Molecular Design and Synthesis towards Functional Organic Materials for Fluorescent Chemosensor, Photodynamic Therapy, and Photothermal Therapy

Abstract

Jablonski diagram represents that a chromophore is excited from ground state to singlet excited states under light irradiation, there are three energy dissipation ways to be relaxed and they are usually: (1) fluorescence emission via radiative relaxation, (2) thermal deactivation via nonradiative relaxation, and (3) intersystem crossing (ISC) process to triplet excited states, sharing the phosphorescence emission and/or reactive oxygen species (ROS). In detail, (1) a fluorophore can emit fluorescence upon light excitation that has been applied in many fields such as fluorescent probe and chemosensor (CS), bioimaging, and organic light-emitting diodes (OLED). A fluorescent CS (FCS) system is connected by fluorophore and receptor via with or without linker and a mechanism for communication between two sites. (2) By using a relatively high-power laser, a photothermal agent (PTA) can produce heat, leading to destroy tumors in cancer photothermal therapy treatment irreversibly. (3) The ROS generation of photosensitizer (PS) can also damage proteins, nucleic acids, lipids, membranes, and organelles, inducing cell apoptosis to treat cancer, bacterial infections, and many other diseases. Thus, lots of chromophores have been developed for fluorescent chemosensors, photothermal therapy, and photodynamic therapy. However, they show several drawbacks such as poor water-solubility, short-wavelength light absorption, non-targeting organelle, and non-multimodal function. Furthermore, FCS or fluorophore moieties have shown relatively low signal-to-noise, selectivity, and fluorescence quantum yield (ՓF). Whereas PTA shows low photothermal conversion efficiency (η). Because of low ROS generation, using PSs are limited in the hypoxia condition. In order to solve these problems, thus studying and developing innovative organic materials for molecular recognition and cancer therapy treatment have been studied in recent years. Over three years, I studied, designed, synthesized, and developed innovative functional organic materials that utilize in fluorescent chemosensor (FCS), photodynamic therapy (PDT), and photothermal therapy (PTT) application, published in several reknown journals. Besides that, I performed review articles about innovative photosensitizers for PDT in Chemical Review, protein for nano theranostics platforms in Coordination Chemistry Review. Among them, I have shown insightful studies to introduce in this thesis, which includes PCDA-based chemosensor for cadmium cation and cysteamine detection in chapter I and II, hypochlorite-activated fluorescence emission and antibacterial activities of imidazole derivatives in chapter III, heavy-atom-free photosensitizers for hypoxia PDT and ClO- detection in chapter IV, and facile preparation of nano platforms for efficient highly photothermal treatment in chapter V.