Hydrogels are of great interest as a class of materials for tissue engineering, axonal regeneration, and controlled drug delivery, as they offer 3D interwoven scaffolds to support the growth of cells. Herein, we extend the family of the aromatic Fmoc-dipeptides with a library of new Fmoc-peptides, which include natural and synthetic amino acids with an aromatic nature. We describe the self-assembly of these Fmoc-peptides into various structures and characterize their distinctive molecular and physical properties. Moreover, we describe the fabrication of the bioactive RGD sequence into a hydrogel. This unique material offers new opportunities for developing cell-adhesive biomedical hydrogel scaffolds, as well as for establishing strategies to modify surfaces with bioactive materials.

No abstract

Copolymer chains consisting of acrylamide units and guanine (G)-containing oligonucleotide-tethered acrylamide units undergo, in the presence of K(+) ions, cross-linking by G-quadruplexes to yield a hydrogel. The hydrogel is dissociated upon addition of 18-crown-6 ether that traps the K(+) ions. Reversible formation and dissociation of the hydrogel is demonstrated by the cyclic addition of K(+) ions and 18-crown-6 ether, respectively. Formation of the hydrogel in the presence of hemin results in a hemin/G-quadruplex-cross-linked catalytic hydrogel mimicking the function of horseradish peroxidase, reflected by the catalyzed oxidation of 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid), ABTS(2-), by H2O2 to ABTS(·-) and by the catalyzed generation of chemiluminescence in the presence of luminol/H2O2. Cyclic "ON" and "OFF" activation of the catalytic functions of the hydrogel are demonstrated upon the formation of the hydrogel in the presence of K(+) ions and its dissociation by 18-crown-6 ether, respectively. The hydrogel is characterized by rheology measurements, circular dichroism, and probing its chemical and photophysical properties.

DNA hydrogels, consisting of Y-shaped nucleic acid subunits or of nucleic acid-functionalized acrylamide chains, undergo switchable gel-to-solution transitions. The Ag(+)-stimulated formation of cytosine-Ag(+)-cytosine complexes results in the crosslinking of the units to yield the hydrogels, while the cysteamine-induced elimination of the Ag(+) ions dissociates the hydrogels into a solution phase.