(79e) Responsive Hydrogel Networks Controlled By Bacterial Metabolism

Responsive Hydrogel Networks Controlled by Bacterial
Metabolism

Austin
J. Graham^1,2, Adrianne M. Rosales^1,2, Benjamin K. Keitz^1,2

¹McKetta
Department of Chemical Engineering, University of Texas at Austin, Austin, TX

²Center
for the Dynamics and Control of Materials, University of Texas at Austin,
Austin, TX

Materials that
respond to their surroundings and exhibit dynamic functions are needed to meet the
demands of diverse chemical and biological environments. Engineered living
materials (ELMs) are one such class of materials defined by their incorporation
of autonomous cells that use biological functions to control material
properties. Our group recently demonstrated that extracellular electron
transfer (EET) from the organism Shewanella
oneidensis can be leveraged to control the redox equilibrium of metal catalysts
and synthesize polymers via atom-transfer radical polymerization¹. Using
this method, we report the production of hydrogel ELMs in which S. oneidensis MR-1 controls the crosslinking of methacrylated
hyaluronic acid. Crosslinking by genetic knockouts demonstrated that hydrogel
formation was closely coupled to the expression of specific EET proteins, as
gelation kinetics and stiffness correlated to the number of removed EET genes. While
traditionally radical-based reactions only succeed in anaerobic environments,
rapid bacterial consumption of dissolved oxygen followed by a shift to
anaerobic metabolism enabled hydrogel synthesis in ambient conditions, without the
need for dedicated oxygen scrubbing. Finally, knockout strains complemented by an
inducible EET gene showed inducer-dependent crosslinking, demonstrating control
of material properties using design principles from synthetic biology. By
coupling EET to crosslink density, we have engineered a platform that utilizes
endogenous bacterial metabolism to control and evolve material properties in
response to environmental cues. Future work will investigate interactions with
relevant cell cultures (e.g. fibroblast activation, stem cell differentiation)
and more sophisticated genetic circuits (e.g. quorum sensing, Boolean logic
gates) to advance our ELM toward potential applications in biosensing,
tissue engineering, and additive manufacturing.

1. G. Fan, C.M.
Dundas, A.J. Graham, N.A. Lynd, B.K. Keitz. Shewanella oneidensis as a living
electrode for controlled radical polymerization. Proc. Natl. Acad. Sci.
U.S.A. 115: 4559-64 (2018).