ANALYSIS OF THE BIOLOGICAL EFFECT OF GOLD NANOPARTICLES REDUCED WITH PUNICA GRANATUM L. EXTRACT ON ESCHERICHIA COLI ATCC (25922)
Name: LETICIA MIRANDA CESARIO
Publication date: 06/10/2023
Examining board:
Name |
Role |
|---|---|
| MARCO CESAR CUNEGUNDES GUIMARAES | Advisor |
Summary: The rise in antimicrobial resistance has become a critical public health concern, requiring new
approaches to face pathogens. Gold nanoparticles (AuNPs) are deemed promising in the fight
against pathogenic biofilms due to their unique physicochemical characteristics, which can be
tailored for specific purposes. In the present study, we employed the green synthesis of
AuNPs, using pomegranate peel extract (Punica granatum L.) as a reducing agent, due to its
antioxidant properties and the inherent non-toxicity of the method. For the synthesis of the
AuNPs, two techniques were employed: sodium citrate chemical reduction and the green
synthesis method using pomegranate extract. The nanoparticles were characterized through
spectroscopic and imaging techniques, such as UV-Vis, Raman spectroscopy, Fourier
Transform Infrared Spectroscopy (FTIR), Inductively Coupled Plasma Mass Spectrometry
(ICP-MS), Dynamic Light Scattering (DLS), and Transmission Electron Microscopy (TEM). The
phenolic compounds present in the extract and in the AuNPs were identified by HighPerformance Liquid Chromatography coupled to mass spectrometry (HPLC-MS). The success
of the AuNP synthesis was initially confirmed by the reddish hue of the resulting colloid and
the absorbance pattern in the UV-Vis spectra. Spectroscopic analyses showed the presence
of various organic compounds in the pomegranate peel, such as amino acids, phenols, ellagic
tannins, and gallic and ellagic acid esters, which participate in the stabilization of the AuNPs.
The gold concentration in the nanoparticles was 42.70 g/mL, while the concentration of
pomegranate extract present in the nanoparticles was 380 g/mL. The AuNPs exhibited a
hydrodynamic size in the range of 68.80 nm and a zeta potential of -16.4 mV, indicating stability
in aqueous solution. The EC50 value obtained through the DPPH assay proved that the
pomegranate extract has high antioxidant activity, greater than that of the Trolox standard. The
evaluation of antimicrobial activity was carried out on the Escherichia coli ATCC 25922 strain.
The highest concentration of gold nanoparticles with pomegranate extract (170.8 g/mL)
exhibited antimicrobial effect, which, although minimal, caused deformations in the bacterial
membrane. In conclusion, the study describes an eco-friendly synthesis of gold nanoparticles
using pomegranate extract, which exhibited high antioxidant potential. Although the AuNPs
showed limited antimicrobial properties, they emerge as promising candidates for biomedical
and nanotechnological applications, requiring additional studies to enhance their potential as
antibacterial agents.
