Theoretical investigation of capsaicin adsorption on doped magnesium oxide fullerene-like nanocages for drug delivery and biosensing applications

Abstract This study employs density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to elucidate the adsorption behavior of Capsaicin (CPC) through the carbonyl and hydroxyl groups on fullerene-like magnesium oxide-based nanocages, including pristine Mg 12 O 12 , aluminum-doped Mg 11 AlO 12 , and aluminum-nitrogen co-doped Mg 11 AlNO 11 structures. Results demonstrate that CPC binds spontaneously and exothermically via its carbonyl group, preferentially coordinating through oxygen atoms, with adsorption energies of − 0.848 eV (Mg 12 O 12 ), − 0.908 eV (Mg 11 AlO 12 ), and − 1.01 eV (Mg 11 AlNO 11 ) in aqueous media. Charge transfer analyses indicate a transfer of approximately 0.275 |e| from the cage to CPC, reducing system hardness and elevating chemical potential, thereby enhancing chemical reactivity. Notably, the CPC-Mg 11 AlO 12 system exhibits the highest dipole moment increase (23.53 Debye), implying improved solubility and potential for biosensing applications. Solvent effects reveal that water stabilizes excitons and enhances absorption features, whereas chloroform induces redshift and spectral broadening, as shown by TD-DFT spectra. Infrared vibrational analysis underscores strong carbonyl interactions, highlighting the role of doping in tuning adsorption characteristics. Our findings illustrate that Mg 11 AlO 12 is more sensitive for detecting the CPC (46.45%) than Mg 12 O 12 (18.65%) and Mg 11 AlNO 11 (6.93%) to exploit as a biochemical sensor. Collectively, these findings suggest that Mg 11 AlNO 11 cages are promising solvent-dependent platforms for biosensing and drug delivery, with tunable optical and electronic properties influenced by environmental conditions.