Photoluminescent Peptide-Based Nanostructures as FRET Donor for Fluorophore Dye

3 years ago

Photoluminescent Peptide-Based Nanostructures as FRET Donor for Fluorophore Dye

Teresa Sibillano, Valentina Roviello, Giancarlo Morelli, Cinzia Giannini, Antonella Accardo, Luigi Vitagliano, Carlo Diaferia

A great interest has been recently generated by the discovery that peptide-based nanostructures (NSs) endowed with cross-β structure may show interesting photoluminescent (PL) properties. It was shown that NSs formed by PEGylated hexaphenylalanine (PEG8-F6, PEG=polyethylene glycol) are able to emit at 460 nm when excited at 370 or 410 nm. Here, the possibility to transfer the fluorescence of these PEG8-F6-based NSs by foster resonance electron transfer (FRET) phenomenon to a fluorescent dye was explored. To achieve this aim, the 4-chloro-7-nitrobenzofurazan (NBD) dye was encapsulated in these NSs. Structural data in solution and in solid state, obtained by a variety of techniques (circular dichroism, Fourier-transform infrared spectroscopy, wide-angle X-ray scattering, and small-angle X-ray scattering), indicated that the organization of the peptide spine of PEG8-F6 NS, which consists of anti-parallel β-sheets separated by a dry interface made of interacting phenylalanine side chains, was maintained upon NBD encapsulation. The spectroscopic characterization of these NSs clearly showed a red-shift of the emission fluorescence peak both in solution and in solid state. This shift from 460 to 530 nm indicated that a FRET phenomenon from the peptide-based to the fluorophore-encapsulated NS occurred. FRET could also be detected in the PEG8-F6 conjugate, in which the NBD was covalently bound to the amine of the compound. On the basis of these results, it is suggested that the red-shift of the intrinsic PL of NSs may be exploited in the bio-imaging field. Don′t you fret: The possibility to transfer by foster resonance electron transfer (FRET) phenomenon the fluorescence of a cross-β material peptide such as PEGylated hexaphenylalanine (PEG8-F6)-based nanostructures to the encapsulated fluorescent dye 4-chloro-7-nitrobenzofurazan (NBD) is explored. The FRET causes a red-shift of the photoluminescence of the nanostructures, thus providing an opportunity for their application in the bio-imaging field.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701381