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New polyphosphoramidate with a spermidine side chain as a gene carrier

2002; Elsevier BV; Volume: 83; Issue: 1 Linguagem: Inglês

10.1016/s0168-3659(02)00180-3

1873-4995

Jun Wang, Pengchi Zhang, Hongfang Lü, Nan Ma, Shu Wang, Hai‐Quan Mao, Kam W. Leong,

Advanced biosensing and bioanalysis techniques

A new cationic polymer (PPA–SP), polyphosphoramidate bearing spermidine side chain, was prepared as a non-viral vector for gene delivery. PPA–SP was synthesized from poly(1,2-propylene H-phosphonate) by the Atherton–Todd reaction. The weight average molecular weight of PPA–SP was 3.44×104 with a number average degree of polymerization of 90, as determined by GPC/LS/RI method. The average net positive charge per polymer chain was 102. PPA–SP was able to condense plasmid DNA efficiently and formed complexes at an N/P ratio (free amino groups in polymer to phosphate groups in DNA) of 2 and above, as determined by agarose gel electrophoresis. This new gene carrier offered significant protection to DNA against nuclease degradation at N/P ratios above 2, and showed lower cytotoxicity than PLL and PEI in cell culture. The LD50 of PPA–SP was 85 μg/ml in COS-7 cells, in contrast to 20 and 42 μg/ml for PLL and PEI, respectively. The complexes prepared in saline at N/P ratios of 5∼10 had an average size of 250 nm and zeta-potential of 26 mV. PPA–SP mediated efficient gene transfection in a number of cell lines, and the transfection protocol was optimized in HEK293 cells using a luciferase plasmid as a marker gene. Gene expression mediated by PPA–SP was greatly enhanced when chloroquine was used in conjunction at a concentration of 100 μM. Under the optimized condition, PPA–SP/DNA complexes yield a luciferase expression level closed to PEI/DNA complexes or Transfast mediated transfection. In a non-invasive CNS gene delivery model, PPA–SP/DNA complexes yielded comparable bcl-2 expression as PEI/DNA complexes in mouse brain stem following injection of the complexes in the tongue.