Effectiveness of photodynamic therapy as an adjunct to topical antiviral therapy in the treatment of herpes labialis: A randomized controlled clinical trial

The use of photodynamic therapy in medical practice

Cancer therapy, especially for tumors near sensitive areas, demands precise treatment. This review explores photodynamic therapy (PDT), a method leveraging photosensitizers (PS), specific wavelength light, and oxygen to target cancer effectively. Recent advancements affirm PDT's efficacy, utilizing ROS generation to induce cancer cell death. With a history spanning over decades, PDT's dynamic evolution has expanded its application across dermatology, oncology, and dentistry. This review aims to dissect PDT's principles, from its inception to contemporary medical applications, highlighting its role in modern cancer treatment strategies.

Combination of Two Photosensitisers in Anticancer, Antimicrobial and Upconversion Photodynamic Therapy

Photodynamic therapy (PDT) is a special form of phototherapy in which oxygen is needed, in addition to light and a drug called a photosensitiser (PS), to create cytotoxic species that can destroy cancer cells and various pathogens. PDT is often used in combination with other antitumor and antimicrobial therapies to sensitise cells to other agents, minimise the risk of resistance and improve overall outcomes. Furthermore, the aim of combining two photosensitising agents in PDT is to overcome the shortcomings of the monotherapeutic approach and the limitations of individual agents, as well as to achieve synergistic or additive effects, which allows the administration of PSs in lower concentrations, consequently reducing dark toxicity and preventing skin photosensitivity. The most common strategies in anticancer PDT use two PSs to combine the targeting of different organelles and cell-death mechanisms and, in addition to cancer cells, simultaneously target tumour vasculature and induce immune responses. The use of PDT with upconversion nanoparticles is a promising approach to the treatment of deep tissues and the goal of using two PSs is to improve drug loading and singlet oxygen production. In antimicrobial PDT, two PSs are often combined to generate various reactive oxygen species through both Type I and Type II processes.

Photodynamic Inhibition of Herpes Simplex Virus 1 Infection by Tricationic Amphiphilic Porphyrin with a Long Alkyl Chain

Photodynamic therapy (PDT) is broadly used to treat different tumors, and it is a rapidly developing approach to inactivating or inhibiting the replication of fungi, bacteria, and viruses. Herpes simplex virus 1 (HSV-1) is an important human pathogen and a frequently used model to study the effects of PDT on enveloped viruses. Although many photosensitizers (PSs) have been tested for their antiviral properties, analyses are usually limited to assessing the reduction in viral yield, and thus the molecular mechanisms of photodynamic inactivation (PDI) remain poorly understood. In this study, we investigated the antiviral properties of TMPyP3-C17H35, a tricationic amphiphilic porphyrin-based PS with a long alkyl chain. We show that light-activated TMPyP3-C17H35 can efficiently block virus replication at certain nM concentrations without exerting obvious cytotoxicity. Moreover, we show that the levels of viral proteins (immediate-early, early, and late genes) were greatly reduced in cells treated with subtoxic concentrations of TMPyP3-C17H35, resulting in markedly decreased viral replication. Interestingly, we observed a strong inhibitory effect of TMPyP3-C17H35 on the virus yield only when cells were treated before or shortly after infection. In addition to the antiviral activity of the internalized compound, we show that the compound dramatically reduces the infectivity of free virus in the supernatant. Overall, our results demonstrate that activated TMPyP3-C17H35 effectively inhibits HSV-1 replication and that it can be further developed as a potential novel treatment and used as a model to study photodynamic antimicrobial chemotherapy.

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.

Photodynamic therapy for treatment of infected burns

Burns are among the most debilitating and devastating forms of trauma. Such injuries are influenced by infections, causing increased morbidity, mortality, and healthcare costs. Due to the emergence of multidrug-resistant infectious agents, efficient treatment of infections in burns is a challenging issue. Antimicrobial photodynamic therapy (aPDT) is a promising approach to inactivate infectious agents, including multidrug-resistant. In this review, studies on PubMed were gathered, aiming to summarize the achievements regarding the applications of antimicrobial photodynamic therapy for the treatment of infected burns. A literature search was carried out for aPDT published reports assessment on bacterial, fungal, and viral infections in burns. The collected data suggest that aPDT could be a promising new approach against multidrug-resistant infectious agents. However, despite important results being obtained against bacteria, experimental and clinical studies are necessary yet on the effectiveness of aPDT against fungal and viral infections in burns, which could reduce morbidity and mortality of burned patients, mainly those infected by multidrug-resistant strains.

Photodynamic and antibiotic therapy in combination against bacterial infections: efficacy, determinants, mechanisms, and future perspectives

Antibiotic treatment, the mainstay for the control of bacterial infections, is greatly hampered by the global prevalence of multidrug-resistant (MDR) bacteria. Photodynamic therapy (PDT) is effective against MDR infections, but PDT-induced bacterial inactivation is often incomplete, causing the relapse of infections. Combination of PDT and antibiotics is a promising strategy to overcome the limitation of both antibiotic treatment and PDT, exerting increased disinfection efficacy on MDR bacterial pathogens versus either of the monotherapies alone. In this review, we present an overview of the therapeutic effects of PDT/antibiotic combinations that have been developed. We further summarize the influencing factors and the governing molecular mechanisms of the therapeutic outcomes of PDT/antibiotic combinations. In the end, we provide concluding remarks on the strengths, limitations, and future research directions of PDT/antibiotic combination therapy to guide its appropriate usage and further development.