Spectral and thermochemical research of the DNA polyplex with chitosan formation process and the influence of anionic and cationic compounds

In this paper, the results of a spectral and thermochemical study of the DNA polyplex formation with chitosan and the effect of ethidium bromide polyplexes, sodium dodecyl sulfate, n-octyltrimethyl ammonium bromide, poly(4-styrenesulfonic acid), and heparin on the stability of the complexes are considered. It has been established that chitosan forms thermodynamically stable complexes with ethidium bromide (EtBr), in which there exists one monomer unit of chitosan for two ethidium bromide ones. The interaction of ethidium bromide with chitosan leads to a charge exchange of the polymer surface. The impact of chitosan on the intercalated DNA-EtBr complex conditions a release of EtBr with a polyplex formation. The process of polyplex formation in the presence of ethidium bromide proceeds endothermically, and in its absence the reaction is exothermic. The polyplex particles formed from DNA after release of EtBr are larger and have a smaller charge, as compared to the polyplex particles obtained without ethidium bromide. It has been found that anionic compounds cause the degradation of polyplexes, and it can prove to be a significant obstacle for using chitosan polyplexes in transfection, since in the presence of heparin in the bloodstream, the complexes will break down before reaching the target.