An Engineering Approach to Biological Materials and Chemistry: Leveraging Nature's Ability to Optimize Toughness, Mass Transfer, and Specific Binding Chemistry

The complex structure of the collagen in the dermal armor of the boxfish provides a rich source of bioinspired engineering for fiber-reinforced composite materials. Advanced imaging and material characterization of this complex collagen structure revealed a Bouligand-type structure common in impact resistance biological materials. These Bouligand-type structures were shown to have several additional characteristics that included helical interfibrillar gaps, unidirectional collagen reinforcement of specific loading axes, and were uniquely organized into higher order structures referred to as a nested-box structure. In situ mechanical tests coupled with finite element simulations were performed to further demonstrate structure and failure mechanics of the dermal armor. The silica cell wall of a diatom, abundant microalgae 1 – 100 µm in size, contains highly ordered hierarchical porosity and is widely available through its fossilized form, diatomite. The research uses diatomite to fabricate a monolith with unidirectional lamellar walls (~15 µm) via freeze casting that allows for efficient mass transport of fluids (i.e., low pressure-drop) while maintaining sufficient mechanical properties. In this study, control over the monoliths was explored by varying the mass ratio of diatomite and sodium carbonate and the solids ratio in the initial slurry before freeze casting. A point-of-care biosensor based on a surface-enhance Raman spectroscopy (SERS) sandwich assay platform is developed using silver nanocubes (AgNCs) on a gold capture substrate. The biosensor leverages the specific binding chemistry of the streptavidin-biotin system, one of the strongest non-covalent interactions in nature, by functionalizing both the AgNCs and the capture substrate with a heterobifunctional ligand, biotin-polyethylene glycol-thiol. The model analyte, streptavidin, is then used to bind the exposed biotin head groups on the AgNCs and the capture substrate to form the sandwich assay. The SERS of a Raman reporter, 2-naphthalenethiol, which is also bound to the AgNC surface is then obtained for a highly sensitive quantification of the streptavidin present. Further functionalization and surface treatment of the capture substrates were performed to reduce the non-specific binding of AgNC