Dextran-Agmatine Derivative-Based Nonviral Trangene Vectors

In this work, the dextran-agmatine bioconjugate (Dex-Agm) was prepared by thenucleophilic substitution reaction between tosyl of tosylated dextran and primaryamine of agmatine; laurate tosylated dextran was synthesized via CDI activation oflauric acid, and then lauric acid modified dextran-agmatine bioconjugates(Dex-L-Agm) was prepared by the analogous nucleophilic substitution reaction.Agarose electrophoresis, TEM and Zeta potential measturements indicated thatdextran-agmatine bioconjugates (Dex-Agm) were capable of condensing DNA intonanocomplexes, and incorporating lauric acid promoted the complexation ofconjugate with DNA supposedly due to the cooperative binding effect attributed tohydrophobic interaction. Higher degree substitution of agmatine and hydrophobicgrafting resulted in increased luciferase activities expressed in COS-7and HEK293cells; Semiquantitative assay of GFP expression by flow cytometry in COS-7,HEK293and CHOK1cells further demonstrated that conjugation of fatty acid couldremarkably increase gene transfection of Dex-Agm in spite of1.1～2.3-fold lowerefficiency compared to Exgen500. The biocompatibilities of Dex-Agm andDex-L-Agm were assessed in detail by hemolytic activity determination, red bloodcell aggregation assay as well as MTT evaluation of degraded products. Dex-Agm andDex-L-Agm were shown to be highly cytocompatible without causing hemolysis andred blood cell aggregation presumably owing to the bidentate hydrogen bonding ofguanidine with the constituents present in cell membrane rather than electrostaticinteractions alone, which could cause cell damage. Importantly, cells cultured with thedegraded products of Dex-Agm and Dex-L-Agm retained more than80%viability,suggesting their potential application as a gene delivery vector.A histamine modified dextran-agmatine bioconjugate (Dex-Agm-His) possessingproton buffering capacity was synthesized by using the abovementioned method withonly changing the feed ratio of agmatine and histamine. Conjugation of histaminecould faciliate the complexation with DNA and also changed the zeta potential andsize of the complexes due to incremental charge density attributed to the secondaryamine of histamine group. Dex-Agm-His-mediated gene transfetion in various celllines will be investigaed in the future.