Size-based cytotoxicity of silver nanoparticles in bovine retinal endothelial cells

Biologically synthesised nanoparticles with distinct shapes and sizes have found tremendous breakthroughs and fondness in various fields of therapeutic and diagnostic applications. In this study, size-controlled green synthesis of silver nanoparticles (Ag-NPs) was performed using Bacillus licheniformis kk2 by response surface methodology. Among the various sizes of Ag-NPs synthesised, two sizes 22.4 and 42.5 nm were investigated for their size-dependent cellular cytotoxic effects in primary bovine retinal endothelial cells (BRECs) in vitro. The Ag-NPs affected the morphology of BRECs in a size-dependent manner over the treatment for 24 h. Further treatments of Ag-NPs induced a direct effect over the mitochondrial function associated with the generation of reactive oxygen species, caspase-3 activation and DNA fragmentation based on their size. In addition, the levels of biological antioxidants such as superoxide dismutase and glutathione were also greatly affected due to oxidative stresses which thereby led to the consequent induction of apoptosis in in vitro system. Hence, this study evidences the effective role of pH, temperature and silver nitrate concentration in influencing the size-based synthesis of Ag-NPs. The size-dependent cytotoxic effect of differently sized Ag-NPs in the retinal system supercharge their impending prospects in therapies for various retinal angiogenic disorders.