Light-activated green drugs: How we can use them in photodynamic therapy and mass-produce them with biotechnological tools

Abstract

Photodynamic therapy (PDT) is a promising therapeutic approach to manage the resolution of cancer. Plants in nature are one of the potential sources for obtaining new photosensitizers (PSs) that are less toxic than synthetic compounds. Although several works have been done regarding PDT in the last decades, relatively minor attention has been paid to the study of extracts of medicinal plants called photoactivatable "green drugs''. The objective of the review was to identify common photoactive groups of PSs found in nature, mainly obtained from plants, analyzing their photochemical characteristics, and making a detailed botanical description of the plant groups from which they are obtained. In addition, biotechnological strategies in the cultivation of plant-based in vitro systems to produce natural PSs on a large scale are discussed. To accomplish it, the retrieval of potentially relevant studies was done by systematically searching scientific databases like Google Scholar and PubMed between the months of June–December of the year 2020. The main keywords used as search terms were related to plant-based photosensitizers, naturally occurring photosensitizers, phototoxins, plant cell cultures, hairy root cultures. Plant-based photoactivable compounds with an adequate botanical description of known and unknown plants used in PDT for the eradication of tumor cells are mandatory in the field of phytomedicine against cancer. On the other hand, potential PSs could be explored based on phototoxic plant species that were associated with photosensitization in animals and humans over time. The underlying principles of biotechnological processes for obtaining the secondary metabolites were addressed due to the need for new technologies to produce these potential pharmaceuticals drugs in an ecofriendly approach. The successes of plant-based PSs in PDT encourage researchers to work together with botanists to identify natural photoactive compounds from different plant species that remain to be identified or studied, and thus, they use them as alternatives for the synthesis of PSs with minimal side effects, low toxicity and greater selectivity in the different cancer treatments using PDT. Furthermore, novel biotechnology-based breeding techniques such as targeted genome editing methods will provide significant opportunities to produce natural products in plants, mainly when associated with the recent developments in scale-up capability and bioreactor design.