Green synthesis and characterization of Ag nanoparticles from Mangifera indica leaves for dental restoration and antibacterial applications

Abstract

Green synthesis has gained a wide recognition as clean synthesis technique in the recent years. In the present investigation, silver nanoparticles were prepared by a novel green synthesis technique using Mangifera indica (Mango leaves) and found to be successfully used in dental applications. The prepared samples were spectroscopically characterized by XRD, PSA, SEM with EDS, and UV-Vis spectroscopy. The crystalline size and lattice strain were analyzed from the XRD data which were counter-verified by W-H plots and particle size analyzer. The XRD peaks revealed that average crystalline size of the as-synthesized Ag nanoparticles was of 32.4 nm with face-centered cubic structure. This was counter-verified by particle size analyzer and Williamson-Hall plots and found to be 31.7 and 33.21 nm in the former and latter, and the crystalline size of Ag NPs could be concluded as 32 ± 2 nm. The morphological structure of the prepared sample was studied through SEM images and the chemical composition was analyzed by the EDS data. The band energy was calculated as 393 nm from UV-Vis, which confirmed the synthesized sample as Ag nanoparticles. To improve the mechanical bonding and hardness of the dentally used glass ionomer cement (GIC), the synthesized silver nanoparticles were incorporated into GIC in 2% weight ratio. The morphology of the prepared specimens was studied using optical microscope images. Vickers microhardness and Monsanto hardness tests were performed on GIC, GIC reinforced with microsilver particles and GIC reinforced with nanosilver particles and the latter derived a promising results. The results of the Monsanto tests confirmed the increase in hardness of the GIC reinforced with AgNps as 14.2 kg/cm² compared to conventional GIC and GIC reinforced with silver microparticle as 11.7 and 9.5 kg/cm². Similarly the Vickers hardness results exhibited the enhanced hardness of GIC-reinforced AgNps as 82 VHN compared to GIC as 54 and GIC-reinforced silver microparticles as 61 VHN. The antibacterial activity of AgNPs was tested by a well-diffusion method on Escherichia coli and Staphylococcus aureus bacteria, and the obtained results exhibited a promising antibacterial activity of the as-synthesized nanoparticles.

Keywords: Antibacterial activity; Ionomer cement; Monsanto hardness; Silver nanoparticles; Vickers hardness.

Fig. 1

Escherichia coli Petri plates with Ag nanoparticles at different concentrations

Fig. 2

Particle size analyzer graph of Ag nanoparticles

Fig. 3

X-ray diffraction patterns of Ag nanoparticles

Fig. 4

Williamson–Hall plot of Ag nanoparticles

Fig. 5

SEM images of Ag nanoparticles

Fig. 6

EDS pattern of Ag nanoparticles

Fig. 7

UV–Vis spectra of Ag nanoparticles

Fig. 8

a–c Microscopic images of GIC, GIC-reinforced silver microparticles and GIC-reinforced silver nanoparticles

Fig. 9

Graph comparing the average results of Monsanto and Vickers hardness tests

Fig. 10

Antimicrobial activity of Ag nanoparticles at different concentrations against Escherichia coli and Staphylococcus aureus

Fig. 11

Zone of inhibition (mm) shown by AgNPs at different concentration