Modern outlook for the use of photosensitizers with aggregation-induced emission in treatment of malignant tumors

Abstract

Photodynamic therapy (PDT) is actively developing, becoming one of the important methods of non-invasive treatment of various oncological and infectious diseases. It is usually carried out using three main components: a photosensitizer, light, and oxygen. The key factors for the effective use of PDT are reactogenic oxygen species, which are produced during the oxidation of photosensitizers under the influence of light irradiation.
 To increase the production of reactogenic oxygen species, a technique was proposed for creating photosensitizers with aggregation-induced emission. At the present stage in oncology, the following PDT methods using photosensitizers with aggregation-induced emission are distinguished: PDT, absorbing near infrared radiation; enzyme- or glutathione-activated PDT; hypoxic PDT, and synergistic therapy.
 Compared to visible light, near infrared radiation (7001700 nm) has been shown to be more effective and safer due to reduced photodamage, less scattering, and deeper light penetration. The development of activated photosensitizers is an effective way to overcome the uncontrolled phototoxicity of photosensitizers during long-term PDT in vivo, providing controlled death of tumor cells. The oxygen concentration in tumor tissue varies depending on tumor progression, angiogenesis, metabolism, and metastasis. Therefore, the development of photosensitizers capable of effectively fluorescing under hypoxic conditions, including catalyzing intracellular substrates with the formation of oxygen and stimulating the production of reactogenic oxygen species through the type I mechanism, has become a potential solution to the problem of PDT of solid tumors.
 The therapeutic efficacy of a single PDT method, as well as most treatment methods in modern oncology, is limited. Therefore, a significant direction is the development of multifunctional treatment systems for synergistic therapy of tumors. Synergistic chemotherapy and PDT is an important area of treatment in oncology. The combination of PDT and immunotherapy is also a promising direction in the treatment of malignant neoplasms.
 There are obvious prospects for PDT in oncology not as a separate method of treatment, but as part of a complex multimodal treatment, including chemotherapy, radiation therapy, surgical treatment, and immunotherapy.