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

Abstract

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.

Analysis of Self-Assembled Low- and High-Molecular-Weight Poly-L-Lysine–Ce6 Conjugate-Based Nanoparticles

“…ROS or singlet oxygen causes significant damage to cellular components, especially the lipids in cell membranes and mitochondrial membranes, leading to cell death. Using this principle, various PDTs such as vascular targeting PDT, cellular PDT, or upconversion-based PDT have been developed [16,17].…”

PDT-Induced Activation Enhanced by Hormone Response to Treatment

“…These three mechanisms are interrelated, and their quantitative contributions depend, among other things, on the dose and type of PS, oxygen concentration in the cancer cells, the wavelength of light, the total dose of PS, irradiation time, and fluctuation rate, meaning the time between exposure to light and administration of PS [ 9 ]. As shown in Figure 1 , PDT is a two-stage procedure consisting of PS administration and successive irradiation of the tumor [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. The use of PDT is possible in the case of a neoplastic tumor of any organ with the use of flexible optical-fiber devices for precise irradiation of the treated tissues.…”