A comparative study of economical separation and aggregation properties of biologically capped and thiol functionalized gold nanoparticles: Selecting the eco-friendly trojan horses for biological applications

• Economical synthesis of gold nanoparticles (GNPs) using A. indica and conventional citrate reduction method.
• Successful separation of GNPs using sucrose density gradient centrifugation and characterization.
• Studying efficiency of surface capping in biogenic and chemogenic GNPs toward stability under physiological conditions.
• Low flocculation parameter of biogenic GNPs proves it to be an ideal candidate to work in biological milieu.

We are presenting facile bio-fabrication of extremely stable gold nanoparticles (GNPs) using medicinal plant Azadirachta indica (commonly called Neem) and its comparison with most commonly used glutathione (GSH) protected GNPs in terms of stability under physiological conditions, seperation using density gradient centrifugation and aggregation properties in the solution. There was dual peak at 536 and 662 nm indicating the presence of non-spherical GNPs including triangles, rods and hexagons in case of A. indica mediated GNPs unlike citrate stabilized GNPs which exhibited single sharp peak. Spherical GNPs were separated from the consortium of uniquely shaped nanoparticles bio-fabricated using A. indica leaf extract using sucrose density gradient centrifugation (SDGC).To comprehend the anti-agglomeration potentials of A. indica leaf mediated GNPs and GSH-GNPs under physiological conditions, flocculation parameters (FP) were calculated and found to be least for A. indica leaf mediated GNPs, indicating their exceptional stability.

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