Limiting the level of tertiary amines on polyamines leads to biocompatible nucleic acid vectors

We have designed an efficient, synthetic nucleic acid vector, which is relatively non-toxic. [N-(2-ethylamino)-6-O-glycolchitosan – EAGC] polymers were 10–50 fold less toxic than Lipofectamine 2000, able to complex DNA, mRNA and siRNA into positively charged (zeta potential = + 40 − 50 mV), 50–450 nm nanoparticles. The level of tertiary amine N-2-ethylamino substitution (DS_tert) was inversely proportional to the IC50 of the EAGC polymers in the A431 cell line: IC50 = 6.18 DS_tert ^−0.9, r² = 0.9991. EAGC polyplexes were stable against a heparin challenge, able to protect the nucleic acids from nuclease degradation and achieve levels of transfection comparable to Lipofectamine 2000 formulations. The relative biocompatibility of the vector allowed 10 fold higher doses of DNA (1 μg compared to 0.1 μg per well with Lipofectamine 2000) and siRNA (10.7 μg per well vs 1.3 μg with Lipofectamine 2000) to be applied to cells, when compared to Lipofectamine 2000. Finally intranasal application of EAGC – siRNA complexes resulted in siRNA transfer to the neurons of the olfactory bulb.