This study outlines the sustainable synthesis of hybrid biopolymer hydrogels supported with octahedral Cu2O nanoparticles (NPs), alongside their biological assessments and characterizations. A composite hydrogel made of chitosan and guar gum (CS-GG) was employed as a template for the environmentally friendly synthesis of nanoparticles. Leveraging their electron-rich functional groups, the biopolymers acted as stabilizing agents for the Cu2O NPs and as green reductants, facilitating the reduction of copper ions. The material’s physicochemical properties were thoroughly examined using advanced techniques, such as X-ray diffraction (XRD), FieldEmission Scanning Electron Microscopes (FE-SEM), Eneregy Dispersive X-ray Electron Spectroscopy (EDX), Fourier Transformed Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) and ICP-OES. The resulting CS-GG/Cu2O NPs nanocomposite was investigated as a reusable heterogeneous nanocatalyst, demonstrating its efficiency in the phosphine-free, palladium-free, and ligand-free synthesis of various stilbene derivatives with high yields through the Sonogashira coupling reaction. The catalyst showed no significant reduction in activity after being reused seven times consecutively. The cytotoxic effects of the CS-GG/Cu2O NPs nanocomposite on NCI-H661 lung cancer cells and normal cells (HUVEC) were assessed over 48 h using MTT assay. The cancer cell’s viability decreased after exposure to the CS-GG/Cu2O NPs, with an IC50 value of 82 μg/ mL. The CS-GG/Cu2O NPs nanocomposite controls the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) system, which in turn impacts apoptosis and cell proliferation in NCI-H661 cells, according to a detailed examination of the mTOR pathway. The pathway could act a role in the cell cycle inhibition and apoptosis induced by the CS-GG/Cu2O NPs nanocomposite. The CS-GG/Cu2O NPs nanocomposite could be a useful natural anti-cancer agent for the treatment of lung cancer
