Stearic acid grafted chitosan oligosaccharide micelle as a promising vector for gene delivery system: Factors affecting the complexation

Stearic acid (SA) grafted chitosan oligosaccharide (CSO-SA) with different molecular weight of chitosan oligosaccharide (CSO) and graft ratio of stearic acid were synthesized by coupling reaction of SA and CSO. The cationic polymeric micelles of CSO-SA via self-assemble formed and used for gene delivery of fish sperm DNA. Factors affecting complexation and stability of the complexes of CSO-SA micelles and DNA were investigated. The results indicated that pKa of CSO-SA with 3 kDa of CSO decreased from 8.16 to 6.02 as the substitution degree of amino groups of CSO in CSO-SA increased from 9.79% to 63.41%, whereas the molecular weight (MW) of CSO less affected the pKa. As for the stability of complexes, ethidium bromide assay data demonstrated that the complexes consisting of CSO-SA with lower amino substitution degree or smaller molecular weight of CSO were more stable than that with the higher amino substitution degree or molecular weight of CSO. The results also presented that the low pH and ionic strength environment were in favor for the stability of complexes.