Metallic nanoparticles in cancer: Types, green synthesis, applications, tumor microenvironment and toxicity considerations

Despite decades of research in the field, treating cancer remains a challenge for clinicians. A new hope is metallic nanoparticles (MNs), which are not only gaining interest from academia, but are also being considered as part of many pharma companies' research and development activities. The objective of the present review is to provide state of the art information about MNs and associated anticancer properties employed in the treatment of cancer. We covered numerous noble and non-noble MNs reported to treat variety of cancer with promising outcomes during laboratory settings such as titanium dioxide (TiO2), silicon dioxide (SiO2) zinc oxide (ZnO), aluminium hydroxides Al (OH)3 and aluminium oxo-hydroxides AlO (OH), iron oxide (Fe2O3), cerium dioxide (CeO2), calcium phosphate (Ca3(PO4)2), calcium carbonate (CaCO3), zirconium dioxide (ZrO2), barium titanate (BaTiO₃), barium sulphate (BaSO4), gold (Au) and silver (Ag). Additionally, the effect of tumour microenvironment on the performance of MNs is discussed. The review also covered the toxicity associated with the use of MNs, current patent status and future prospects.