Green synthesis of SnO₂ nanoparticles using Calophyllum inophyllum seed shell extract and their biological and...

In this research, tin oxide nanoparticles (SnO₂ NPs) were green synthesized using Calophyllum inophyllum seed shell extract (CISSE) as both the stabilising and capping agent, providing an ecologically friendly, sustainable, and cost-efficient synthesis route. The synthesized nanoparticles were comprehensively characterized to determine their optical properties, crystalline structure, functional groups, morphology, particle size, elemental composition, surface chemistry, and colloidal stability. The most prominent absorption peak (λ_max) in the UV-visible spectrum was found at 280 nm. FESEM and HR-TEM examination indicated that the synthesised nanoparticles had quasi spherical to spherical shape with an average size of 19.29 ± 5.25 nm. According to DLS analysis, the polydispersity index (PDI) was 0.389, and the mean hydrodynamic size was 85 nm. The zeta potential value of -27.9 mV suggested notable colloidal stability. Raman spectroscopy revealed a unique vibrational peak at 631 cm^-1, indicating the effective production of crystalline SnO₂ NPs. XPS analysis confirmed the presence of Sn and O, with Sn 3d peaks consistent with Sn⁴⁺ in SnO₂ and C 1s signals indicating oxygen-containing carbonaceous species associated with the nanoparticle surface. The biosynthesized SnO₂ NPs exhibited potent larvicidal, antibacterial, antibiofilm, antiproliferative, and photocatalytic activities. They showed effective larvicidal activity against Aedes aegypti (LC₅₀ = 9.0 mg/L) and Culex quinquefasciatus (LC₅₀ = 7.5 mg/L) with minimal toxicity toward non-target organisms. The nanoparticles demonstrated strong antibacterial activity, with maximum inhibition zones of 23 mm against Staphylococcus aureus and Escherichia coli, and pronounced antibiofilm activity, achieving 91.08% biofilm inhibition against Acinetobacter baumannii. Furthermore, SnO₂ NPs exhibited enhanced antiproliferative activity against SiHa cervical cancer cells (IC₅₀ = 57.81 μg/mL) compared with the crude extract (IC₅₀ = 233.56 μg/mL). Also, the synthesized SnO₂ NPs efficiently photocatalytically degraded ibuprofen under UV irradiation, highlighting its prospects for therapeutic and environmental uses.