Silver nanoparticles biogenically synthesised using Maclurodendron porteri extract and their bioactivities

Abstract

Silver nanoparticle is widely used in various field including medical, cosmetic, food and industrial purposes due to their unique properties in electrical conductivity, thermal, and biological activities. In the medical field, silver nanoparticles (AgNPs) have been reported to have strong antimicrobial and cytotoxic activities. This study aimed to synthesize and characterize silver nanoparticles (AgNPs) using Maclurodendron porteri (MP) extract and to evaluate the antimicrobial and cytotoxic activities of the synthesised MP-AgNPs. Green method of Ultrasound Assisted Extraction (UAE) was used to extract the leaves of M. porter. Liquid Chromatography -Mass Spectrometry/Quadrupole time-of-flight (LC-MS/QTOF) was used to identify the compounds in the leaf extract of M. porteri. Characterisation of the synthesised nanoparticles involved ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FTIR), scanning electromagnetic microscopy (SEM), Zeta potential Analyzer and Particle Size Analyzer. The cytotoxic assay was conducted on MCF-7 and Caco-2 cell lines by MTT assay. Antimicrobial activity was tested on Gram-negative and Gram-positive bacteria using the disc diffusion method. Based on LC-MS/QTOF analysis, 430 compounds were found. The identified major compounds consist of amino acids, polyphenols, steroids, terpenoids and heterocyclic compounds which possibly act as reducing agents. 1 mM, 5 mM and 10 mM of silver nitrate solution were mixed with the leaf extract to form silver nanoparticles. 1.2 mg/ml of MP-AgNPs were found to have antibacterial activity against B. subtilis, S. aureus, E. coli, and P. aeruginosa with inhibitory zones of 8.0 ± 0.36 mm, 8.5 ± 0.45 mm, 7.5 ± 0.36 mm, and 9.0 ± 0.40 mm respectively. MP-AgNPs showed no cytotoxic activity against Caco-2 and MCF-7 cells. In conclusion, the presence of major amine compounds such as 10,11-dihydro-10,11-dihydroxyprotriptyline and harderoporphyrin in the extract facilitated the synthesis of AgNPs and the nanoparticle showed weak bioactivities in the assay conducted.

Keywords: Antibacterial activity; Cytotoxic activity; Green synthesis; Maclurodendron porteri; Silver nanoparticles.

Fig. 1

LC-MS Chromatogram of M. porteri extract. LC was run on a Agilent ZORBAX Eclipse Plus C18 Rapid Resolution HT column (2.1 mm × 100 mm × 1.8 μm, Agilent Technologies, SA, USA) at the temperature of 40 °C. The flow rate used was 0.25 mL/min with solvent A (0.1% formic acid in distilled water) and solvent B (0.1% formic acid in acetonitrile). The mass spectrometer was set to positive electrospray ionisation (ESI) mode with an optimal gas temperature of 325 °C, gas flow of 11 L/min, and nebulizer pressure of 35 psi.

Fig. 2

Yield of MP-AgNPs with different concentrations of AgNO₃ solution. Different concentration of AgNO₃ (1, 5 or 10 mM) was added to undergo the biogenic synthesis with the extract.

Fig. 3

Visual observation of MP-AgNPs formation. The reaction was observed at 1,2,6,8 and 24 h. The amount of synthesised AgNPs was monitored.

Fig. 4

UV–Vis spectra of MP-AgNPs at 1, 2, 6, 8 and 24 h. The wavelength range used between 350 and 800 nm.

Fig. 5

FTIR Spectra of M. porteri extract (A) and MP-AgNPs (B).

Fig. 6

SEM image of synthesised MP-AgNPs. The indicated size is 93.04 nm.

Fig. 7

(a) Size distribution of synthesised MP-AgNPs analysis using particle size analyzers. (b) Zeta potential distribution of synthesised MP-AgNPs using zetasizer.

Fig. 8

Antibacterial activity of MP-AgNPs, M. porteri extract and AgNO₃ against four bacterial strains. (S1: MP-AgNPs, S2: M. porteri extract, -ve: Negative control (Deionised water), +1: Positive control (Amoxicillin), and +2: Positive control (Streptomycin)).