Hybrid 3D Printing of Interfacial Polyelectrolyte Complex Formed between Hyaluronic Acid and Poly-L-lysine Hydrogels

Hyaluronic acid (HA), a principal component of the extracellular matrix (ECM), exhibits excellent biocompatibility, high water-retention capacity, and inherent biodegradability. α-Poly-L-lysine (PLL), a cationic polypeptide with favorable biocompatibility, is widely employed for surface modification to promote cell adhesion and proliferation. Electrostatic interactions between oppositely charged polyelectrolytes enable the formation of interfacial polyelectrolyte complexes (IPC) in the absence of chemical cross-linking agents. In this study, IPC hydrogels were fabricated from HA and PLL and processed via a combination of hybrid and gravity-compensated embedded three-dimensional (3D) printing techniques to generate both two-dimensional (2D) and 3D scaffolds for tissue engineering applications. Using this approach, anisotropic 2D membranes with submicrometer groove topographies were produced, together with mechanically stable 3D fibrous architectures. The resulting IPC hydrogels retained structural integrity under aqueous conditions, demonstrating high morphological controllability and highlighting their substantial potential as scaffolding materials in tissue engineering.