The intracellular delivery of plasmid DNA using cationic reducible carbon nanotube - Disulfide conjugates of polyethylenimine.

A series of polyethylenimine conjugates of single-walled carbon nanotube (PEI-SWNT) containing bioreducible disulfide bonds was synthesized and evaluated for their transfection efficiency. Different molecular weights of polyethylenimine (PEI) were thiolated with different mole ratio of 2-iminothiolane (2-IT). Single-walled carbon nanotube (SWNT) was first carboxylated and then three different cysteine-functionalized SWNT formulations were synthesized via introduced linkers: a) carbonyl group b) spermidine c) 1,8-diamino 3,6-dioxo octane. The final nanocarriers were fabricated upon conjugation of thiolated PEIs and thiolated SWNT via oxidative disulfide bond formation. All PEI-disulfide-SWNT conjugates were capable of DNA condensation and showed improved viability and transfection efficiency compared to PEI itself. Transfection efficiencies were up to 1500 times greater than PEI 25kDa (C/P=0.8). The results of this study suggest that the synthesized formulations based on SWNT-CO-Cysteine and PEI 1.8kDa were the most efficient carriers. Considering the decreased cytotoxicity and higher transfection levels, the conjugates bear the potential for effective delivery of genetic materials.