In vivo studies in rats exposed to aerosols of GNPs revealed that the NPs were rapidly taken into the system with the highest accumulation in the lungs, aorta, esophagus and olfactory bulb . Moreover, particles of nano-dimension are believed to be more biologically reactive than their bulk counter parts due to their small size and larger surface area to volume ratio [1, 2].
Gold in its bulk form has long been considered an inert, noble metal with some therapeutic and even medicinal value hence GNPs are thought also to be relatively non-cytotoxic . Yet there are differing reports of the extent of the toxic nature of these particles owing to the different modifications of the GNPs, surface functional attachments and shape and diameter size of the nanospheres [4, 5]. Moreover, the metallic nature of the metal derived NPs and the presence of transition metals encourages the production of reactive oxygen species (ROS) leading to oxidative stress [6, 7].
Although some scientists consider NPs as nontoxic, other studies reporting the toxic effects induced by NPs [8–10]. Although some NPs may appear to be nontoxic, other cellular mechanisms such as cell signaling and other normal cellular functions may be disrupted and are currently undergoing further investigation [11, 12]. The toxicity of NPs is being addressed by a number of standardized approaches with in vitro, in vivo as well as detailed genomic or biodistribution studies .
It has been shown that NPs may produce in vitro toxicity in some cell-based assays, but not in others. This may be a result of interference with the chemical probes, differences in the innate response of particular cell types, or other factors . In addition, GNPs are used as carriers for the delivery of drugs and genes .
The histological and the histochemical characterization in the hepatic tissues due to GNPs have not yet been identified and documented. In the present study, an attempt has been made to characterize the possible histological alterations in the hepatic tissues following intraperitoneal administration of GNPs and, if so, whether are related to the size of these NPs and the time of exposure.
The present study was carried out to investigate the particle-size effect of GNPs on the hepatic tissue in an attempt to cover and understand the toxicity and potential threat of their therapeutic and diagnostic use in relation with the time of exposure.