title: The effect of formulation parameters on the size of poly-((2-dimethylamino)ethyl methacrylate)-plasmid complexes.
abstract: The aim of this study was to gain insight into the formulation parameters affecting the size of poly((2-dimethylamino)ethyl methacrylate)-plasmid complexes (polyplexes). Experimental designs were applied to screen and optimize several variables, which may influence the complex size. In a screening design, it was demonstrated that at a fixed concentration of plasmid (40 micrograms/ml) after incubation with polymer, the size of the resulting polyplexes was highly dependent on the polymer/plasmid ratio as well as on the pH, viscosity (i.e. sucrose concentration) and ionic strength of the aqueous solution. However, the temperature, PEG 600 (up to 5% (v/v)) and Tween 80 (up to 0.2%) had a marginal effect on the size of the polyplexes. In an optimization design, the effect of the pH, polymer/plasmid ratio and Tween on the size of the polymer/plasmid complexes prepared at relatively high concentration of plasmid (50-200 micrograms/ml) was evaluated. Based on the results of the optimization design, a mathematical model was derived, which describes the relationship between the size of the polyplexes and the different formulation parameters. This model shows that even at high plasmid concentration (200 micrograms/ml), small sized polyplexes were formed at low pH and ionic strength, especially when the solution contains 20% (w/v) sucrose. This concentrated polyplex dispersion (polymer/plasmid ratio > 3/1 (w/w), 200 micrograms plasmid/ml) can be diluted down to 5 micrograms/ml plasmid without significant changes in particle size and transfection potential. At lower ratios, a growth in particle size was observed upon dilution of the complexes, which might also explain the low transfection efficiency of these polyplexes in vitro.
authors.affiliation: Department of Pharmaceutics, Utrecht University, The Netherlands.
authors.forename: J Y
authors.initials: JY
authors.lastname: Cherng
authors.forename: H
authors.initials: H
authors.lastname: Talsma
authors.forename: R
authors.initials: R
authors.lastname: Verrijk
authors.forename: D J
authors.initials: DJ
authors.lastname: Crommelin
authors.forename: W E
authors.initials: WE
authors.lastname: Hennink
mesh_terms: D000818:Animals; D019556:COS Cells; D002461:Cell Line, Transformed; D004337:Drug Carriers; D010957:Plasmids; D011109:Polymethacrylic Acids / Q000138:chemical synthesis; D011994:Recombinant Proteins / Q000096:biosynthesis; D013539:Simian virus 40 / Q000235:genetics; D014162:Transfection / Q000379:methods*; D001616:beta-Galactosidase / Q000235:genetics*
chemical_list: D004337:Drug Carriers; D011109:Polymethacrylic Acids; D011994:Recombinant Proteins; D001616:beta-Galactosidase