Self-Assembly and Gelation in Aqueous Solutions of the Amino Acid L-Cysteine, Silver Nitrate and Polysaccharide Carrageenan

Abstract

With the help of physicochemical methods (viscometry, UV spectroscopy, dynamic light scattering and scanning electron microscopy), the viscosity and structural characteristics of solutions and hydrogels based on L-cysteine and silver nitrate (cysteine–silver solution, CSS) and polysaccharide carrageenan (CAR) are studied. It is found that transparent, stable over time CSS–CAR solutions are formed, if CAR concentration in the samples is varied in the range of 0.0010–0.0030 mg/mL. We assume that association of opposite charged chain structures of cysteine–silver solution with CAR macromolecules due to electrostatic interactions takes place in CSS–CAR samples. Addition of an electrolyte (CuSO₄) into CSS–CAR solution initiates gelation, electrolyte ions join as a linker CSS cluster chains, the same as in CSS–CuSO₄ gels. A scheme of self-assembly and gelation in CSS–CAR and CSS–CAR–CuSO₄ hydrogels is suggested.