Prospects in the use of gold nanoparticles as cancer theranostics and targeted drug delivery agents

Cancer is a dreadful disease and among the prominent causes of death worldwide. The major reasons for the high mortality rate among cancer patients are elevated toxicity, improper oral bioavailability, hydrophobicity, low therapeutic indices, inconsistent circulation, nonspecific biodistribution and inefficiency, and inability to deliver therapeutic agents only to the target sites without inducing adverse effects on healthy tissues and organs. All this has prompted researchers to identify new agents that can treat and/or diagnose cancer efficiently. Apart from this, site-specific drug delivery is an important area of research that is expected to increase the efficacy of the therapeutics and thereby reduce its potential side effects. Recent advances in nanotechnology have opened a new arena in the field of theranostics as well as targeted drug delivery. Considerable work has been done, which has led to the development of non-invasive, efficacious therapeutics and diagnostics modalities as well as a targeted cancer treatment by using nanoscale metallic particles like gold. These gold nanoparticles which are being used in these applications are solid colloidal particles with a 10-100 nm range of size, unique physiochemical and optical properties, a sub-cellular size, and biocompatibility; therefore, they have theranostic potential and could retain and transport a therapeutic agent that is dispersed in a polymer carrier matrix, encapsulated within a polymer shell, covalently attached or adsorbed to the particle surface, or encapsulated within a structure. The review discusses the synthesis, unique properties, and wide spectrum of roles that gold-derived nanoparticles can perform in cancer diagnosis, targeted drug delivery, and therapeutics. Further clinical trials involving gold nanoparticles and the list of technologies that have got patented in cancer treatment and diagnosis have also been discussed.