(35a) Manipulating Nanostructure Formation in Silk Fibroin-Based Materials to Stabilize Bioactive Cargo and Alter Material Properties

The quest to develop new, efficient ways to deliver bioactive cargo to meet the needs of the drug and protein delivery community never ends. Bioactive cargos, such as proteins or enzymes, can be challenging to deliver as each molecule comes with its own requirements, and thus the delivery and packaging strategy necessitates adjustments and optimization. Many material formats have been developed that can protect a bioactive cargo from destruction by the body until it reaches the desired destination. Substantial work in the liposome and polymersome communities highlights the complexity of the stabilization and delivery process, recognizing that this problem is multifaceted- stabilizing the cargo, stabilizing the formulation, targeting the delivery, and releasing the cargo at the right place and time.

In our work, we are interested in leveraging the nanostructures formed by the silk fibroin protein to stabilize bioactive cargos, creating another strategy to meet the needs of delivery systems. Silk fibroin, often isolated from Bombyx mori silkworms, is a protein with a high propensity to form secondary β-sheet structures. As engineers, we can leverage or control the formation of these nanoscale structures to kinetically trap bioactive cargos, such as extracellular matrix proteins, growth factors, and most recently, hemoglobin. For example, we have leveraged the phase separation of the silk fibroin protein under sonication conditions to entrap the hemoglobin, creating stable nano- and microparticles that can serve as hemoglobin based oxygen carriers. These particles range from 200 nm to >10 μm in diameter, as a function of silk fibroin concentration, the ratio of polymers within the system, and the molecular weight of silk fibroin.

Furthermore, we can also control the formation and organization of these structures to alter mechanical behavior of materials formed through modulation of the rate of β-sheet formation, ultimately impacting crystal size. The influence of these nanoscale protein domains on material properties allows for a wide range of material formats capable of entrapping bioactive cargo. This talk will highlight both the fundamentals of protein crystallization as it relates to material formulations and kinetic entrapment of bioactive cargos alongside some of the potential exciting biomedical applications for these materials.