A mesoporous silica nanoparticle (MSNP) based co-delivery system is developed in order to deliver simultaneously drug and single strand DNA (ssDNA) in a controlled manner. Negatively charged ssDNA as a model gene is immobilized onto the surface of positively charged ammonium-functionalized MSNPs through electrostatic interaction, effectively blocking the loaded drugs within the mesopores of MSNPs. When the pre-installed disulfide bond on the ammonium unit is broken by the addition of the reducing agent such as dithiothreitol or glutathione, the ssDNA network on the surface is freed, leading to the release of the loaded drug molecules from the mesopores. The cell investigations indicate that the functional nanoparticles have a very low cytotoxicity under the concentrations measured. The doxorubicin-loaded and ssDNA-coated nanoparticles show an enhanced cellular internalization, leading to a successful drug/ssDNA co-delivery in vitro for significant apoptosis of Hela cancer cells as compared with that of free doxorubicin. The obtained experimental results indicate promising applications of the functional nanoparticles in cancer treatment.