Double-Network Polyurethane-Gelatin Hydrogel with Tunable Modulus for High-Resolution 3D Bioprinting

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Regenerative Medicine

Background:

• Three-dimensional (3D) bioprinting utilizes bioinks to create customized tissues for regeneration or organoids for drug screening.
• Developing advanced bioinks with tunable properties is crucial for successful bioprinting applications.

Purpose of the Study:

• To develop and characterize a series of biodegradable polyurethane (PU)-gelatin hydrogels as a novel bioink for 3D bioprinting.
• To evaluate the printability, mechanical properties, stability, and biological performance of the developed PU-gelatin hydrogel.

Main Methods:

• Synthesis of biodegradable PU-gelatin hydrogels with tunable mechanical properties and degradation rates.
• Assessment of printability, including complex structure formation, working window, stacking ability, and resolution using various nozzle sizes.
• Evaluation of structural stability via Ca2+ chelation and thermal gelation, and mechanical property enhancement.
• Incorporation and assessment of Mesenchymal Stem Cells (MSCs) viability, mobility, and proliferation within the hydrogel constructs.
• Investigation of MSC-laden construct chondrogenesis in the presence of a small molecule drug.

Main Results:

• The PU-gelatin hydrogel exhibited good printability at 24-31 °C and could form complex shapes.
• The bioink demonstrated excellent shear thinning, fast strain recovery, a long working window (>24 h), stacking ability (80 layers), and high-resolution printing (80 μm nozzle).
• Stable structures were formed via a two-stage double-network without toxic reagents, with mechanical modulus increasing threefold after CaCl2 treatment and further upon incubation.
• Printed MSCs showed good viability, high mobility, and significant proliferation (∼200-300% in 10 days).
• MSC-laden constructs underwent chondrogenesis within 10 days.

Conclusions:

• The novel PU-gelatin hydrogels offer tunable mechanical properties, a long working window, and high-resolution printing capabilities.
• These hydrogels provide a convenient and effective bioink platform for 3D bioprinting of various tissues.
• The developed bioink supports cell viability, proliferation, and differentiation, showing promise for regenerative medicine.