pH-Responsive Conformational-Switching Cationic Fusion Protein for Promoted Plasmid DNA Delivery and Transfection

Gene therapy holds great promise for treating various diseases, but challenges such as delivery efficiency, immune response, and long-term effects still remain. Protamine is a frequently used gene delivery vector for its strong nucleic acid binding capacity, but its application is constrained by inadequate nucleic acid release, resulting in low transfection efficiency. Here, we introduce a fusion protein by integrating LAH4 peptides on both ends of protamine's DNA-binding motif. This fusion protein exhibits lower cytotoxicity compared to protamine. At pH 7.4, its uniform charge distribution and α-helical structure enable robust DNA condensation and DNase resistance. Under acidic conditions (pH 5.8), the conformational change of the protein weakens its DNA binding, facilitating controlled release in endosomes/lysosomes. Simultaneously, it interacts with the endosomal membrane to form pores, aiding in the endosomal escape of the nucleic acids, thereby significantly improving transfection efficiency. This fusion protein offers the potential for efficient and safe nucleic acid delivery.