Marco Rolandi, Materials Science and Engineering Department, University of Washington, Seattle, WA, USA
Hydrogen bonding is omnipresent in nature and, in addition to water, determines the structure and properties of most biological molecules. These molecules include the essential components of living systems such as nucleic acids, lipids, proteins, and polysaccharides. The ability to tailor the properties of these components has contributed to great advances in bionanotechnology.Here, I will present two examples of dialing microstructure and conductivity with hydrogen bonding in a polysaccharide model system, chitin. Chitin is present in the insect cuticle, squid pen, the shell of crustaceans, and the wall of certain fungi. In the first example, hydrogen bonding is disrupted in squid pen β-chitin with dissolution in a protic solvent to yield self-assembled α-chitin nanofibers upon drying. This “chitin nanofiber ink” is coupled with airbrushing, replica molding, and microcontact printing to manufacture chitin nanofiber structures across length scales. Applications of these structures in tissue engineering and drug delivery will be discussed. Co-assembly in a protein matrix yields a nanofiber biocomposite with excellent mechanical and optical properties. In the second example, chitin is functionalized with hydrophilic groups to increase hydrogen bonding with water. This increased hydrogen bonding creates proton wires along which H+ translate following the Grotthuss mechanism. Doped wires with H+ from acidic groups and doped wires with OH- from basic groups are the foundations to complimentary protonic field effect transistors analogous to CMOS.In nature, protonic and ionic (not electronic) currents are used to communicate information across cell membranes. As such, these biocompatible protonic devices are a versatile biotic-abiotic interface for bionanoelectronics.
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