Title of Seminar: "Dynamic Hydrogels for Biological Applications"
Presenter: Dr. Adrianne Rosales, Ph.D., Assistant Professor – Department of Chemistry
Date: February 18th, 2022
The extracellular matrix (ECM) is the human body’s “natural material niche” which is present in all tissues and organs. It provides a physical scaffolding for cellular components and influences biochemical and physical cues. The ECM is attached to various structures with a variety of viscoelastic properties.
Currently, the Rosales Group is investigating synthetic ECMs and tissue engineering scaffolds. Potential applications include: treating critical wounds, studying how disease develops, and protecting cells from shear/mechanical forces.
The use of hydrogels is common in tissue engineering scaffolds. Hydrogels are water-swollen networks that may consist of polymers. They can match the elasticity of biological tissues and be functionalized with proteins. Examples of current applications include: eye contact coating, wound dressings and coatings, and alternative sources of leather or meat.
A challenge presented by Dr. Rosales was whether it is possible to design strategies for tuning hydrogel viscoelastic properties to better mimic native tissues. One approach to this is the investigation of using dynamic linkages in synthetic hydrogels to give or increase their reconfigurability. The relation between different reaction rate constants and viscoelastic properties was covered with detail. Two applications presented were the oral delivery of medication and injectable cell delivery.
Dynamic covalent hydrogels (DCH) have a dynamic covalent bond, can break and reform, and are pH-responsive. At a low pH (pH 3), crosslinks between two separate DCH pieces were slow to form (still separate even after 90 minutes). At a high pH (pH 7), crosslinks formed after 5 minutes and diffusion of the interface was evident after 90 minutes. This response to pH is important for the oral delivery of drugs that require absorption after the stomach.
The injection force required to administer a hydrogel through a syringe increased as the reaction rate of the hydrogel increased. Reframed, fast-exchanging hydrogels are stiffer than slow-exchanging hydrogels and therefore required more force to push through a syringe. The Rosales group is currently experimenting with the encapsulation of various cells in both fast- and slow- exchanging hydrogel and measuring the viability of the cells both pre- and post- injection. In closure, the importance of synthetic hydrogels stems from our ability to side-step some of the negative reactions associated with using biologically-derived hydrogels. By providing a closer match to host tissue properties, we can reduce rejection by the immune system of therapeutics or the reliance on immunosuppressants in mitigating rejection of treatments.
For more information about Dr. Adrianne Rosales and her research, please visit https://www.arosalesgroup.com/research