Sennoside-functionalized ZrO₂ nanoparticles via Cassia angustifolia: Gram-selective antibacterial and anticancer nanoplatform with green synthesis

Sennoside-functionalized zirconium dioxide nanoparticles (Sen–ZrO₂ NPs) were engineered via a single-step green synthesis route using Cassia angustifolia leaf extract as both a bio reductant and stabilizer. Structural characterization confirmed phase-pure tetragonal ZrO₂ formation through X-ray diffraction (XRD), while Fourier-transform infrared spectroscopy (FTIR) verified sennoside anchoring via characteristic CO and O–H vibrations at 1680 cm⁻¹ and 3605 cm⁻¹. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS) revealed spherical morphologies with uniform elemental distribution. The Sen–ZrO₂ NPs exhibited pronounced Gram-selective antibacterial activity, demonstrating a fourfold potency enhancement against Staphylococcus aureus (MIC = 64 µg mL⁻¹) compared to unmodified ZrO₂. Time-kill assays further demonstrated a rapid 4-log reduction in bacterial viability within 6 h. Against MCF-7 breast cancer cells, the nanoparticles displayed dose-dependent cytotoxicity (IC₅₀ = 61.44 µg mL⁻¹), representing a 2.3-fold improvement over bare ZrO₂. This dual bioactivity is attributed to sennoside-mediated redox modulation and surface functionalization, which act synergistically to enhance membrane disruption and reactive oxygen species (ROS) generation. This work establishes a sustainable plant-engineered ZrO₂ nanoplatform with integrated antibacterial–anticancer functionality, presenting a viable green approach to advanced nanotherapeutics for combating antimicrobial resistance and cancer.