Supragel Assembly of HA-NIPAAm Microgels via UV-Crosslinking Using a Low-Cost LEGO 3D Printer
Klaudija Janic, Maximilian Löckener, Birte Achilles, Magnus Lücking, Julian Thiele, Institute of Chemistry, Otto-von-Guericke University, Magdeburg; Germany
Hyaluronic acid (HA) is a biomaterial widely used in tissue engineering, regenerative medicine, and drug delivery. While HA-based bioinks support cell viability and tissue-specific functions, their low viscosity often limits printability, necessitating modifications [1]. We address this challenge by preparing microgel suspensions from HA to tailor ink viscosity by microgel size and concentration. For added functionality, microgels made from poly(N-isopropylacrylamide) (PNIPAAm), a thermo-responsive polymer chosen for its ease of functionalization and ability to maintain cell viability, are mixed in [2]. These particle-based PNIPAAm and HA inks are combined at varying volumetric ratios, extruded via 3D printing, and exposed to UV light for inter-particle crosslinking via [2+2] cycloaddition of DMMIAAm groups on the microgel’s surface with a PEG-based crosslinker incorporating dynamic thiol-ester bonds into the microgel assembly [3, 4]. Our dual-microgel ink system provides high biocompatibility, tunable rheological properties, improved 3D printing fidelity, making it ideal for advanced bioprinting. Integration of thiol-ester bonds in the scaffolds promotes stimuli-responsive behavior, controlled degradation, and stress-relaxing properties, fostering an environment conducive to tissue regeneration, remodeling, and enhanced cell-material interactions. As a 3D printing platform, we use a modular, customizable 3D printer built from LEGO Technic bricks, advancing a protocol by A. Moukachar et al [5]. platforming detail, we develop micrometer-precise extrusion nozzles, fabricated via projection-microstereolithography (PμSL), designed to fit LEGO pieces with pin-like lock geometry. Four nozzle geometries are introduced, each optimizing the printing process further by varying internal channel design. These nozzles improve control over material flow and prevent clogging due to microgel agglomeration.
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