Photosensitizers Used in the Photodynamic Therapy of Rheumatoid Arthritis

Abstract

Photodynamic Therapy (PDT) has become one of the most promising treatment against autoimmune diseases, such as rheumatoid arthritis (RA), as well as in the treatment of different types of cancer, since it is a non-invasive method and easy to carry out. The three main ingredients of PDT are light irradiation, oxygen, and a photosensitizer (PS). Light irradiation depends on the type of molecule or compound to be used as a PS. The concentration of O2 fluctuates according to the medium where the target tissue is located and over time, although it is known that it is possible to provide oxygenated species to the treated area through the PS itself. Finally, each PS has its own characteristics, the efficacy of which depends on multiple factors, such as solubility, administration technique, retention time, stability, excitation wavelength, biocompatibility, and clearance, among others. Therefore, it is essential to have a thorough knowledge of the disease to select the best PS for a specific target, such as RA. In this review we will present the PSs used in the last three decades to treat RA under PDT protocol, as well as insights on the relevant strategies.

Superior Properties and Biomedical Applications of Microorganism-Derived Fluorescent Quantum Dots

“…ROS interacts with cells and intracellular macromolecules, such as nucleic acids and proteins, and several subcellular organelles undergo cellular apoptosis or necrosis. Several parameters affect the success of the PDT process, including photosensitizer type and concentration in the targeted cells, laser wavelength irradiation type, duration and intensity and oxygen content of the micro-environment surrounding the targeted cells [ 133 ]. Photosensitizers are distinct molecules which can endure photochemical reactions once exposed to light.…”

Energy Conversion-Based Nanotherapy for Rheumatoid Arthritis Treatment

“…In the RA treatment, type II therapy is dominant. The basic principle is that under the light excitation of a specific wavelength, PSs directly transfer energy to the oxygen of the basic energy form ( 3 O 2 ) and then generate reactive oxygen species (ROS), mainly including 1 O 2 ,·OH, and H 2 O 2 (Gallardo-Villagrán et al, 2019 ). ROS can affect all components of the cells, such as proteins and DNA, causing necrosis or apoptosis of RA inflammatory cells (Tørring et al, 2014 ).…”

“…ROS can affect all components of the cells, such as proteins and DNA, causing necrosis or apoptosis of RA inflammatory cells (Tørring et al, 2014 ). Since the 1990s, PDT has been continuously explored for its therapeutic potential on synovium destruction or down-regulation of RA immune activity (Gallardo-Villagrán et al, 2019 ). Synovium hyperplasia of RA shows local tumor-like changes (infiltration and destruction of articular cartilages, bones, tendons and ligaments) (Senolt et al, 2006 ).…”

“…In order to overcome the shortcomings of traditional PSs, nanosized PSs have been broadly studied and applied in PDT treatment of RA very recently. The rational combination of PSs and nanomaterials can enhance drug targeting, reduce side effects and improve PDT efficacy in RA treatment (Liu et al, 2018 ; Gallardo-Villagrán et al, 2019 ).…”

“…Type II: PSs transfer energy directly to 3 O 2 , producing ROS. Reproduced with permission from Gallardo-Villagrán et al ( 2019 ). Copyright 2019, MDPI.…”