Strong Electro‐Optic Effect and Spontaneous Domain Formation in Self‐Assembled Peptide Structures

Abstract

Short peptides made from repeating units of phenylalanine self‐assemble into a remarkable variety of micro‐ and nanostructures including tubes, tapes, spheres, and fibrils. These bio‐organic structures are found to possess striking mechanical, electrical, and optical properties, which are rarely seen in organic materials, and are therefore shown useful for diverse applications including regenerative medicine, targeted drug delivery, and biocompatible fluorescent probes. Consequently, finding new optical properties in these materials can significantly advance their practical use, for example, by allowing new ways to visualize, manipulate, and utilize them in new, in vivo, sensing applications. Here, by leveraging a unique electro‐optic phase microscopy technique, combined with traditional structural analysis, it is measured in di‐ and triphenylalanine peptide structures a surprisingly large electro‐optic response of the same order as the best performing inorganic crystals. In addition, spontaneous domain formation is observed in triphenylalanine tapes, and the origin of their electro‐optic activity is unveiled to be related to a porous triclinic structure, with extensive antiparallel beta‐sheet arrangement. The strong electro‐optic response of these porous peptide structures with the capability of hosting guest molecules opens the door to create new biocompatible, environmental friendly functional materials for electro‐optic applications, including biomedical imaging, sensing, and optical manipulation.

Peptide Nanophotonics: From Optical Waveguiding to Precise Medicine and Multifunctional Biochips

“…Peptide nanophotonics is an emerging bio‐optical field. Found fundamental optical effects such as linear (optical absorption (OA), visible fluorescence), nonlinear optical (second harmonic generation (SHG)), Pockels' electroptic, and optical waveguiding in ultrashort di‐ and tripeptide nanostructures of different origin indicate highly promising applications of these new bioinspired nanomaterials for multifunctional bio‐optical chips …”

“…This reconformed peptide supramolecular fiber architecture exhibits deep modification at all levels (molecular, morphological, peptide secondary structure, electronic, optical and more) providing new physical properties, which are not observed in the original biomolecule monomers and their self‐assembled native nanostructures . In the native α‐helical phase, FF‐, LL‐nanotubes and FFF‐nanospheres possess asymmetric structure and demonstrate unique physical properties such as piezoelectric, nonlinear optical and electro‐optical effects. In the thermally induced phase, these phenomena disappear as a result of the newly reassembled centrosymmetric structure.…”

“…Recent research revealed in peptide nanostructures a unique set of optical properties, such as nonlinear optical, electro‐optical, and optical waveguiding effects . These previously unknown phenomena paved the way toward new physics of light propagation in biological and bioinspired nanostructures followed by nanotechnology of optical peptide waveguides.…”

“…Such nanoscale light waveguides promise breakthrough applications toward biomedical theranostics and multifunctional optical implantable biochips where they are integrated with operating electronics. This new field of peptide nanophotonics is the main goal of this Review.…”

“…We overview in this paper fundamental and applied photonic research of bioinspired peptide nanomaterials and highlight technological development of their applications in emerging field of peptide integrated optics . Their exceptional optical properties such as broadband optical transparency from ultraviolet (UV) to near infrared (IR), nonlinear optical, and Pockles electro‐optic effects, combined with natural elongated morphology of self‐assembled peptide nanostructures (nanotubes, nanofibers, and nanotapes) make them promising for optical linear and nonlinear waveguiding . In contrast to well‐known biomaterials' counterparts applied in implantable photonics, for instance, silk fibers, polymers, hydrogels, and more, these peptide‐based nanostructures have significantly higher refractive index ≈1.6 providing strong optical confinement of peptide optical waveguides .…”