Open AccessSelf-assembly of PEGylated tetra-phenylalanine derivatives: structural insights from solution and solid state studies
Author(s) -
Carlo Diaferia,
Flavia Anna Mercurio,
Cinzia Giannini,
Teresa Sibillano,
Giancarlo Morelli,
Marilisa Leone,
Antonella Accardo
Publication year - 2016
Publication title -
scientific reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.24
H-Index - 213
ISSN - 2045-2322
DOI - 10.1038/srep26638
Subject(s) - fourier transform infrared spectroscopy , monomer , small angle x ray scattering , gadolinium , solid state nuclear magnetic resonance , chelation , materials science , mri contrast agent , chemistry , nuclear chemistry , chemical engineering , nuclear magnetic resonance , organic chemistry , polymer , physics , optics , scattering , engineering
Water soluble fibers of PEGylated tetra-phenylalanine (F4), chemically modified at the N-terminus with the DOTA chelating agent, have been proposed as innovative contrast agent (CA) in Magnetic Resonance Imaging (MRI) upon complexation of the gadolinium ion. An in-depth structural characterization of PEGylated F4-fibers, in presence (DOTA-L 6 -F4) and in absence of DOTA (L 6 -F4), is reported in solution and at the solid state, by a multiplicity of techniques including CD, FTIR, NMR, DLS, WAXS and SAXS. This study aims to better understand how the aggregation process influences the performance of nanostructures as MRI CAs. Critical aggregation concentrations for L 6 -F4 (43 μM) and DOTA-L 6 -F4 (75 μM) indicate that self-aggregation process occurs in the same concentration range, independently of the presence of the CA. The driving force for the aggregation is the π-stacking between the side chains of the aromatic framework. CD, FTIR and WAXS measurements indicate an antiparallel β-sheet organization of the monomers in the resulting fibers. Moreover, WAXS and FTIR experiments point out that in solution the nanomaterials retain the same morphology and monomer organizations of the solid state, although the addition of the DOTA chelating agent affects the size and the degree of order of the fibers.