Co-regulation of gelatin content and Hofmeister effect on 3D-printed high internal phase emulsion gel characteristics for resveratrol delivery

Abstract

The study investigated the influence of gelatin (GE) content and the Hofmeister effect on the physicochemical, rheological, and printing properties of high internal phase emulsion (HIPE) gels. Incremental GE content introduced more triple helix structures (junction zones) in the continuous phase of HIPE. By soaking in a sodium citrate (Na₃Cit)-glycerol-water solution, polymer chain bundling, hydrophobic interactions, and abundant hydrogen bonds between GE and glycerol further increased, achieving a more compact crosslinking density and internal network. The optimized HIPE-GE-Cit^3- gel with 1.5 wt% GE displayed improved shape retention, generating smoother and firmer gels with enhanced freezing and heat resistance. Its excellent mechanical strength and viscoelasticity can resist large deformations and maintain reversible structures. HIPE-GE gel with 1.5 wt% GE demonstrated satisfactory printing suitability with clear outlines, favorable visual aesthetics, and minimal dimensional deviation. This post-soaking (Hofmeister effect) also eliminated rough surfaces and visible layered lines, improved mechanical properties and more elastic networks. The printed HIPE-GE_1.5-Cit^3- gel with higher rigidity and elasticity impeding molecular release, protected encapsulated resveratrol against degradation, especially from heat, and enhanced the release rate in the small intestine, achieving sustained release. This work produced customizable HIPE gels by 3D printing with multiple advantages to develop personalized nutraceutical carriers with high-temperature tolerance.