Antisense oligonucleotides (anti-ODNs), which are able to interfere with gene expression at the mRNA level, have potential activity in the treatment of viral infections or cancer. However, the application of therapies based on anti-ODNs is hampered by their instability to cellular nuclease and their weak intracellular penetration. Among the many efforts to increase their stability and cellular penetration have been modifications of ODNs and introduction of particulate carriers. Here we report an anti-ODNs carrier based on amino silica nanoparticles (NH(2)SiNPs) and its preliminary applications in cancer cells. The positively charged NH(2)SiNPs were synthesized by a water-in-oil microemulsion method. The NH(2)SiNP-ODN complexes were formed by electrostatic interaction, and their cellular uptake was visualized by using fluorescein isothiocyanate (FITC)-labeled ODNs and NH(2)SiNPs doped with rhodamine 6G isothiocyanate (RITC) as fluorescent signal indicators. The antisense inhibition efficiency of anti-ODNs delivered by NH(2)SiNPs was evaluated using MTT (3,4,5-dimethylthiazol-2,5-diphenyl tetrazolium bromide) assay and western blot analysis. Uniform NH(2)SiNPs with an average diameter of 25 nm were obtained and could combine with anti-ODNs to form a bioconjugate favorable for cellular uptake. The NH(2)SiNPs were able to protect anti-ODNs from degradation by DNase I. In vitro experiments showed that the NH(2)SiNPs could greatly improve the inhibition efficiency of anti-ODNs for the proliferation and survivin expression in Hela cells and A549 cells. Compared with liposomes, the NH(2)SiNPs presented a better biocompatibility and had almost no cytotoxicity at the concentrations required for efficient transfection. Our results suggest that the NH(2)SiNPs may be a promising carrier for delivery of anti-ODNs.