Evaluation of effect of gold nanorods and spherical gold nanoparticles of different sizes on X-ray attenuation in computed tomography

Introduction: To date, gold nanoparticles (GNPs) have been demonstrated to have great potential as contrast agent for CT imaging and therapeutics. This study was designed to evaluate any effect on X-ray attenuation that might result from using GNPs with a variety of size, surface chemistries and shapes.   Materials and Methods: Spherical GNPs and gold nanorods (GNRs) were synthesized for CT imaging application. X-ray attenuation was quantified by Hounsfield unit (HU) in CT. Transmission electron microscopy (TEM) was performed to investigate morphology and size of the GNPs. The concentrations of GNPs in μg/ml were measured by the inductively coupled plasma optical emission spectrometry (ICP-OES). Chemical component was also determined by a Raman Spectrometer. Results: Our results indicated that smaller spherical GNPs (13 nm) had higher X-ray attenuation than larger ones (60 nm) and GNRs with larger aspect ratio exhibited great effect on X-ray attenuation. Moreover, poly ethylene glycol (PEG) coating on GNRs declined X-ray attenuation as a result of limiting the aggregation of GNRs. Overall, smaller spherical GNPs can be suggested as a better alternative to conventional contrast agent (ie; Omnipaque) , for CT imaging. Conclusion: The X-ray attenuation and the ease of the surface functionalization, make GNPs promising multifunctional probes for simultaneous imaging and drug or gene delivery applications. Size, morphology, concentration and surface of GNPs can effect on X-ray attenuation.