Hydrogels from supersaturated phenylalanine solutions: Preparation and characterization

Abstract

This study investigated the gelation properties and structural characteristics of L-phenylalanine (L-Phe) hydrogels prepared through supersaturated L-Phe solutions with supersaturation degrees of 1.75, 2.05, and 2.33, both with and without calcium ions. Results revealed that the supersaturation degree of L-Phe significantly influenced gel formation, thermal properties, and microstructure. Higher supersaturation degrees led to decreased solution stability and reduced gel quality, while lower degrees produced more stable and homogeneous gels. The addition of calcium ions modulated L-Phe interactions, enhancing gel reversibility particularly at lower supersaturation degrees. Rheological studies demonstrated weak strain overshoot behavior and solid-like characteristics across all samples, with both supersaturation degree and calcium presence affecting viscoelastic properties. Microstructural analysis confirmed a fibrous network structure stabilized by weak intermolecular interactions, with evidence of lamellar organization at the nanoscale. Water holding capacity was found to decrease at higher supersaturation degrees, attributed to changes in network structure and hydrophobic interactions. This comprehensive characterization of L-Phe hydrogels provides valuable insights into a novel, clean, and green method for preparing functional L-Phe hydrogels without chemical modification.