Metallic nanoentities: Bio-engineered silver, gold, and silver/gold bimetallic nanoparticles for biomedical applications

This present study reports the biogenic synthesis of silver nanoparticles (AgNPs), gold nanoparticles (AuNPs) and Ag/Au bimetallic nanoparticles (BNPs) using bark extract of plant <i>Tamarix aphylla</i> (T.A). The bark extract contained total polyphenolic compounds and total flavonoids as 0.0362 mg/mg and 0.2928 mg/mg of the dried bark extract respectively. Silver nitrate (AgNO₃) and hydrogen tetra chloroaurate trihydrate (HAuCl₄.3H₂O) were used as precursors while deionised water and methanol (CH₃OH) were used as solvents. Synthesized nanoparticles were characterized through UV-visible spectroscopy, SEM (scanning electron microscopy), TEM (transmission electron microscopy) and FTIR (Fourier transform infrared) for their morphology, structure, and identification of different functional groups. The UV-visible spectra of AgNPs, AuNPs and Ag/Au BNPs showed peaks at 436, 532 and 527 nm respectively due to the excitation of Surface Plasmon Resonance. SEM and TEM images showed spherical and well distributed nanoparticles (NPs) with particle size as 29 nm (AgNPs), 13 nm (AuNPs) and 26 nm (Ag/Au BNPs). The synthesized NPs are significantly active against inhibition of free radicals, α-amylase, α-glucosidase and have anti inflammatory potential with AgNPs having the highest percent activity at 400 μg/ml, followed by Ag/Au BNPs. The same trend (AgNPs > Ag/AuBNPs > AuNPs) has been observed at all concentrations i.e. 100 μg/ml, 200 μg/ml and 400 μg/ml. AuNPs have shown lowest activity at all concentrations. So the current study strongly confirms use of T.A bark extract as reducing agent for synthesis of metal NPs and opens up a new possibility of using these green synthesized NPs as biomedicines. We also suggest further <i>in vivo</i> investigation to report any side effects if present.