Creating Physicochemical Gradients in Modular Microporous Annealed Particle Hydrogels via a Microfluidic Method

Area of Science:

• Biomaterials Engineering
• Microfluidics
• Tissue Engineering

Background:

• Microporous annealed particle (MAP) hydrogels offer controlled heterogeneity for biomaterial development.
• Creating precise physicochemical gradients within hydrogels is challenging but crucial for mimicking native tissue environments.

Purpose of the Study:

• To develop a microfluidic method for fabricating poly(ethylene glycol)-based MAP hydrogels with controlled physicochemical gradients.
• To evaluate the stability of these gradients after injection and their impact on human mesenchymal stem cell (hMSC) behavior.

Main Methods:

• Utilized a microfluidic system combining mixing and droplet generation modules to produce microgels with varying properties.
• Adjusted precursor solution flow rates to control gradient formation, collected microgels layer-by-layer, and annealed them using thiol-ene click chemistry.
• Assessed gradient stability in vitro and after mock implantation, and studied hMSC responses to gradients in stiffness and degradability.

Main Results:

• Successfully generated continuous physicochemical gradients within MAP hydrogels.
• Demonstrated that the gradient profile was maintained after injection, indicating suitability for in situ applications.
• Observed that hMSC spreading and proliferation increased with stiffness, and robust spreading occurred above a critical degradability threshold.

Conclusions:

• The developed microfluidic approach enables the creation of MAP hydrogels with stable, tunable physicochemical gradients.
• These gradient hydrogels provide a powerful platform for investigating cell-material interactions and advancing tissue engineering strategies.
• The method offers a novel route for developing advanced biomaterials for regenerative medicine.