History and Basic Principles of Photodynamic Therapy Use in Ophthalmology

Photodynamic therapy (PDT) is a therapy that uses drugs, called photosensitizers or photosensitizing agents, and a specific type of light. When photosensitizers are exposed to certain wavelengths of light, they produce oxygen that kills nearby cells. PDT is achieved by a photodynamic reaction induced by the excitation of a photosensitizer exposed to light. In the field of ophthalmology, PDT was approved for the first time about ten years ago for cases of age-related macular degeneration (AMD). Neovascular age-related macular degeneration (AMD) is a vision-threatening disease characterized by pathological macular neovascularization. After that, PDT was approved for use in choroidal neovascularization (CNV) cases in pathological myopia.3 This literature review aims to describe the history of PDT use and the basic principles of photodynamic therapy in ophthalmology.

Application of Gold Nanoparticle-Based Materials in Cancer Therapy and Diagnostics

Several metal nanoparticles have been developed for medical application. While all have their benefits, gold nanoparticles (AuNPs) are ideal in cancer therapy and diagnosis as they are chemically inert and minimally toxic. Several studies have shown the potential of AuNPs in the therapeutic field, as photosensitizing agents in sonochemical and photothermal therapy and as drug delivery, as well as in diagnostics and theranostics. Although there is a significant number of reviews on the application of AuNPs in cancer medicine, there is no comprehensive review on their application both in therapy and diagnostics. Therefore, considering the high number of studies on AuNPs’ applications, this review summarizes data on the application of AuNPs in cancer therapy and diagnostics. In addition, we looked at the influence of AuNPs’ shape and size on their biological properties. We also present the potential use of hybrid materials based on AuNPs in sonochemical and photothermal therapy and the possibility of their use in diagnostics. Despite their potential, the use of AuNPs and derivatives in cancer medicine still has some limitations. In this review, we provide an overview of the biological, physicochemical, and legal constraints on using AuNPs in cancer medicine.

The Role of Melanoma Cell-Derived Exosomes (MTEX) and Photodynamic Therapy (PDT) within a Tumor Microenvironment

Photodynamic Therapy (PDT), an unconventional cancer therapy with optimistic desirable effects, utilizes the delivery of a photosensitizer (PS) that is activated by light at a particular wavelength and inducing oxidative cytotoxic damage of a tumor and its surrounding vasculature. Deeper seated tumors such as internally metastasized melanomas are more difficult to treat with PDT as the penetration of laser light to those sites is less. Limitations in targeting melanomas can also be attributed to melanin pigments that hinder laser light from reaching targeted sites. Exosomes serve as naturally occurring nanoparticles that can be re-assembled with PSs, improving targeted cellular absorption of photosensitizing agents during PDT. Additionally, studies indicate that exosomes released from PDT-treated tumor cells play a critical role in mediating anti-tumor immune responses. This review collates the role of Melanoma Cell-Derived Exosomes (MTEX) in immune response mediation and metastasis. Tumor Cell-Derived Exosomes (TEX) post PDT treatment are also reviewed, as well as the effects of exosomes as carriers of photosensitizers and delivery systems for PDT. The understanding and research on the role of melanoma exosomes induced by Photodynamic Therapy and their tumor microenvironment will assist in future research in treatment prospects and implications.

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.

Inorganic Nanoparticles for Cancer Treatment

The application of porphyrins and their derivatives have been investigated extensively over the past years for phototherapy cancer treatment. Phototherapeutic Porphyrins have the ability to generate high levels of reactive oxygen with a low dark toxicity and these properties have made them robust photosensitizing agents. In recent years, Porphyrins have been combined with various nanomaterials in order to improve their bio-distribution. These combinations allow for nanoparticles to enhance photodynamic therapy (PDT) cancer treatment and adding additional nanotheranostics (photothermal therapy—PTT) as well as enhance photodiagnosis (PDD) to the reaction. This review examines various porphyrin-based inorganic nanoparticles developed for phototherapy nanotheranostic cancer treatment over the last three years (2017 to 2020). Furthermore, current challenges in the development and future perspectives of porphyrin-based nanomedicines for cancer treatment are also highlighted.

Recent Advances in Porphyrin-Based Inorganic Nanoparticles for Cancer Treatment

The application of porphyrins and their derivatives have been investigated extensively over the past years for phototherapy cancer treatment. Phototherapeutic Porphyrins have the ability to generate high levels of reactive oxygen with a low dark toxicity and these properties have made them robust photosensitizing agents. In recent years, Porphyrins have been combined with various nanomaterials in order to improve their bio-distribution. These combinations allow for nanoparticles to enhance photodynamic therapy (PDT) cancer treatment and adding additional nanotheranostics (photothermal therapy—PTT) as well as enhance photodiagnosis (PDD) to the reaction. This review examines various porphyrin-based inorganic nanoparticles developed for phototherapy nanotheranostic cancer treatment over the last three years (2017 to 2020). Furthermore, current challenges in the development and future perspectives of porphyrin-based nanomedicines for cancer treatment are also highlighted.

Titanium Dioxide Nanoparticles: Prospects and Applications in Medicine

Metallic and metal oxide nanoparticles (NPs), including titanium dioxide NPs, among polymeric NPs, liposomes, micelles, quantum dots, dendrimers, or fullerenes, are becoming more and more important due to their potential use in novel medical therapies. Titanium dioxide (titanium(IV) oxide, titania, TiO2) is an inorganic compound that owes its recent rise in scientific interest to photoactivity. After the illumination in aqueous media with UV light, TiO2 produces an array of reactive oxygen species (ROS). The capability to produce ROS and thus induce cell death has found application in the photodynamic therapy (PDT) for the treatment of a wide range of maladies, from psoriasis to cancer. Titanium dioxide NPs were studied as photosensitizing agents in the treatment of malignant tumors as well as in photodynamic inactivation of antibiotic-resistant bacteria. Both TiO2 NPs themselves, as well as their composites and combinations with other molecules or biomolecules, can be successfully used as photosensitizers in PDT. Moreover, various organic compounds can be grafted on TiO2 nanoparticles, leading to hybrid materials. These nanostructures can reveal increased light absorption, allowing their further use in targeted therapy in medicine. In order to improve efficient anticancer and antimicrobial therapies, many approaches utilizing titanium dioxide were tested. Results of selected studies presenting the scope of potential uses are discussed in this review.

Use of photodynamic therapy for photodamage skin (review of literature)

The article provides an overview of the use of photodynamic therapy for photodamage of the skin. The causes, pathogenesis and clinical manifestations of skin photodamage are considered. The definition, principle of action of photodynamic therapy, including the sources of light used, the classification of photosensitizers and their main characteristics are given. Analyzed studies that show the effectiveness and comparative evaluation in the selection of various light sources and photosensitizing agents for photodynamic therapy in patients with clinical manifestations of photodamage.