB was aspirated, and 1% lipid emulsion infused to homogenize light dose at the cavity wall. An optical fiber was advanced to the approximate center of the abscess for 665 nm laser illumination at 20 mW/cm 2 .

Results

MB-PDT at the time of abscess drainage was safe and feasible in all cases, with no evidence of fat embolism due to lipid emulsion or adverse reaction to MB observed. No study-related adverse or serious adverse events were encountered, and the procedure was well tolerated by all subjects. While the study was not designed or powered to determine efficacy, time to resolution of clinical symptoms was significantly decreased in subjects receiving higher fluences (p=0.028). Additionally, drainage catheter output post-procedure was decreased in subjects receiving higher fluences (ρ=-0.18), although this difference was not significant (p=0.43).

Conclusion

MB-PDT is a safe and feasible adjunct to image-guided percutaneous abscess drainage. Clinical measures indicate a dose-dependent response to PDT, motivating future Phase 2 studies evaluating the efficacy of MB-PDT in this patient population.

First in human measurements of abscess cavity optical properties and methylene blue uptake prior to photodynamic therapy by in vivo diffuse reflectance spectroscopy

Significance

Efficacious photodynamic therapy (PDT) of abscess cavities requires personalized treatment planning. This relies on knowledge of abscess wall optical properties, which we report for the first time in human subjects.

Aim

The objective was to extract optical properties and photosensitizer concentration from spatially-resolved diffuse reflectance measurements of abscess cavities prior to methylene blue (MB) PDT, as part of a Phase 1 clinical trial.

Approach

Diffuse reflectance spectra were collected at the abscess wall of 13 human subjects using a custom fiber-optic probe and optical spectroscopy system, before and after MB administration. A Monte Carlo lookup table was used to extract optical properties.

Results

Pre-MB abscess wall absorption coefficients at 665 nm were 0.15±0.1 cm -1 (0.03-0.36 cm -1 ) and 10.74±15.81 cm -1 (0.08-49.3 cm -1 ) post-MB. Reduced scattering coefficients at 665 nm were 8.45±2.37 cm -1 (4.8-13.2 cm -1 ) and 5.6±2.26 cm -1 (1.6-9.9 cm -1 ) for pre-MB and post-MB, respectively. Oxygen saturations were found to be 58.83±35.78% (5.6-100%) pre-MB and 36.29±25.1% (0.0001-76.4%) post-MB. Determined MB concentrations were 71.83±108.22 µM (0-311 µM).

Conclusions

We observed substantial inter-subject variation in both native wall optical properties and methylene blue uptake. This underscores the importance of making these measurements for patient-specific treatment planning.

A Uniform Design Method Can Optimize the Combinatorial Parameters of Antimicrobial Photodynamic Therapy, Including the Concentrations of Methylene Blue and Potassium Iodide, Light Dose, and Methylene Blue's Incubation Time, to Improve Fungicidal Effects on Candida Species

The optimal combinatorial parameters of antimicrobial photodynamic therapy (aPDT) mediated by methylene blue (MB) with the addition of potassium iodide (KI) against Candida species have never been defined. This study aimed to optimize the combinatorial parameters of aPDT, including the concentrations of MB (X1, 0.1-1.0 mM) and KI (X2, 100-400 mM), light dose (X3, 10-70 J/cm2), and MB's incubation time (X4, 5-35 min) for three Candida species. The best MB + KI-aPDT fungicidal effects (Y) against Candida albicans ATCC 90028 (YCa), Candida parapsilosis ATCC 22019 (YCp), and Candida glabrata ATCC 2950 (YCg) were investigated using a uniform design method. The regression models deduced using this method were YCa = 7.126 + 1.199X1X3 - 1.742X12 + 0.206X22 - 0.361X32; YCp = 10.724 - 0.867X1 - 1.497X2 + 0.560X3 + 1.298X22; and YCg = 0.892 - 0.956X1 + 2.296X3 + 1.299X42 - 3.316X3X4. The optimal combinatorial parameters inferred from the regression equations were MB 0.1 mM, KI 400 mM, a light dose of 20 J/cm2, and a 5-minute incubation time of MB for Candida albicans; MB 0.1 mM, KI 400 mM, a light dose of 70 J/cm2, and a 5-minute incubation time of MB for Candida parapsilosis; MB 0.1 mM, KI 100 mM, a light dose of 10 J/cm2, and a 35-minute incubation time of MB for Candida glabrata. The uniform design method can optimize the combinatorial parameters of aPDT mediated by MB plus KI to obtain the best aPDT fungicidal effects on Candida species, providing a new method to optimize the combinatorial parameters of aPDT for different pathogens in the future.

Methylene blue in anticancer photodynamic therapy: systematic review of preclinical studies

Background: Methylene blue has a long history of clinical application. Thanks to phenothiazine chromophore, it has potential in photodynamic anticancer therapy. In spite of the growing body of literature that has evaluated the action of this dye on different types of cancer, the systematic understanding of this problem is still lacking. Therefore, this systematic review was performed to study the efficacy of methylene blue in photodynamic anticancer therapy. Methods: This systematic review was carried out in accordance with the PRISMA guidelines, and the study protocol was registered in PROSPERO (CRD42022368738). Articles for the systematic review were identified through the PubMed database. SYRCLE's risk of bias tool was used to assess the studies. The results of systematic analysis are presented as narrative synthesis. Results: Ten studies met the inclusion criteria and these full texts were reviewed. In the selected articles, the dosage of dye infusion ranged from 0.04 to 24.12 mg/kg. The effectiveness of photodynamic therapy with methylene blue against different types of cancer was confirmed by a decrease in tumor sizes in seven articles. Conclusion: The results of the systematic review support the suggestions that photodynamic therapy with methylene blue helps against different types of cancer, including colorectal tumor, carcinoma, and melanoma. In cases of nanopharmaceutics use, a considerable increase of anticancer therapy effectiveness was observed. The further research into methylene blue in photodynamic anticancer therapy is needed. Systematic Review Registration: (https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=368738), identifier (CRD42022368738).

Antimicrobial Resistance: Is There a 'Light' at the End of the Tunnel?

In recent years, with the increases in microorganisms that express a multitude of antimicrobial resistance (AMR) mechanisms, the threat of antimicrobial resistance in the global population has reached critical levels. The introduction of the COVID-19 pandemic has further contributed to the influx of infections caused by multidrug-resistant organisms (MDROs), which has placed significant pressure on healthcare systems. For over a century, the potential for light-based approaches targeted at combatting both cancer and infectious diseases has been proposed. They offer effective killing of microbial pathogens, regardless of AMR status, and have not typically been associated with high propensities of resistance development. To that end, the goal of this review is to describe the different mechanisms that drive AMR, including intrinsic, phenotypic, and acquired resistance mechanisms. Additionally, the different light-based approaches, including antimicrobial photodynamic therapy (aPDT), antimicrobial blue light (aBL), and ultraviolet (UV) light, will be discussed as potential alternatives or adjunct therapies with conventional antimicrobials. Lastly, we will evaluate the feasibility and requirements associated with integration of light-based approaches into the clinical pipeline.

Synergistic Photodynamic/Antibiotic Therapy with Photosensitive MOF-Based Nanoparticles to Eradicate Bacterial Biofilms

Bacterial biofilms pose a serious threat to human health, as they prevent the penetration of antimicrobial agents. Developing nanocarriers that can simultaneously permeate biofilms and deliver antibacterial agents is an attractive means of treating bacterial biofilm infections. Herein, photosensitive metal-organic framework (MOF) nanoparticles were developed to promote the penetration of antibiotics into biofilms, thereby achieving the goal of eradicating bacterial biofilms through synergistic photodynamic and antibiotic therapy. First, a ligand containing benzoselenadiazole was synthesized and incorporated into MOF skeletons to construct benzoselenadiazole-doped MOFs (Se-MOFs). The growth of the Se-MOFs could be regulated to obtain nanoparticles (Se-NPs) in the presence of benzoic acid. The singlet oxygen (¹O₂) generation efficiencies of the Se-MOFs and Se-NPs were evaluated. The results show that the Se-NPs exhibited a higher ¹O₂ generation efficacy than the Se-MOF under visible-light irradiation because the small size of the Se-NPs was conducive to the diffusion of ¹O₂. Afterward, an antibiotic drug, polymyxin B (PMB), was conjugated onto the surface of the Se-NPs via amidation to yield PMB-modified Se-NPs (PMB-Se-NPs). PMB-Se-NPs exhibit a synergistic antibacterial effect by specifically targeting the lipopolysaccharides present in the outer membranes of Gram-negative bacteria through surface-modified PMB. Benefiting from the synergistic therapeutic effects of antibiotic and photodynamic therapy, PMB-Se-NPs can efficiently eradicate bacterial biofilms at relatively low antibiotic doses and light intensities, providing a promising nanocomposite for combating biofilm infections.

Photodynamic therapy for infected foot ulcers in people with diabetes mellitus: a systematic review

BACKGROUND

Ulceration of the feet in patients with diabetes is a frequent complication that increases morbidity, mortality, hospitalization, treatment costs, and non-traumatic amputations.

OBJECTIVE

To present a systematic review of the treatment of patients with diabetes mellitus and infected foot ulcers using photodynamic therapy.

DESIGN AND SETTING

A systematic review was performed in the postgraduate program in nursing at the Universidade da Integração Internacional da Lusofonia Afro-Brasileira, Ceará, Brazil.

METHODS

PubMed, CINAHL, Web of Science, EMBASE, Cochrane Library, Scopus, and LILACS databases were screened. The methodological quality, risk of bias, and quality of evidence of each study were assessed. Review Manager was used for the meta-analysis.

RESULTS

Four studies were included. They highlighted significantly better outcomes in patient groups treated with photodynamic therapy than those in the control groups that were treated with topical collagenase and chloramphenicol (P = 0.036), absorbent (P < 0.001), or dry covers (P = 0.002). Significant improvements were noted in terms of the microbial load in the ulcers and tissue repair, with a reported reduction in the need for amputation by up to 35 times. Photodynamic therapy resulted in significantly better outcomes between the experimental and control groups (P = 0.04).

CONCLUSION

Photodynamic therapy is significantly more effective in treating infected foot ulcers than standard therapies.

SYSTEMATIC REVIEW REGISTRATION

International Prospective Register of Systematic Reviews (PROSPERO) - CRD42020214187, https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=214187.

Antimicrobial phyto-photodynamic activity inducing by polyphenol-supported Methylene Blue co-loaded into multifunctional bilosomes: Advanced hybrid nanoplatform in the skin infections treatment?

Widespread skin infections caused primarily by bacteria and yeast, pose a growing threat to healthcare systems. Phyto-photodynamic antimicrobial therapy is a promising treatment strategy with a few mild side effects for both superficial and deeper skin infections. The combination of natural plant products (polyphenols) with conventional photosensitizers makes it possible to improve the outcome of skin infections. In the present study, nanoengineered self-assembling bilosomes were used as a nanoplatform to deliver two compounds with different solubility, i.e., curcumin applied as a hydrophobic phytochemical compound and Methylene Blue used as a hydrophilic photosensitizer. Compared with the encapsulation of Methylene Blue alone, the double-loaded bilosomes (curcumin-supported Methylene Blue) showed higher efficiency in generating reactive oxygen species. Importantly, in our study, we also confirmed that bioinspired bilosomes prevent the rapid photobleaching of Methylene Blue, thereby enhancing its photoactivity. The post-irradiation antimicrobial action was tested against two pathogens - the Gram-positive bacterium (Staphylococcus aureus) and yeast (Candida albicans). The irradiation was provided after 10, 20, and 30 min, at a specific wavelength (λ = 640 nm) corresponding to 63, 126, and 189 J cm^-2 energy fluences. The most effective reduction in the microbial cells number was found 30 min post-irradiation and was 99.994% for double-loaded bilosomes compared to 99.989% killing S. aureus for bilosomes with Methylene Blue alone. For C. albicans fungal cells, the mortality was 99.669% in the presence of a Methylene Blue and curcumin mixture compared to 98.229% of those killed without the addition of curcumin. The overall results of our contribution provide evidence that curcumin in combination with MB enhances the photo-eradication efficiency of S. aureus and C. albicans planktonic cultures. Thus, the mixture of the phytochemicals with photosensitizers and their encapsulation in multifunctional bilosomes may contribute to the development of innovative antimicrobial phyto-photodynamic therapy in the future.

Improving the Management and Treatment of Diabetic Foot Infection: Challenges and Research Opportunities

Diabetic foot infection (DFI) management requires complex multidisciplinary care pathways with off-loading, debridement and targeted antibiotic treatment central to positive clinical outcomes. Local administration of topical treatments and advanced wound dressings are often used for more superficial infections, and in combination with systemic antibiotics for more advanced infections. In practice, the choice of such topical approaches, whether alone or as adjuncts, is rarely evidence-based, and there does not appear to be a single market leader. There are several reasons for this, including a lack of clear evidence-based guidelines on their efficacy and a paucity of robust clinical trials. Nonetheless, with a growing number of people living with diabetes, preventing the progression of chronic foot infections to amputation is critical. Topical agents may increasingly play a role, especially as they have potential to limit the use of systemic antibiotics in an environment of increasing antibiotic resistance. While a number of advanced dressings are currently marketed for DFI, here we review the literature describing promising future-focused approaches for topical treatment of DFI that may overcome some of the current hurdles. Specifically, we focus on antibiotic-impregnated biomaterials, novel antimicrobial peptides and photodynamic therapy.

Effective Biofilm Eradication on Orthopedic Implants with Methylene Blue Based Antimicrobial Photodynamic Therapy In Vitro

Periprosthetic joint infections (PJI) are difficult to treat due to biofilm formation on implant surfaces, often requiring removal or exchange of prostheses along with long-lasting antibiotic treatment. This in vitro study investigated the effect of methylene blue photodynamic therapy (MB-PDT) on PJI-causing biofilms on different implant materials. MB-PDT (664 nm LED, 15 J/cm²) was tested on different Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Cutibacterium acnes strains in both planktonic form and grown in early and mature biofilms on prosthetic materials (polyethylene, titanium alloys, cobalt-chrome-based alloys, and bone cement). The minimum bactericidal concentration with 100% killing (MBC_100%) was determined. Chemical and topographical alterations were investigated on the prosthesis surfaces after MB-PDT. Results showed a MBC_100% of 0.5-5 μg/mL for planktonic bacteria and 50-100 μg/mL for bacteria in biofilms-independent of the tested strain, the orthopedic material, or the maturity of the biofilm. Material testing showed no relevant surface modification. MB-PDT effectively eradicated common PJI pathogens on arthroplasty materials without damage to the materials, suggesting that MB-PDT could be used as a novel treatment method, replacing current, more invasive approaches and potentially shortening the antibiotic treatment in PJI. This would improve quality of life and reduce morbidity, mortality, and high health-care costs.

Clinical applications of antimicrobial photodynamic therapy in dentistry

Given the emergence of resistant bacterial strains and novel microorganisms that globally threaten human life, moving toward new treatment modalities for microbial infections has become a priority more than ever. Antimicrobial photodynamic therapy (aPDT) has been introduced as a promising and non-invasive local and adjuvant treatment in several oral infectious diseases. Its efficacy for elimination of bacterial, fungal, and viral infections and key pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Candida albicans, and Enterococcus faecalis have been investigated by many invitro and clinical studies. Researchers have also investigated methods of increasing the efficacy of such treatment modalities by amazing developments in the production of natural, nano based, and targeted photosensitizers. As clinical studies have an important role in paving the way towards evidence-based applications in oral infection treatment by this method, the current review aimed to provide an overall view of potential clinical applications in this field and summarize the data of available randomized controlled clinical studies conducted on the applications of aPDT in dentistry and investigate its future horizons in the dental practice. Four databases including PubMed (Medline), Web of Science, Scopus and Embase were searched up to September 2022 to retrieve related clinical studies. There are several clinical studies reporting aPDT as an effective adjunctive treatment modality capable of reducing pathogenic bacterial loads in periodontal and peri-implant, and persistent endodontic infections. Clinical evidence also reveals a therapeutic potential for aPDT in prevention and reduction of cariogenic organisms and treatment of infections with fungal or viral origins, however, the number of randomized clinical studies in these groups are much less. Altogether, various photosensitizers have been used and it is still not possible to recommend specific irradiation parameters due to heterogenicity among studies. Reaching effective clinical protocols and parameters of this treatment is difficult and requires further high quality randomized controlled trials focusing on specific PS and irradiation parameters that have shown to have clinical efficacy and are able to reduce pathogenic bacterial loads with sufficient follow-up periods.

Optical spectral diagnostics of the oxygenation level in periodontal tissues and photodynamic therapy using methylene blue in children with cerebral palsy

Dental diseases occur in children with cerebral palsy three times higher than in healthy children. Low values of the unstimulated salivation rate (<0.3 ml per minute), pH and buffer capacity, changes in enzyme activity and sialic acid concentration, as well as increased saliva osmolarity and total protein concentration, which indicates impaired hydration, are the factors in the development of a gingiva disease in case of cerebral palsy. This leads to increased bacterial agglutination and the formation of acquired pellicle and biofilm, leading to the formation of dental plaque. There is a tendency toward an increase in the concentration of hemoglobin and a decrease in the degree of hemoglobin oxygenation, as well as an increase in the generation of reactive oxygen and nitrogen species. Photodynamic therapy (PDT) with the use of photosensitizer methylene blue improves blood circulation and the degree of oxygenation in periodontal tissues, as well as eliminates a bacterial biofilm. Analysis of back diffuse reflection spectra makes it possible to conduct non-invasive monitoring determine tissue areas with a low level of hemoglobin oxygenation for precision photodynamic exposure.

Aim

To improve the effectiveness of phototheranostics methods using, namely PDT with simultaneous optical-spectral control, for the treatment of gingivitis in children with complex dental and somatic status (cerebral palsy).

Methods

The study involved 15 children (6-18 y.o.) with various forms of cerebral palsy, in particular, spastic diplegia and atonic-astatic form and with gingivitis. The degree of hemoglobin oxygenation was measured in tissues before PDT and on the 12th day. PDT was performed using laser radiation (λ = 660 nm) with a power density of 150 mW/cm² with a five-minute application of 0.01% MB. The total light dose was 45 ± 15 J/cm². For statistical evaluation of the results, a paired Student's t-test was used.

Results

The paper presents the results of phototheranostics using methylene blue in children with cerebral palsy. An increase in the level of hemoglobin oxygenation from 50 to 67% (p < 0.001) and a decrease in blood volume in the microcirculatory bed of periodontal tissues were shown.

Conclusion

Photodynamic therapy methods with application of methylene blue make it possible to assess the state of the gingival mucosa tissue diseases objectively in real time, and to provide effective targeted therapy for gingivitis in children with cerebral palsy. There is a prospect that they can become widely used clinical methods.

Advanced methylene blue - nanoemulsions for in vitro photodynamic therapy on oral and cervical human carcinoma

Photodynamic therapy (PDT) is a therapeutic modality with high contributions in the treatment of cancer. This approach is based on photophysical principles, which presents as a less invasive strategy than conventional therapies. Combined with nanotechnology, the therapy becomes more efficient because nanoparticles (NPs) have advantageous characteristics such as biocompatibility, controlled, and targeted release, promoting solubility and decreasing the toxicity and side effects involved. In this work were developed nanoemulsions containing the methylene blue photosensitizer (MB) (MB/NE) and in the empty form (unloaded/NE). Subsequently, the mentioned nanomaterials were characterized by the measurement of dynamic light scattering (DLS). The MB/NE and unloaded/NE showed appropriate physical and chemical characteristics, with particle size ≤ 200 nm, polydispersity index close to 0.3, and zeta potential exhibiting negative charge, showing stable values during the analysis. The incorporation of the MB did not cause changes in the photophysical profile of the photosensitizer. The quantification performed showed an incorporation rate of 81.9%. Viability studies showed an absence of cytotoxicity for MB/NE in the concentrations of 10-75 µmol·L^-1, free MB at the concentration of 75 µmol·L^-1, and unloaded NE 47.5% (v/v), presenting viability close to 90%, respectively. PDT in vitro protocols applied to OSCC and HeLa cells showed a decrease in cell viability through only one irradiation, evidencing the photodynamic activity of the formulation when applied to cancer cells. The results obtained were superior to those found in the literature where they use free MB, showing that the association between nanotechnology and PDT optimizes the proposed protocol. From the results obtained, it is possible to indicate that the NE have high stability, with satisfactory physical-chemical parameters, in addition to not presenting cytotoxicity in the tested concentrations, showing their in vitro biocompatibility, in addition to presenting satisfactory effects when combined MB/NE with PDT, showing the potential of MB/NE as a very promising nanostructured photosensitizer for the treatment of some types of cancer.

5-Aminolevulinic Acid and Red Led in Endodontics: A Narrative Review and Case Report

The present study aims to discuss the main factors involving the use of 5-aminolevulinic acid together with red LED light and its application in endodontic treatment through a narrative review and a case report. Persistence of microorganisms remaining on chemical-mechanical preparation or intracanal dressing is reported as the leading cause of failure in endodontics. Photodynamic therapy has become a promising antimicrobial strategy as an aid to endodontic treatment. Being easy and quick to apply, it can be used both in a single session and in several sessions, as well as not allowing forms of microbial resistance. 5-aminolevulinic acid in combination with red LED light has recently been studied in many branches of medicine, with good results against numerous types of bacteria including Enterococuss faecalis. The case report showed how bacterial count of CFU decreased by half (210 CFU/mL), after 45 min of irrigation with a gel containing 5% of 5-aminolevulinic acid compared to the sample before irrigation (420 CFU/mL). The subsequent irradiation of red LED light for 7 min, the bacterial count was equal to 0. Thus, it is concluded that the use of 5-aminolevulinic acid together with red LED light is effective in endodontic treatment.

Efficacy of Antimicrobial Photodynamic Therapy Mediated by Photosensitizers Conjugated with Inorganic Nanoparticles: Systematic Review and Meta-Analysis

Antimicrobial photodynamic therapy (aPDT) is a method that does not seem to promote antimicrobial resistance. Photosensitizers (PS) conjugated with inorganic nanoparticles for the drug-delivery system have the purpose of enhancing the efficacy of aPDT. The present study was to perform a systematic review and meta-analysis of the efficacy of aPDT mediated by PS conjugated with inorganic nanoparticles. The PubMed, Scopus, Web of Science, Science Direct, Cochrane Library, SciELO, and Lilacs databases were searched. OHAT Rob toll was used to assess the risk of bias. A random effect model with an odds ratio (OR) and effect measure was used. Fourteen articles were able to be included in the present review. The most frequent microorganisms evaluated were Staphylococcus aureus and Escherichia coli, and metallic and silica nanoparticles were the most common drug-delivery systems associated with PS. Articles showed biases related to blinding. Significant results were found in aPDT mediated by PS conjugated with inorganic nanoparticles for overall reduction of microorganism cultured in suspension (OR = 0.19 [0.07; 0.67]/p-value = 0.0019), E. coli (OR = 0.08 [0.01; 0.52]/p-value = 0.0081), and for Gram-negative bacteria (OR = 0.12 [0.02; 0.56/p-value = 0.0071). This association approach significantly improved the efficacy in the reduction of microbial cells. However, additional blinding studies evaluating the efficacy of this therapy over microorganisms cultured in biofilm are required.

The Effects of 5% 5-Aminolevulinic Acid Gel and Red Light (ALAD-PDT) on Human Fibroblasts and Osteoblasts

This study aimed to evaluate the effects of a new photodynamic protocol (ALAD-PDT), consisting of 5% 5-aminolevulinic acid-gel and 630 nm-LED, already used for antibacterial effects in the treatment of periodontitis, on human gingival fibroblasts (HGF) and primary human osteoblasts (HOB). HGF and HOB were incubated with different ALAD concentrations for 45 min, and subsequently irradiated with 630 nm-LED for 7 min. Firstly, the cytotoxicity at 24 h and proliferation at 48 and 72 h were assessed. Then the intracellular content of the protoporphyrin IX (PpIX) of the ROS and the superoxide dismutase (SOD) activity were investigated at different times. Each result was compared with untreated and unirradiated cells as the control. Viable and metabolic active cells were revealed at any concentrations of ALAD-PDT, but only 100-ALAD-PDT significantly enhanced the proliferation rate. The PpIX fluorescence significantly increased after the addition of 100-ALAD, and decreased after the irradiation. Higher ROS generation was detected at 10 min in HGF, and at 30 min in HOB. The activity of the SOD enzyme augmented at 30 min in both cell types. In conclusion, ALAD-PDT not only showed no cytotoxic effects, but had pro-proliferative effects on HGF and HOB, probably via ROS generation.

Antimicrobial Photodynamic Therapy as a treatment option for inoperable cases of medication-related Osteonecrosis of the jaws

The present study aims to report conservative treatment of an extreme case of MRONJ in a patient illegible for surgical treatment. A 69-year-old female patient, diagnosed with Multiple Myeloma underwent treatment with bisphosphonate. After a turbinectomy, she was referred to a dental clinic with painful oral symptoms, presence of necrotic and suppurative bone exposures in maxilla compatible with MRONJ. As surgery was not indicated, the treatment of option was to control infection and pain. PENTO protocol, antibiotic therapy and photodynamic therapy were instituted. The patient has been under dental follow-up for more than 1 year, with an important reduction in the areas of bone exposure, absence of active infection and painful symptoms, characterizing a significant improvement in the oral condition. The conservative approach achieved satisfactory results for the case, where the patient is ineligible for a surgery due to local and general conditions, and quality of life being prioritized.

Photodynamic inactivation of Streptococcus pneumoniae with external illumination at 808 nm through the ex vivo porcine thoracic cage

Pneumonia is responsible for high mortality rates around the world, and its major treatment is based on antibiotic treatment. Antimicrobial resistance has been increasing in the last years, resulting in relevant public health concern. A promising alternative for pneumonia is antimicrobial photodynamic therapy. The purpose of this study was to investigate whether 808 nm wavelength is able to be transmitted through the biological tissues of the thoracic wall and be delivered in enough energy inside the cage to activate indocyanine green and promote photodynamic response. A light source panel was developed composed of 200 lasers centered at 808 nm with an irradiance of 77.8 ± 10.0 mW/cm² and tested in an ex vivo thoracic cage model. Monte Carlo simulations were used to understand the photon migration through all the tissues at the thoracic wall. It was observed that tissues responsible for the major absorption of photons are the skin and subcutaneous fat. Experimental measurement of the irradiance was obtained after the light pass-through ex vivo pig thoracic cage, obtaining 3% to 5% of the emitted irradiance. Finally, it was observed that even with 3% of the initial irradiance, a 99.9% reduction of the Streptococcus pneumoniae was successfully achieved after 42.6 minutes of irradiation.

How can biophotonics help dentistry to avoid or minimize cross infection by SARS-CoV-2?

Biophotonics is defined as the combination of biology and photonics (the physical science of the light). It is a general term for all techniques that deal with the interaction between biological tissues/cells and photons (light). Biophotonics offers a great variety of techniques that can facilitate the early detection of diseases and promote innovative theragnostic approaches. As the COVID-19 infection can be transmitted due to the face-to-face communication, droplets and aerosol inhalation and the exposure to saliva, blood, and other body fluids, as well as the handling of sharp instruments, dental practices are at increased risk of infection. In this paper, a literature review was performed to explore the application of Biophotonics approaches in Dentistry focusing on the COVID-19 pandemic and how they can contribute to avoid or minimize the risks of infection in a dental setting. For this, search-related papers were retrieved from PubMED, Scielo, Google Schoolar, and American Dental Association and Centers for Disease Control and Prevention databases. The body of evidence currently available showed that Biophotonics approaches can reduce microorganism load, decontaminate surfaces, air, tissues, and minimize the generation of aerosol and virus spreading by minimally invasive, time-saving, and alternative techniques in general. However, each clinical situation must be individually evaluated regarding the benefits and drawbacks of these approaches, but always pursuing less-invasive and less aerosol-generating procedures, especially during the COVID-19 pandemic.

Optical property recovery with spatially-resolved diffuse reflectance at short source-detector separations using a compact fiber-optic probe

We describe a compact fiber-optic probe (2 mm outside diameter) that utilizes spatially-resolved diffuse reflectance for tissue optical property recovery. Validation was performed in phantoms containing Intralipid 20% as scatterer, and methylene blue (MB), MnTPPS, and/or India ink as absorbers. Over a range of conditions, the reduced scattering coefficient was recovered with a root mean square error (RMSE) of 0.86-2.7 cm^-1 (average error = 3.8%). MB concentration was recovered with RMSE = 0.26-0.52 µM (average error = 15.0%), which did not vary with inclusion of MnTPPS (p=0.65). This system will be utilized to determine optical properties in human abscesses, in order to generate treatment plans for photodynamic therapy.

New Applications of Photodynamic Therapy in the Management of Candidiasis

The most important aetiological agent of opportunistic mycoses worldwide is Candida spp. These yeasts can cause severe infections in the host, which may be fatal. Isolates of Candida albicans occur with greater frequency and variable resistance patterns. Photodynamic therapy (PDT) has been recognised as an alternative treatment to kill pathogenic microorganisms. PDT utilises a photosensitizer, which is activated at a specific wavelength and oxygen concentration. Their reaction yields reactive oxygen species that kill the infectious microorganism. A systematic review of new applications of PDT in the management of candidiasis was performed. Of the 222 studies selected for in-depth screening, 84 were included in this study. All the studies reported the antifungal effectiveness, toxicity and dosimetry of treatment with antimicrobial PDT (aPDT) with different photosensitizers against Candida spp. The manuscripts that are discussed reveal the breadth of the new applications of aPDT against Candida spp., which are resistant to common antifungals. aPDT has superior performance compared to conventional antifungal therapies. With further studies, aPDT should prove valuable in daily clinical practice.

Methylene Blue-Based Nano and Microparticles: Fabrication and Applications in Photodynamic Therapy

Methylene blue (MB) has been used in the textile industry since it was first extracted by the German chemist Heinrich Caro. Its pharmacological properties have also been applied toward the treatment of certain diseases such as methemoglobinemia, ifosfamide-induced encephalopathy, and thyroid conditions requiring surgery. Recently, the utilization of MB as a safe photosensitizer in photodynamic therapy (PDT) has received attention. Recent findings demonstrate that photoactivated MB exhibits not only anticancer activity but also antibacterial activity both in vitro and in vivo. However, due to the hydrophilic nature of MB, it is difficult to create MB-embedded nano- or microparticles capable of increasing the clinical efficacy of the PDT. This review aims to summarize fabrication techniques for MB-embedded nano and microparticles and to provide both in vitro and in vivo examples of MB-mediated PDT, thereby offering a future perspective on improving this promising clinical treatment modality. We also address examples of MB-mediated PDT in both cancer and infection treatments. Both in-vitro and in-vivo studies are summarized here to document recent trends in utilizing MB as an effective photosensitizer in PDT. Lastly, we discuss how developing efficient MB-carrying nano- and microparticle platforms would be able to increase the benefits of PDT.

Highly Potent Photoinactivation of Bacteria Using a Water-Soluble, Cell-Permeable, DNA-Binding Photosensitizer

Antimicrobial photodynamic therapy (APDT) employs a photosensitizer, light, and molecular oxygen to treat infectious diseases via oxidative damage, with a low likelihood for the development of resistance. For optimal APDT efficacy, photosensitizers with cationic charges that can permeate bacteria cells and bind intracellular targets are desired to not limit oxidative damage to the outer bacterial structure. Here we report the application of brominated DAPI (Br-DAPI), a water-soluble, DNA-binding photosensitizer for the eradication of both Gram-negative and Gram-positive bacteria (as demonstrated on N99 Escherichia coli and Bacillus subtilis, respectively). We observe intracellular uptake of Br-DAPI, ROS-mediated bacterial cell death via one- and two-photon excitation, and selective photocytotoxicity of bacteria over mammalian cells. Photocytotoxicity of both N99 E. coli and B. subtilis occurred at submicromolar concentrations (IC₅₀ = 0.2-0.4 μM) and low light doses (5 min irradiation times, 4.5 J cm^-2 dose), making it superior to commonly employed APDT phenothiazinium photosensitizers such as methylene blue. Given its high potency and two-photon excitability, Br-DAPI is a promising novel photosensitizer for in vivo APDT applications.

Graft-versus-host disease and herpes simplex virus oral injuries in onco-hematological patient: Case report

INTRODUCTION

Graft-versus-host disease (GVHD) is a systemic complication that can affect patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) and the mouth is one of the places affected by the disease (oGVHD). Topical corticosteroids are used to control the painful symptoms, causing a local immunosuppression and increasing the risk for opportunistic infections.

OBJECTIVE

This study aims to report a case of a 42-year-old woman, diagnosed with Chronic Myeloid Leukemia, who developed oGVHD and herpes simplex virus (HSV) infection after HSCT.

CASE REPORT

oGVHD was confirmed by incisional biopsy and viral infection by HSV types 1 and 2 was confirmed by PCR. Topical and systemic corticotherapy and antiviral therapies were instituted. The immunosuppression intensified viral infection and antimicrobial photodynamic therapy (aPDT) was instituted as an adjuvant treatment. aPDT application, along with the patient's immune recovery, antivirals and corticosteroids resulted in clinical improvement of oral lesions.

FINAL CONSIDERATIONS

This study highlights aPDT as an effective adjunct therapy in the local treatment of opportunistic infections in onco-hematological patients.

Molecular characteristics of the photosensitizer TONS504: Comparison of its singlet oxygen quantum yields and photodynamic antimicrobial effect with those of methylene blue

TONS504 (C51H58O5I2) is a chlorin derivative that exhibits a photodynamic antimicrobial effect (PAE) on various infectious keratitis pathogens. However, the molecular characteristics of TONS504 are not well understood. This study aimed to investigate the molecular characteristics of TONS504 by comparing its singlet oxygen (¹O₂) quantum yields and PAE with those of methylene blue (MB). To measure the ¹O₂ quantum yields, TONS504 and MB were dissolved in phosphate-buffered saline and phosphate-buffered saline containing 1% Triton X-100. The solutions were then activated by a Nd:YAG laser with an average output power of 8 mW. Near-infrared ¹O₂ luminescence was detected as an indicator of the ¹O₂ quantum yields. To evaluate the PAE, TONS504 and MB were activated by a light-emitting diode with a total light energy of 30 J/cm². We compared the minimum molar concentration of each photosensitizer to show apparent PAEs on Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. TONS504 exhibited higher ¹O₂ quantum yields than MB in PBS/Triton X-100 but not in PBS. S. aureus and C. albicans were reduced by TONS504 at lower concentrations than by MB, but this was not the case for P. aeruginosa. Our results provide insight on the molecular characteristics of TONS504 and suggest that TONS504 has excellent ¹O₂ quantum yields and PAE. Compared with MB, TONS504 in PBS has stronger efficacy toward some infectious keratitis pathogens but not others.

Antimicrobial photodynamic therapy using optical fiber for oral fistula resulting from mandibular osteoradionecrosis

Osteoradionecrosis (ORN) is considered one of the most severe complications of radiotherapy (RT). Treatment modalities for ORN may vary considerably, including conservative or surgical procedures. Recently, alternative managements such as the combination of photobiomodulation therapy (PBMT) and antimicrobial photodynamic therapy (aPDT) have also yielded promising results in patients presenting ORN or delayed healing post-RT. Herein, it is reported a case of ORN manifested as an oral fistula on the mandibular alveolar mucosa in which a combination of PBMT and aPDT was used every 15 days for six weeks. A laser device with an optical fiber was introduced into the fistula for light delivery. Seven days after the first laser session, it was noted complete resolution of both edema and erythema; after six weeks, the ORN fistula was no longer present. According to the current case, the combination of PBMT and aPDT with an optical fiber to deliver the laser light seems to be a suitable alternative for restricted areas such as fistula paths.

Antimicrobial photodynamic therapy can be an effective adjuvant for surgical wound healing in cattle

BACKGROUND

Rumenostomy is a useful procedure commonly performed in cattle for medical treatment of domestic ruminants with forestomach diseases. Methylene blue (MB)-mediated antimicrobial photodynamic therapy (APDT) has been broadly investigated to treat infected wounds.

AIM

The aim of the study was to evaluate the effectiveness of MB-mediated APDT (MB-APDT) combined with chlorhexidine and zinc oxide ointment on wound healing process after rumenostomy.

METHODS

Fourteen Nelore bulls were subjected to rumenostomy procedure. Animals were randomly divided into MB-APDT (MB associated with a red diode laser performed immediately after surgery and repeated on days 3, 5, 7 and 10) and control groups. Daily care included topical cleaning with chlorhexidine 2% followed by topical zinc oxide ointment. Animals were followed-up until the 28th day.

RESULTS

Wounds presented a better post-surgical profile in MB-APDT group when it was compared with the control group. In MB-APDT group, it was also possible to observe less pain on palpation of wounds borders, less edema and inflammatory exudate. Additionally, animals from MB-APDT group were faster discharged from the cattle care facility.

CONCLUSION

Our results support the use of MB-APDT for the post-surgical management of rumenostomy. This pilot study ratifies the use of APDT in cattle and also suggests that it could be performed for other surgical procedures as a complementary approach or an alternative for topical administration of antibiotics.

Leucomethylene blue probe detects a broad spectrum of reactive oxygen and nitrogen species

A broad spectrum ROS/RNS sensing butylated phenol tethered leucomethylene blue is presented. This probe detects a variety of ROS/RNS, with up to 100-fold gain in fluorescence in the red range, is suitable for microscopic and macroscopic in vivo fluorescence imaging.

Photooxidation Activity Control of Dimethylaminophenyl-tris-(N-methyl-4-pridinio)porphyrin by pH

To control the activity of photodynamic agents by pH, an electron donor-connecting cationic porphyrin, meso-(N',N'-dimethyl-4-aminophenyl)-tris(N-methyl-p-pyridinio)porphyrin (DMATMPyP), was designed and synthesized. The photoexcited state (singlet excited state) of DMATMPyP was deactivated through intramolecular electron transfer under a neutral condition. The pK a of the protonated DMATMPyP was 4.5, and the fluorescence intensity and singlet oxygen-generating activity increased under an acidic condition. Furthermore, the protonation of DMATMPyP enhanced the biomolecule photooxidative activity through electron extraction. Photodamage of human serum albumin (HSA) was observed under a neutral condition because a hydrophobic HSA environment can reverse the deactivation of photoexcited DMATMPyP. However, an HSA-damaging mechanism of DMATMPyP under a neutral condition was explained by singlet oxygen production. Therefore, it is indicated that the protein photodamaging activity of DMATMPyP goes into an OFF state under a neutral hypoxic condition. Under an acidic condition, the HSA photodamaging quantum yield by DMATMPyP through electron extraction could be preserved in the presence of a singlet oxygen quencher. Photooxidation of nicotinamide adenine dinucleotide by DMATMPyP was also enhanced under an acidic condition. This study demonstrated the concept of using pH to control photosensitizer activity via inhibition of the intramolecular electron transfer deactivation and enhancement of the oxidative activity through the electron extraction mechanism. Specifically, biomolecule oxidation through electron extraction may play an important role in photodynamic therapy to treat tumors under a hypoxic condition.

Carbon Nanodots in Photodynamic Antimicrobial Therapy: A Review

Antibiotic resistance development in bacteria is an ever-increasing global health concern as new resistant strains and/or resistance mechanisms emerge each day, out-pacing the discovery of novel antibiotics. Increasingly, research focuses on alternate techniques, such as antimicrobial photodynamic therapy (APDT) or photocatalytic disinfection, to combat pathogens even before infection occurs. Small molecule "photosensitizers" have been developed to date for this application, using light energy to inflict damage and death on nearby pathogens via the generation of reactive oxygen species (ROS). These molecular agents are frequently limited in widespread application by synthetic expense and complexity. Carbon dots, or fluorescent, quasi-spherical nanoparticle structures, provide an inexpensive and "green" solution for a new class of APDT photosensitizers. To date, reviews have examined the overall antimicrobial properties of carbon dot structures. Herein we provide a focused review on the recent progress for carbon nanodots in photodynamic disinfection, highlighting select studies of carbon dots as intrinsic photosensitizers, structural tuning strategies for optimization, and their use in hybrid disinfection systems and materials. Limitations and challenges are also discussed, and contemporary experimental strategies presented. This review provides a focused foundation for which APDT using carbon dots may be expanded in future research, ultimately on a global scale.