Synthesis, Rheological Properties, and Hemocompatibility of Alginic Acid Modified with Ethylenediamine Fragments

An alginic acid derivative containing amide and amino groups was synthesized by adding ethylenediamine to the carboxyl groups of the polysaccharide activated by carbodiimide. Our analysis of its structure using NMR spectroscopy confirms that the addition of ethylenediamine occurs with the formation of an amide bond and the appearance of free primary amino groups in an equimolar ratio. Using the methods of rotational and capillary viscometry in combination with dynamic light scattering and potentiometric titration, it was shown that the critical concentration for the transition to the solution mode with Ce entanglements correlates with the degree of substitution and the change in the zeta potential of the modified polysaccharides. The latter are characterized by a lower Ce concentration and, on average, a lower activation energy for the viscous flow of solutions than sodium alginate. In the pH range 6.5–6.0 for semi-diluted solutions of modified polysaccharide and sodium alginate, an oppositely directed change in the size of macromolecular aggregates is observed. The hemocompatibility of the modified polysaccharide was studied in vitro in tests of blood recalcification time, activated partial thromboplastin time, and platelet aggregation. It was shown that the modified polysaccharide does not affect blood coagulation (at concentrations of 0.033 and 2.22 mg/mL), plasma coagulation (at concentrations up to 0.0465 mg/mL), and platelet aggregation (at concentrations up to 0.182 mg/mL).