In vitro antiplatelet activity of silver nanoparticles synthesized using the microorganism Gluconobacter roseus: an AFM-based study

In this work, the synthesis of silver nanoparticles (AgNPs) from Gluconobacter roseus, their characterization and their antiplatelet activity has been described. Gluconobacter roseus, an electrochemically active bacterium, mediates the synthesis of silver nanoparticles in the solution containing AgNO3 as a precursor and sorbitol as an electron donor. The bacteria act as a whole-cell biocatalyst to oxidise the sorbitol substrate and produce electrons for the reduction of Ag+ ions. The detailed characterization of the purified nanoparticles was carried out using UV-vis spectroscopy, EDAX (Energy dispersive X-ray spectroscopy), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared Spectroscopy (FTIR). From the analysis of the UV-vis spectroscopy and EDAX, the formation of AgNPs was confirmed. The average particle size was found out to be 10 nm using TEM. FTIR results indicated the presence of amide groups which might be involved in stabilizing the nanoparticles. After the detailed characterization, the antiplatelet activity of synthesized AgNPs was investigated using aggregation assay and spreading studies. The AgNPs showed dose-dependent antiplatelet activity against ADP-induced activation of the blood platelets. AgNPs significantly decreased the aggregation by up to 87%. Spreading studies were made using Atomic Force Microscopy (AFM). Lactate dehydrogenase (LDH) assay was performed to check the cytotoxicity of the nanoparticles and interestingly the nanoparticles do not confer toxicity to the platelets. AFM is presented as a new method to assess the relative amounts of antiplatelet activity.