Physical hydrogels are supramolecular materials obtained by self-assembly of small molecules called gelators. Aromatic amino acids and small peptides containing aromatic rings are good candidates as gelators due to their ability to form weak bonds as π-π interactions and hydrogen bonds between NH and CO of the peptide chain. In this paper we show our results in the preparation of a transparent hydrogel that was obtained by self-assembly of a fluorine-containing dipeptide that relies on the additional formation of halogen bonds due to the fluorine atoms contained in the dipeptide. We used Boc-D-F2Phe-L-Oxd-OH (F2Phe = 3,4-difluorophenylalainine; Oxd = 4-methyl-5-carboxy-oxazolidin-2-one) that formed a strong and transparent hydrogel in 0.5% w/w concentration at pH = 4.2. The formation of a hydrogel made of unnatural fluorinated amino acids may be of great interest in the evaluation of patients with parkinsonian syndromes and may be used for controlled release.

L-Dopa (3,4-dihydroxyphenylalanine) is a chiral amino acid generated via biosynthesis from L-tyrosine in plants and some animals. The presence of multiple interacting sites makes L-Dopa a multifunctional building block for...

Imines or Schiff bases (SB) are formed by the condensation of an aldehyde or a ketone with a primary amine, with the removal of a water molecule. Schiff bases are central molecules in several biological processes for their ability to form and cleave by small variation of the medium. We report here the controlled hydrolysis of four SBs that may be applied in the fragrance industry, as they are profragrances all containing odorant molecules: methyl anthranilate as primary amine, and four aldehydes (cyclamal, helional, hydroxycitronellal and triplal) that are very volatile odorants. The SB stability was assessed over time by HPLC-MS in neutral or acidic conditions, both in solution and when trapped in low molecular weight gels. Our results demonstrate that it is possible to control the hydrolysis of the Schiff bases in the gel environment, thus tuning the quantity of aldehyde released and the persistency of the fragrance.

Controlling the formation and directional growth of hydrogels is a challenge. In this paper, a new methodology to program the gel formation both over space and time is proposed, using the diffusion and subsequent hydrolysis of 1,1′-carbonyldiimidazole from an immiscible organic solution to the aqueous gel media.

The removal of Diclofenac sodium from waste waters has a high relevance since it belongs to the therapeutic group most commonly found in wastes. An aromatic-free and low-impact technology that efficiently entraps aqueous pollutants is highly desirable. We synthesised two Boc-protected and aromatic-free tripeptides (Boc-L-Ala-Aib-L-Val-OH and Boc-L-Val-Aib-L-Val-OH) and studied their ability to form gels with mixtures of water and alcohols, such as methanol, ethanol and 2-propanol. Boc-L-Ala-Aib-L-Val-OH forms a strong hydrogel in 2-propanol/water mixtures able to trap up to 97.8% of Eosin Y model molecule and up to 92.0% of Diclofenac sodium from aqueous solutions. The hydrogel is also thixotropic, thermoreversible and biocompatible. This outcome is very encouraging and paves the way to a new approach for developing new materials using aromatic-free hydrogels, useful for water remediation.