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Updated: Jul 30, 2025

Author Spotlight: Advancing Therapeutics with Biocompatible Sodium Alginate Hydrogel Microspheres
Published on: June 7, 2024
Binary and ternary complexes of epinephrine with alginate and biologically and environmentally relevant metal cations
Anna Irto1, Rosalia Maria Cigala1, Chiara Alessandrello1
1Dipartimento di Scienze Chimiche, Biologiche, Farmaceutiche ed Ambientali, Messina, Italy.
Abstract:
The speciation of epinephrine (Eph -) in the presence of alginate (Alg 2-) and two biological and environmental relevant metal cations (Cu2+, UO2 2+) was investigated at T = 298.15K, I = 0.15-1.00 mol dm-3 in NaCl(aq). The formation of binary and ternary complexes was evaluated and, since epinephrine can behave as a zwitterion, the Eph -/Alg 2- interaction was studied by means of DOSY NMR. The dependence of the equilibrium constants on ionic strength was studied using an extended Debye-Hückel type equation and the SIT approach. The effect of temperature was investigated by means of isoperibolic titration calorimetry: the entropic contribution was the driving force for the Cu2+/Eph - complexes formation. The sequestering ability of Eph - and Alg 2- on Cu2+, evaluated by the pL0.5 calculation, increased with pH and ionic strength. The determination of pM parameter showed that Eph - had a higher Cu2+ affinity with respect to Alg 2-. The formation of Eph -/Alg 2- species was also investigated by UV-Vis spectrophotometry and 1H NMR measurements. The ternary Cu2+/Eph -/Alg and Cu2+/UO2 2+/Eph - interactions were also studied. The "extra-stability" calculated for the mixed ternary species confirmed that their formation was thermodynamically favorable.
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