A Mini Review: Enhancement of Photodynamic therapy for Cancer Treatment

Abstract

Cancer touches more lives than our knowledge. In the past time, many researchers have focused on conventional treatments to cut off the effects of cancer rate[1]. The nature of tumors becomes extremely heterogeneous through cancer development, generating mixed inhabitants of cells characterized by diverse molecular features and varied responsivity to treatments. One of the enduring areas of both scientists and oncologists is to establish a structure for the comprehensive cure of cancer with a smaller amount of toxic contrary effect and better-quality of life for patients[2]. Photodynamic therapy is one of the well documented, modern, non-invasive, novel therapeutic techniques that deals with photosensitizers which is excited at an appropriate wavelength can produce reactive oxygen species which could destroy the nearby cancer cells thus restricting the growth of tumor tissues[3]. The photosensitizers, light wavelength, light intensity, site, depth of tumor tissue located from the surface and tissue oxygenation(i.e.,ROS- Reactive Oxygen Species)generation determines photodynamic therapy efficacies for a particular patient(Fig.1. describes the Jablonski diagram explaining the photophysical and photochemical mechanism of Photodynamic Therapy). The three main processes through which PDT causes tumor annihilation are as follows:-. (1) direct destruction of tumor cells, (2) causing damage to the tumor vasculature, construction of thrombus, succeeding tumor infarction, (3) stimulation of an immune response in contrast to the cancer cells[4]–[7].

In this current era, treatments are frequently evolving with fresh breakthroughs and discoveries but determining which grouping of therapies would go right is grave. The notion of enhancing photodynamic therapy through new combining channels was to overcome the hindrances which will play a novelty in treating malignant tumor cells. Numerous difficulties were faced while using the photosensitizers and light like:

• High Toxicity,
• Non-target specific,
• Less stability time,
• Low quantum yield,
• No integrative ability,
• Non-solubility in water,
• Particular light-wavelength,
• Less penetrating power,
• Low excitation states,
• Non-forgiving.

We aim to mix few photosensitizers and then will conjugate them with upconversion nanoparticles as the latter prevents the premature release of the former. When light a prime operator is shined of the appropriate wavelength, the nano-photosensitizers generate tissue oxygenation(i.e., ROS- Reactive Oxygen Species) due to high quantum yield eliciting cancer cell death. Our main objectives:

• Photodynamic therapy will be linked with other noble therapeutics.
• Use of natural agents.
• Low toxic photosensitizers.
• High quantum yield.
• Cost-effective.

Additionally, for the past short time period the glory and refinement of nano-medicines allowed to integrate the agents responsible for imaging, helps in delivery of modules of light. The accelerative usage of nano-medicines in photodynamic therapy in the current art state is carried out effectively in in-vitro and in-vivo research and also to show the outlook on the potentials and challenges of photodynamic therapy concerning successful conversion into enormous clinical applications[8](Table 1. describes the comprehensive data of completed clinical trials in PDT). PDT is synthesizing targeted delivery of photosensitizers at the site using small molecule drugs or antibodies or aptamers conjugated to the photosensitizers. Targeted therapeutics have also been superior to other conventional therapeutics since it has the ability to reduce the bystander effect and target specifically the tumor cells.