Antibacterial silver nanoparticles using different organs of Ficus deltoidea Jack var. kunstleri (King) Corner

Abstract

Biosynthesis of silver nanoparticles (AgNP) using plant extracts is considered as an advanced method of synthesising AgNP using the green method. Although the leaf and the root of Ficus deltoidea Jack var. kunstleri (King) Corner (Mas Cotek) are known to have medicinal benefits, the study on its organs (leaf, stem, fig and root) to synthesise AgNP is still scarce. Therefore, this study determined the optimal synthesising conditions for AgNP-Leaf, AgNP-Stem, AgNP-Fig, and AgNP-Root, involving the volumes of plant extracts (1.0, 1.0, 0.8 and 3.0 mL), reaction times (30, 21, 33 and 21 h), reaction temperatures (60, 90, 100 and 90 °C), and solution pH (10, 12, 10 and 12). Thermogravimetric analysis (TGA) discovered that AgNP-Stem had the highest organic decomposition. All biosynthesised AgNPs exhibited spherical and crystal structures, with the particle sizes in the order of AgNP-Root (15.4 ± 3.4 nm) < AgNP-Stem (20.5 ± 2.4 nm) < AgNP-Fig (21.3 ± 4.2 nm) < AgNP-Leaf (22.9 ± 4.3 nm), as measured by transmission electron microscope (TEM). Meanwhile, in the disc diffusion technique (DDT) and minimum inhibitory/bactericidal concentration (MIC/MBC) analyses, AgNP-Root exhibited more significant antibacterial activity against Escherichia coli (ATCC 11229) and Staphylococcus aureus (ATCC 6538) bacteria compared to other organs. Visible damage was found on the bacterial wall of S. aureus treated with AgNP-Stem when observed using field emission scanning electron microscopy (FESEM). Hence, the phytochemical compounds found in the F. deltoidea organs significantly influenced the characteristics of AgNP and subsequently impacted the antibacterial activity.