pH-responsive drug release and real-time fluorescence detection of porous silica nanoparticles

In this work, pH-sensitive "dual-switch" porous silica (pSiO₂) nanoparticles (NPs) were constructed for drug delivery. Poly(acrylic acid) (PAA) was grafting onto the internal and external surfaces of amino groups functionalized porous silica (pSiO₂-NH₂) NPs by the amidation between the amino groups and the carboxyl groups of PAA for pH triggered drug release. The resultant pSiO₂/PAA NPs have an average diameter of 50-60nm and high specific surface area (914m²·g^-1). To improve the loading capacity, ZnO quantum dots (QDs) were used to block the partial pores of pSiO₂/PAA and the loading capacity reached to 28% for methotrexate (MTX) model drug. The in vitro cellular cytotoxicity test and a hemolysis assay demonstrated that the pSiO₂/PAA/ZnO NPs were highly biocompatible and suitable to utilize as drug carriers. The MTX-loaded pSiO₂/PAA/ZnO NPs displayed more efficient cytotoxic to HepG2 cells than free MTX. The pSiO₂/PAA/ZnO NPs displayed low premature, pH-responsive release and pH-dependent fluorescence. Moreover, pH-dependent fluorescence enables to trace MTX release behavior.