Synthesis and characterization of stearyl protamine and investigation of their complexes with DNA for gene delivery

A novel gene carrier, stearyl protamine (SP) was synthesized by the reaction of natural protamine with an N-hydroxysuccinimide (NHS) ester of stearic acid. This SP was characterized by FT-IR, stearyl content measurement and dynamic light scattering (DLS). Then, the SP was evaluated as a gene delivery carrier. The SP with higher stearyl group content (SP3) can self-assemble into aggregates with an average diameter of ca. 110 nm in water and has relatively higher in vitro gene transfection efficiency than protamine and SP with lower stearyl group content. A possible mechanism is proposed for the formation of complex of SP/DNA. The SP also shows a low cytotoxicity similar to protamine.