Coupling of a bifunctional peptide R13 to OTMCS-PEI copolymer as a gene vector increases transfection efficiency and tumor targeting

Background:A degradable polyethylenimine (PEI) derivative coupled to a bifunctional peptide R13 was developed to solve the transfection efficiency versus cytotoxicity and tumor-targeting problems of PEI when used as a gene vector. Methods: We crossed-linked low molecular weight PEI with N-octyl-N-quaternary chitosan (OTMCS) to synthesize a degradable PEI derivative (OTMCS-PEI), and then used a bifunctional peptide, RGDC-Tat (49-57) called R13 to modify OTMCS-PEI so as to prepare a new gene vector, OTMCS-PEI-R13. This new gene vector was characterized by various physicochemical methods. Its cytotoxicity and gene transfection efficiency were also determined both in vitro and in vivo. Results: The vector showed controlled degradation and excellent buffering capacity. The particle size of the OTMCS-PEI-R13/DNA complexes was around 150-250 nm and the zeta potential ranged from 10 mV to 30 mV. The polymer could protect plasmid DNA from being digested by DNase I at a concentration of 23.5 U DNase I/mu g DNA. Further, the polymer was resistant to dissociation induced by 50% fetal bovine serum and 400 mu g/mL sodium heparin. Compared with PEI 25 kDa, the OTMCS-PEI-R13/DNA complexes showed higher transfection efficiency both in vitro and in vivo. Further, compared with OTMCS-PEI, distribution of OTMCS-PEI-R13 at tumor sites was markedly enhanced, indicating the tumor-targeting specificity of R13. Conclusion: OTMCS-PEI-R13 could be a potential candidate as a safe and efficient gene delivery carrier for gene therapy.