1. BIND (Biofilm-Integrated Nanofiber Display)
There is an ever-increasing need for materials that combine the performance and customizability of synthetic polymers with the sustainability of biopolymers. One approach, which is already being used to produce pharmaceuticals, specialty chemicals, and biofuels, is to harness the biosynthetic potential of microbes through genetic engineering and fermentation in order to create functional materials. The specific approach that we have pursued in our lab is inspired by the ways in which biological systems build structures – genetic control over polymer sequence, extracellular export, and molecular self-assembly. Accordingly, we have developed a technology platform that we call Biofilm Integrated Nanofiber Display (BIND), which repurposes the curli secretion machinery form E. coli to produce nanofibrous materials. A major advantage of this approach is that we have a high level of control over the molecular structure of our material through straightforward genetic engineering approaches, but it can be produced by bacterial fermentation, which is an industrially scalable process. Many of our projects focus on exploring new functional properties that make this material interesting for biomedical, biomanufacturing, sensing, and other applications (see below for more details).
Manufacturing: In order for BIND to be a viable way to produce macroscopic materials for many applications, several core challenges must be addressed. Accordingly, we are investigating the following areas:
- Optimization of the cellular chassis for curli fiber production
- Understanding the self-assembly and nanostructures of curli fiber-based materials
- Exploring composites that combine curli fibers with other materials synergistically
Relevant Publications: Nguyen, et al. Nat Comm 2014; Dorval-Courchesne, et al. ACS Biomat Sci Eng 2017
Bootstrapping Biocatalysis: Biocatalytic transformations generally rely on purified enzymes or whole cells to perform complex transformations that are used on industrial scale for chemical, drug and biofuel synthesis, pesticide decontamination, and water purification. However, both of these systems have inherent disadvantages related to the costs associated with enzyme purification, the long-term stability of immobilized enzymes, catalyst recovery, and compatibility with harsh reaction conditions. We have developed a BIND-based material capable of immobilizing and purifying enzymes in a single step, and the material scaffold is itself produced by fermentation. We are exploring the use of this platform as a cell-free system for biocatalysis. Relevant Publications: Botyanszki, et al. Biotech Bioeng 2016
Gut Bacteria Engineering: During colonization of a host, curli fibers are used by naturally occurring bacteria to adhere to host tissues and also interact with the host immune system. We are interested in repurposing their use in vivo by using engineered probiotic bacterial strains to produce modified curli fibers inside the GI tract. Thus, the modified curli fibers modulate their biological and biophysical surroundings based on the display of specific protein domains with therapeutic function, ultimately acting as a resident living biomaterial.
Hydrogels: We have developed a method to create functionalized hydrogels using the BIND platform by concentrating whole bacterial cultures. We are currently investigating the properties that make them potentially useful for a range of biomedical applications. Relevant Publications: Coming soon.
Thin Films and Macroscopic 3D Structures: In addition to hydrogels, the BIND platform can be used to create films with a range of interesting properties, including the ability to adopt 3D molded shapes. Relevant Publications: Coming soon.
2. Bio-Nano Interactions
Supramolecule-Based Assembled BioHybrids: Many cellular organisms use extracellular encasements to protect themselves and mediate interactions with their environment. We are developing synthetic “shells” that can be applied to the outside of cells using straightforward protocols. We are investigating the ability of these shells to make the cells more resistant to harsh conditions, enhance cellular energy utilization, and mediate communication with abiotic interfaces. Relevant Publications: Coming soon.
Human Microbe Nanoengineering: Human microbes such as bacteria and yeast were functionalized through supramolecule-based nanotechnology. This technology provides a new method for the engineering of microbial properties. This technology has potentials for the functionalization and management of human microbe. Relevant Publications: Coming soon.
3. Polymeric and Supramolecular Materials
Clickable Hydrogels: Several chemical crosslinking strategies used to form hydrogels from biopolymers exhibit less than desirable biocompatibility due to their lack of chemoselectivity. We have developed a method to form covalently crosslinked hydrogels using tetrazine-norbornene click-chemistry, which is fast, easy to use, and bio-orthogonal, so it is suitable for the encapsulation of cells, proteins, and other biomolecules without harming their structure. Relevant Publications: Desai, et al. Biomaterials 2015; Koshy, et al. Adv Health Mat 2016.
Cyclic Peptides: The rigid geometry and tunable chemistry of D,L-cyclic peptides makes them an intriguing building-block for the rational design of nano- and microscale hierarchically structured materials. We have characterized their nanomechanical properties, which rival the stiffest known proteinaceous materials, and explored their use as mechanical fillers that can reinforce polymeric structures. Relevant Publications: Rubin, et al. ACS Nano 2015; Rubin, et al. Biomacromolecules 2013.