Physicochemical characterization of nanoparticles formed between DNA and phosphorylcholine substituted chitosans

• Published in: Journal of colloid and interface science 2009-08, Vol.336 (1), p.125-133
• Main Authors: Casé, Ana Helena, Picola, Isadora Pfeifer Dalla, Zaniquelli, Maria Elisabete Darbello, Fernandes, Júlio Cesar, Taboga, Sebastião Roberto, Winnik, Françoise M., Tiera, Marcio José
• Format: Article
• Language: English
• Subjects: Animals; Carbohydrate Sequence; Cattle; Chemistry; Chitosan; Chitosan - analogs & derivatives; Colloidal state and disperse state; Colloids; Deoxyribonucleic acid; Derivatives; DNA; DNA - chemistry; Electrophoresis, Agar Gel; Ethidium; Exact sciences and technology; Fluorescence; Fluorescent Dyes; Gene therapy; General and physical chemistry; Hydrogen-Ion Concentration; Molecular Sequence Data; Nanoparticles; Nanoparticles - chemistry; Particle Size; Phosphorylcholine; Phosphorylcholine - chemistry; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Static Electricity; Surface physical chemistry; Thymus Gland - chemistry
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2009.02.069

Phosphorylcholine-substituted chitosan enables the formation of sterically stabilised DNA–chitosan nanoparticles. 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 40CH 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.