Advances in Gold Nanoparticles: Synthesis, Functionalization Strategies, and Theranostic Applications in Cancer

Cancer is among the leading causes of mortality and morbidity in the world. Metallic nanoparticles, especially gold nanoparticles (AuNPs) have emerged to be attractive systems to circumvent the associated adverse effects. By the virtue of their unique properties of tunable size, shape, composition, optical properties, biocompatibility, minimal toxicity, multivalency, fluorescence-luminescence property and surface plasmon resonance; AuNPs have the potential to be used as drug delivery systems. It is vital to ensure that the drug reaches the target site of action for selective kill of cancer cells without harm to healthy cells. These AuNPs can be easily functionalized with a wide array of ligands like peptides, oligonucleotides, polymers, carbohydrates for active targeting to ensure site specific delivery and reduced systemic effects. AuNPs have been in-vestigated as carriers for gene delivery, drug delivery with or without photothermal therapy, in diagnosis based on radiation or spectroscopy. They have emerged as attractive theranostic approach in the overall management of cancer with superior benefit to risk features. In this review, we have discussed synthesis of different AuNPs (nanorods, spherical nanoparticles, and hollow AuNPs), their functionalization strategies and their applications in biomedical domain. Various research studies and clinical trials on application of AuNPs in diagnosis and therapeutics are highlighted.