Fluorine Effect in the Gelation Ability of Low Molecular Weight Gelators

Abstract

The three gelators presented in this work (Boc-D-Phe-L-Oxd-OH F0, Boc-D-F1Phe-L-Oxd-OH F1 and Boc-D-F2Phe-L-Oxd-OH F2) share the same scaffold and differ in the number of fluorine atoms linked to the aromatic ring of phenylalanine. They have been applied to the preparation of gels in 0.5% or 1.0% w/v concentration, using three methodologies: solvent switch, pH change and calcium ions addition. The general trend is an increased tendency to form structured materials from F0 to F1 and F2. This property ends up in the formation of stronger materials when fluorine atoms are present. Some samples, generally formed by F1 or F2 in 0.5% w/v concentration, show high transparency but low mechanical properties. Two gels, both containing fluorine atoms, show increased stiffness coupled with high transparency. The biocompatibility of the gelators was assessed exposing them to fibroblast cells and demonstrated that F1 and F2 are not toxic to cells even in high concentration, while F0 is not toxic to cells only in a low concentration. In conclusion, the presence of even only one fluorine atom improves all the gelators properties: the gelation ability of the compound, the rheological properties and the transparency of the final materials and the gelator biocompatibility.

Solvent-Induced Transient Self-Assembly of Peptide Gels: Gelator–Solvent Reactions and Material Properties Correlation

“…Red-shifts of the weaker, longer wavelength n → π* transitions corresponding to the CO carbonyl and N–H amide groups, respectively, are observed to be significant as the precursors’ aromaticity increases ( 3 < 1 < 2 ). This suggests hydrogen-bonding-type interactions from these groups, consistent with the literature. ,− …”

A short oxazolidine‐2‐one containing peptide forms supramolecular hydrogels under controlled conditions

“…As in previous work, we observed that a similar scaffold containing the Oxd moiety coupled with 3,4-diflurophenylalanine underwent hydrolysis when dissolved in the presence of NaOH, 59,60 we checked the stability of the gelator under these conditions by means of HPLC-MS (Table 1). Even though the major component of the final material was 1, we could detect a significative percentage of the Boc-L-Phe-OH, ranging between 3% and 22%, which increases with the gelator concentration, in line with the kinetics parameters of the reaction.…”

“…The hydrogels D, E, G, and H, prepared with Ca 2+ ions as trigger, are even more elastic since they do not present a crossover point (breaking point of the gel network) in the range of shear strain studied, having the G′ always higher than the G″ . In addition, hydrogels A, D, and G show high transparency, taken as the value of transmittance at 630 nm, 60 ranging between 58.8% and 77.8%, in contrast with their modest strength, which ranges between 0.26 and 1.64 kPa. Reasonably, as the gelator concentration increases, the stiffness of the gel increases accordingly, while the transparency drops (Figure S9).…”

Controlled Lactonization of o-Coumaric Esters Mediated by Supramolecular Gels

“…In particular, supramolecular gels based on low-molecular-weight gelators (LMWGs) have recently attracted great attention due to their wide applicability in many fields, being used in optoelectronics [ 9 ], nanomaterials, shape memories, templated synthesis and crystallization, [ 10 ] as well as drug carriers and cell culture medium [ 11 , 12 , 13 , 14 ]. The formation of LMW gels is driven by weak noncovalent interactions, such as ion−ion, H-bonding, π−π stacking, and van der Waals [ 15 , 16 ]. These interactions facilitate the generation of a 3D network of self-assembled fibers that immobilize the solvent within the entangled supramolecular structure, leading to the gel formation.…”