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Soft, Deformable Polyurethane-Boronic Acid Nanoparticles as Dynamic Cross-Linkers to Construct 3D-Bioprintable
Yung-Chen Chang1, Tsai-Yu Chen1, Yi-Ming Sun2
1Institute of Polymer Science and Engineering, National Taiwan University, Taipei 106319, Taiwan, Republic of China.
ACS Applied Materials & Interfaces
|July 8, 2025
Summary
Soft, deformable nanoparticles enhance 3D hydrogel printing. Ellipsoidal polyurethane nanoparticles improve hydrogel stackability and filament resolution by elongating and packing densely during gelation, leading to better 3D bioprinting inks.
Area of Science:
- Materials Science
- Biomaterials Engineering
- Nanotechnology
Background:
- Hydrogel printability can be improved by incorporating nanoparticles.
- The influence of soft, deformable nanoparticles on hydrogel network printability remains underexplored.
Purpose of the Study:
- To investigate the role of soft, dynamic nanocross-linkers in constructing 3D bioprintable hydrogels.
- To explore how nanoparticle morphology and deformation affect hydrogel properties and printability.
Main Methods:
- Synthesis of two boronic acid-functionalized polyurethane (PU) nanoparticles (PUB and PUB') with different soft segment compositions.
- Characterization of nanoparticle morphology using Small-angle X-ray scattering (SAXS).
- Fabrication and mechanical testing (shear modulus, creep resistance) of poly(ethylene glycol) hydrogels cross-linked with PUB or PUB' via dynamic click chemistry.
- Evaluation of 3D printability, including stackability and filament resolution, using a 160 μm nozzle.
- Time-resolved SAXS analysis to observe nanoparticle behavior during gelation.
- Assessment of endothelial cell viability within the hydrogels.
Main Results:
- PUB' nanoparticles, with a mixed soft segment (PCL/PDLLA/PHB), are ellipsoidal and enhance hydrogel shear modulus and creep resistance compared to spherical PUB nanoparticles (PCL only).
- PUB'-based hydrogels show superior 3D printability, including better stackability and filament resolution.
- Time-resolved SAXS reveals PUB' nanoparticles elongate and maintain ellipsoidal shape during gelation, leading to high packing density (38%).
- PUB nanoparticles flatten during gelation, resulting in lower packing density (18%).
- Endothelial cell viability remains high (~92%) in both hydrogel types.
Conclusions:
- Soft nanoparticle morphology and its dynamic deformation during gelation significantly impact the packing density and 3D stackability of dynamic self-healing hydrogels.
- Ellipsoidal PU-boronic acid nanoparticles that elongate and maintain shape during gelation are crucial for designing high-performance 3D hydrogel inks with enhanced printability.
- Particle packing density is a key factor in optimizing 3D hydrogel ink design for bioprinting applications.
