Green Synthesis and Characterisation of Psidium Guajava -Mediated Magnesium Oxide Nanoparticles with Anticancer, Antioxidant, and Antibiofilm Activities

Objectives Nanoparticles are increasingly studied for their unique physicochemical properties and biomedical potential. Magnesium oxide nanoparticles (MgONPs) can be synthesised using plant extracts, offering a green, eco-friendly approach. Material and Methods MgONPs were prepared using Psidium guajava leaf extract. Characterisation was performed by UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and UPLC-MS for guava leaves metabolomic profiling. Biological activities were evaluated through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assays, antioxidant assays 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-Azino-bis(3 ethylbenzothiazoline-6-sulfonic acid) (ABTS), and antibiofilm testing against Bacillus subtilis and Pseudomonas aeruginosa . Results TEM and SEM revealed spherical MgONPs with an average size of 66.8 ± 8.2 nm. FTIR confirmed phytochemical capping agents (proteins, phenolics, carbohydrates, flavonoids) that stabilised the nanoparticles. MgONPs showed selective cytotoxicity, inhibiting Caco-2 colorectal cancer cells (IC₅₀ = 98.02 ± 2.14 μg/mL) while exhibiting lower toxicity toward Vero cells (IC₅₀ = 271.71 ± 5.48 μg/mL). Antioxidant activity was demonstrated with IC₅₀ values of 388.28 ± 16.29 μg/mL (DPPH) and 204.99 ± 21.01 μg/mL (ABTS). Moderate biofilm inhibition occurred at 1000 μg/mL. Conclusion Guava-mediated MgONPs exhibit promising anticancer, antioxidant, and antibiofilm properties, highlighting their potential as safe, plant-derived therapeutic agents.