PREPARATION OF CHITOSAN SELF-AGGREGATES AS A GENE DELIVERY SYSTEM

Hydrophobically modified chitosan containing 5.1 deoxycholic acid grou ps per 100 anhydroglucose units was synthesized by an EDC-mediated cou pling reaction. Formation and characteristics of self-aggregates of hy drophobically modified chitosan were studied by fluorescence spectrosc opy and dynamic light scattering method. The critical aggregation conc entration (cac) of the self-aggregate was determined by measuring the fluorescence intensity of pyrene as a fluorescent probe. The cac value in PBS solution (pH 7.2) was 1.7 x 10(-2) mg/ml. Mean diameter of sel f-aggregates in PBS solution (pH 7.2) was 162 +/- 18 nm with an unimod al size distribution. Charge complex formation between self-aggregates and plasmid DNA was confirmed by electrophoresis on an agarose gel. M igration of DNA on an agarose gel was completely retarded above a char ge ratio (+/-) of 4/1 at pH 7.2. The free DNA dissociated from the com plexes was observed by electrophoresis above pH 8.0 at a fixed charge ratio of 4/1. An efficient transfection of COS-1 cells was achieved by self-aggregates/DNA complexes. (C) 1998 Elsevier Science B.V.