Seamless metallic coating and surface adhesion of self-assembled bioinspired nanostructures based on di-(3,4-dihydroxy-L-phenylalanine) peptide motif.

The noncoded aromatic 3,4-dihydroxy-L-phenylalanine (DOPA) amino acid has a pivotal role in the remarkable adhesive properties displayed by marine mussels. These properties have inspired the design of adhesive chemical entities through various synthetic approaches. DOPA-containing bioinspired polymers have a broad functional appeal beyond adhesion due to the diverse chemical interactions presented by the catechol moieties. Here, we harnessed the molecular self-assembly abilities of very short peptide motifs to develop analogous DOPA-containing supramolecular polymers. The DOPA-containing DOPA-DOPA and Fmoc-DOPA-DOPA building blocks were designed by substituting the phenylalanines in the well-studied diphenylalanine self-assembling motif and its 9-fluorenylmethoxycarbonyl (Fmoc)-protected derivative. These peptides self-organized into fibrillar nanoassemblies, displaying high density of catechol functional groups. Furthermore, the Fmoc-DOPA-DOPA peptide was found to act as a low molecular weight hydrogelator, forming self-supporting hydrogel which was rheologically characterized. We studied these assemblies using electron microscopy and explored their applicative potential by examining their ability to spontaneously reduce metal cations into elementary metal. By applying ionic silver to the hydrogel, we observed efficient reduction into silver nanoparticles and the remarkable seamless metallic coating of the assemblies. Similar redox abilities were observed with the DOPA-DOPA assemblies. In an effort to impart adhesiveness to the obtained assemblies, we incorporated lysine (Lys) into the Fmoc-DOPA-DOPA building block. The assemblies of Fmoc-DOPA-DOPA-Lys were capable of gluing together glass surfaces, and their adhesion properties were investigated using atomic force microscopy. Taken together, a class of DOPA-containing self-assembling peptides was designed. These nanoassemblies display unique properties and can serve as multifunctional platforms for various biotechnological applications

Seamless Metallic Coating and Surface Adhesion of Self-Assembled Bioinspired Nanostructures Based on Di-(3,4-dihydroxy‑l‑phenylalanine) Peptide Motif

The noncoded aromatic 3,4-dihydroxy-l-phenyl­alanine (DOPA) amino acid has a pivotal role in the remarkable adhesive properties displayed by marine mussels. These properties have inspired the design of adhesive chemical entities through various synthetic approaches. DOPA-containing bioinspired polymers have a broad functional appeal beyond adhesion due to the diverse chemical interactions presented by the catechol moieties. Here, we harnessed the molecular self-assembly abilities of very short peptide motifs to develop analogous DOPA-containing supra­molecular polymers. The DOPA-containing DOPA–DOPA and Fmoc–DOPA–DOPA building blocks were designed by substituting the phenyl­alanines in the well-studied diphenyl­alanine self-assembling motif and its 9-fluorenyl­methoxy­carbonyl (Fmoc)-protected derivative. These peptides self-organized into fibrillar nanoassemblies, displaying high density of catechol functional groups. Furthermore, the Fmoc–DOPA–DOPA peptide was found to act as a low molecular weight hydro­gelator, forming self-supporting hydrogel which was rheologically characterized. We studied these assemblies using electron microscopy and explored their applicative potential by examining their ability to spontaneously reduce metal cations into elementary metal. By applying ionic silver to the hydrogel, we observed efficient reduction into silver nanoparticles and the remarkable seamless metallic coating of the assemblies. Similar redox abilities were observed with the DOPA–DOPA assemblies. In an effort to impart adhesiveness to the obtained assemblies, we incorporated lysine (Lys) into the Fmoc–DOPA–DOPA building block. The assemblies of Fmoc–DOPA–DOPA–Lys were capable of gluing together glass surfaces, and their adhesion properties were investigated using atomic force microscopy. Taken together, a class of DOPA-containing self-assembling peptides was designed. These nano­assemblies display unique properties and can serve as multi­functional platforms for various bio­technological applications

Switchable Catalytic Acrylamide Hydrogels Cross-Linked by Hemin/G-Quadruplexes

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