Metallic nanoparticles as X-Ray computed tomography (CT) contrast agents: A review

X-ray computed tomography vastly used in both medical purposes and in the research of biological and non-biological materials/samples. Some of the medical applications performed in the clinics requires special protocols where contrast agents may be needed to enhance the contrast. Iodine based contrast agents are commonly used in such applications. Iodine based contrast agents were found hazardous to the environment and some patients has iodine in tolerance due to thyroid origin diseases. Scientists from different fields try to develop contrast agents which can be an alternative to iodine based contrast agents. Metallic nanoparticles have potential to be used as CT contrast agent since metals has high X-ray attenuation and high density. Metal nanoparticles considered as toxic to the living organisms. Covering nanoparticles with organic molecule often reduce toxicity and enhance the biocompatibility. Decoration of nanoparticles with function groups give them targeting properties where special organ and/or tissue can be targeted. Up to now, different studies illustrated the importance of the multipurpose properties of the metallic nanoparticles. In this report, we assessed the metal nanoparticles reported as X-ray computed tomography contrast agent. For the first time in the literature we listed in vivo contrast enhancement, targeted drug delivery and dual/multipurpose imaging properties of each metallic nanoparticles. Therapeutic effects of metallic nanoparticles such as photothermal therapy and magnetic hyperthermia were also addressed. A chart showing relative contrast enhancement properties of the nanoparticles were produced.