Advance on adsorption of amino-functionalized silica nanocarrier for the delivery of therapeutic ampicillin as drug model

Abstract

The adsorption of ampicillin drug on SiO2(0 0 1) and SiO2(1 1 1) hydroxylated surfaces have been studied by Density Functional Theory calculations. The improvement on adsorption when the silica is functionalized with amino groups, are analyzed. The ampicillin molecule is adsorbed on both surfaces, adopting the geometry where its N and O atoms point towards the surface; resulting more stable on SiO2 (0 0 1) (ΔE = −3.33 eV vs. ΔE = −1.26 eV). The stability depends on the H−bonds formed according to the higher silanol density of SiO2(0 0 1). The stability of ampicillin on SiO2(1 1 1) is favored when the surface is amino-functionalized (ΔE = −1.76 eV). The major adsorption energy is observed in presence of the deprotonated specie at basic pH (ΔE = −2.68 eV). The changes are mainly related to the modification of the frontier orbitals comparing with the neutral specie and, in consequence, the new interactions with the amino-functionalized surface that contribute with new states in the Fermi region.