Synthesis Of Cationic Polymers And The Influence Of Guandination On Gene Transfection Efficiency

Guanidine groups have great cellular penetrating ability and they will facilitate cellular uptake of the cationic polymers if grafting guanidine groups to them. The guanidine groups could also delocalize the charge present on primary amines of the polymers thereby leading to increase in transfection efficiency along with reduction in cytotoxicity. In the present study, a novel guanidinylation reagent was designed and synthesized and used to modify three kinds of polymers in order to increase their transfection efficiency.Polyethylenimine(PEI) is one of the most efficient polycationic non-viral gene delivery vectors. Its efficiency and cytotoxicity depends on its molecular weight, high molecular weight leads to high efficiency, but also high cytotoxicity. In this paper, PEI of different molecular and cross-linked PEI derivatives were modified with guanidinylation reagents. The influence of guanidination degree and the length between PEI and guanidine groups on the transfection efficiency was discussed. Besides, poly(β-amino ester) is also an efficient polycationic gene vectors. Here poly(P-amino esters) were synthesized through the Michael addition of 1,4-butanediol diacrylate and 5-amino-l-pentanol, and were end-modified with various diamine monomers. Then the amino groups on the end-modified poly(β-amino esters) were modified with guanidinylation reagents in order to further increase its transfection efficiency.The polymers with good water-solubility were assessed when B16F10 cells were used as receptor cells and enhanced green fluorescent protein (EGFP) was used as gene reporter. Among these polymers, we got some polymers with high transfection efficiency. It was found that in B16F10 cells, guanidinated PEI(2700Da) showed 82% of green color expressing cells, almost 8 times higher than that of native PEI itself. The cytotoxicity of guanidinated polymer-DNA complexes was also reduced considerably in comparison to non-guanidinated polymer, as determined by MTT colorimetric assay. The hydrodynamic diameter of P10-DNA complexes was found to be in the range of 141-197nm. All these results demonstrated that the transfection efficiency can be increased by introduction guanidine groups into the polymers and P10 is a safe and efficient transfection agent in vitro.