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

Background/Objectives: The main objective of this study is to report the green synthesis of copper oxide nanoparticles (CuONPs) using an aqueous extract from Pelargonium x hortorum (P. hortorum) leaves. It also aims to evaluate its biological activity as well as assess its cytotoxic effects on human gingival fibroblasts (HGFs). Methods: Copper oxide nanoparticles (CuONPs) were synthesized through chemical precipitation using an aqueous extract from P. hortorum 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). Results: 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 P. hortorum. 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 Streptococcus mutans (S. mutans) and Candida albicans (C. albicans). 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. Conclusions: This study successfully synthesized CuONPs via a green method, highlighting its potential as a biocompatible antimicrobial and antifungal agent.