Effect of silica hydroxylation on ampyra adsorption: DFT study

E. NOSEDA GRAU; G. ROMAN; G. DODERO; A. DIAZ COMPAÑY; S. SIMONETTI

Simposio; 8th Latin American Symposium on Coordination and Organometallic Chemistry; 2022

Studies have shown that silica matrixes could improve drug delivery. To designdrug adsorbent, it is crucial to understand the adsorption mechanisms. DFTtheoretical calculations are performed to study the adsorption of Ampyra drugon the different crystallographic planes of β-cristobalite: the hydroxylated(111) and (100) surfaces. β-cristobalite can sustain the two types of silanolgroups identified experimentally on the amorphous silica surface, the singlesilanols typical of the (111) surface and the geminal silanols which are typicalof the (100) surface. The Ampyra-silica interaction is most favored on the (100)surface where the entire ring of the molecule interacts with the surface, whileon the (111) face lesser exchange and fewer non-polar atoms are involved.Calculations show that the interactions mainly occur at the interface betweenAmpyra and the closest silanol groups according to the formation of the Hbondinginteractions. β-cristobalite (100) has a silanol density of 7.9 OH nm-2while the (111) face has a silanol density of 4.5 OH nm-2. The results indicatethat the H-bonds formed have a vital influence on the adsorption of Ampyra,and the surface hydroxyl density has an important effect on the amount of theH-bonds. In consequence, the adsorption on (111) surface is observed to alesser extent than on (100) surface according the smaller hydroxyl density. Theconcentration, distribution, and nature of silanols mainly establish theadsorption properties of hydroxylated silica surfaces.