Phase IIa randomized, placebo-controlled study of antimicrobial photodynamic therapy in bacterially colonized, chronic leg ulcers and diabetic foot ulcers: a new approach to antimicrobial therapy

Antimicrobial photodynamic effect of the photosensitizer riboflavin, alone and in combination with colistin, against pandrug-resistant Pseudomonas aeruginosa clinical isolates

INTRODUCTION

Development of multi-, extensively-, and pandrug-resistant (MDR, XDR, and PDR) strains of Pseudomonas aeruginosa remains a major problem in medical care. The present study evaluated the effect of antimicrobial photodynamic therapy (aPDT) as a monotherapy and in combination with colistin against P. aeruginosa isolates.

METHODS

Two P. aeruginosa isolates recovered from patients with respiratory tract infections were examined in this study. Minimum inhibitory concentration (MIC) of colistin was determined by the colistin broth disk elution (CBDE) and the reference broth microdilution (rBMD) methods. aPDT was performed using the photosensitizer (Ps) riboflavin at several concentrations and a light-emitting diode (LED) emitting blue light for different irradiation times with or without colistin at 1/2 × MIC concentration.

RESULTS

Both PA1 and PA2 isolates were identified as colistin-resistant P. aeruginosa with a MIC ≥4 μg/mL by the CBDE and MICs of 512 μg/mL and 256 μg/mL, respectively, by the rBMD. In aPDT, neither riboflavin nor LED light alone had antibacterial effects. The values of colony forming units per milliliter (CFU/mL) in both isolates were significantly reduced by LED + Ps treatments in a time-dependent manner (LED irradiation time) and dose-dependent manner (Ps concentration). In comparison with control, treatment with Ps (50 μM) + LED (120 s) and Ps (100 μM) + LED (120 s) resulted in 0.27 log10 CFU/mL and 0.43 log10 CFU/mL reductions in PA1, and 0.28 log10 CFU/mL and 0.34 log10 CFU/mL reductions in PA2, respectively, (P < 0.01). The best results were obtained after the combination of aPDT followed by colistin, which increased bacterial reduction, resulting in a 0.41-0.7 log10 CFU/mL reduction for PA1 and 0.35-0.83 log10 CFU/mL reduction for PA2 (P = 0.001).

CONCLUSIONS

This study suggests the potential implications of aPDT in combination with antibiotics, such as colistin for treatment of difficult-to-treat P. aeruginosa infections.

A meta-analysis and systematic review of photodynamic therapy for diabetic foot ulcers

BACKGROUND

Diabetic foot ulcer (DFU) is a chronic and challenging condition, addressed through various treatments including photodynamic therapy (PDT) and standard of care (SOC), yet lacking consensus on the optimal approach. This study presents a comprehensive meta-analysis of randomized controlled trials to evaluate the efficacy and safety of PDT versus SOC in managing DFU.

METHODS

An extensive literature search was conducted across PubMed, Embase, and the Cochrane Library databases to identify RCTs that compared the effectiveness of PDT with SOC in treating DFU. The primary metrics evaluated included changes in ulcer area, wound healing indices, and pain levels experienced by the patients.

RESULTS

This meta-analysis incorporated data from 6 RCTs, encompassing 458 patients with 467 DFUs. The analysis indicated that while PDT led to a faster reduction in ulcer size compared to SOC, the difference was not statistically significant [mean difference (MD): 2.73cm², 95 % Confidence Interval (CI) -2.98 to 8.44; p > 0.05]. However, a notable improvement was observed in the wound healing rate in the PDT group [MD: 29.26 %, 95 % CI 7.24 to 51.28; p = 0.01]. Based on the Visual Analog Scale (VAS), pain assessment revealed no significant difference between the two treatment groups [MD: 2.35, 95 % CI -2.36 to 7.06; p = 0.33].

CONCLUSION

The study suggests that PDT might offer an enhanced healing rate for DFUs compared to SOC alone, potentially leading to improved patient outcomes. Importantly, our findings highlight the superiority of photodynamic therapy in accelerating ulcer healing without an associated increase in complications.

PROSPERO

2023 CRD42023493930.

Membrane Disruption-Enhanced Photodynamic Therapy against Gram-Negative Bacteria by a Peptide-Photosensitizer Conjugate

Photodynamic therapy (PDT) emerges as a promising strategy for combating bacteria with minimal drug resistance. However, a significant hurdle lies in the ineffectiveness of most photosensitizers against Gram-negative bacteria, primarily attributable to their characteristic impermeable outer membrane (OM) barrier. To tackle this obstacle, we herein report an amphipathic peptide-photosensitizer conjugate (PPC) with intrinsic outer membrane disruption capability to enhance PDT efficiency against Gram-negative bacteria. PPC is constructed by conjugating a hydrophilic ultrashort cationic peptide to a hydrophobic photosensitizer. PPC could efficiently bind to the OM of Gram-negative bacteria through electrostatic adsorption, and subsequently disrupt the structural integrity of the OM. Mechanistic investigations revealed that PPC triggers membrane disruption by binding to both lipopolysaccharide (LPS) and phospholipid leaflet in the OM, enabling effective penetration of PPC into the Gram-negative bacteria interior. Upon light irradiation, PPC inside bacteria generates singlet oxygen not only to effectively decrease the survival of Gram-negative bacteria P. aeruginosa and E. coli to nearly zero in vitro, but also successfully cure the full-thickness skin infection and bacterial keratitis (BK) induced by P. aeruginosa in animal models. Thus, this study provides a broad-spectrum antibacterial phototherapeutic design strategy by the synergistic action of membrane disruption and PDT to combat Gram-negative bacteria.

The effect of low-dose photodynamic therapy using the photosensitizer chloroaluminum phthalocyanine on a scratch wound model in skin fibroblasts

Different approaches on wound healing have been developed over the years but they suffer from high costs and adverse effects for the patients. The current paper was designed to study low dose PDT, a novel healing approach, in an in vitro fibroblasts wound healing model. Chloroaluminum phthalocyanine (AlClPc) was used as photosensitizer and was activated by a red diode laser at 661 nm. After PDT optimization, wound closure rate and reactive oxygen species were quantified by image processing and analysis. Our results revealed that wound healing rates were significantly higher in PDT treated groups than in the control. Additionally, the study revealed that a prolonged ROS increase did not promote wound closure, while a small increase acted as a trigger, resulting in faster wound closure. Concluding, low dose PDT using AlClPc enhances wound healing in vitro in a ROS dependent manner, allowing the assumption of similar positive effects in vivo.

Photodynamic inactivation of E. coli with cationic imidazolyl-porphyrin photosensitizers and their synergic combination with antimicrobial cinnamaldehyde

Bacterial infections are a global health concern, particularly due to the increasing resistance of bacteria to antibiotics. Multi-drug resistance (MDR) is a considerable challenge, and novel approaches are needed to treat bacterial infections. Photodynamic inactivation (PDI) of microorganisms is increasingly recognized as an effective method to inactivate a broad spectrum of bacteria and overcome resistance mechanisms. This study presents the synthesis of a new cationic 5,15-di-imidazolyl porphyrin derivative and the impact of n-octanol/water partition coefficient (logP) values of this class of photosensitizers on PDI efficacy of Escherichia coli. The derivative with logP = -0.5, IP-H-OH2+, achieved a remarkable 3 log CFU reduction of E. coli at 100 nM with only 1.36 J/cm2 light dose at 415 nm, twice as effective as the second-best porphyrin IP-H-Me2+, of logP = -1.35. We relate the rapid uptake of IP-H-OH2+ by E. coli to improved PDI and the very low uptake of a fluorinated derivative, IP-H-CF32+, logP ≈ 1, to its poor performance. Combination of PDI with cinnamaldehyde, a major component of the cinnamon plant known to alter bacteria cell membranes, offered synergic inactivation of E. coli (7 log CFU reduction), using 50 nM of IP-H-OH2+ and just 1.36 J/cm2 light dose. The success of combining PDI with this natural compound broadens the scope of therapies for MDR infections that do not add drug resistance. In vivo studies on a mouse model of wound infection showed the potential of cationic 5,15-di-imidazolyl porphyrins to treat clinically relevant infected wounds.

Evaluation of the potential of Delta-aminolevulinic acid for simultaneous detection of bioburden and anti-microbial photodynamic therapy of MRSA infected wounds in Swiss albino mice

BACKGROUND

The dramatic increase of drug-resistant bacteria necessitates urgent development of platforms to simultaneously detect and inactivate bacteria causing wound infections, but are confronted with various challenges. Delta amino levulinic acid (ALA) induced protoporphyrin IX (PpIX) can be a promising modality for simultaneous bioburden diagnostics and therapeutics. Herein, we report utility of ALA induced protoporphyrin (PpIX) based simultaneous bioburden detection, photoinactivation and therapeutic outcome assessment in methicillin resistant Staphylococcus aureus (MRSA) infected wounds of mice.

METHODS

MRSA infected wounds treated with 10% ALA were imaged with help of a blue LED (∼405 nm) based, USB powered, hand held device integrated with a modular graphic user interface (GUI). Effect of ALA application time, bacteria load, post bacteria application time points on wound fluorescence studied. PpIX fluorescence observed after excitation with blue LEDs was used to detect bioburden, start red light mediated antimicrobial photodynamic therapy (aPDT), determine aPDT effectiveness and assess selectivity of the approach.

RESULTS

ALA-PpIX fluorescence of wound bed discriminates infected from uninfected wounds and detects clinically relevant load. While wound fluorescence pattern changes as a function of ALA incubation and post infection time, intra-wound inhomogeneity in fluorescence correlates with the Gram staining data on presence of biofilms foci. Lack of red fluorescence from wound granulation tissue treated with ALA suggests selectivity of the approach. Further, significant reduction (∼50%) in red fluorescence, quantified using the GUI, relates well with bacteria load reduction observed post topical aPDT.

CONCLUSION

The potential of ALA induced PpIX for simultaneous detection of bioburden, photodynamic inactivation and "florescence-guided aPDT assessment" is demonstrated in MRSA infected wounds of mice.

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.

Low-level photodynamic therapy in chronic wounds

BACKGROUND

Chronic wounds refer to those that can't reconstruct anatomical and physical functional integrity, and are usually associated with signs of microbial infection. Current therapies include debridement and dressing change, local or systemic application of antibiotics, and medical dressing care, which are not ideal for the healing of chronic wounds.

OBJECTIVE

To explore the efficacy and safety of photodynamic therapy (ALA-PDT) for the treatment of chronic infectious wounds.

MATERIALS AND METHODS

ALA-PDT was used in ten patients with persistent wound infections and systemic complications who did not respond to conventional treatment. 5 % ALA solution was applied to the wound surface after debridement, incubated for 3 h with light protection, and then irradiated with red light for 20 min. This procedure was repeated every two weeks, and any adverse reactions were recorded. After the end of three treatments, the patients were followed up for 3 months.

RESULTS

Patients who exhibit resistance to traditional therapies demonstrate a favorable therapeutic outcome with ALA-PDT, although complications may impede wound healing. All participants successfully underwent ALA-PDT treatment and subsequent monitoring, with 90 % achieving complete healing. Common adverse reactions to ALA-PDT encompass treatment-related pain, temporary erythema, and swelling, all of which are well-tolerated by patients without enduring severe consequences.

CONCLUSIONS

ALA-PDT proves to be an efficacious intervention for managing chronic wounds, irrespective of the presence of localized infections or systemic complications.

Antimicrobial photodynamic therapy with Brazilian green propolis controls intradermal infection induced by methicillin-resistant Staphylococcus aureus and modulates the inflammatory response in a murine model

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the leading causes of skin and soft tissue infections worldwide. This microorganism has a wide range of antibiotics resistance, a fact that has made the treatment of infections caused by MRSA difficult. In this sense, antimicrobial photodynamic therapy (aPDT) with natural products has emerged as a good alternative in combating infections caused by antibiotic-resistant microorganisms. The objective of the present study was to evaluate the effects of aPDT with Brazilian green propolis against intradermal MRSA infection in a murine model. Initially, 24 Balb/c mice were infected intradermally in the ears with 1.5 × 108 colony-forming units of MRSA 43300. After infection, they were separated into 4 groups (6 animals per group) and treated with the vehicle, only Brazilian green propolis, only blue LED light or with the aPDT protocol (Brazilian green propolis + blue LED light). It was observed in this study that aPDT with Brazilian green propolis reduced the bacterial load at the site of infection. Furthermore, it was able to inhibit weight loss resulting from the infection, as well as modulate the inflammatory response through greater recruitment of polymorphonuclear cells/neutrophils to the infected tissue. Finally, aPDT induced an increase in the cytokines IL-17A and IL-12p70 in the draining retromaxillary lymph node. Thus, aPDT with Brazilian green propolis proved to be effective against intradermal MRSA infection in mice, reducing bacterial load and modulating the immune response in the animals. However, more studies are needed to assess whether such effects are repeated in humans.

Effects of photodynamic therapy in patients with infected skin ulcers: A meta-analysis

The purpose of the meta-analysis was to evaluate and compare the photodynamic therapy's effectiveness in treating infected skin wounds. The results of this meta-analysis were analysed, and the odds ratio (OR) and mean difference (MD) with 95% confidence intervals (CIs) were calculated using dichotomous or contentious random- or fixed-effect models. For the current meta-analysis, 6 examinations spanning from 2013 to 2021 were included, encompassing 154 patients with infected skin wounds were the used studies' starting point. Photodynamic therapy had a significantly lower wound ulcer size (MD, -4.42; 95% CI, -7.56--1.28, p = 0.006), better tissue repair (MD, -8.62; 95% CI, -16.76--0.48, p = 0.04) and lower microbial cell viability (OR, 0.13; 95% CI, 0.04-0.42, p < 0.001) compared with red light exposure in subjects with infected skin wounds. The examined data revealed that photodynamic therapy had a significantly lower wound ulcer size, better tissue repair and lower microbial cell viability compared with red light exposure in subjects with infected skin wounds. However, given that all examinations had a small sample size, consideration should be given to their values.

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.

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.

AIE-active Ir(III) complexes as type-I dominant photosensitizers for efficient photodynamic therapy

The ability of a photosensitizer (PS) to generate reactive oxygen species (ROS) including type I oxygen free radicals and type II ¹O₂ is pivotal for photodynamic therapy. Luminescent Ir(III) complexes are effective PSs with high ¹O₂ generation ability owing to their high intersystem crossing ability and effective energy transfer to ³O₂. However, so far, reports on type I ROS based on ˙OH generation induced by Ir(III) PS are still rare. In this work, four novel aggregation-induced emission (AIE)-active Ir(III) PSs, namely MFIriqa, MFIrqa, SFIriqa, and SFIrqa have been designed and synthesized, which show highly efficient emission in the aggregated state. Cell imaging experiment results indicate that all four Ir(III) PSs can effectively improve the signal-to-noise ratio of imaging by reducing the interference from the background due to their fascinating AIE properties. Importantly, in vitro, Ir(III) PSs MFIrqa, SFIriqa, and SFIrqa nanoparticles show obvious photodynamic activity toward cancer cells upon irradiation accompanied by type I ˙OH generation, which may be attributed to the unique excited-state characteristics of Ir(III) complexes. This work will provide guidance for the construction of a type I photosensitizer based on the AIE-active Ir(III) complex, which offers great advantages for potential clinical applications under hypoxic conditions.

The first evidence of antibiofilm action of Proteus mirabilis with tetra-cationic porphyrins containing cisplatin by antimicrobial photodynamic therapy

Biofilms are responsible for up to 80% of antimicrobial-resistant nosocomial infections. Most of these infections are associated with medical devices such as urinary catheters, and in this context, it is estimated that 90-100% of patients who undergo long-term catheterization develop infections. Proteus mirabilis, the most prevalent microorganism, is responsible for 20-45% of these infections. Thus, this study aimed to evaluate, for the first time, the antimicrobial and antibiofilm effects of cationic porphyrins on P. mirabilis. Neutral porphyrins 3-H₂TPyP and 4-H₂TpyP and tetra-cationic derivatives 3-cis-PtTPyP and 4-cis-PtTPyP were evaluated in broth microdilution tests to determine the minimum inhibitory and bactericidal concentrations. Time-kill curves, checkerboard test, reactive oxygen species (ROS) scavenger assays, conventional biofilm formation, and biofilm assay with catheters were also performed. The microdilution tests showed greater efficacy against P. mirabilis when 3-cis-PtTPyP was exposed to white-light conditions; this also occurred when the microbial time-kill curve was performed at 0, 2, 6, and 12 h. The radical superoxide species was possibly responsible for photoinactivation in the ROS scavenger assays. In biofilm assays (conventional and catheter), 3-cis-PtTPyP obtained better results when irradiated with a white-light source. In the checkerboard assay, the same compound showed no differences when tested in association with ciprofloxacin hydrochloride. Our findings lead us to conclude that antimicrobial photodynamic therapy and cationic porphyrins obtained positive results and are promising alternatives to treat P. mirabilis biofilms.

Photodynamic therapy for treating infected skin wounds: A systematic review and meta-analysis from randomized clinical trials

BACKGROUND

Infected skin wounds represent a public health problem that effects 20 million people worldwide. Photodynamic therapy (PDT) is a treatment option with excellent results against several infections.

OBJECTIVE

This study aimed to perform a systematic review and meta-analysis on PDT efficacy for treating infected wounds based on randomized clinical trials (RCTs).

METHODS

PubMed, Scopus, Web of Science, SciELO, and the Cochrane library were searched. The Delphi List criteria and the Revised Cochrane risk-of-bias (Rob 2) were used for evaluating the quality of clinical trials. Meta-analyses were performed with the random-effect model. The odds ratio was the effect measure for binary outcomes, while the standard mean difference was used for continuous outcomes. The trim-and-fill method was used to detect small-study effects. The quality of evidence was verified for each outcome.

RESULTS

Only four out of 573 articles were selected for the qualitative and quantitative analyses. The most frequent cause of infected wounds was impaired venous circulation (75%). All studies used red LED light. PDT reduced healing time and improved the healing process and wound oxygenation. Patients treated with PDT showed 15% to 17% (p = 0.0003/ I²=0%) lower microbial cell viability in the wound and a significantly smaller wound size (0.72 cm²/p = 0.0187/I²=0%) than patients treated with placebo or red-light exposure. There was a high level of evidence for each meta-analysis outcome.

CONCLUSION

PDT can be an excellent alternative treatment for infected skin wounds, though larger trials are needed.

Polymicrobial Infections and Biofilms: Clinical Significance and Eradication Strategies

Biofilms are population of cells growing in a coordinated manner and exhibiting resistance towards hostile environments. The infections associated with biofilms are difficult to control owing to the chronicity of infections and the emergence of antibiotic resistance. Most microbial infections are contributed by polymicrobial or mixed species interactions, such as those observed in chronic wound infections, otitis media, dental caries, and cystic fibrosis. This review focuses on the polymicrobial interactions among bacterial-bacterial, bacterial-fungal, and fungal-fungal aggregations based on in vitro and in vivo models and different therapeutic interventions available for polymicrobial biofilms. Deciphering the mechanisms of polymicrobial interactions and microbial diversity in chronic infections is very helpful in anti-microbial research. Together, we have discussed the role of metagenomic approaches in studying polymicrobial biofilms. The outstanding progress made in polymicrobial research, especially the model systems and application of metagenomics for detecting, preventing, and controlling infections, are reviewed.

Photo-oxidative stress response and virulence traits are co-regulated in E. faecalis after antimicrobial photodynamic therapy

Knowledge of photo-oxidative stress responses in bacteria that survive antimicrobial photodynamic therapy (aPDT) is scarce. Whereas aPDT is attracting growing clinical interest, subsequent stress responses are crucial to evaluate as they may lead to the up-regulation of pathogenic traits. Here, we aimed to assess transcriptional responses to sublethal aPDT-stress and identify potential connections with virulence-related genes. Six Enterococcus faecalis strains were investigated; ATCC 29212, three dental root-canal isolates labelled UmID1, UmID2 and UmID3 and two vancomycin-resistant isolates labelled A1 and A2. TMPyP was employed as a photosensitiser. A viability dose-response curve to increasing concentrations of TMPyP was determined by culture plating. Differential expression of genes involved in oxidative stress responses (dps and hypR), general stress responses (dnaK, sigma-factor^V and relA), virulence-related genes (ace, fsrC and gelE) and vancomycin-resistance (vanA) was assessed by reverse-transcription qPCR. TMPyP-mediated aPDT inactivated all strains with comparable efficiencies. TMPyP at 0.015 μM was selected to induce sublethal photo-oxidative stress. Despite heterogeneities in gene expression between strains, transcriptional profiles revealed up-regulations of transcripts dps, hypR as well as dnaK and sigma factor^V after exposure to TMPyP alone and to light-irradiated TMPyP. Specifically, the alternative sigma factor^V reached up to 39 ± 113-fold (median ± IQR) (p = 0.0369) in strain A2. Up-regulation of the quorum sensing operon, fsr, and its downstream virulence-related gelatinase gelE were also observed in strains ATCC-29212, A1, A2 and UmID3. Finally, photo-oxidative stress induced vanA-type vancomycin-resistance gene in both carrier isolates, reaching up to 3.3 ± 17-fold in strain A2 (p = 0.015). These findings indicate that, while aPDT successfully inactivates vancomycin-resistant and naïve strains of E. faecalis, subpopulations of surviving cells respond by co-ordinately up-regulating a network of genes involved in stress survival and virulence. This includes the induction of vancomycin-resistance genes in carrier isolates. These data may provide the mechanistic basis to circumvent bacterial responses and improve future clinical protocols.

The photosensitizer-based therapies enhance the repairing of skin wounds

Wound repair remains a clinical challenge and bacterial infection is a common complication that may significantly delay healing. Therefore, proper and effective wound management is essential. The photosensitizer-based therapies mainly stimulate the photosensitizer to generate reactive oxygen species through appropriate excitation source irradiation, thereby killing pathogenic microorganisms. Moreover, they initiate local immune responses by inducing the recruitment of immune cells as well as the production of proinflammatory cytokines. In addition, these therapies can stimulate the proliferation, migration and differentiation of skin resident cells, and improve the deposition of extracellular matrix; subsequently, they promote the re-epithelialization, angiogenesis, and tissue remodeling. Studies in multiple animal models and human skin wounds have proved that the superior sterilization property and biological effects of photosensitizer-based therapies during different stages of wound repair. In this review, we summarize the recent advances in photosensitizer-based therapies for enhancing tissue regeneration, and suggest more effective therapeutics for patients with skin wounds.

Synergic dual phototherapy: Cationic imidazolyl photosensitizers and ciprofloxacin for eradication of in vitro and in vivo E. coli infections

The emergence of new microorganisms with resistance to current antimicrobials is one of the key issues of modern healthcare that must be urgently addressed with the development of new molecules and therapies. Photodynamic inactivation (PDI) in combination with antibiotics has been recently regarded as a promising wide-spectrum therapy for the treatment of localized topical infections. However, further studies are required regarding the selection of the best photosensitizer structures and protocol optimization, in order to maximize the efficiency of this synergic interaction. In this paper, we present results that demonstrate the influence of the structure of cationic imidazolyl-substituted photosensitizers and light on the enhancement of ciprofloxacin (CIP) activity, for the inactivation of Escherichia coli. Structure-activity studies have highlighted the tetra cationic imidazolyl porphyrin IP-H-Me⁴⁺ at sub-bactericide concentrations (4-16 nM) as the most promising photosensitizer for combination with sub-inhibitory CIP concentration (<0.25 mg/L). An optimized dual phototherapy protocol using this photosensitizer was translated to in vivo studies in mice wounds infected with E. coli. This synergic combination reduced the amount of photosensitizer and ciprofloxacin required for full E. coli inactivation and, in both in vitro and in vivo studies, the combination therapy was clearly superior to each monotherapy (PDI or ciprofloxacin alone). Overall, these findings highlight the potential of cationic imidazolyl porphyrins in boosting the activity of antibiotics and lowering the probability of resistance development, which is essential for a sustainable long-term treatment of infectious diseases.

Efficacy and safety of ALA-PDT in treatment of diabetic foot ulcer with infection

BACKGROUND

Diabetic foot ulcers (DFUs) with infection is a major clinical issue, as the infection not only potentially devastate the wound healing, but also is the factor that most often leads to amputation. Nevertheless, traditional antibiotic treatment is often insufficient to clear the infection, which could lead to side effects. Photodynamic therapy (PDT) has broad-spectral antibacterial activity. Meanwhile, it is difficult to induce antibiotic resistance. Here, we aim to evaluate the safety and efficacy of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) in the treatment of DFUs with infection.

METHODS

In our study, 5 diabetic patients with infectious DFUs were diagnosed by pathological examination and the depth of wound was examined by X-Ray. All patients' wounds were firstly irradiated with 20% ALA-PDT (635 nm, 100 J/cm², 80 mW/cm²) using the red LED to control the infection. Treatment will be combined with debridement if there is granulation necrosis or secretion on the wound surface. PDT sessions were performed weekly in all patients until healing was achieved. All patients were followed up for 0.6-1.2 years after treatment.

RESULTS

In 5 patients, the DFUs with infection was completely controlled by ALA-PDT. There was no recurrence of DFUs in the follow-up of 0.9 years (range, 0.6-1.2 years) after the treatment.

CONCLUSIONS

ALA-PDT treatment for DFUs with infection show successful outcomes and might ultimately avoid amputation.

Randomized and Controlled Clinical Studies on Antibacterial Photodynamic Therapy: An Overview

The emergence of drug-resistant bacteria is considered a critical public health problem. The need to establish alternative approaches to countering resistant microorganisms is unquestionable in overcoming this problem. Among emerging alternatives, antimicrobial photodynamic therapy (aPDT) has become promising to control infectious diseases. aPDT is based on the activation of a photosensitizer (PS) by a particular wavelength of light followed by generation of the reactive oxygen. These interactions result in the production of reactive oxygen species, which are lethal to bacteria. Several types of research have shown that aPDT has been successfully studied in in vitro, in vivo, and randomized clinical trials (RCT). Considering the lack of reviews of RCTs studies with aPDT applied in bacteria in the literature, we performed a systematic review of aPDT randomized clinical trials for the treatment of bacteria-related diseases. According to the literature published from 2008 to 2022, the RCT study of aPDT was mostly performed for periodontal disease, followed by halitosis, dental infection, peri-implantitis, oral decontamination, and skin ulcers. A variety of PSs, light sources, and protocols were efficiently used, and the treatment did not cause any side effects for the individuals.

Novel Diagnostic Technologies and Therapeutic Approaches Targeting Chronic Wound Biofilms and Microbiota

Purpose of Review

To provide an up-to-date overview of recent developments in diagnostic methods and therapeutic approaches for chronic wound biofilms and pathogenic microbiota.

Recent Findings

Biofilm infections are one of the major contributors to impaired wound healing in chronic wounds, including diabetic foot ulcers, venous leg ulcers, pressure ulcers, and nonhealing surgical wounds. As an organized microenvironment commonly including multiple microbial species, biofilms develop and persist through methods that allow evasion from host immune response and antimicrobial treatments. Suppression and reduction of biofilm infection have been demonstrated to improve wound healing outcomes. However, chronic wound biofilms are a challenge to treat due to limited methods for accurate, accessible clinical identification and the biofilm's protective properties against therapeutic agents. Here we review recent approaches towards visual markers for less invasive, enhanced biofilm detection in the clinical setting. We outline progress in wound care treatments including investigation of their antibiofilm effects, such as with hydrosurgical and ultrasound debridement, negative pressure wound therapy with instillation, antimicrobial peptides, nanoparticles and nanocarriers, electroceutical dressings, and phage therapy.

Summary

Current evidence for biofilm-targeted treatments has been primarily conducted in preclinical studies, with limited clinical investigation for many therapies. Improved identification, monitoring, and treatment of biofilms require expansion of point-of-care visualization methods and increased evaluation of antibiofilm therapies in robust clinical trials.

The evolution of clinical guidelines for antimicrobial photodynamic therapy of skin

Antimicrobial photodynamic therapy has become an important component in the treatment of human infection. This review considers historical guidelines, and the scientific literature to envisage what future clinical guidelines for treating skin infection might include. Antibiotic resistance, vertical and horizontal infection control strategies and a range of technologies effective in eradicating microbes without building up new resistance are described. The mechanism of action of these treatments and examples of their clinical use are also included. The research recommendations of NICE Guidelines on the dermatological manifestations of microbial infection were also reviewed to identify potential applications for PDT. The resistance of some microbes to antibiotics can be halted, or even reversed through the use of supplementary drugs, and so they are likely to persist as a treatment of infection. Conventional PDT will undoubtedly continue to be used for a range of skin conditions given existing healthcare infrastructure and a large evidence base. Daylight PDT may find broader antimicrobial applications than just Acne and Cutaneous Leishmaniasis, and Ambulatory PDT devices could become popular in regions where resources are limited or daylight exposure is not possible or inappropriate. Nanotheranostics were found to be highly relevant, and often include PDT, however, new treatments and novel applications and combinations of existing treatments will be subject to Clinical Trials.

Precise Molecular Engineering of Type I Photosensitizers with Near-Infrared Aggregation-Induced Emission for Image-Guided Photodynamic Killing of Multidrug-Resistant Bacteria

Multidrug resistance (MDR) bacteria pose a serious threat to human health. The development of alternative treatment modalities and therapeutic agents for treating MDR bacteria-caused infections remains a global challenge. Herein, a series of near-infrared (NIR) anion-π⁺ photosensitizers featuring aggregation-induced emission (AIE-PSs) are rationally designed and successfully developed for broad-spectrum MDR bacteria eradication. Due to the strong intramolecular charge transfer (ICT) and enhanced highly efficient intersystem crossing (ISC), these electron-rich anion-π⁺ AIE-PSs show boosted type I reactive oxygen species (ROS) generation capability involving hydroxyl radicals and superoxide anion radicals, and up to 99% photodynamic killing efficacy is achieved for both Methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant Escherichia coli (MDR E. coli) under a low dose white light irradiation (16 mW cm^-2 ). In vivo experiments confirm that one of these AIE-PSs exhibit excellent therapeutic performance in curing MRSA or MDR E. coli-infected wounds with negligible side-effects. The study would thus provide useful guidance for the rational design of high-performance type I AIE-PSs to overcome antibiotic resistance.

Effects of patient-specific treatment planning on eligibility for photodynamic therapy of deep tissue abscess cavities: retrospective Monte Carlo simulation study

SIGNIFICANCE

Antimicrobial photodynamic therapy (PDT) effectively kills bacterial strains found in deep tissue abscess cavities. PDT response hinges on multiple factors, including light dose, which depends on patient optical properties.

AIM

Computed tomography images for 60 abscess drainage subjects were segmented and used for Monte Carlo (MC) simulation. We evaluated effects of optical properties and abscess morphology on PDT eligibility and generated treatment plans.

APPROACH

A range of abscess wall absorptions (μa  ,  wall) and intra-cavity Intralipid concentrations were simulated. At each combination, the threshold optical power and optimal Intralipid concentration were found for a fluence rate target, with subjects being eligible for PDT if the target was attainable with <2000  mW of source light. Further simulations were performed with absorption within the cavity (μa  ,  cavity).

RESULTS

Patient-specific treatment planning substantially increased the number of subjects expected to achieve an efficacious light dose for antimicrobial PDT, especially with Intralipid modification. The threshold optical power and optimal Intralipid concentration increased with increasing μa  ,  wall (p  <  0.001). PDT eligibility improved with patient-specific treatment planning (p  <  0.0001). With μa  ,  wall  =  0.2  cm  -  1, eligibility increased from 42% to 92%. Increasing μa  ,  cavity reduced PDT eligibility (p  <  0.0001); modifying the delivered optical power had the greatest impact in this case.

CONCLUSIONS

MC-based treatment planning greatly increases eligibility for PDT of abscess cavities.

Recent Advances in Photodynamic Therapy against Fungal Keratitis

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

Antimicrobial Photodynamic Therapy: Latest Developments with a Focus on Combinatory Strategies

Antimicrobial photodynamic therapy (aPDT) has become a fundamental tool in modern therapeutics, notably due to the expanding versatility of photosensitizers (PSs) and the numerous possibilities to combine aPDT with other antimicrobial treatments to combat localized infections. After revisiting the basic principles of aPDT, this review first highlights the current state of the art of curative or preventive aPDT applications with relevant clinical trials. In addition, the most recent developments in photochemistry and photophysics as well as advanced carrier systems in the context of aPDT are provided, with a focus on the latest generations of efficient and versatile PSs and the progress towards hybrid-multicomponent systems. In particular, deeper insight into combinatory aPDT approaches is afforded, involving non-radiative or other light-based modalities. Selected aPDT perspectives are outlined, pointing out new strategies to target and treat microorganisms. Finally, the review works out the evolution of the conceptually simple PDT methodology towards a much more sophisticated, integrated, and innovative technology as an important element of potent antimicrobial strategies.

Photodynamic disinfection and its role in controlling infectious diseases

Photodynamic therapy is witnessing a revival of its origins as a response to the rise of multi-drug resistant infections and the shortage of new classes of antibiotics. Photodynamic disinfection (PDDI) of microorganisms is making progresses in preclinical models and in clinical cases, and the perception of its role in the clinical armamentarium for the management of infectious diseases is changing. We review the positioning of PDDI from the perspective of its ability to respond to clinical needs. Emphasis is placed on the pipeline of photosensitizers that proved effective to inactivate biofilms, showed efficacy in animal models of infectious diseases or reached clinical trials. Novel opportunities resulting from the COVID-19 pandemic are briefly discussed. The molecular features of promising photosensitizers are emphasized and contrasted with those of photosensitizers used in the treatment of solid tumors. The development of photosensitizers has been accompanied by the fabrication of a variety of affordable and customizable light sources. We critically discuss the combination between photosensitizer and light source properties that may leverage PDDI and expand its applications to wider markets. The success of PDDI in the management of infectious diseases will ultimately depend on the efficacy of photosensitizers, affordability of the light sources, simplicity of the procedures, and availability of fast and efficient treatments.

Investigation of the triplet excited state and application of cationic meso-tetra(cisplatin)porphyrins in antimicrobial photodynamic therapy

In this manuscript, we report, the photophysical study of triplet excited states and antimicrobial photoinactivation of positively charged tetra-cisplatin porphyrin derivatives against Gram + and Gram ‒ bacterial strains. Isomeric cisplatin-porphyrins were used and applied in aPDT assays in the bacilli Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa (Gram negative) and a cocci Staphylococcus aureus (Gram positive) strains. The results show that compound substituted at meta position (3-cis-PtTPyP) is the more efficient photosensitizer against bacteria culture. In this way, tetra-cationic porphyrins containing cisplatin derivatives might be promising aPDT agents with potential applications in clinical infections.

Follow-up of pressure ulcer treatment with photodynamic therapy, low level laser therapy and cellulose membrane

OBJECTIVE

A pressure ulcer (PU) is an area of tissue trauma caused by continuous and prolonged pressure, often associated with hospitalised patients immobilised due to neurological problems, negatively affecting their quality of life, and burdening the public budget. The aim of this study was to report the follow-up, for 45 weeks, of three patients with neurological lesions due to trauma who subsequently developed PUs, and who were treated with a combination of photodynamic therapy (PDT), low level laser therapy (LLLT) and cellulose membrane (CM).

METHOD

PDT was mediated by the photosensitiser curcumin on a 1.5% emulsion base. Blue LED light at 450 nm was delivered continuously for 12 minutes at an irradiance of 30mW/cm² and total energy delivered to the tissue was 22J/cm². LLLT was performed with 660 nm laser, punctuated and continuous, twice a week with parameters: spot size 0.04cm², power of 40mW, 10 seconds per point, fluence of 10J/cm² and irradiance of 1000mW/cm².

RESULTS

All PUs had a significant reduction (range: 95.2-100%) of their area after 45 weeks of follow-up and two PUs had complete healing at 20 weeks and 30 weeks. All of the PUs showed a reduction in contamination with the PDT treatments in different proportions.

CONCLUSION

From the results obtained, we conclude that the combination of PDT, LLLT and CM is a promising treatment for PU healing.

A systematic review and meta-analysis of the effect of photodynamic therapy for the treatment of oral mucositis

BACKGROUND

Oral mucositis is a significant reaction to antineoplastic treatment characterized with pain, nutritional compromise, impact on the quality of life, interruption in cancer therapy and risk for infection. There is no effective standard protocol for the treatment of oral mucositis. This study aims to synthesize the scientific evidence available about the effects of photodynamic therapy on treatment of oral mucositis.

METHODS

PubMed, Scopus, Web of Science, Science Direct, Scielo, Embase and Cochrane libraries were searched. Two independent and calibrated researchers (kappa = 0.92) performed all systematic steps according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). To access the risk of bias, RoB 2 and Delphi list criteria for clinical trials were used. Meta-analysis was conducted using the R software with "META" package.

RESULTS

Clinical and randomized clinical trials were included with a total of five articles. Meta-analysis, level of evidence, and risk of bias assessment were performed showing that photodynamic therapy was effective in reducing healing time in association with low-power laser therapy when compared to low-power laser therapy alone (p = 0.0005).

CONCLUSION

Photodynamic therapy presents promising results for the treatment of oral mucositis. It may be an effective therapeutic option, contributing to the healing of injured tissues especially in the time needed for repair.

Photodynamic Therapy for the Treatment of Infected Leg Ulcers-A Pilot Study

Chronic and infected leg ulcers (LUs) are painful, debilitating, resistant to antibiotics, and immensely reduce a patient’s quality of life. The purpose of our study was to demonstrate the efficacy of photodynamic therapy (PDT) for the treatment of infected chronic LUs. Patients were randomized into two experimental groups: the first group received 5-aminolevulinic acid photodynamic therapy (ALA-PDT) (10 patients), and the second group of 10 patients received local octenidine dihydrochloride (Octenilin gel) exposed to a placebo light source with an inserted filter that mimiced red light. In the PDT group, we used 20% ALA topically applied for 4 hrs and irradiation from a Diomed laser source with a wavelength of 630 nm at a fluency of 80 J/cm². ALA-PDT was performed 10 times during a 14-day hospitalization in 10 patients of both sexes aged 40–85 years with chronic leg ulcers. Treatments were carried out at 3-week intervals for 3–5 cycles. At 8-month follow-up with the PDT group, complete remission (CR) was obtained in four patients (40%), partial response (>50% reduction in ulcer diameter) in four patients (40%), and no response in two patients (20%) who additionally developed deterioration of the local condition with swelling, erythema, and inflammation. To assess the degree of pain during the trials, we used a numeric rating scale (NRS). From the preliminary results obtained, we concluded that PDT can be used to treat leg ulcers as a minimally invasive and effective method with no serious side effects, although further studies on a larger group of patients with LUs are warranted.

The effect of indocyanine green-mediated photodynamic therapy in healing of experimentally induced oral mucosal traumatic ulcer in rat

Photodynamic therapy (PDT) is a promising approach for the healing of ulcerative lesions. This study aimed to investigate the effect of PDT using indocyanine green (ICG) in the healing of the experimentally induced oral mucosal traumatic ulcer in rat. Sixty adult male Sprague-Dawley rats were recruited in this experimental study. The ulceration was surgically made in the left cheek mucosa, and the rats were randomly assigned into four equal groups (n = 15). Oral ulcers in groups 1 and 2 were treated with the sterile saline solution (0.9%) and ICG (1 mg/ml). In group 3, laser irradiation was applied using the 810 nm diode laser in the continuous-wave mode for 30 s (light dose: 55 J/cm2, power: 300 mW, spot size: 4.5 mm). Following the topical application of ICG (1 mg/ml) in group 4, laser irradiation was performed in the same way as the previous group. After 24 h, treatments were repeated once more in all groups. The healing process was histopathologically assessed at the 3rd, 7th, and 14th days after ulceration. Wound healing was significantly accelerated in the ICG-mediated PDT group in comparison to the control group at all sampling time points (p < 0.005). However, the other groups displayed a similar healing rate (p > 0.05). Data suggest that ICG-mediated PDT has the potential to accelerate wound healing and prevent clinical infection in oral mucosal traumatic ulcers. However, further studies are required to confirm whether our results can be generalized to other wounds.

An Insight into the Role of Non-Porphyrinoid Photosensitizers for Skin Wound Healing

The concept behind photodynamic therapy (PDT) is being successfully applied in different biomedical contexts such as cancer diseases, inactivation of microorganisms and, more recently, to improve wound healing and tissue regeneration. The effectiveness of PDT in skin treatments is associated with the role of reactive oxygen species (ROS) produced by a photosensitizer (PS), which acts as a "double agent". The release of ROS must be high enough to prevent microbial growth and, simultaneously, to accelerate the immune system response by recruiting important regenerative agents to the wound site. The growing interest in this subject is reflected by the increasing number of studies concerning the optimization of relevant experimental parameters for wound healing via PDT, namely, light features, the structure and concentration of the PS, and the wound type and location. Considering the importance of developing PSs with suitable features for this emergent topic concerning skin wound healing, in this review, a special focus on the achievements attained for each PS class, namely, of the non-porphyrinoid type, is given.

Synthesis and ultrasound mediated antibacterial activity of ferrocene-triazole-porphyrin derivative

The [3 + 2]-cycloaddition reaction of various azides with ferrocenylmethylpropargyl ester in the presence of copper (I) salt lead to the formation of ferrocenyl-containing derivatives, including porphyrin, which exhibit pronounced cytotoxicity against Escherichia coli under ultrasound irradiation.

Effects of ALA-PDT on the Healing of Mouse Skin Wounds Infected With Pseudomonas aeruginosa and Its Related Mechanisms

Photodynamic therapy (PDT) is a promising new method to eliminate microbial infection and promote wound healing. Its effectiveness has been confirmed by some studies; however, the mechanisms of PDT in wound healing remain obscure. We used mouse skin wounds infected with Pseudomonas aeruginosa as a research object to explore the therapeutic effects and mechanisms of 5-aminolevulinic acid photodynamic therapy (ALA-PDT). ALA-PDT treatment significantly reduced the load of P. aeruginosa in the wound and surrounding tissues and promoted the healing of skin wounds in mice. Hematoxylin-eosin (HE) and Sirius red staining showed that ALA-PDT promoted granulation tissue formation, angiogenesis, and collagen regeneration and remodeling. After ALA-PDT treatment, the expression of inflammatory factors (TNF-α and IL-1β) first increased and then decreased, while the secretion of growth factors (TGF-β-1 and VEGF) increased gradually after treatment. Furthermore, ALA-PDT affected the polarization state of macrophages, activating and promoting macrophages from an M1 to an M2 phenotype. In conclusion, ALA-PDT can not only kill bacteria but also promote wound healing by regulating inflammatory factors, collagen remodeling and macrophages. This study further clarifies the mechanism of PDT in the healing of infectious skin wounds and provides further experimental evidence for its clinical treatment of skin wounds infected by P. aeruginosa.

Design of Photosensitizing Agents for Targeted Antimicrobial Photodynamic Therapy

Photodynamic inactivation of microorganisms has gained substantial attention due to its unique mode of action, in which pathogens are unable to generate resistance, and due to the fact that it can be applied in a minimally invasive manner. In photodynamic therapy (PDT), a non-toxic photosensitizer (PS) is activated by a specific wavelength of light and generates highly cytotoxic reactive oxygen species (ROS) such as superoxide (O2-, type-I mechanism) or singlet oxygen (1O2*, type-II mechanism). Although it offers many advantages over conventional treatment methods, ROS-mediated microbial killing is often faced with the issues of accessibility, poor selectivity and off-target damage. Thus, several strategies have been employed to develop target-specific antimicrobial PDT (aPDT). This includes conjugation of known PS building-blocks to either non-specific cationic moieties or target-specific antibiotics and antimicrobial peptides, or combining them with targeting nanomaterials. In this review, we summarise these general strategies and related challenges, and highlight recent developments in targeted aPDT.

Photodynamic therapy to control microbial biofilms

Microorganisms thrive in well-organized biofilm ecosystems. Biofilm-associated cells typically show increased resistance to antibiotics and contribute significantly to treatment failure. This has prompted investigations aimed at developing advanced and novel antimicrobial approaches that could effectively overcome the shortcomings associated with conventional antibiotic therapy. Studies are ongoing to develop effective curative strategies ranging from the use of peptides, small molecules, nanoparticles to bacteriophages, sonic waves, and light energy targeting various structural and physiological aspects of biofilms. In photodynamic therapy, a light source of a specific wavelength is used to irradiate non-toxic photosensitizers such as tetrapyrroles, synthetic dyes or, naturally occurring compounds to generate reactive oxygen species that can exert a lethal effect on the microbe especially by disrupting the biofilm. The photosensitizer preferentially binds to and accumulates in the microbial cells without causing any damage to the host tissue. Currently, photodynamic therapy is increasingly being used for the treatment of oral caries and dental plaque, chronic wound infections, infected diabetic foot ulcers, cystic fibrosis, chronic sinusitis, implant device-associated infections, etc. This approach is recognized as safe, as it is non-toxic and minimally invasive, making it a reliable, realistic, and promising therapeutic strategy for reducing the microbial burden and biofilm formation in chronic infections. In this review article, we discuss the current and future potential strategies of utilizing photodynamic therapy to extend our ability to impede and eliminate biofilms in various medical conditions.

Photodynamic antimicrobial chemotherapy using indocyanine green in experimentally induced intraoral ulcers in rats

BACKGROUND

Photodynamic antimicrobial chemotherapy (PACT) is a promising modality for eradication of microorganisms from the wound. This study aimed to investigate the effectiveness of PACT using indocyanine green (ICG) for reduction of bacterial load of oral ulcers in rats and its impact on the healing process.

METHODS

In this experimental study, 50 adult male Sprague Dawley rats were recruited. Oral ulcers were surgically made on the left cheek mucosa, and animals were randomly assigned into five groups (n = 10). Wound site in groups 1, 2, and 3 was irrigated with the sterile saline (0.9%), chlorhexidine (CHX; 0.2%), and ICG solutions (1 mg/mL), respectively. Group 4 was exposed to laser irradiation using 810 nm diode laser on continuous-wave mode for 30 seconds (fluence: 55 J/cm² , power: 300 mW, spot size: 4.5 mm). In group 5, PACT was performed using topical application of ICG followed by laser irradiation in the same way as the previous group. Bacterial load of oral ulcers was assessed before and after each treatment modality. Besides, rats were sacrificed on the 5th day post ulceration and histological features of healing were evaluated.

RESULTS

Bacterial load was significantly reduced merely in the PACT-ICG-treated group by one log (P < .0001). Animals in the PACT-ICG-treated group also showed an accelerated healing in comparison with others on the 5th day of an experiment.

CONCLUSION

Photodynamic antimicrobial chemotherapy using topical application of ICG has a potential to reduce the bacterial load of oral ulcers and accelerate wound repair. Therefore, it can be considered as an alternative to currently available modalities for wound management.

Antibacterial photodynamic activity of photosensitizer-embedded alginate-pectin-carboxymethyl cellulose composite biopolymer films

Antimicrobial photodynamic therapy (APDT) is a promising approach for treatment of wounds infected with antibiotic-resistant bacteria. In this approach, delivery of appropriate concentration of photosensitizer (PS) at the infected site is a critical step; it is therefore essential that PS need to be administered at the infected site in a suitable formulation. Here, we report preparation of PS-embedded composite biopolymer films and their photobactericidal properties against methicillin-resistant Staphylococcus aureus (MRSA) and biocompatibility. Sodium alginate (SA), pectin (PC), and carboxymethyl cellulose (CMC) were used for preparing films containing chlorin p₆ (Cp₆, anionic PS) or methylene blue (MB, cationic PS). Films containing 1% CMC (15 mm diameter; 110 ± 09 μm thickness) showed ~ 55% light transmission in 500 to 750 nm region and high swelling rate as indicated by ~ 38% increase in diameter within 1 h. Absorption spectroscopic studies of PS-embedded films revealed that while Cp₆ existed mainly in monomeric state, MB existed in both dimeric and monomeric forms. MRSA incubated with the film for 1 h displayed substantial uptake of Cp₆ and MB as indicated by the presence of Cp₆ fluorescence and MB staining in cells under the microscope. Furthermore, photodynamic treatment (660 nm, 10 J/cm²) of MRSA with Cp₆ embedded in film or free Cp₆ resulted in ~ 3 log reduction in colony-forming units (cfu), whereas decrease in cfu was less (~ 1 log) for MB-embedded film than for free MB (~ 6 logs). Studies on human keratinocyte (HaCaT) cells showed that there was no significant change in the viability of cells when they were incubated with solubilized films (plain) for 24 h or subjected to treatment with PS-containing films followed by PDT. These results suggest that films are biocompatible and have potential application in photodynamic treatment of MRSA-infected wounds.

European Dermatology Forum guidelines on topical photodynamic therapy 2019 Part 1: treatment delivery and established indications - actinic keratoses, Bowen's disease and basal cell carcinomas

Topical photodynamic therapy (PDT) is a widely approved therapy for actinic keratoses, Bowen's disease (squamous cell carcinoma in situ), superficial and certain thin basal cell carcinomas. Recurrence rates when standard treatment protocols are used are typically equivalent to existing therapies, although inferior to surgery for nodular basal cell carcinoma. PDT can be used both as lesional and field therapies and has the potential to delay/reduce the development of new lesions. A protocol using daylight to treat actinic keratoses is widely practised, with conventional PDT using a red light after typically a 3-h period of occlusion employed for other superficial skin cancer indications as well as for actinic keratoses when daylight therapy is not feasible. PDT is a well-tolerated therapy although discomfort associated with conventional protocol may require pain-reduction measures. PDT using daylight is associated with no or minimal pain and preferred by patient. There is an emerging literature on enhancing conventional PDT protocols or combined PDT with another treatment to increase response rates. This guideline, published over two parts, considers all current approved and emerging indications for the use of topical PDT in dermatology, prepared by the PDT subgroup of the European Dermatology Forum guidelines committee. It presents consensual expert recommendations reflecting current published evidence.

Evaluation of ALA-PDT combined with antibiotics for the treatment of skin ulcers with sinus tract formation: A pilot study

BACKGROUND

Photodynamic therapy (PDT) is considered an important and innovative treatment for healing skin wounds. Skin ulcers with sinus tract formation are rare and difficult to treat in the field of dermatology. Herein, we utilized optical fibers as a light source to penetrate the sinus tract and applied PDT to treat the sinus tract.

OBJECTIVES

To evaluate the efficacy and safety of 5-aminolevulinic acid photodynamic therapy (ALA-PDT) and provide insight into the use of ALA-PDT in the treatment of skin ulcers with sinus tracts.

METHODS

Seven patients with skin ulcers with sinus tract formation who were previously unsuccessfully treated with systemic antibiotics, debridement and dressing changes were examined. In the present study, these patients also received ALA-PDT treatment (the ulcers were irradiated with a red LED, and the sinus tracts were irradiated with semiconductor laser optical fibers), which was locally administered every 10 days with a total of 1-5 sessions.

RESULTS

Six patients enrolled in the study were fully cured after receiving combination therapy with ALA-PDT and antibiotics for three months. The sinus tract of one patient was cured and the ulcer area of this patient was reduced. All patients experienced varying degrees of redness and pain during treatment but no severe discomfort, and all patients were satisfied with the outcome of the treatment.

CONCLUSION

Local ALA-PDT combined with antibiotics could be a safe and effective treatment approach for skin ulcers with sinus tract formation.

Guidelines on the diagnosis and treatment of foot infection in persons with diabetes (IWGDF 2019 update)

The International Working Group on the Diabetic Foot (IWGDF) has published evidence-based guidelines on the prevention and management of diabetic foot disease since 1999. This guideline is on the diagnosis and treatment of foot infection in persons with diabetes and updates the 2015 IWGDF infection guideline. On the basis of patient, intervention, comparison, outcomes (PICOs) developed by the infection committee, in conjunction with internal and external reviewers and consultants, and on systematic reviews the committee conducted on the diagnosis of infection (new) and treatment of infection (updated from 2015), we offer 27 recommendations. These cover various aspects of diagnosing soft tissue and bone infection, including the classification scheme for diagnosing infection and its severity. Of note, we have updated this scheme for the first time since we developed it 15 years ago. We also review the microbiology of diabetic foot infections, including how to collect samples and to process them to identify causative pathogens. Finally, we discuss the approach to treating diabetic foot infections, including selecting appropriate empiric and definitive antimicrobial therapy for soft tissue and for bone infections, when and how to approach surgical treatment, and which adjunctive treatments we think are or are not useful for the infectious aspects of diabetic foot problems. For this version of the guideline, we also updated four tables and one figure from the 2016 guideline. We think that following the principles of diagnosing and treating diabetic foot infections outlined in this guideline can help clinicians to provide better care for these patients.

Efficacy and safety of photodynamic therapy with RLP068 for diabetic foot ulcers: a review of the literature and clinical experience

This article is the second part of a literature review concerning diabetic foot ulcers (DFUs) and the use of antimicrobial photodynamic therapy (PDT). PDT involves the topical application of a photosensitiser into the tissue, followed by illumination that induces the formation of reactive oxygen species (ROS). PDT provides bacterial inactivation and promotes wound healing, and it can be used to manage the infection and microbial colonisation of DFUs. It has pivotal advantages in comparison with chemotherapeutics, such as no potential to induce resistance, and a wide spectrum of activity. Tetracationic Zn(II) phthalocyanine derivatives have been developed for PDT. Among these, we would like to focus on RLP068, whose antimicrobial activity has been widely demonstrated in preclinical studies and in a clinical trial. This article reports previously published evidence and presents four unpublished clinical cases of DFUs treated in the real-life setting with PDT.

Polymyxin-based photosensitizer for the potent and selective killing of Gram-negative bacteria

The methylene blue-polymyxin conjugate demonstrated high selectivity, sensitivity and phototoxicity against Gram-negative bacteria, including in early biofilm models.

Antimicrobial Photodynamic Therapy in Infected Diabetic Foot Ulcers: A Multicenter Preliminary Experience

BACKGROUND

The increasing resistance of bacteria to antibiotics and the frequency of comorbid conditions of patients make the treatment of diabetic foot infections problematic. In this context, photodynamic therapy could be a useful tool to treat infected wounds. The aim of this study was to evaluate the effect of repeated applications of a phthalocyanine derivative (RLP068) on the bacterial load and on the healing process.

METHODS

The present analysis was performed on patients with clinically infected ulcers who had been treated with RLP068. A sample for microbiological culture was collected at the first visit before and immediately after the application of RLP068 on the ulcer surface, and the area was illuminated for 8 minutes with a red light. The whole procedure was repeated three times per week at two centers (Florence and Arezzo, Italy) (sample A), and two times per week at the third center (Stuttgart, Germany) (sample B) for 2 weeks.

RESULTS

Sample A and sample B were composed of 55 and nine patients, respectively. In sample A, bacterial load decreased significantly after a single treatment, and the benefit persisted for 2 weeks. Similar effects of the first treatment were observed in sample B. In both samples, the ulcer area showed a significant reduction during follow-up, even in patients with ulcers infected with gram-negative germs or with exposed bone.

CONCLUSIONS

RLP068 seems to be a promising topical wound management procedure for the treatment of infected diabetic foot ulcers.

Non-antibiotic antimicrobial interventions and antimicrobial stewardship in wound care

Control of wound infection today relies largely on antibiotics, but the continual emergence of antibiotic-resistant microorganisms threatens a return to the pre-antibiotic era when physicians used antiseptics to prevent and manage infection. Some of those antiseptics are still used today, and others have become available. A diverse variety of non-antibiotic antimicrobial interventions are found on modern formularies. Unlike the mode of action of antibiotics, which affect specific cellular target sites of pathogens, many non-antibiotic antimicrobials affect multiple cellular target sites in a non-specific way. Although this reduces the likelihood of selecting for resistant strains of microorganisms, some have emerged and cross-resistance between antibiotics and antiseptics has been detected. With the prospect of a post-antibiotic era looming, ways to maintain and extend our antimicrobial armamentarium must be found. In this narrative review, current and emerging non-antibiotic antimicrobial strategies will be considered and the need for antimicrobial stewardship in wound care will be explained.