Eco-Friendly Synthesis of Copper Oxide Nanoparticles Using Geranium Pelargonium x hortorum Leaf Extract and Its Biological Applications

<b>Background/Objectives</b>: The main objective of this study is to report the green synthesis of copper oxide nanoparticles (CuONPs) using an aqueous extract from <i>Pelargonium</i> x <i>hortorum</i> (<i>P. hortorum</i>) leaves. It also aims to evaluate its biological activity as well as assess its cytotoxic effects on human gingival fibroblasts (HGFs). <b>Methods</b>: Copper oxide nanoparticles (CuONPs) were synthesized through chemical precipitation using an aqueous extract from <i>P. hortorum</i> leaves. These CuONPs were characterized with various techniques, including UV-Vis, Fourier transform infrared (FT-IR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). <b>Results</b>: The UV-Vis spectrum showed a characteristic absorption peak for CuONPs. FT-IR spectroscopy identified alkoxide and aromatic groups associated with flavonoids and phenolic compounds from <i>P. hortorum</i>. The Cu-O bond was also observed in the same analysis. XRD confirmed that the CuONPs had a monoclinic CuO structure and XPS revealed copper was in the Cu (II) oxidation state bonded to oxygen, consistent with CuO. The nanoparticles were spherical with an average size of 40-53 nm as shown by TEM. The biological activities of CuONPs were tested against <i>Streptococcus mutans</i> (<i>S. mutans</i>) and <i>Candida albicans</i> (<i>C. albicans</i>). The minimum inhibitory concentration (MIC) was 20 µg/mL. Cytotoxicity tests on human gingival fibroblasts (HGFs) after 24 h showed a non-linear, dose-dependent cell viability profile, indicating CuONPs did not exhibit cytotoxicity within the tested range and could even promote cell proliferation at low and intermediate concentrations. <b>Conclusions</b>: This study successfully synthesized CuONPs via a green method, highlighting its potential as a biocompatible antimicrobial and antifungal agent.