Green Synthesis of Zinc Oxide Nanoparticles and Their Application in Anticancer Drug Delivery - A Review

Metal and metal oxide nanoparticles have many promising applications in biomedicine and pharmacy. One of the applications that has been widely studied over the last decade is their use as anticancer drug carriers. This review fills a gap in the literature by concentrating exclusively on biosynthesized zinc oxide nanoparticles (ZnO NPs) for targeted anticancer drug delivery. ZnO NPs have been suggested as a feasible prospect, among other metal-based NPs, because of their unique properties and biocompatible nature. The use of ZnO NPs in drug delivery could reduce the dosage of drugs used for cancer treatment and reduce other side effects, by aiming the specific sites of cancer cells. Green methods of synthesis, with the use of natural products and living organisms, have become very popular in last decades due to their numerous advantages. They are not only eco-friendly and less expensive but they also allow to avoid the waste of energy and receive the NPs with well-defined size and morphology. The biosynthesized ZnO NPs have inherent advantages because they are made with the use of bioactive capping agents. Therefore, they show enhanced performance in drug delivery as they have improved stability, biocompatibility and targeting. This review includes a comparative analysis of synthesis methods and a comprehensive survey of their application as nanocarriers for various anticancer drugs. Their development faces several challenges related to synthesis, toxicity, scalability of the process, and limited understanding of the biochemical mechanisms involved in reduction and stabilization of metal ions through biological agents. Although biosynthesized ZnO NPs show a lot of potential as nanocarriers in laboratory conditions, their use in clinical trials is very challenging and requires collaboration between scientists, process engineers, clinicians and regulatory agencies. However, if these challenges are addressed and treated properly, their full commercial value and widespread applications will be enabled.