Amphiphilic CCK peptides assembled in supramolecular aggregates: structural investigations and in vitro studies

Abstract

Supramolecular aggregates obtained by self-aggregation of five new cationic amphiphilic CCK8 peptides have been obtained in water solution and characterized for: (i) aggregate structure and stability; (ii) CCK8 peptide conformation and bioavailability on the external aggregate surface; and (iii) for their cell binding properties. The cationic amphiphilic CCK8 peptides self-aggregate giving a combination of liposomal and micelle structures, with radii ranging between ~60 nm and ~90 nm, and between ~5 and ~10 nm, respectively. The presence of CCK8 peptide well-exposed on the aggregate surface is demonstrated by fluorescence measurements. Peptide conformation changes in the five supramolecular aggregates: the CCK8 conformational behaviour is probably induced by the presence of three charged lysine residues close to the bioactive peptide sequence. Only aggregates in which the CCK8 peptide presents a structural arrangement similar to that found for the same peptide in DPC micelles give promising binding properties to CCK2-R receptors overexpressed by transfected A431 cells. Chemical modifications on the CCK8 N-terminus seem to play an important role in stabilizing the peptide active conformation, either when the peptide derivative is in monomeric or in aggregate form. For their easy preparation procedures and their binding properties, supramolecular aggregates based on cationic peptide amphiphiles can be considered as promising candidates for target selective drug carriers on cancer cells.

Intrinsically disordered amphiphilic peptides as potential targets in drug delivery vehicles

“…These values indicate that the introduction of the ethoxilic linker slightly affects the formation of aggregates capable of capturing the ANS, but they also confirm the high stability of both the resulting aggregates. Furthermore, these values comply with those previously found for peptide amphiphiles containing the same hydrophobic moiety28,29 . Nonetheless, the CMC values of both the amphiphilic derivatives of PepE are higher than the corresponding ones for PepK.…”

“…All four PAs are strongly aggregated and poorly soluble at high concentrations (0.50-1.0 mM). These characteristics made them unsuitable for a characterization performed by means of solution NMR techniques; even after changing the experimental conditions such as implementing buffers at different pHs and temperatures.CMC values comply with those previously found for peptide amphiphiles containing the same hydrophobic moiety and they point out the high stability of the aggregates 28,29. The higher CMC values of (C18) 2 -PepE and (C18) 2 -L-PepE indicates a lower propensity to aggregate if compared with the corresponding PepK derivatives.…”

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

“…Determination of the critical aggregation concentration (CAC) value of Gd-2Nal 2 was carried out using a fluorescence-based method, in which ANS was used as fluorescent probe. This dyeis completely silent at the fluorescence in aqueous solution, but emits in the range 460–480 nm when is surrounded by a hydrophobic environment 10 . A solution of ANS in cuvette (20 μM) was titrated with Gd-2Nal 2 and the fluorescence intensities maximum measured at 470 nm have been plotted in Figure S3.…”

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

“…Conformational changes are strictly related to the kind of spacer introduced between the peptide moiety and the alkyl chains. 11 The spectrum of PA-[1000], reported in Figure 2A, shows a shape typical of a-helix peptide conformation, with two negative bands around 208 and 222 nm, respectively. Spectra were recorded between 195 and 260 nm on samples in 10 mM phosphate buffer (pH and ionic strength conditions) at 2 3 10 24 M peptide concentration.…”

“…Under specific condition of pH or temperatures, PA molecules are able to self-assemble, in water solution, in well-ordered supramolecular structures with distinctive features with respect to traditional surfactants. 10 Recently, we reported the synthesis of a set of five peptide amphiphiles with common formula (C18) 2 -L-CCK8, 11 in which (C18) 2 -is symbolically used to indicate the dioctadecyl hydrophobic moiety; CCK8 is the carboxyl terminal sequence of the peptide hormone cholecystokinin (Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe-Amide) able to bind, with high affinity, both CCK1-R and CCK2-R cholecystokinin receptors overexpressed by cancer cells in several human tumors; 12 and -L-is here used to indicate a neutral or charged spacer [five ethoxylic linker (AdOO 5 8-amino-3,6-dioxaoctanoic acid) or three lysine residues and an AdOO unit variably positioned]. [1][2][3][4][5][6] Moreover, several examples of PAs able to form fibers and gels are also reported.…”