NiO@GO Nanocomposites: Solvent-mediated Green Synthesis and Comparative Therapeutic Potential Assessment

Abstract This study evaluates the biological potential of green-synthesized nickel oxide (NiO) nanoparticles (NPs) and its nanocomposite with graphene oxide (NiO@GO), derived from aqueous (aq) and ethanolic (et) leaf extracts of Elettaria cardamomum (E. cardamomum). The plant extracts were quantified for phytochemicals, including total phenolic contents (TPC) and total flavonoid contents (TFC). The NPs and NiO@GO nanocomposites (NCs) were evaluated for their antioxidant potential via DPPH and FRAP assays, antibacterial activity against E. coli and B. subtilis. The biocompatibility was evaluated against red blood cells (RBCs) and the anticancer activity against HepG2 cell line using MTT assay. The TPC and TFC of the extracts ranged from 37 ± 0.35 to 44 ± 0.20 mg GAE/g and from 51 ± 0.25 to 57 ± 0.30 mg QE/g, respectively. The retention of TPC and TFC in the nanocomposites was found to be 18–19 and 8–10%, respectively. The NiOet@GO NCs demonstrated the highest radical scavenging activity (59.65%) and FRAP activity (49.03%), confirming their enhanced electron-donating potential. The NiOet@GO NCs also exhibited higher antibacterial activity against E. coli, with a 24 mm zone of inhibition, and demonstrated biocompatibility, as hemolysis was observed only at higher concentrations. The anticancer activity against HepG2 liver cancer cells revealed a dose-dependent decrease in cell viability, with NiOet@GO NCs reducing cell viability to 80.87% at 200 µg/mL. The synergistic interaction between GO and ethanolic phytoconstituents with NiO NCs has enhanced the biological activity and therapeutic potential of E. cardamomum-derived NiO@GO NCs. These findings demonstrate that E. cardamomum-mediated NiO@GO NCs, particularly NiOet@GO NCs, possess promising multifunctional therapeutic potential due to their enhanced antioxidant, antibacterial activities and hemocompatibility. These green-synthesized NCs may serve as effective candidates for future biomedical and therapeutic applications.