Phytogenic Aluminum Oxide Nanoparticles as a Sustainable Weapon Against Multidrug-Resistant Bacteria: Green Synthesis Using Aloe vera with In Vitro Biological and Computational Evaluation

The green production of metal oxide nanoparticles using plant extracts has received the attention of researchers. In this work, we produced aluminum oxide nanoparticles (Al2O3-NPs) using Aloe vera leaf extract to stabilize and reduce them. UV–Vis spectroscopy showed a substantial absorption peak at about 300–320 nanometers, confirming nanoparticle production. The developed material had a nanocrystalline structure, as seen based on several sharp XRD peaks that matched crystalline aluminum oxide material. Functional groups such as C=O, O–H, and Al–O were identified using Fourier transform infrared spectroscopy (FT-IR). Zeta potential analysis of an Al2O3 nanoparticle solution exhibited a continuous, low-frequency signal. The particle size distribution was narrow, with an average hydrodynamic diameter of 1000–1200 nanometers, according to DLS tests. Uneven nanoparticles formed platelet-like agglomerations in SEM pictures. Energy dispersive X-ray spectroscopy revealed aluminum and oxygen nanoparticles. SAED patterns indicated polycrystalline nanoparticles, whereas TEM exhibited uneven layers and mesoporousness. A GC-MS analysis of the Aloe vera extract revealed various bioactive chemicals that are known to have the ability of reduction and potential for stabilizing nanoparticles. The biosynthesized Al2O3-NPs exhibited antioxidant activity, with IC50 values of 20.12 µg/mL for DPPH, 20.34 µg/mL for ABTS, and 45.99 µg/mL for H2O2 scavenging. However, the relatively higher IC50 value of 96.06 µg/mL observed in normal WI-38 lung fibroblast cells indicates comparatively lower cytotoxicity toward normal cells, while further studies are needed to optimize and confirm the selectivity of the nanoparticles. Cytotoxicity assays revealed strong anticancer activity against A549 lung carcinoma cells (12.24 µg/mL) and HepG2 liver cancer cells (15.65 µg/mL). The nanoparticles exhibited substantial suppression against Klebsiella pneumoniae (K. pneumoniae ATCC 43816) and multidrug-resistant Proteus vulgaris (P. vulgaris ATCC 6380), but moderate to no action against P. aeruginosa, L. monocytogenes, and Staphylococcus. In-silico molecular docking showed that 9-octadecenoic acid (Z)-, methyl ester, the main Aloe vera phytoconstituent, may interact with heme oxygenase, contributing to its antioxidant effect.