Fluorescein Binding with Chitosan and a Chitosan-Based Polyelectrolyte Complex in Aqueous Solutions

Polyelectrolyte complexes of chitosan (ChTS) with κ-carrageenan (CARR) have been obtained and characterized as potential adsorbents of fluorescein (FLC) nanomarker in aqueous media at different pH values. The binding of FLC to ChTS and the κ-CARR–ChTS complex has been studied by spectroscopic methods. The efficiency and mechanism of fluorone dye adsorption on the synthesized complexes have been investigated by analyzing equilibrium adsorption isotherms. The isotherm of FLC adsorption on particles of the polyelectrolyte complex has been adequately described within the framework of the Freundlich model. Data on fluorescence quenching have been used to determine the effective Stern–Volmer constants of FLC with ChTS and the κ-CARR–ChTS complex and to show that the nanomarker is bound to biopolymers via different interaction mechanisms.