Mesoporous silica nanoparticles equipped with surface nanovalves for pH-controlled liberation of doxorubicin

Silica carriers equipped with molecular and supramolecular pH-sensitive nanovalves were designed by combination of sol-gel synthesis and selective postsynthetic modification. Mesoporous structure of synthesized materials was characterized by low-temperature nitrogen adsorption-desorption, small-angle X-ray diffraction and transmission electron microscopy. Chemical immobilization of N-[N'-(N'-phenyl)-2-aminophenyl]aminoalkyl groups was confirmed by IR spectral and chemical analyses of surface layer. Loading and release behaviour of synthesized drug carriers was studied in phosphate buffer solutions with pH 5.0 and pH 7.0 using doxorubicin (Dox) as a test molecule. It was found that the loading efficiency of synthesized materials determined by UV spectroscopy measurements reached 59-76%, whereas cumulative value of Dox released from silica materials equipped with molecular and supramolecular nanovalves into the phosphate buffer solution with pH 5.0 reached up to 48% and 51%, respectively. It was proved that aromatic amino groups and surface supramolecular structures localized near pore openings play an essential role in pH-controlled Dox release.