Growing tool–kit of photosensitizers for clinical and non–clinical applications

Photosensitizers are photosensitive molecules utilized in clinical and non-clinical applications by taking advantage of light-mediated reactive oxygen generation, which triggers local and systemic cellular toxicity. Photosensitizers used for diverse biological applications such as spatio-temporal inactivation of a protein in a living system by chromophore assisted light inactivation, localized cell photoablation, photodynamic and immuno-photodynamic therapy, and correlative light-electron microscopy imaging. Substantial effort has been made to develop several genetically encoded, chemically synthesized, and nanotechnologically driven photosensitizers for successful implementation in redox biology applications. Genetically encoded photosensitizers (GEPSs) or reactive oxygen species (ROS) generating proteins have the advantage of using them in the living system since they can be manipulated by genetic engineering with a variety of target-specific genes for precise spatio-temporal control of ROS generation. The GEPS pellet is limited but expanding with a variety of newly emerging GEPS proteins. Apart from GEPS, a large pellet of chemical and nanotechnologically empowered photosensitizers developed with a major focus on photodynamic therapy based cancer treatment alone or in combination with pre-existing treatment methods. Recently, immuno-photodynamic therapy has emerged as an effective cancer treatment method using smartly designed photosensitizers to initiate and engage the patient’s immune system to empower the photosensitizers effect. In this review, we discussed various types of photosensitizers, their clinical and non-clinical applications and implementation toward intelligent efficacy, ROS efficiency, and target specificity in biological system.