Principles Of Photodynamic Therapy Research Articles

Nanoemulsion applications in photodynamic therapy.

Nanoemulsion, or nanoscaled-size emulsions, is a thermodynamically stable system formed by blending two immiscible liquids, blended with an emulsifying agent to produce a single phase. Nanoemulsion science has advanced rapidly in recent years, and it has opened up new opportunities in a variety of fields, including pharmaceuticals, biotechnology, food, and cosmetics. Nanoemulsion has been recognized as a potential drug delivery technology for various drugs, such as photosensitizing agents (PS). In photodynamic therapy (PDT), PSs produce cytotoxic reactive oxygen species under specific light irradiation, which oxidize the surrounding tissues. Over the past decades, the idea of PS-loaded nanoemulsions has received researchers' attention due to their ability to overcome several limitations of common PSs, such as limited permeability, non-specific phototoxicity, hydrophobicity, low bioavailability, and self-aggregation tendency. This review aims to provide fundamental knowledge of nanoemulsion formulations and the principles of PDT. It also discusses nanoemulsion-based PDT strategies and examines nanoemulsion advantages for PDT, highlighting future possibilities for nanoemulsion use.

Recent Progress in Chemical Modifications of Chlorophylls and Bacteriochlorophylls for the Applications in Photodynamic Therapy.

Since photodynamic therapy emerged as a promising cancer treatment, the development of photosensitizers has gained great interest. In this context, the photosynthetic pigments, chlorophylls and bacteriochlorophylls, as excellent natural photosensitizers, attracted much attention. In effect, several (bacterio) chlorophyll-based phototherapeutic agents have been developed and (or are about to) enter the clinics. The aim of this review article is to give a survey of the advances in the synthetic chemistry of these pigments which have been made over the last decade, and which are pertinent to the application of their derivatives as photosensitizers for photodynamic therapy (PDT). The review focuses on the synthetic strategies undertaken to obtain novel derivatives of (bacterio)chlorophylls with both enhanced photosensitizing and tumorlocalizing properties, and also improved photo- and chemical stability. These include modifications of the C- 17-ester moiety, the isocyclic ring, the central binding pocket, and the derivatization of peripheral functionalities at the C-3 and C-7 positions with carbohydrate-, peptide-, and nanoparticle moieties or other residues. The effects of these modifications on essential features of the pigments are discussed, such as the efficiency of reactive oxygen species generation, photostability, phototoxicity and interactions with living organisms. The review is divided into several sections. In the first part, the principles of PDT and photosensitizer action are briefly described. Then the relevant photophysical features of (bacterio)chlorophylls and earlier approaches to their modification are summarized. Next, a more detailed overview of the progress in synthetic methods is given, followed by a discussion of the effects of these modifications on the photophysics of the pigments and on their biological activity.

Periungual Bowen's disease successfully treated with photodynamic therapy

Bowen's disease or squamous cell carcinoma in situ is a malignancy of the skin confined to the epidermis that unusually involves the nail apparatus. The ideal treatment should complete clear the tumor, with preservation of the cosmetics and the function of the finger, which can be very difficult to achieve depending on tumor's location and the extension. The high cure rates for Bowen's disease and the principles of photodynamic therapy, suggest that this technique may be a great option in the management of this kind of lesion. Therefore, this is a case report of a 47-years-old man with diabetes and HIV+ serology who presented a patch of Bowen's disease at the distal phalange of the finger treated with photodynamic therapy in order to avoid surgical complications, a more aggressive treatment or even mutilation. An excellent response was reached, preserving all the structures of the nail, with clinical and histopathological cure and complete remission after two years of follow up.

Concepts and Principles of Photodynamic Therapy as an Alternative Antifungal Discovery Platform

Opportunistic fungal pathogens may cause superficial or serious invasive infections, especially in immunocompromised and debilitated patients. Invasive mycoses represent an exponentially growing threat for human health due to a combination of slow diagnosis and the existence of relatively few classes of available and effective antifungal drugs. Therefore systemic fungal infections result in high attributable mortality. There is an urgent need to pursue and deploy novel and effective alternative antifungal countermeasures. Photodynamic therapy (PDT) was established as a successful modality for malignancies and age-related macular degeneration but photodynamic inactivation has only recently been intensively investigated as an alternative antimicrobial discovery and development platform. The concept of photodynamic inactivation requires microbial exposure to either exogenous or endogenous photosensitizer molecules, followed by visible light energy, typically wavelengths in the red/near infrared region that cause the excitation of the photosensitizers resulting in the production of singlet oxygen and other reactive oxygen species that react with intracellular components, and consequently produce cell inactivation and death. Antifungal PDT is an area of increasing interest, as research is advancing (i) to identify the photochemical and photophysical mechanisms involved in photoinactivation; (ii) to develop potent and clinically compatible photosensitizers; (iii) to understand how photoinactivation is affected by key microbial phenotypic elements multidrug resistance and efflux, virulence and pathogenesis determinants, and formation of biofilms; (iv) to explore novel photosensitizer delivery platforms; and (v) to identify photoinactivation applications beyond the clinical setting such as environmental disinfectants.

Photodynamic Therapy: Porphyrins and Phthalocyanines as Photosensitizers

The present work is focussed on the principles of photodynamic therapy (PDT), emphasizing the photochemical mechanisms of reactive oxygen species formation and the consequent biochemical processes generated by the action of reactive oxygen species on various biological macromolecules and organelles. This paper also presents some of the most used photosensitizers, including Photofrin, and the new prototypes of photosensitizers, analysing their physicochemical and spectroscopic properties. At this point, the review discusses the therapeutic window of absorption of specific wavelengths involving first- and second-generation photosensitizers, as well as the principal light sources used in PDT. Additionally, the aggregation process, which consists in a phenomenon common to several photosensitizers, is studied. J-aggregates and H-aggregates are discussed, along with their spectroscopic effects. Most photosensitizers have a significant hydrophobic character; thus, the study of the types of aggregation in aqueous solvent is very relevant. Important aspects of the coordination chemistry of metalloporphyrins and metallophthalocyanines used as photosensitizers are also discussed. The state-of-the-art in PDT is evaluated, discussing recent articles in this area. Furthermore, macrocyclic photosensitizers, such as porphyrins and phthalocyanines, are specifically described. The present review is an important contribution, because PDT is one of the most auspicious advances in the therapy against cancer and other non-malignant diseases.

Photodynamic therapy: esophagus.

Photodynamic therapy (PDT) is a minimally invasive, organ-preserving therapeutic modality, involving three separate components - light, oxygen and a photosensitizing drug. The principles of PDT are described, and the indications for its use are reviewed. Although a widespread clinical application for PDT has not yet emerged, PDT may establish itself as an endoscopic procedure with few or no side effects in the treatment of Barrett's esophagus (high-grade dysplasia and early carcinoma) and, in selected cases, for the treatment of early squamous cell carcinoma.

Photodynamic Therapy for Cancer: Principles

The principles of photodynamic therapy (PDT), using drugs (photosensitizers) that are activated by light to become cytotoxic, provide the basis for understanding the current and potential future clinical applications in gastroenterology, general oncology and other specialties. The properties of photosensitizers are key to their biological efficacy, while lasers and optical fibres allow convenient and flexible light delivery for endoscopic use. PDT has several distinct and unique advantages, both as a stand-alone treatment and in combination with other established modalities. The current limitations are also recognized, as is the need for rigorous randomized trials of this emerging technology. The fluorescence of many photosensitizers may be useful, either for (endoscopic) diagnosis or for PDT treatment guidance and monitoring.

Photodynamic therapy of age-related macular degeneration: History and principles

We briefly review the history and principles of photodynamic therapy (PDT), especially as it is applied to choroidal neovascularization (CNV) in age-related macular degeneration (AMD). After a brief general history of PDT, we discuss the relationship between the physicochemical structure and photodynamic activity of the second-generation photosensitizers, such as those in current clinical use. We then discuss the basic photophysics of photosensitizer molecules, and describe the initial chemical reactions induced by activated sensitizers. We outline a novel method for screening photosensitizers to be used in treating CNV, as well as the complex biomolecular pathways modulated by PDT-induced oxidative stress and the vascular effects of PDT in solid tumors. The paper closes with a discussion of how all this information might be used to improve the selectivity and efficacy of clinically useful photosensitizers.