Theoretical modelling of electrostatic interactions in pH-dependent drug loading and releasing by functionalized mesoporous silica nanoparticles

In this article, we provide a theoretical model that predicts the electrostatic attractive and repulsive interactions between an assembly of a host and a guest that exhibits acid–base characteristics in a pH-dependent manner. By using provided experimental data and DFT-based estimates of pH-dependent drug loading and release by functionalized mesoporous silica nanoparticles, the model is proven to be accurate. Alendronate and sulfasalazine are the two drug molecules selected for the two model carrier matrix, propylamine- and trimethylammonium-functionalized mesoporous silica nanoparticles, respectively. The pH-dependent loading and releasing for both the drug molecules agreed well with experimental observations as well as density functional theory calculations. The degree of functionalization modifies the onset of pH for loading and releasing the drug, whereas the concentration of the drug modifies the electrostatic interaction energy. The electrostatic interaction energy reduces as drug concentration increases; however, the releasing pH shifts to higher pH values as functionalization degree rises. Doxorubicin is an anti-cancer therapeutic molecule that is projected to be loaded and released by propylamine-, trimethylammonium-, and poly(acrylic)-functionalized mesoporous silica nanoparticles in a pH-dependent manner. The drug must be functionalized using propylamine at 60% and trimethylammonium at 40% in order for the drug to release at basic pH and stay intact at acidic pH with the carrier matrix. On the other hand, as the degree of functionalization is increased, the releasing pH range for functionalization with poly(acrylic) acid shifts to a lower pH range.