Controlled Mechanical Property Gradients Within a Digital Light Processing Printed Hydrogel-Composite Osteochondral...

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Mechanical Engineering

Background:

• Tissue engineered scaffolds require mechanical properties that match native tissues to guide cell behavior.
• Current scaffolds often lack the precise control over stiffness gradients needed to emulate complex tissue microenvironments.

Purpose of the Study:

• To design and fabricate micro-truss scaffolds with spatially varying geometry and controlled stiffness gradients.
• To emulate micrometer-scale strain gradients within tissues to guide cell mechanobiological responses.
• To create scaffolds for osteochondral defect regeneration with distinct cartilage and bone layers.

Main Methods:

• Utilized a custom projection microstereolithography (μSLA) system with digital light projection (DLP) and photopolymerizable poly(ethylene glycol) diacrylate (PEGDA) hydrogel monomers.
• Developed three designs: uniform structure, gradient structure, and osteochondral bilayer, with feature sizes < 200 μm.
• Employed finite element models (FEM) for design guidance and predicted mechanical environments, validated with X-ray microscopy (XRM) and compression tests.

Main Results:

• Achieved target moduli for cartilage (1 MPa) and bone (7 MPa) while maintaining 68-81% porosity.
• FEM accurately predicted regional stiffnesses, validated by XRM imaging and compression of micro-truss structures.
• FEM demonstrated stress-shielding effects and predicted strain distributions within the hydrogel infill.

Conclusions:

• Composite scaffolds from μSLA-printed polymers support physiological loads and allow controlled mechanical property gradients.
• These advanced scaffolds show potential for improving in vivo outcomes in osteochondral defect tissue regeneration.
• Integrated 3D imaging and FE analysis offer crucial insights into the cellular mechanical environment within composite scaffolds.