Metal-decorated graphdiyne nanocarriers for favipiravir delivery: a DFT investigation

Favipiravir (FAV) is a broad-spectrum antiviral drug whose therapeutic efficacy is limited by poor bioavailability, motivating the development of nanoscale delivery platforms. Herein, density functional theory (DFT) calculations are employed to systematically investigate the adsorption behavior of FAV on pristine and transition-metal-decorated graphdiyne (GDY) nanosheets. Ni, Cu, and Ti modifiers are introduced to tune interfacial interactions at the atomic scale. Calculations at the B3LYP/6-31G(d) level, in both gas and implicit solvent environments, reveal that pristine GDY enables moderate, reversible physisorption (-0.26 eV; 2.45 Å), suitable for controlled release. In contrast, metal decoration significantly strengthens adsorption, with FAV(N/O)-GDY-Ni, -Cu, and -Ti exhibiting binding energies of -4.41, -3.96, and -5.79 eV, respectively, alongside reduced interaction distances. Electronic structure analyses (FMO, DOS, NBO, and RDG-NCI) confirm enhanced charge transfer and interaction localization upon metal incorporation, supported by thermodynamic favorability. These findings highlight metal-decorated GDY as a tunable nanoplatform for improving drug loading and stability, offering a computational framework for guiding future experimental work.