Double-Crosslinking Strategy in the Synthesis and Control of Properties of Pectin-Based Hydrogels

The application of a double-crosslinking strategy to the synthesis of hydrogels based on highly methoxylated pectin was demonstrated. The covalent crosslinking was formed through the reaction of the ester groups of pectin with succinic acid dihydrazide to form an acylhydrazone bond. The physical crosslinking was established through ionic interactions between the acidic groups of pectin and calcium ions. The combination of physical and covalent crosslinking was shown to enhance the mechanical strength of the hydrogels, resulting in a 35–75-fold increase in the shear modulus (depending on the crosslinker concentration) compared to hydrogels prepared by covalent crosslinking alone. At the same time, double crosslinking led to a 1.9–2.5-fold reduction in swelling in a neutral medium and a 1.3–6.0-fold increase in the total degradation time.