title: Supramolecular Hydrogels Based on Minimalist Amphiphilic Squaramide-Squaramates for Controlled Release of Zwitterionic Biomolecules.
abstract: Supramolecular hydrogels with tunable properties have innovative applications in biomedicine, catalysis, and materials chemistry. Minimalist low-molecular-weight hydrogelators based on squaramide and squaramic acid motifs have been designed. This approach benefits from the high acidity of squaramic acids and the aromaticity of squaramides. Moreover, substituents on the aryl ring tune the π density of the arylsquaramide motif. Thus, materials featuring distinct thermal and mechanical properties have been successfully prepared. The hydrogel (G'≈400 Pa, G''≈57 Pa; at 1.0 % w/v; 1 Hz) obtained from 4-nitrophenylsquaramide motif 1 is thermoreversible (T=57 °C at 0.2 % w/v), thixotropic, self-healable, and undergoes irreversible shrinking in response to saline stress. Furthermore, the hydrogel is injectable and can be loaded with substantial amounts (5:1 excess molar ratio) of zwitterionic biomolecules, such as l-carnitine, γ-aminobutyric acid (GABA), or d,l-Ala-d,l-Ala, without any loss of structural integrity. Then, the release of these molecules can be modulated by saline solutions.
authors.affiliation: Departament de Química, Facultad de Ciències, Universitat de les Illes Balears, Ctra. Valldemossa, Km. 7.5, Palma, 07122, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: López
authors.affiliation: Departament de Química, Facultad de Ciències, Universitat de les Illes Balears, Ctra. Valldemossa, Km. 7.5, Palma, 07122, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Ximenis
authors.affiliation: Departament de Química, Facultad de Ciències, Universitat de les Illes Balears, Ctra. Valldemossa, Km. 7.5, Palma, 07122, Spain.
authors.forename: Francisca
authors.initials: F
authors.lastname: Orvay
authors.affiliation: Departament de Química, Facultad de Ciències, Universitat de les Illes Balears, Ctra. Valldemossa, Km. 7.5, Palma, 07122, Spain.
authors.forename: Carmen
authors.identifier: http://orcid.org/0000-0003-2478-3807
authors.initials: C
authors.lastname: Rotger
authors.affiliation: Departament de Química, Facultad de Ciències, Universitat de les Illes Balears, Ctra. Valldemossa, Km. 7.5, Palma, 07122, Spain.
authors.forename: Antonio
authors.identifier: http://orcid.org/0000-0002-9418-7798
authors.initials: A
authors.lastname: Costa
keywords: gels; noncovalent interactions; squaramides; supramolecular chemistry; zwitterions