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GRANULAR HYDROGELS

Granular hydrogels consists of hydrogel microparticles, or "microgels", that are jammed together. Imagine Dippin' Dots made of Jell-O, but the "dots" are ~100x smaller - that's a granular hydrogel! Compared to bulk hydrogels (think - a block of solid Jell-O), granular hydrogels have many advantageous properties, including flowability and injectability, as well as microscale porosity in the interstitial space for enhanced cell migration and molecule transport. Further, the "building block" nature of granular hydrogels allows for many microgel populations to easily be combined into one highly tunable material. My thesis research focuses on designing, fabricating, and utilizing granular hydrogels for bioengineering applications. Learn more about my current projects below!

 

CHEMICAL MODIFICATION OF (BIO)POLYMERS

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I am interested in how (bio)polymers can be processed and chemically modified to fabricate hydrogel networks with beneficial properties. In my thesis work, I have explored how hyaluronic acid can be chemically modified with functional groups to create hydrogels that are covalently photocrosslinked, or reversibly crosslinked with dynamic covalent or physical interactions. See more in my Chemical Reviews article on chemical modification of biopolymers here.

MICROGEL FABRICATION METHODS

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In my thesis work, I have investigating how microgel fabrication method (i.e., microfluidics v. batch emulsions v. mechanical fragmentation) influences microgel and granular hydrogel material properties. One of my ongoing interests is exploring microgel fabrication techniques as a tool to design granular materials for specific applications. Check on my ACS Biomaterials Science and Engineering article on this work here.

ADHESION BETWEEN MICROGELS

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While granular hydrogels offer many advantages, they tend to have weaker mechanical properties, as microgels can easily slide past one another upon loading. In my thesis work, I am investigating how dynamic covalent interparticle adhesion can be used to significantly enhance mechanical integrity of granular hydrogels while maintaining injectability.

EXTRUSION PRINTING WITH GRANULAR HYDROGELS

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Biofabrication is a rapidly growing field, offering the potential to fabricate complex tissue architecture and scaffolds in vitro. For my thesis work, I am investigating how granular hydrogels can be designed and utilized as extrusion printing inks. In the future, I am interested in using granular hydrogel bioinks to create in vitro tissue models.

INJECTABLE TISSUE REPAIR

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Due to their injectability, granular hydrogels offer the potential for use as a minimally-invasive tissue repair strategy. Currently, I am collaborating with Dr. Sarah Gullbrand to translate injectable granular hydrogels for treating degenerative disc disease.

UNDERSTANDING POROSITY IN GRANULAR ASSEMBLIES

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Simulation offers the potential to screen properties of many granular assemblies without fabricating the materials. In my thesis work, I mentored and collaborated with a Penn undergraduate student to simulate pore properties in granular assemblies and correlate simulation outcomes to granular hydrogels fabricated in lab and the behavior of cells within those materials. The outcomes of this work is featured in our biorxiv preprint here​.

 

PUBLICATIONS

1. T.H. Qazi, J. Wu, V.G. Muir, S. Weintraub, D. Lee, S. Gullbrand, D. Issadore, J.A. Burdick. “Anisotropic Rod-Shaped Particles Influence Injectable Granular Hydrogel Properties and Cell Invasion”. bioRxiv preprint. (LINK)

2. V.G. Muir, T.H. Qazi, J. Shan, J. Groll, J.A. Burdick, “Influence of Microgel Fabrication Technique on Granular Hydrogel Properties”, ACS Biomater. Sci. Eng. 2021, 7, 9, 4269–4281 (LINK)

3. V.G. Muir and J.A. Burdick, “Chemically-modified Biopolymers for the Formation of Biomedical Hydrogels”, Chem. Rev. 2021, 121, 18, 10908–10949 (LINK)

4. *C.T. Greco, *V.G. Muir, T.H. Epps, III, and M.O. Sullivan. “Efficient tuning of siRNA dose response by combining mixed polymer nanocarriers with simple kinetic modeling.” Acta Biomaterialia. 50:407-416, 2017. *Denotes co-first authors (LINK)


Forthcoming Publications

1. V.G. Muir, S. Weinstraub, B. Moldanado, P. Arratia, and J.A. Burdick. “Sticking Together: Injectable Granular Hydrogels with Dynamic Covalent Interparticle Adhesion for Enhanced Material Properties”. In preparation.

 

Schematics made with the help of biorender.com, a fantastic science communication and illustration tool!