Gene transfection in complex media using PCBMAEE-PCBMA copolymer with both hydrolytic and zwitterionic blocks

Safety and high efficacy of vectors are essential requirements for gene therapy. To address these challenges, poly(carboxy betaine methacrylate ethyl ester)-poly(carboxy betaine methacrylate) (PCBMAEE-PCBMA) diblock copolymers were synthesized to form core–shell vector for gene delivery. The hydrophobic PCBMAEE segment, a polyzwitterionic precursor, can condense plasmid DNA (pDNA) into a hydrophobic core, which improves pDNA protection from nuclease attack and maintains the condensed structure against dilution. Moreover, the hydrolysis of PCBMAEE in uptaken gene vectors can enhance the pDNA release and reduce the cytotoxicity caused by the cationic polymer accumulation in the host cells. The PCBMA segment, zwitterionic fouling resistant material, is utilized to stabilize the gene vector in the complex medium and reduce the interference from serum proteins without impeding the endocytosis of DNA vector like PEG protection layer. Results showed that the complex formed by PCBMAEE₅₀-PCBMA₁₄ with luciferase or pEGFP gene exhibit higher transfection efficacy of pDNA than that formed by PEI 25 kDa or Lipofectamine^® 2000 in tested cell lines (COS-7, HepG-2, HeLa, and HUVEC), especially, in difficult-to-transfect ones, such as HeLa and HUVEC. The luciferase expression level infected by the vectors of PCBMAEE₅₀-PCBMA₁₄/pGL-4 at N/P = 20/1 is 27 times of the branched PEI 25 kDa in COS-7 cells and 16 times of Lipofectamine^® 2000 in HUVEC. Furthermore, the complex formed by PCBMAEE₅₀-PCBMA₁₄ also show advantages in transfection rate, dosage effectiveness and preservation of transfecting activity in serum contained growth medium. The luciferase expression of the vectors of PCBMAEE₅₀-PCBMA₁₄/pGL-4 at N/P = 20/1 is 230 times higher than that of PEI complex at low vector dosage (the 5% standard dosage). And the transfection rate is 25 times higher than that of PEI complex in 10% serum contained growth medium. In short, all these results indicated that the polymeric gene vector, consisted of convertible hydrophobic polyzwitterionic precursor and fixed polyzwitterionic fouling resistant segment, is a promising candidate for high and stable gene transfection in complex growth medium.