title: Thermo and pH responsive polymers as gene delivery vectors: effect of polymer architecture on DNA complexation in vitro.
abstract: Poly(N-isopropylacrylamide) (PNIPAm) co-polymers responsive to temperature and pH were prepared with side chain chemistries in order to exhibit phase transitions under physiologically relevant conditions. Fluorescence spectroscopy, gel retardation assays, dynamic light scattering and atomic force microscopy were used to characterize the binding of plasmid DNA to these materials and to control polymers poly(ethyleneimine) (PEI) and poly(ethyleneimine)-octanamide. Complexes of plasmid DNA with thermoresponsive cationic polymers containing PNIPAm displayed variations in gel retardation behaviour above and below polymer phase transition temperatures, with a high molecular weight linear cationic PNIPAm co-polymer forming complexes with reduced affinity above LCST whereas a branched PEI-PNIPAm co-polymer bound with higher affinity above the PNIPAm phase transition. The thermoresponsive polymers also exhibited changes in particle morphology across the same temperature ranges with polymer DNA complexes prepared at N/P ratios of 2:1 generating spherical particles varying in radius between 30-70 nm at 25 degrees C and 60-100 nm at 40-45 degrees C. The transport of DNA within these complexes to cell nuclei was demonstrated to occur within 24 h in tissue culture via confocal microscopy, and low level transfection of mouse muscle cells by a reporter gene encoding green fluorescent protein was achieved with the branched thermoresponsive PEI-PNIPAm conjugate.
authors.affiliation: School of Pharmacy and Biomedical Sciences, and Institute of Biomedical and Biomolecular Science, University of Portsmouth, St. Michael's Building, White Swan Road, Portsmouth PO1 2DT UK.
authors.forename: Beverley R
authors.initials: BR
authors.lastname: Twaites
authors.forename: Carolina
authors.initials: C
authors.lastname: de las Heras Alarcón
authors.forename: David
authors.initials: D
authors.lastname: Cunliffe
authors.forename: Matthieu
authors.initials: M
authors.lastname: Lavigne
authors.forename: Sivanand
authors.initials: S
authors.lastname: Pennadam
authors.forename: James R
authors.initials: JR
authors.lastname: Smith
authors.forename: Dariusz C
authors.initials: DC
authors.lastname: Górecki
authors.forename: Cameron
authors.initials: C
authors.lastname: Alexander
mesh_terms: D000818:Animals; D004247:DNA / Q000008:administration & dosage* / Q000235:genetics / Q000493:pharmacokinetics; D016503:Drug Delivery Systems / Q000379:methods*; D005822:Genetic Vectors / Q000008:administration & dosage* / Q000235:genetics / Q000493:pharmacokinetics; D006863:Hydrogen-Ion Concentration; D051379:Mice; D032446:Myoblasts / Q000187:drug effects / Q000378:metabolism; D011108:Polymers / Q000008:administration & dosage* / Q000493:pharmacokinetics; D013696:Temperature
chemical_list: D011108:Polymers; D004247:DNA