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

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.

pH‐Stimulated DNA Hydrogels Exhibiting Shape‐Memory Properties

“…Also, the reversible and cyclic transitions of DNA between hydrogel and solution phases using pH changes [ 31 ] or by the K + -stimulated formation of G-quadruplex cross-bridges and their separation by crown-ethers [ 32 ] were demonstrated. Different applications of stimuli-responsive hydrogels were suggested, including controlled drug release, [ 33 ] sensors, [ 34 ] separation of substrates, [ 35 ] and more.…”

Visual optical biosensors based on DNA-functionalized polyacrylamide hydrogels

“…A switchable sol-gel transition was created by Willner and co-workers in the presence of K + [57]. When free K + was introduced, G-rich DNA attached to polymer chains formed G-quadruplex to crosslink the gel.…”

Aptamer-Based Hydrogels and Their Applications

“…The second method involves modification of hydrophilic polymer chains with nucleic acids as chain branches and subsequent formation of the DNA hydrogel by cross-linking the branches. For example, polyacrylamide chains functionalized with nucleic acids form hydrogels by hybridization between the nucleic acids [31] or by G-quadruplex formation in the presence of K + [55]. As a third method, polymerization of organic monomer and cross-linker to form polymer networks with tethered or entrapped functional nucleic acids [56][57][58].…”