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W1.08 - Nanoscale Piezoelectricity in Fmoc-Diphenylalanine Hydrogels and Their Potential for Application as Multi-Functional Scaffolds 
April 22, 2014   11:15am - 11:30am

Fluorenylmethyloxycarbonyl diphenylalanine (Fmoc-FF) hydrogels have biocompatibility and viscoelasticity comparable to extracellular matrices and commonly used biopolymers. As such, they are proposed as a promising new material for regenerative medicine applications. Fmoc-FF hydrogels self-assemble through molecular stacking of molecules to form three-dimensional networks of ordered fibril structures, ideal for use as tissue engineering scaffolds or biomedical device coatings. Additionally, the self-assembly process is a simple, cost effective method for manufacturing these nanomaterials on a large scale. The existence of piezoelectric properties could facilitate the further application of Fmoc-FF fibrous networks to applications where electrical or mechanical stimuli can be used to promote tissue regeneration. For example, bone and nerve regeneration have both been identified as being sensitive to piezoelectric properties. The direct piezoelectric effect has been linked with the ability of bone to remodel in response to an applied stress. Piezoelectricity has also been shown to promote in-vitro axonal regeneration following nerve injury. Here, we report local shear piezoelectricity in self-assembled peptide hydrogels composed of Fmoc-FF nanofibrils, measured by piezoresponse force microscopy (~1-2 pm/V - comparable to collagen ~1-2 pm/V). The nanofibrillar nature of the gel is further confirmed by scanning electron microscopy, transmission electron microscopy, and helium ion microscopy. Also, comparisons of fluorescence emission spectra measured for Fmoc-FF in solvent and in the gel phase suggest that pi-stacking interactions between Fmoc moieties facilitate nanofibril formation. Structural analyses (circular dichroism and attenuated total reflectance-Fourier transform infrared spectroscopy) confirm the Fmoc-FF molecules within the fibrous network are predominantly in a β-sheet conformation, similar to the dominant structure observed in diphenylalanine nanotubes. Therefore, the non-centrosymmetric nature of the β-sheet is likely to be responsible for the observed piezoelectricity in the Fmoc-FF hydrogels as well.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis