We have prepared a small library of 13 peptidomimetics containing the L‐Phe‐D‐Oxd unit (or the isosteric L‐Phe‐D‐pGlu unit), which is a privileged scaffold for the preparation of supramolecular materials. These compounds were prepared in solution in excellent yields and tested as organogelators and/or hydrogelators at 10 mM concentration with a plethora of solvents and solvent mixtures. Two molecules were very efficient gelators: one is a organogelator and the other is a hydrogelator. As these compounds have quite different skeletons, a rationale to explain the different behaviour of these molecules as gelators takes into consideration their hydrophobicity, expressed as log P. Finally, Fmoc‐L‐Phe‐D‐pGlu‐OH (6b) efficiently gelated phosphate‐buffered saline (PBS 1X) at 1.5 % w/w concentration and is an excellent candidate for the preparation of novel materials for applications in, for example, drug release, biological assays, and tissue engineering.

Several parameters have a critical importance for the stabilization of either polyproline I (PPI) or polyproline II (PPII) helices in a hydrophobic environment. Among them, it was found out that the concentration is crucial as polyprolines at 3 mM concentration stably fold in PPII helices, that are organized in aggregates stable even after several days and are detectable by dynamic light scattering analysis. In more diluted concentration the same molecules stably fold in PPI helices, and no aggregates are found. In contrast, the introduction of a (4S,5R)-4-carboxy-5-methyloxazolidin-2-one (L-Oxd) moiety always inhibits the formation of the PPI helix, regardless of the L-Oxd position and the solution concentration.

Four new low molecular weight hydrogelators (LMWGs) have been prepared in multigram scale and their attitude to form hydrogels has been tested. The gelation trigger is pH variation. The resulting gels have been characterized with several techniques: measurement of the melting points (T(gel)), transparency, gelation time, and viscoelastic properties, together with ECD analysis. Among them, Fmoc-L-Tyr-D-Oxd-OH 1 is an excellent gelator that leads to the preparation of strong, transparent, and viscoelastic gels, by pH variation. UV-visible analyses have demonstrated that the gels obtained with the LMWG 1 possess high transparency, with a transmittance up to 25.6% at a wavelength of 600 nm. Results of the amplitude sweep experiments showed that the elastic response component (G') was approximately an order of magnitude larger than the viscous component, indicating an elastic rather than viscous attitude of the gels, confirmed by the frequency independence of G' and G″ values, in the range from 0.1 to 100 rad·s(-1). The thermal behavior of gel obtained from Fmoc-L-Tyr-D-Oxd-OH 1 was characterized performing an "ad hoc" rheological temperature sweep experiment, that indicated that G' remained almost constant from 23 °C up to about 65 °C while G″ increased in the same temperature range. At higher temperatures, both G' and G″ values started to slightly decrease without displaying a crossover point.

We present herein the preparation of four different hydrogels based on the pseudopeptide gelator Fmoc-l-Phe-d-Oxd-OH (Fmoc=fluorenylmethyloxycarbonyl), either by changing the gelator concentration or adding graphene oxide (GO) to the water solution. The hydrogels have been analysed by rheological studies that demonstrated that pure hydrogels are slightly stronger compared to GO-loaded hydrogels. Then the hydrogels efficiency to trap the cationic methylene blue (MB) and anionic eosin Y (EY) dyes has been analyzed. MB is efficiently trapped by both the pure hydrogel and the GO-loaded hydrogel through π-π interactions and electrostatic interactions. In contrast, the removal of the anionic EY is achieved in less satisfactory yields, due to the unfavourable electrostatic interactions between the dye, the gelator and GO.

Peptide-functionalized gold nanoparticles are supramolecular systems that can mimic natural proteins or DNA. In this work, we describe the preparation, the analysis, and the biological evaluation of gold nanoparticles linked to pseudopeptide foldamers containing one to eight L-Ala-D-Oxd (Ala = alanine; Oxd = 4-carboxy-5-methyloxazolidin-2-one) residues. The nanoparticles become increasingly organized as the number of such moieties increases. Moreover, from the analysis of chiroptical signals we find that the chirality of the gold surface becomes more evident with decreasing foldamer length. Finally, these systems display no cytotoxicity towards HeLa cells and are good candidates to promote drug delivery once equipped with biologically active moieties