title: Synthesis and evaluation of diethylethylamine-chitosan for gene delivery: composition effects on the in vitro transfection efficiency.
abstract: Chitosan has been indicated as a safe and promising polycation vector for gene delivery. However its low transfection efficiency has been a challenging obstacle for its application. To address this limitation, we synthesized chitosan derivatives which had increasing amounts of diethylethylamine groups (DEAE) attached to the chitosan main chain. The plasmid DNA VR1412 (pDNA), encoding the ß-galactosidase (ß-gal) reporter gene was used to prepare nanoparticles with the chitosan derivatives, and the transfection studies were performed with HeLa cells. By means of dynamic light scattering and zeta potential measurements, it was shown that diethylethylamine-chitosan derivatives (DEAE(x)-CH) were able to condense DNA into small particles having a surface charge depending on the polymer/DNA ratio (N/P ratio). Nanoparticles prepared with derivatives containing 15 and 25% of DEAE groups (DEAE(15)-CH and DEAE(25)-CH) exhibited transfection efficiencies ten times higher than that observed with deacetylated chitosan (CH). For derivatives with higher degrees of substitution (DS), transfection efficiency decreased. The most effective carriers showed low cytotoxicity and good transfection activities at low charge ratios (N/P). Vectors with low DS were easily degraded in the presence of lysozyme at physiological conditions in vitro  and the nontoxicity displayed by these vectors opens up new opportunities in the design of DEAE-chitosan-based nanoparticles for gene delivery.
authors.affiliation: Department of Chemistry and Environmental Sciences, IBILCE, São Paulo State University-UNESP, São José do Rio Preto, São Paulo, Brazil.
authors.forename: Franciele
authors.initials: F
authors.lastname: de Paula Pansani Oliveira
authors.forename: Isadora Pfeifer
authors.initials: IP
authors.lastname: Dalla Picola
authors.forename: Qin
authors.initials: Q
authors.lastname: Shi
authors.forename: Hellen Franciane Gonçalves
authors.initials: HF
authors.lastname: Barbosa
authors.forename: Vera Aparecida de Oliveira
authors.initials: VA
authors.lastname: Tiera
authors.forename: Júlio Cesar
authors.initials: JC
authors.lastname: Fernandes
authors.forename: Marcio José
authors.initials: MJ
authors.lastname: Tiera
mesh_terms: D002021:Buffers; D016923:Cell Death / Q000187:drug effects; D048271:Chitosan / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D004587:Electrophoresis, Agar Gel; D004996:Ethidium / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008027:Light; D009682:Magnetic Resonance Spectroscopy; D053758:Nanoparticles / Q000737:chemistry; D010316:Particle Size; D010957:Plasmids / Q000378:metabolism; D012542:Scattering, Radiation; D012996:Solutions; D055672:Static Electricity; D014162:Transfection / Q000379:methods*
chemical_list: D002021:Buffers; D012996:Solutions; C583771:diethylethylamine-chitosan; D048271:Chitosan; D004996:Ethidium