(727c) Controlled Assembly of Functional Hydrogel Biomaterials with Precisely Patterned Nanostructures

Samuel Lim, Dominic J. Glover, Francois Carruzzo, Gi Ahn Jung, and Douglas S. Clark, Department of Chemical & Biomolecular Engineering, University of California, Berkeley, CA 94720

Keywords: self-assembly, hydrogels, enzymes, nanoscale patterning

Hydrogels are widely used as biomaterials because of their biocompatibility and viscoelastic properties that are similar to native tissues. In particular, hydrogels can be functionalized to carry out sequential metabolic reactions or encapsulate cells through incorporation of protein domains or peptide motifs. Precise positioning of biomolecules can enhance catalytic activity through substrate channeling or increase cell binding affinity. However, exerting nanoscale spatial control within a functionalized hydrogel backbone remains challenging. We aim to overcome this difficulty by using protein building blocks designed to assemble periodically in programmable order.

The g-prefoldin (g-PFD) is a filamentous protein isolated from the hyperthermophilic archaeon Methanocaldococcus jannaschii; its remarkable stability, unique modularity, and self-assembly into filaments with chaperone activity render it an ideal building block for the bottom-up construction of precisely patterned protein nanostructures. We have engineered g-PFD subunits that enable periodic positioning of multiple enzymes along the template by replacing the assembly interface with combinations of helical coil pairs that specifically bind each other. Subsequently, we verified successful patterning of fluorescent proteins as well as sequential metabolic enzymes.

In addition, precisely patterned g-PFD fragments were assembled into hydrogels through the introduction of terminal cysteine residues and subsequent crosslinking with PEG polymers through maleimide chemistry. Hybrid g-PFD-PEG hydrogels formed rapidly, and possessed tunable viscoelastic properties. This system is being utilized to develop biocatalytic gels with spatial control over incorporated enzymes. Ultimately, the ability to position functional molecules in a controlled manner within hydrogels will considerably improve our ability to fabricate advanced multifunctional biomaterials with enhanced performances.