Hyaluronic acid-based Pickering emulsion filled gels with cascaded pH-responsiveness: A promising 3D printable inks

This study demonstrated the fabrication of hyaluronic acid-based Pickering emulsion-filled gels with cascaded stimuli-responsiveness through interfacial engineering. Core-shell polymer particles featuring amino group-functionalized surfaces were first synthesized via RAFT-mediated polymerization-induced self-assembly (PISA), followed by post-polymerization hydrolysis under acidic conditions. The resulting particles were employed to stabilize corn oil-in-water Pickering emulsions, which were subsequently incorporated into an aqueous solution of aldehyde-functionalized hyaluronic acid (AHA) to form Pickering emulsion-filled gels. Gelation was achieved through a Schiff base reaction between the amino groups on the Pickering emulsifiers and the aldehyde groups on the AHA backbones. The resulting gels exhibited tunable mechanical properties, injectability, rapid self-healing capability, and cascaded pH-responsiveness, enabling sequential transitions from gels to sols and ultimately to phase-separated corn oil/water binary systems. Due to these properties, the cascade-responsive Pickering emulsion-filled gels could serve as promising 3D-printable inks, exhibiting diverse applications in personalized food, pharmaceuticals, and cosmetics.