Exploring the adsorption of Gemcitabine on silicon nanotubes using density functional theory

In this study, density functional theory (DFT) was employed to examine the adsorption behavior of Gemcitabine (GEM) on single-walled silicon nanotubes (SWSiNTs) in both vacuum and aqueous environments to assess their potential for drug delivery applications. The adsorption energies confirm that the adsorption of GEM on SWSiNTs is predominantly governed by physisorption, with the parallel orientation (GEM‖SWSiNT) being the most stable, characterized by an adsorption energy of -5.05 eV and an O-Si bond length of 1.50 Å. Thermodynamic parameters, including enthalpy (ΔH) and Gibbs free energy (ΔG), indicate that adsorption is exothermic and spontaneous in all studied configurations, confirming the thermal stability of the complexes. Hirshfeld charge analysis reveals that charge redistribution occurs at the interface, where SWSiNTs donate electrons while GEM acts as an acceptor. Density of states (DOS) analysis shows moderate band-gap modulation, suggesting potential for both drug delivery and sensing. Recovery time estimations reveal that release behavior is highly dependent on the adsorption geometry and temperature; the parallel configuration ensures longer retention, whereas the perpendicular configuration supports faster desorption at elevated temperatures. Furthermore, vibrational frequency analysis shows the absence of imaginary frequencies, confirming the dynamic stability of the complexes. These findings establish SWSiNTs as thermodynamically stable, electronically tunable, and orientation-sensitive nanocarriers, highlighting their potential in controlled drug delivery and biomedical applications.