Understanding the effect of phytochemical coated silver nanoparticles on mammalian cells and the protein interactions with the surface corona of these nanoparticles.

Silver nanoparticles (AgNPs) are currently the most common nanomaterial in commercial products; however, there is insufficient evidence on the long term toxicity of AgNPs on mammalian cells. There is also no information on the extent to which the surface coating on the AgNPs influences the toxic effects produced in cells. Yet another area lacking information is the impact the surface coating might have on the interaction of these AgNPs with proteins found in blood serum, which would be useful information if these AgNPs are to be used for medical purposes. To shed light on these aspects, this project used silver nanoparticles (AgNPs) synthesised with bi- and polyphenolic compounds viz. curcumin (cur) and epigallocatechin gallate (EGCG), phytochemicals from turmeric and green tea, respectively to study the effects on cancer cells and on the interaction with human serum albumin (HSA). L-Tyrosine (tyr), a monophenolic amino acid was used as a control since it is found in all organisms and is non-toxic.

The results of this project suggest that the phytochemical coating on the AgNPs can work synergistically with the silver ions generated from the AgNPs to cause toxicity. It also provided an understanding of the residual effects AgNPs can have on mammalian cells even after only 24h of exposure. The results further suggest that the concentration of the phytochemicals on the AgNPs can affect the mechanism of action of these AgNPs. For example, the CurAgNPs which acted as pro-oxidant agents in the cells and caused an increase in ROS levels and cell adhesion and migration, possibly due to the low quantity of curcumin on the surface. Hence these CurAgNPs would be unsuitable as anticancer agents, however they would be useful for other applications such as wound healing. With regards to the interaction of these AgNPs with HSA, once again the surface coating plays a role in dictating the extent to which the interaction occurs. The CurAgNPs showed the greatest interaction with serum proteins, while EGCGAgNPs were capable of increasing the α-helix of HSA. These results suggest that the surface coating on the AgNPs could possibly be the determining factor when deciding the purpose for which the AgNPs will be used.