Advances in photosensitizer-related design for photodynamic therapy

Abstract

Photodynamic therapy (PDT) is highly effective in treating tumors located near body surface, offering strong tumor suppression and low damage to normal tissue nearby. PDT is also effective for treating a number of other conditions. PDT not only provide a precise and selective method for the treatment of various diseases by itself, it can also be used in combination with other traditional therapies. Because PDT uses light as the unique targeting mechanism, it has simpler and more direct targeting capability than traditional therapies. The core material of a PDT system is the photosensitizer which converts light energy to therapeutic factors/substances. Different photosensitizers have their distinct characteristics, leading to different advantages and disadvantages. These could be enhanced or compensated by using proper PDT system. Therefore, the selected type of photosensitizer would heavily influence the overall design of a PDT system. In this article, we evaluated major types of inorganic and organic PDT photosensitizers, and discussed future research directions in the field.

Zinc(II) Sulfanyltribenzoporphyrazines with Bulky Peripheral Substituents—Synthesis, Photophysical Characterization, and Potential Photocytotoxicity

“…It was found by Gierszewski et al [38] that porphyrazines with eight peripheral isophtaloxyalkylsulfanyl substituents generate singlet oxygen with Φ ∆ values between 0.01 and 0.04 in DMF and that incorporating Mg 2+ ions into the Pzs improves their capability to generate single oxygen. The exchange of Mg 2+ (3,6) to Zn 2 (4, 7) in the tribenzoporphyrazine ring influenced the singlet oxygen generation quantum yield values, which increased from 0.05 (3) to 0.24 (4) and from 0.20 (6) to 0.59 (7). In Figures 7 and 8, the Q-bands of 6 and 7 demonstrate only minimal to no changes during irradiation, thus indicating their good stability during measurements.…”

“…Metal-free Pz derivative 5 (92 mg, 0.075 mmol), N,N-dimethylformamide (DMF, 25 mL), and zinc(II) acetate (41 mg, 0.225 mmol) were stirred in a round-bottomed flask under inert gas at 70 • C for 24 h. After that, the solvent was evaporated, and the residual blue oil was subjected to column chromatography (dichloromethane/methanol 50:1 then 20:1), leading to a cerulean blue product 6 (79 mg, 71% yield). R f = 0.71 (dichloromethane/methanol, 20:1, v/v (7) Lithium aluminum hydride (13 mg, 0.353 mmol) was suspended in tetrahydrofuran (THF) precooled to 0 • C and stirred for 30 min. Porphyrazine derivative 6 (95 mg, 0.074 mmol) was dissolved in THF (14 mL), and the solution was added dropwise to the reaction mixture over 40 min.…”

“…The absorption of light in the range of 650-850 nm, which is often described as the phototherapeutic window, as well as the generation of reactive oxygen species in the photodynamic reaction, make Pzs especially relevant for medical applications, in particular photodynamic therapy (PDT) [6]. The PDT principle is based on the photodynamic reaction, which starts from the exposure of the photosensitizer to light of an appropriate wavelength [7]. Upon irradiation, the photosensitizer situated in a specific tumor tissue is activated from the ground singlet state to the first excited state and next, by the chain of transitions, to the triplet state.…”

Tissue Engineering and Photodynamic Therapy: A New Frontier of Science for Clinical Application -An Up-To-Date Review

“…Has been carried out by combining second-generation photosensitizers with receptor molecules to the desired target, such as proteins or lipoproteins that are used by pathogenic cells for their proliferation, monoclonal antibodies targeting a specific antigen of the target cell, surface markers such as, growth factors, hormones, or transferrin receptors ( Muehlmann et al, 2014 ; Zhang et al, 2018 ). These strategies allow greater delivery of the photosensitizer to the target tissue, that is, greater selectivity, which improves the effectiveness of PDT, in addition to decreasing the doses needed for desired therapeutic responses ( Calixto et al, 2016 ; Zhou et al, 2021 ).…”

Modified Titanium Dioxide as a Potential Visible-Light-Activated Photosensitizer for Bladder Cancer Treatment

“…Still, some studies have also demonstrated that inorganic PS can be targeted to specific tissues, which represents a great advantage in its use for photodynamic therapy. 12 …”