The Use of Photodynamic Therapy for Head, Neck, and Brain Diseases

Abstract

Head–neck cancers as a group have the 7th highest rate of incidence worldwide. The most often diagnosed disease of the head and neck is squamous cell carcinoma (90% of cases). Another specific group of tumors is brain tumors. These can be divided into primary tumors and secondary tumors associated with metastasis. Research shows that treating head and neck cancers continues to be problematic and challenging, and researchers are actively seeking new treatments that would improve survival rates and reduce side effects. Irradiation of tumor tissue with the optimal wavelength of light in photodynamic therapy (PDT) generates predominantly singlet oxygen in tissue-based photosensitizers (PSs) or reactive oxygen radicals in the case of vascular PSs leading to cellular apoptosis and necrosis. A very important feature of PDT is that cells cannot become immune to the effects of singlet oxygen or reactive oxygen radicals. However, photosensitizer (PS) transport is influenced by the specific structures of cancer tumors and the concentration of PS decreases in cells far from the vessel lumen. Therefore, PSs may not reach tumor interiors, which decreases therapy effectiveness. The use of drug carriers and 3rd generation PSs that contain biocompatible functional groups makes it possible to control transport. This review of the current literature on PDT was conducted through databases such as PubMed and Scopus. The types of publications considered included clinical studies and most of the articles included were published in English. Based on the publications collected, we conclude that researchers have demonstrated the potential of PDT as a therapeutic platform for head, neck, and brain diseases.

PDT-Induced Activation Enhanced by Hormone Response to Treatment

“…1 O 2 has lifetimes from microseconds to milliseconds. The diffusion distance of 1 O 2 ranges from nanometers to millimeters [55][56][57]. Cancer cells are typical examples in biology where hypoxic processes take place.…”

“…However, PDT needs ground-state triplet O 2 for production of 1 O 2 . Equations ( 1) and ( 2) show the standard PDT reaction in cells [56][57][58][59]:…”

“…However, PDT needs ground-state triplet O 2 for production of 1 O 2 . Equations (1) and (2) show the standard PDT reaction in cells [ 56 , 57 , 58 , 59 ]: PS + visible light (hν) -> PS* PS* + 3 O 2 -> PS + 1 O 2 …”

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

“…Among them, PDT is a method of inducing cell death used primarily for treating various cancers, utilizing photosensitizers, light of a specific wavelength, and oxygen [8,9]. Various types of PDT have been developed and are being used to fight the growing problem of antimicrobial resistance or treat different cancers such as pancreatic tumors, skin cancer and head and neck cancer [10][11][12][13]. In PDT, the excited photosensitizer directly reacts with cellular substrates to produce free radicals and reactive oxygen species (ROS).…”

Porphyrin photosensitizer molecules as effective medicine candidates for photodynamic therapy: electronic structure information aided design

“…PDT is predicated on the generation of reactive oxygen species (ROS) to induce apoptosis in cancerous tissues [4] . The PDT process involves photosensitizers (PS), molecular oxygen, and light source [5] . Mechanistically, the effect occurs when appropriate energy is absorbed optically by PS, transiting from ground state (S 0 ) to the rst singlet excited state (S 1 ).…”