An <em>In Vitro</em> Approach to Photodynamic Therapy

Abstract

Photodynamic therapy (PDT) is a medical procedure that involves incubation of an exogenously applied photosensitizer (PS) followed by visible light photoactivation to induce cell apoptosis. The Federal Drug Administration has approved PDT for the treatment of actinic keratosis, and clinical guidelines recommend PDT as a treatment for certain non-melanoma skin cancers and acne vulgaris. PDT is an advantageous therapeutic modality as it is low cost, non-invasive, and associated with minimal adverse events and scaring. In the first step of PDT, a PS is applied and allowed to accumulate intracellularly. Subsequent light irradiation induces reactive oxygen species formation, which may ultimately lead to cell apoptosis, membrane disruption, mitochondrial damage, immune modulation, keratinocyte proliferation, and collagen turnover. Herein, we present an in vitro method to study PDT in an adherent cell line. This treatment protocol is designed to simulate PDT and may be adjusted to studying the use of PDT with various cell lines, photosensitizers, incubation temperatures, or photoactivation wavelengths. Squamous cell carcinoma cells were incubated with 0, 0.5, 1.0, and 2 mM 5-aminolevulinic acid (5-ALA) for 30 min and photoactivated with 417 nm blue light for 1,000 s. The primary outcome measure was apoptosis and necrosis, as measured by annexin-V and 7-aminoactinomycin D flow cytometry. There was a dose-dependent increase in cell apoptosis following thirty-minute incubation of 5-ALA. To achieve high inter-test validity, it is important to maintain consistent incubation and light parameters when performing in vitro PDT experiments. PDT is a useful clinical procedure and in vitro research may allow for the development of novel PSs, optimization of protocols, and new indications for PDT.

Photodynamic Therapy Using a New Folate Receptor-Targeted Photosensitizer on Peritoneal Ovarian Cancer Cells Induces the Release of Extracellular Vesicles with Immunoactivating Properties

“…A number of preclinical studies on several animal models have described the pro-inflammatory effect of PDT, capable of inducing an antitumor immune response [15]. In fact, recent evidence suggests that vessel occlusion, ischemia, and direct destruction of tumor cells caused by PDT lead to a significant local inflammatory response [16]. More specifically, the damage induced by the PDT generates various alarm signals that could be detected by the effectors of innate immunity [17].…”

Photodynamic therapy as an up-to-date medical technology for the treatment of vulgar acne

“…Существуют также фотосенсибилизаторы, инкапсулированные в липосомы с целью улучшения проникновения в кожу и снижения системной абсорбции. Однако данные исследования проводились преимущественно in vitro [28]. Тем не менее следует отметить результаты двух исследований, выполненных до 2017 года (то есть вне рамок «временного горизонта» нашего исследования), фотодинамических методов лечения акне, в которых изучалась применимость липосомальной формы метиленового синего (ЛМС), являющегося фотосенсибилизирующим красителем, производным фенотиазина, с максимальной абсорбцией в условиях воздействия света с длиной волны 668 и 609 нм [29,30].…”

Topical photodynamic therapy in the treatment of benign oral mucosal lesions: A systematic review

“…Photodynamic therapy (PDT) relies on the interaction between a photosensitizer, the appropriate activating wavelength of light, and oxygen. The reaction generates reactive oxygen species (ROS), causing cell death by necrosis or apoptosis, but minimally affects the surrounding tissue 1 . Furthermore, PDT can directly alter immune cells' function (cytokine production, cell signaling events, and surface receptor expression) and, therefore, relieve immune‐mediated disease 2 …”