Biosynthesis of phyto-functionalized silver nanoparticles using olive fruit extract and evaluation of their antibacterial and antioxidant properties

Abstract

The green synthesis of nanomaterials is of utmost interest as it offers an eco-friendly approach over chemical synthetic routes. However, the reported biosynthesis methods are often time-consuming and require heating or mechanical stirring. The current study reports a facile one-pot biosynthesis of silver nanoparticles (AgNPs) mediated by olive fruit extract (OFE) and sunlight irradiation of only 20 s. OFE acts as both a reducing and a capping agent for the formation of OFE-capped AgNPs (AgNPs@OFE). The as-synthesized NPs were systematically characterized by UV-vis spectrometry, Fourier transform infrared (FTIR) spectroscopy, scanning electrochemical microscopy with energy-dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), dynamic light scattering (DLS), and cyclic voltammetry. SEM images confirmed the successful formation of monodispersed spherical AgNPs@OFE of approximately 77 nm. FTIR spectroscopy suggested the involvement of functional groups of phytochemicals from the OFE in the capping and reduction of Ag+ to Ag. The particles revealed excellent colloidal stability as evidenced from the high zeta potential (ZP) value (−40 mV). Interestingly, using the disk diffusion method, AgNPs@OFE revealed higher inhibition efficiency against Gram-negative bacteria (Escherichia coli, Klebsiella oxytoca, and extensively drug-resistant (XDR) Salmonella typhi) than Gram-positive bacteria (Staphylococcus aureus), with Escherichia coli showing the highest inhibition zone of 27 mm. In addition, AgNPs@OFE exhibited maximum potent antioxidant scavenging potential against H2O2, followed by DPPH, O2−, and OH− free radicals. Overall, OFE can be considered an effective source for the sustainable production of stable AgNPs with potential antioxidant and antibacterial activities for biomedical applications.

A highly selective Hg2+ colorimetric sensor and antimicrobial agent based on green synthesized silver nanoparticles using Equisetum diffusum extract

“…The mechanism of the formation of AgNPs using plant extract includes reduction, nucleation and growth steps, as described in detail in our previous work. 13 These results agree with our previous work on sunlight-mediated synthesis of AgNPs. 12,13 Hence, only a few tens of seconds of sunlight irradiations were needed to synthesize AgNPs via a simple, sustainable and cost-effective synthetic route, rendering our approach favourable over other classical chemical reduction or vapor deposition methods.…”

“…04-0783). 13,35 This pattern, therefore, confirms that the AgNPs formed via the reduction of Ag + by ED extract have crystalline nature. A few additional sharp peaks, marked with asterisks in the XRD pattern, were observed.…”

“…30 The peaks at 1622 or 1614 cm −1 for both samples could be assigned to N–H amide bending, CO stretching vibration or the stretching of aromatic rings. 13,31 The bands recorded at 1085 and 1112 cm −1 for ED and ED-AgNPs, respectively, mostly correspond to C–N stretching of aliphatic amine. 30 The bands at 1381 and 1413 cm −1 for the two materials could be assigned to C–N of an amine group or C–O of phenol.…”

“…The most common antibacterial mechanism of AgNPs was described in our previous work. 13 Briefly, the mechanism involves the adsorption of the NPs onto the surface of the bacteria, followed by their entry into the bacterial cell due to their small size. AgNPs can disrupt the bacterial membrane and create holes in it.…”

“…This green approach avoids the use of hazardous chemicals and instead exploits the reducing and stabilizing capabilities of bioactive compounds present in plants, that are normally discarded in the trash. 13–15 Various plant extracts with different compositions and phytochemical profiles, such as those from Olea europaea L., 13 Pistacia atlantica , 16 Citrullus lanatus , 17 Myrsine africana leaf 18 and Spilanthes acmella leaf 19 have been reported for the synthesis of Ag NPs. The use of biosynthesized Ag NPs as sensing probes for heavy metal ions such as Hg 2+ and Cu 2+ has gained enormous interest in the last decade.…”