Phyto-capped CuO Nanoparticles with Enhanced Antimicrobial and Anticancer Efficacy Against MCF-7 Cell Line: A Green Nanotherapeutic Approach.

Aqueous leaf extract of Orthosiphon stamineus, a medicinal plant rich in phytoconstituents, served as a reducing and stabilizing agent for the green synthesis of copper oxide nanoparticles (CuO NPs). Qualitative analysis confirmed the presence of tannins, flavonoids, phenols, terpenoids, and alkaloids. The synthesized nanoparticle is characterized with DLS measurements, UV-vis, FT-IR spectroscopy, FE-SEM, TEM, XRD and EDX. The formation of nanoparticles was indicated by a visible colour change and characterized by a surface plasmon resonance peak at 459.82 nm using UV-visible spectroscopy. Dynamic light scattering measurements revealed a hydrodynamic diameter of 191.2 nm and a zeta potential of -14.6 mV, indicating moderate colloidal stability. Scanning & Transmission electron microscopy showed spherical and reasonably dispersed nanoparticles, while X-ray diffraction confirmed a monoclinic crystalline phase. Fourier-transform infrared spectroscopy identified functional groups involved in metal ion reduction and capping, a finding supported by energy-dispersive X-ray spectroscopy. The biosynthesized CuO NPs demonstrated significant antioxidant and antibacterial activity against both Gram-positive and Gram-negative bacterial strains. Furthermore, they exhibited potent, concentration-dependent cytotoxicity against MCF-7 breast cancer cells, with an IC₅₀ value of 71.3 µg/mL. Apoptotic cell death was confirmed by acridine orange/ethidium bromide staining, and a reduction in viable cell count was validated via trypan blue exclusion assay. These results establish O.Stamineus-derived CuO NPs as a promising phytogenic platform with multifunctional biological activities for potential therapeutic applications.