Influence of PEG length on conformational and binding properties of CCK peptides exposed by supramolecular aggregates

Abstract

Five novel peptide amphiphiles (PAs), with common formula (C18)2-PEGx-CCK8 in which the CCK8 peptide and the (C18)2-hydrophobic moiety are spaced by polyethylene linkers of different length (PEG moieties with molecular weights of 700, 1000, 1500, 2000, and 3000 Daltons) are described. They act as potential target-selective nanocarriers towards tumor cells overexpressing cholecistokynin receptors. PAs self-assemble in supramolecular aggregates, with hydrodynamic radius ranging between 63 and 104 nm, as indicated by DLS measurements. Fluorescence studies suggested that, irrespective from the PEG length, the tryptophan residue located at the center of the CCK8 sequence is completely surrounded by water molecules at high mobility. This result indicates a potential capability of all formulated nanovectors to recognize the overexpressed CCK-2 receptors. CD data suggest that CCK8 peptide, in most of PAs in their aggregate form, adopts a conformation allowing the interaction with the receptor. Anyway, biological data obtained by flow cytometry analysis indicate that the five PAs have a different binding ability towards the CCK-2 receptors, with higher binding properties shown by PA containing PEG with MW of 2000 Dalton. Therefore, PEG2000 can be considered as the best spacer in the formulation of nanovectors based on CCK8 peptide amphiphiles.

Cross-beta nanostructures based on dinaphthylalanine Gd-conjugates loaded with doxorubicin

“…DOTA-L 6 -F2 and DOTA-L 6 -(2Nal) 2 were synthesized as previously reported 6, 25, 26 . Briefly, peptide conjugates were synthesized on Rink amide MBHA resin (scale 0.2 mmol, substitution grade 0.65 mmol / g).…”

Peptide Materials Obtained by Aggregation of Polyphenylalanine Conjugates as Gadolinium‐Based Magnetic Resonance Imaging Contrast Agents

“…The amino acid coupling was achieved by adding twofold molar excess of amino acid, mixed with equimolar amounts of 1‐hydroxybenzotriazole (HOBt), benzotriazol‐1‐yl‐oxy‐tris‐pyrrolidino‐phosphonium (PyBop), and fourfold molar excess of diisopropylethylamine (DIPEA) in DMF. All couplings were performed twice for 1 h. Chelating agents and the ethoxylic spacers (Fmoc‐AdOO‐OH and Fmoc‐Ahoh‐OH) were coupled as previously described . Peptides were fully deprotected and from the resin with the TFA (trifluoroacetic acid)/TIS (triisopropylsilane)/H 2 O (95.5/2.0/2.5 v/v/v) mixture at room temperature.…”

Gadolinium containing telechelic PEG‐polymers end‐capped by di‐phenylalanine motives as potential supramolecular MRI contrast agents

“…1 H‐NMR studies were also performed in CD 3 OD solution at 600 MHz and the mono‐dimensional spectrum is reported in Figure C. The complexation of gadolinium(III) ions to the DOTA containing peptide conjugates to obtain FF‐DOTA(Gd)‐FF and ff‐DOTA(Gd)‐FF has been carried out by adding equimolar amounts of GdCl 3 to the aqueous solutions of the DOTA derivatives at neutral pH and room temperature, as already reported .…”

“…The amino acid coupling was achieved by adding twofold molar excess of amino acid, mixed with equimolar amounts of 1‐hydroxybenzotriazole (HOBt), benzotriazol‐1‐yl‐oxy‐tris‐pyrrolidino‐phosphonium (PyBop), and fourfold molar excess of diisopropylethylamine (DIPEA) in DMF. All couplings were performed twice for 1 h. Fmoc‐AdOO‐OH ethoxylic spacer was coupled as previously described . DOTA(OtBu) 3 ‐OH was coupled to the Lys side chain after selective removal of Mtt protecting group from the lysine epsilon amine function.…”