PEG-PCL-DEX polymersome-protamine vector as an efficient gene delivery system via PEG-guided self-assembly.

AIM: The nonviral carrier system based on the triblock copolymer PEG-PCL-DEX (PPD) and protamine was developed for nucleic acid delivery. MATERIALS & METHODS: Self-assembly occurred in the PEG continuous phase to form 'dextran-interior' polymersomes. siRNA can be condensed by protamine and encapsulated into PPD polymersomes in order to form the PPD-protamine siRNA nanoparticles by thermodynamically preferential partition between the PEG continuous phase and the dextran cavity. RESULTS: This system can package siRNA into PPD polymersomes to form 145.2 ± 8.02-nm (± standard deviation) nanoparticles, and the ζ-potential can be reduced to approximately 0 mV. PPD-protamine siRNA nanoparticles achieved cellular uptake of siRNA in SMMC-7721 cells with negligible cytotoxicity, and the GL3 gene expression can be reduced to 61.73 ± 6.25%. A biodistribution study of nanoparticles suggested that the PPD-protamine siRNA nanoparticles mainly accumulated in liver. CONCLUSION: All of these results suggest that PPD-protamine carriers may offer a promising gene delivery strategy for the treatment of liver-related disease.

Synthetic polyspermine imidazole-4, 5-amide as an efficient and cytotoxicity-free gene delivery system.

A chemically dynamic spermine-based polymer: polyspermine imidazole-4, 5-amide (PSIA, Mw > 7 kDa) was designed, synthesized, and evaluated in terms of its ability to deliver nucleic acids. This polymer was made from an endogenous monomer professionally condensing genes in sperms, spermine, and a known safety drug metabolite, imidazole-4, 5-dicarboxylic acid, through a bis-amide bond conjugated with the imidazole ring. This polymer can condense pDNA at a W/W ratio above 10 to form polyplexes (100-200 nm in diameter), which is consistent with the observation by transmission electron microscopy (TEM), and the zeta potential was in the range of 10-20 mV. The pDNA packaged polymer was stable in phosphate buffer solution (PBS) at pH 7.4 (simulated body fluid) while the polyplexes were releasing pDNA into the solution at pH 5.8 (simulated endo-lysosomes) due to the degradation of the bis-amide linkages in response to changes in pH values. PSIA-polyplexes were able to achieve efficient cellular uptake and luciferase gene silencing by co-transfection of pDNA and siRNA in COS-7 cells and HepG2 cells with negligible cytotoxicity. Biodistribution of Rhodamine B-labeled PSIA-polyplexes after being systemically injected in BALB/c nude-mice showed that the polyplexes circulated throughout the body, accumulated mainly in the kidney at 4 hours of sample administration, and moved to the liver and spleen after 24 hours. All the results suggested that PSIA offered a promising example to balance the transfection efficiency and toxicity of a synthetic carrier system for the delivery of therapeutic nucleic acids.