Uniform double-shelled silica hollow spheres: acid/base selective-etching synthesis and their drug delivery application

Uniform mono-disperse double-shelled silica hollow spheres (DSH) with controllable inner structure have been successfully synthesized via an alternating acid/base selective etching strategy. The void spacing between the shells can be tuned during the synthesis. The formation mechanism was proposed by monitoring the synthesis process at different reaction time and comparative investigation of the used surfactants. Anti-cancer drug, mitoxantrone (Mito) was chosen as a probing molecule in drug delivery and release experiments, and the results showed that these double-shelled silica hollow spheres exhibit higher drug loading capacity and desired release rates compared with conventional single-shelled silica hollow spheres due to their hierarchically mesoporous structures. The in vitro cellular internalization of DSH was evaluated by designing fluorescein isothiocyanate labeled DSH with green fluorescence (DSH@FITC). The in vitro study of Human liver carcinoma cells of Hep-G2 cells also proves that the DSH–Mito has reduced toxicity and enhanced therapeutic efficacy, and the DSH is an ideal carrier for drug delivery.