Sono-Biosynthesis and Characterization of AuNPs from Danube Delta Nymphaea alba Root Extracts and Their Biological Properties

Abstract

Root extracts from Danube <i>Delta Nymphaea alba</i> were used to prepare gold nanoparticles (AuNPR_n) by reducing HAuCl₄ at different pHs (6.4-8.4) using ultrasonic irradiation: an easy, cheap, eco-friendly and green approach. Their antibacterial and anticancer activities were evaluated against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i>, and A2780 ovarian cancer cells, respectively. The AuNPR_n were characterized concerning their phytoconstituents (polyphenols, flavonoids and condensed tannins) and gold content. All of the nanoparticles were negatively charged. AuNPR_n exhibited a hydrodynamic size distribution ranging from 32 nm to 280 nm, with the larger nanoparticles being obtained with an Au/root extract ratio of 0.56, pH 7 and 10 min of sonication (AuNPR₁), whereas the smallest were obtained with an Au/root extract ratio of 0.24, pH 7.8 and 40 min of sonication (AuNPR₄). The TEM/SEM images showed that the AuNPR_n had different shapes. The ATR-FTIR indicated that AuNPRn interact mainly with hydroxyl groups present in the polyphenol compounds, which also confirm their high antioxidant capacity, except for AuNPR₂ obtained at pH 6.4. Among the AuNPR_n, the smallest ones exhibited enhanced antimicrobial and anticancer activities.