We demonstrate facile and green synthesis of gold deposited zein nanoshells (AuZNS) using environmental benign solvent ethanol. Water soluble glycol chitosan is used for stabilization as well as for cationic functionalization of zein nanoparticles. Gold deposition is performed via ex-situ method at ambient conditions. AuZNS is of size around 100 nm and shows high inertness and biocompatibility even at double the therapeutic dosage. The absorbance is tuned at 808 nm for imaging-guided plasmonic photothermal therapy of cancer. Highly effective killing of cancer cells irrespective of their chemorefractory status is noticed at a very low therapeutic dosage of 25 μg and 5 min of biologically acceptable (500 mW) 808 nm laser irradiation. AuZNS also exhibit better X-ray attenuation in comparison to the commercially available iodine based contrast agent. © 2018 Elsevier B.V.