Polyphosphoramidate gene carriers: effect of charge group on gene transfer efficiency

Abstract

Cationic polymeric carriers have been widely used for gene delivery. However, the structure-function relationship, especially the effect of charge groups of cationic polymeric carriers on the transfection activity, is poorly understood. To examine this important parameter, a series of cationic polymers, polyphosphoramidates (PPAs) with an identical backbone, same side chain spacer, similar molecular weights but different charge groups containing primary to quaternary amino groups (PPA-EA, PPA-MEA, PPA-DMA and PPA-TMA, Figure 1) were synthesized. The DNAbinding affinity of these four PPAs increased in the order of PPA-EAoPPA-MEAoPPA-DMABPPA-TMA. The cytotoxicity decreased in the order of PPA-EA4PPA-MEA4PPA-DMA4PPA-TMA. Particle size and zeta potential of four different types of PPA/DNA nanoparticles did not show significant correlation with PPA structure. These PPAs did not show significant buffering capacity within pH 5-7, even though transfection mediated by PPA-EA was the only one that seemed to be limited by endolysomal escape. Endocytosis of DNA mediated by PPAs was also similar (17-22%) for all four PPAs. However, the transfection efficiency of these PPAs varied significantly. In vitro transfection efficiency of PPAs decreased in the order of PPA-EA4PPA-MEA4PPA-DMABPPA-TMA. Nanoparticles with PPA-EA containing primary amino groups gave the highest transfection efficiency in cell lines at the charge ratios from 6/1 to 20/1 ( þ /À). Matching the trend of transfection efficiency observed in vitro, PPA-EA mediated the highest transgene expression, comparable to that of polyethylenimine, in the spinal cord following intrathecal injection of the nanoparticles. These results establish that PPA gene carriers with primary amino group side chains are more potent than those with secondary, tertiary or quaternary amino groups in vitro and in the intrathecal gene delivery model.

Ph-Triggered Release of Vancomycin from Protein-Capped Porous Silicon Films

“…In one of such reports, a series of cationic polymers, polyphosphoramidates (PPAs), with an identical backbone, same side chain spacer, similar molecular weights but different charge groups containing primary to quaternary amino groups have been synthesized (Wang et al 2004). These PPAs did not show significant capacity to buffer endosomes within pH 5–7, even though transfection mediated by PPA-EA seemed to be limited by endolysomal escape.…”

Biocleavable Polycationic Micelles as Highly Efficient Gene Delivery Vectors

“…[1-4]. Various cationic polymers have been applied in in vitro and in vivo gene delivery, including polylysine (PLL) [5,6], polyethylenimine (PEI) [7,8], polyamidoamine dendrimer [9-12], cationic polyester [13,14], poly(beta-aminoester) [15,16], polyphosphoester and polyphosphoramidate [17-21]. In general, water-soluble polycations were directly used to condense negatively charged DNA or RNA to from nanosized polyelectrolyte complexes (polyplexes), which can associate with the negatively charged surface of the cells and facilitate the cells uptake of polycation/DNA (or RNA) complexes.…”

Bioreducible crosslinked low molecular weight branched PEI-PBLG as an efficient gene carrier

“…The linkages include phosphoesters, carbon ester, acetals, glycosides and disulfide etc. [22][23][24]. For example, Forrest et al have synthesized branched PEI (800 Da) crosslinked with 1,3-butanediol diacrylate [25], and Kloeckner et al have used 1,6-hexanediol diacrylate tocross-link OEI800 at low and high temperature, respectively [26].…”