title: Physicochemical characterization of nanoparticles formed between DNA and phosphorylcholine substituted chitosans.
abstract: The interactions between phosphorylcholine-substituted chitosans (PC-CH) and calf-thymus DNA (ct-DNA) were investigated focusing on the effects of the charge ratio, the pH, and phosphorylcholine content on the size and stability of the complexes using the ethidium bromide fluorescence assay, gel electrophoresis, dynamic light scattering, and fluorescence microscopy. The size and colloidal stability of deacetylated chitosan (CH/DNA) and PC-CH/DNA complexes were strongly dependent on phosphorylcholine content, charge ratios, and pH. The interaction strengths were evaluated from ethidium bromide fluorescence, and, at N/P ratios higher than 5.0, no DNA release was observed in any synthesized PC-CH/DNA polyplexes by gel electrophoresis. The PC-CH/DNA polyplexes exhibited a higher resistance to aggregation compared to deacetylated chitosan (CH) at neutral pH. At low pH values highly charged chitosan and its phosphorylcholine derivatives had strong binding affinity with DNA, whereas at higher pH values CH formed large aggregates and only PC-CH derivatives were able to form small nanoparticles with hydrodynamic radii varying from 100 to 150 nm. Nanoparticles synthesized at low ionic strength with PC-CH derivatives containing moderate degrees of substitution (DS=20% and 40%) remained stable for weeks. Photomicroscopies also confirmed that rhodamine-labeled PC(40)CH derivative nanoparticles presented higher colloidal stability than those synthesized using deacetylated chitosan. Accordingly, due to their improved physicochemical properties these phosphorylcholine-modified chitosans provide new perspectives for controlling the properties of polyplexes.
authors.affiliation: Department of Physics, Institute of Biosciences, Humanities, and Exact Sciences, IBILCE, São Paulo State University, UNESP, São José do Rio Preto, São Paulo, Brazil.
authors.forename: Ana Helena
authors.initials: AH
authors.lastname: Casé
authors.forename: Isadora Pfeifer
authors.initials: IP
authors.lastname: Dalla Picola
authors.forename: Maria Elisabete Darbello
authors.initials: ME
authors.lastname: Zaniquelli
authors.forename: Júlio Cesar
authors.initials: JC
authors.lastname: Fernandes
authors.forename: Sebastião Roberto
authors.initials: SR
authors.lastname: Taboga
authors.forename: Françoise M
authors.initials: FM
authors.lastname: Winnik
authors.forename: Marcio José
authors.initials: MJ
authors.lastname: Tiera
mesh_terms: D000818:Animals; D002240:Carbohydrate Sequence; D002417:Cattle; D048271:Chitosan / Q000031:analogs & derivatives*; D004247:DNA / Q000737:chemistry*; D004587:Electrophoresis, Agar Gel; D004996:Ethidium; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D010767:Phosphorylcholine / Q000737:chemistry*; D055672:Static Electricity; D013950:Thymus Gland / Q000737:chemistry
chemical_list: D005456:Fluorescent Dyes; D010767:Phosphorylcholine; D004247:DNA; D048271:Chitosan; D004996:Ethidium