Size tunable gold nanoparticle and its characterization for labeling application in animal health

Aim: The aim of the present study was to synthesize different sizes of gold nanoparticles (GNPs) and their characterization for use as a label in lateral flow assay particular for the detection of bluetongue in small ruminants. Materials and Methods: Size controlled synthesis of GNPs was done by using different concentration of sodium citrate. In this study, five different types of GNP were synthesized by using trisodium citrate (Na3C6H5O72H2O) that reduces 20 mM concentration of gold solution (HAuCl4). These different types of GNPs were characterized in terms of morphology, size, shape and λmax by transmission electron microscopy and ultraviolet-visible spectroscopy respectively. Results: In the present work, it was found that the size of GNP mainly depends upon the concentration of sodium citrate. By use of 0.09375%, 0.1875%, 0.375%, 0.75% and 1.5% of sodium citrate solution, GNPs were synthesized. In our study, the size of GNP was found ranging from 25 nm to 230 nm. The size was found large with less concentration of sodium citrate (i.e. with 0.09735%) and small with large concentration of sodium citrate (1.5%) and λmax was found to be 450-530 nm in all size of GNP. Conclusions: The size of GNPs is mainly dependant on the concentration of trisodium citrate, gold salt concentration, optimum pH and temperature. The GNP synthesized by this method has been used as a label for the development of lateral flow assay against diagnosis of bluetongue disease in small ruminant.