Arsenic and its various forms have been in use in ancient Chinese medicine for more than 2000 years. Arsenicals have gained importance for having remedial effects for various diseases from syphilis to cancer thus highlighting its role as a therapeutic agent even though it has been labelled as a potential 'poison'. The ability of arsenic, specifically arsenic trioxide, to treat acute promyelocytic leukaemia has radically changed the perception of this poison and has been the main factor for the re-emergence of this candidate to Western medicine for the treatment of leukaemia and other solid tumours. This review highlights the glorious history of arsenic and its various forms with major emphasis on arsenic trioxide as a therapeutic agent. The mechanism of action, pathogenesis, pharmacokinetic profile, safety concerns, ongoing clinical trials and various new forms of arsenic trioxide are discussed. The review also outlines the therapeutic ability of this drug, discusses the latest developments and recent investigations and potential advancement of arsenic trioxide as nanoformulations that has made it emerge as a potential remedial agent.

The anticancer properties of arsenic trioxide (As2O3) are accompanied by highly cytotoxic effects on normal cells. This necessitates developing modalities towards the targeted delivery of As2O3. Albumins, on account of their large structure and presence of several interacting groups, are ideal for encapsulating or carrying various drugs. In the present study, human serum albumin (HSA) was chosen as a coating agent to increase the biocompatibility of As2O3. An in situ chemical precipitation method was adopted for the synthesis of HSA-coated As2O3 nanoparticles (HSA-As2O3NPs) that were further characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), ultraviolet-visible (UV-vis) spectroscopy, inductively coupled plasma atomic emission spectrometry (ICP-AES), zeta potential and transmission electron microscopy (TEM). HSA-As2O3NPs were assessed for their biocompatibility using mouse fibroblast cells (NIH-3T3) and human dermal fibroblast (HDF) cells by a time- and dose-dependent cytocompatibility MTT assay. The safety of the HSA-As2O3 nanoparticles was assessed using haemolysis and blood cell aggregation studies. Molecular simulation studies provided evidence of interaction between HSA and As2O3. Herein, we report the development of a protein-based delivery system for As2O3 with improved biocompatibility.