Small interfering RNAs (siRNAs) delivery remains a bottleneck for RNA interference (RNAi) - based therapies in the clinic. In the present study, a fusion protein with two cell-penetrating peptides (CPP), Hph1-Hph1, and a double-stranded RNA binding domain (dsRBD), was constructed for the siRNA delivery: dsRBD was designed to bind siRNA, and CPP would subsequently transport the dsRBD/siRNA complex into cells. We assessed the efficiency of the fusion protein, Hph1-Hph1-dsRBD, as a siRNA carrier. Calcium-condensed effects were assessed on GAPDH and green fluorescent protein (GFP) genes by western blot, real time polymerase chain reaction (RT-PCR), and flow cytometry analysis in vitro. Evaluations were also made in an in vivo heart transplantation model. The results demonstrated that the fusion protein, Hph1-Hph1-dsRBD, is highly efficient at delivering siRNA in vitro, and exhibits efficiency on GAPDH and GFP genes similar to or greater than lipofectamine. Interestingly, the calcium-condensed effects dramatically enhanced cellular uptake of the protein-siRNA complex. In vivo, Hph1-Hph1-dsRBD transferred and distributed ^ targeted siRNA throughout the whole mouse heart graft. Together, these results indicate that Hph1-Hph1-dsRBD has potential as an siRNA carrier for applications in the clinic or in biomedical research.
