Question

What happens to polymer crosslinking in hydrogels over time when cells interact with stress relaxing hydrogels compared to purely elastic nondegrading hydrogels?

Based on your answer above, would you predict that cells undergo less or more cell spreading in stress relaxing gels compared to purely elastic nondegrading gels? Provide reasons to support your prediction?

Would you use stress relaxing hydrogels or purely elastic, but degradable hydrogels to engineer bone tissues from MSCs? Provide reasons to support your preference.

Answer 1

Polymer cross-linking is a method to improvise the characteristics of a polymer, like flexibility, resistance to flow, tensile strength, etc. Cross-linking can be done by two methods such as chemical or by electron irradiation.

Chemical cross-linking of the polymers is termed as vulcanization and in the electron irradiation, high energy electrons are bombarded in the polymer molecules where they release molecular hydrogen and forms bond between the polymer.

Hydrogels are cross-linked hydrophilic polymers having the ability to hold the water molecules or the biological fluids. They are insoluble in water as well considered as soft tissue hence their application in medical and in agricultural fields are very wide.

Cells adhered to the stress relaxing hydrogels show faster cell proliferation and spreading when compared to the elastic non-degrading Hydrogels. Hydrogels are purely elastic when we culture cells in these hydrogels it shows constant growth. In the natural extracellular matrix, they show a property called visco-elasticity so the cells grow to show an exponential increase in the cell spreading and proliferation.

In stress relaxing hydrogels, they alter there property independent on their initial elastic modulus, degradation, and cell adhesion ligand density and results in the visco-elastic property shown by the natural extracellular matrix. And finally leads to improved cell spreading and proliferation.

The usage of the stress relaxing hydrogels is most preferred for the growth of bone tissues from the mesenchymal stem cells(MSCs). In our body, the muscle cells exhibit Viscoelasticity and due to its stress relaxation makes the myoblasts for its cell proliferation and spreading. Hence this is also a similar case, with the bone tissue the most preferred for the growth is the stress relaxing hydrogels.