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Synergistic Release of DNA from pH Responsive Polyion Complexes (PICs)

G. Harper
WetaScience, UK

DNA controlled release pH responsive polyion complex

Polyelectrolyte complexes based on an outer layer of cationic polyhydroxylamine (PT) were prepared on carboxylated microparticles pretreated with polyamine (A) and a middle layer of Polyacrylic Acid (PA). A synergistic effect between PT and PA layers provides greater binding with release of DNA (11.5 µg/mg, 0.36se) on pH change compared to PT adsorbed without a supporting polyanion (7.95 µg/mg, 0.38se). Historically polyelectrolyte complexes formed in solution between polyions of opposite charge, polycations and polyanions, were considered to be largely stoichiometric in structure1. More recent evidence suggests that non-stoichiometry occurs within PECs according to formulation conditions2. The formation of PEC multilayers or nanolayers on substrates is now receiving attention3. Our development of a polycationic polyhydroxylamine with a pKa below 9 allows the synthesis of alternating polyion layers on a magnetic bead substrate . These beads have the capability to bind polyanionic DNA at low pH (4) and elution at a moderate pH(8), with obvious utility in isolation and purification of DNA in aqueous media.
pH dependent DNA binding and elution from polyhydroxylamine [PT] containing PECs is described. Significantly greater binding and subsequent release of DNA is achieved by PT, as a PEC, than as a simply adsorbed polycation (Fig 6.). Synergism exists between anionic PA, as a supporting layer, and cationic PT providing a significant increase in DNA binding and elution (11.6 (0.4se) vs 7.9 (0.4se) µgDNA/mg beads) . Polyanion and polycation layer presence is confirmed by both zeta potential and dye binding results. NR dye recovery from PA with PT present (C/AF/PA/PT) provides evidence that the electrosteric architecture of each polyion layer is largely conserved between adjacent polyion layers.

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