Gene delivery with amphiphilic lower generation polypropylenimine dendrimer

• Main Author: Bolton, Katherine
• Published: University of Strathclyde 2007
• Subjects: 615.895
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487864

In this work a novel lower generation amphiphilic polypropylenimine (PPI) dendrimer with good aqueous solubility was developed and tested as a gene delivery agent. PPI dendrimer generation 3 (DAB-16-Am) was substituted with a low level of cetyl chains (less than 5 molar percent) by reaction with 1-bromohexadecane under carefully controlled conditions. Structural characterisation was carried out using nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis. Cetylated DAB-16 spontaneously self-assembled in an aqueous environment and in the presence of cholesterol (50% w/w) formed unilamellar vesicles of approximately 50nm in diameter. Cetylation tripled the DNA binding capacity of the dendrimer, supporting the hypothesis that the presence of hydrophobic alkyl chains would improve the packaging of DNA by the dendrimer. Apparent DNA binding enthalpies were also significantly more favourable. The size, surface charge and morphologies of the resulting complexes were found to be dependent upon the composition of the dendrimer. Cetylated dendrimer was able to stabilise complexes against electrostatic disruption but differing biophysical characteristics of complexes did not influence the protection of DNA against nuclease activity. The introduction of hydrophobic moieties increased the haemolytic potential of the dendrimer and enhanced cytotoxic effects in three immortalised cell lines. Cetylated DAB-16 formulations were able to transfect these cell lines although the dendrimer dose applied to cells must balance intracellular access and toxicity. Cetylated DAB-16 was also well tolerated when administered intravenously at doses required for in vivo gene delivery. These features suggest that cetylated DAB-16 has a potential application in anti-tumour gene therapy.