Network architecture dependent mechanical response in temperature responsive collagen-PNIPAM composites

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Biophysics

Background:

• Collagen is a key component of the extracellular matrix, crucial for tissue structure and function.
• Developing in-vitro collagen-based materials with tunable mechanical properties is vital for biomedical and tissue engineering.
• Thermo-responsive polymers offer potential for dynamic control over material characteristics.

Purpose of the Study:

• To investigate the reversible mechanical switching behavior of a biocompatible composite material.
• To explore the role of poly(N-isopropylacrylamide) (PNIPAM) microgel particles in modulating collagen network mechanics.
• To understand how temperature-induced changes in microgel size affect composite properties.

Main Methods:

• Fabrication of a composite material using collagen networks and thermo-responsive PNIPAM microgel particles.
• Utilizing the lower critical solution temperature (LCST) of PNIPAM to induce swelling and de-swelling of microgel particles.
• Measuring the shear modulus of the composite material under varying temperature conditions.
• Employing confocal imaging to visualize microgel particle distribution and collagen network architecture.

Main Results:

• The composite exhibits reversible mechanical switching, with enhanced shear modulus observed when microgel particle diameter deviates from the polymerization temperature.
• This mechanical enhancement is independent of whether the particles are swelling or de-swelling.
• The extent of shear modulus enhancement is significantly correlated with the collagen network's mesh size, which is temperature-dependent.
• Confocal imaging demonstrated that reversible microgel clustering above LCST is critical for the observed switching response.

Conclusions:

• Collagen-PNIPAM microgel composites display tunable mechanical properties through temperature-induced changes in microgel size.
• The collagen network architecture plays a significant role in mediating the mechanical response of the composite.
• This study provides insights into designing smart biomaterials with controllable mechanical functions for advanced applications.