The nonviral gene delivery system is an attractive alternative to cancer therapy. A new kind of gelatin-silica nanoparticles (GSNPs) was developed through a two-step sol-gel procedure. To improve the transfection efficacy, GSNPs modified with different fusion peptides (Tat, HA2, R8, Tat/HA2, and Tat/R8) were prepared for particle size, zeta potential, cellular uptake, hemolysis activity at physiological pH (7.0) or acidic pH (5.0), and condensation of plasmid DNA. The results suggest that the sizes and zeta potentials of GS-peptide conjugates were 147 - 161 nm and 19 - 33 mV, respectively; GS-peptide conjugates exhibited low cytotoxicity; the plasmid DNA was readily entrapped at a GS-peptide/pDNA weight ratio of 50 - 200. The in vitro and in vivo studies demonstrated that the synergistic effects of cell-penetrating peptide Tat and fusogenic peptide HA2 could promote the efficient cellular internalization, endosome escape, and nucleus targeting, hence delivering the therapeutic nucleic acid efficiently. From the Clinical Editor: This team of investigators demonstrates that the efficacy of organosilica particles utilized in gene delivery can be optimized via cell-penetrating peptide TAT and fusogenic peptide HA2, which were observed to result in a synergistic effect on cellular internalization and gene transduction. The above delivery system will likely become an important subject of future investigations for gene delivery methods. (C) 2012 Elsevier Inc. All rights reserved. ; National Basic Research Program of China (973 Program) [2010CB732402]; National Natural Science Foundation of China [30970733, 30901175, 81171448]