Gellan Hydrogel Reinforced by WPI Amyloid Fibrils

Amyloid Fibrils (AF) are highly organized structures formed by the aggregation of proteins into long chains of β-sheet structures, resulting in high aspect ratio and enhanced mechanical properties. The addition of AF to biopolymeric networks represents a promising approach to overcome the inherent mechanical weakness of some hydrogels. In this work, we reinforced Gellan (G) hydrogels with different WPI structures (native or fibrillated) and compared with the improvements achieved by increasing G concentration (0.5%, 1.0%, and 1.5% w/w). AF were obtained from WPI (2% w/w) at pH 2 and 90 °C for 8 h. Fibrillation kinetics, evaluated by the difference between initial and final protein content during the fibrillation process, indicated fibril formation after 1 h of treatment, with stabilization after 4 h. Spectrophotometric scanning with Congo red (1 mM) showed increased absorbance at 500 nm, indicating a higher concentration of β-sheet structures after fibrillation process. The fibril solution was applied to G hydrogels (1:5 v/v AF/G) at pH 3.5 and compared with hydrogels containing native protein solution and control hydrogels with G only at the same concentrations. The mechanical properties of the hydrogels were evaluated by uniaxial compression tests. The 0.5% G hydrogel without AF/WPI addition did not form a self-supporting gel. Increasing G concentration improved rupture stress, Hencky strain, and stiffness across all treatments. Hydrogels with WPI or AF addition showed higher rupture stress and Hencky strain, as well as improved structural stiffness than pure G hydrogels, with AF-reinforced hydrogels showing significantly greater mechanical reinforcement at all G concentrations. The incorporation of AF significantly enhanced the mechanical properties of G hydrogels, being a successful strategy for developing more resistant biomaterials for food applications.