Biomedical potential of silver nanoparticles biosynthesized using gallnut extract

The green synthesis of silver nanoparticles (AgNPs) is a good approach to avoiding the drawbacks associated with by-products formed in chemical synthesis. The present investigation was intended to synthesize AgNPs using gallnut extract as reducing agent and evaluate their potential biomedical applications. The ultraviolet-visible spectroscopy provided a preliminary indication of AgNP synthesis. Changing the pH of the reaction mixture from pH 3 to 10 revealed a significant impact of pH on the synthesis of AgNPs with the wavelength shift from red to blue. Transmission electron microscope characterizations showed that the synthesized AgNPs at pH 3-10 were spherical with average sizes of 51, 27, 18, 30, 10, 8, 5 and 4 nm. The synthesized AgNPs were further characterized by different techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy and powder X-ray diffraction. The AgNPs biosynthesized using gallnut extract showed higher antioxidant activity (81%) than AgNPs chemically synthesized using sodium borohydride (56%), indicating that AgNP-capping molecules such as tannic acid play an important role in antioxidant function. The biosynthesized AgNPs showed potent anticancer activity on four cervical cancer cell lines, namely, ME180, SiHa, HeLa and CaSki.