Photodynamic Cancer Therapy: Organic Photosensitizers and Reactive Oxygen Species

Photodynamic therapy (PDT), as an alternative non-invasive strategy for radiotherapy and chemotherapy, relies on photosensitizers (PSs) to induce the reactive oxygen species (ROS) that combat cancer cells. PDT has been extensively investigated through various nanomaterials for cancer treatments due to its non-invasive nature, precise spatial operation, high selectivity, safety, low toxicity, and minimal recurrence with minimum side effects. The main factor for the success of PDT is PSs that generate ROS to eliminate cancer cells upon the absorption of light. For smart treatments, some bio and small molecule drugs can be conjugated with nanomaterials and nano-vectors in order to achieve more stability, low toxicity, and good biocompatibility with better targeting capability; for instance, PSs with excellent ROS generation efficiency using PDT-inert molecules in conjunction with porous covalent organic frameworks (COFs). Another option is the physical overlap of the hydrophobic anticancer drug doxorubicin (DOX), which has shown a great potential for advanced photodynamic therapy, with micelles and COFs as dual drug carriers. Despite the above challenges, it seems that COF-based nanomedicine cancer therapy will become a new growth area in the field of PDT cancer treatment and needs systematic research studies. Gaps and challenges remain, notably that COF-based nanomaterials in cancer therapy are still in their early stages. The clinical application of efficient molecular PSs is largely limited by the frontier orbital requirements and their low biocompatibility, poor oxygenation, hydrophobicity, and poor photostability within PDT environment and low cell/tissue specificity and undesirable aggregation in tumors, leading to a low efficiency of ROS generation. Unfortunately, light-responsive micelle systems have been developed by incorporating photochromic moieties into their structure, most of which are toxic. In addition, multiphoton excitation requires very high laser power or strong UV rays and light. Moreover, these systems are mostly based on non-degradable polymer compositions that are limited in biocompatibility or too bulky to easily enter the cell.

Special Issue topics of interest: The following topics are expected for this section:

New generation of PSs to improve efficient photodynamic anti-tumor/cancer therapy;

AIE PSs from the perspectives of anti-bacterial, anti-fungal and anti-viral aspects and anti-cancer;

Two-dimensional carbon-based nanocarriers for drug delivery systems;

Optoelectronic properties and quantum mechanics studies of photosensitive conjugated organic small molecules, efficient for solar cells;

Molecular dynamics simulation of nanocarrier/multifunctional small molecules for the adsorption and co-loading of drugs from aqueous solutions for synergistic multi-therapy of cancer;

COF-based nanomaterials in PDT and/or drug delivery systems and combinational therapy;

COF-based photosensitizers efficient for nano-energy, nano-bio-energy, and solar bio-cells

 Artificial intelligence systems for the above challenges.

Dr. Abbas Amini
Guest Editor

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• photodynamic therapy
• reactive oxygen species
• photocatalyst
• cancer therapy
• photosensitizer
• nanocarriers
• aggregation-induced emission
• covalent organic frameworks
• solar cells
• drug delivery system