A Shape Memory Acrylamide/DNA Hydrogel Exhibiting Switchable Dual pH‐Responsiveness

Abstract

6867wileyonlinelibrary.com of the nucleic acids between two states. [ 7 ] Different stimuli, such as pH, [ 8 ] metal-ion/ ligand, [ 9 ] or photo nic signal, [ 10 ] were applied to switch DNA structures such as duplex DNAs, i-motif, or G-quadruplex structures, and these triggering signals were used to design DNA switches or DNA devices in solutions [ 11 ] and on surfaces. [ 12 ] DNAbased hydrogels attract recent research efforts, and stimuli-responsive hydrogels undergoing switchable hydrogel/solution transitions were developed. [ 13 ] pH-responsive hydrogels composed of i-motif [ 13g ] or nucleic acid triplex bridges, [ 14 ] metal-ionassisted cooperative bridging of duplex nucleic acids [ 15 ] or K + -ion-stabilized G-quadruplex bridges, [ 13b ] and their dissociation in the presence of ligands or receptors were applied to reversibly switch hydrogels-tosolution transitions. Different applications of stimuli-responsive hydrogels were suggested, including controlled drug release, [ 16 ] sensors, [ 17 ] switchable catalysis, [ 13b ] tailoring of separation matrices, [ 18 ] and the activation of enzyme cascades. [ 19 ] Recently, a pH-responsive shape memory acrylamide DNA-hydrogel was reported. [ 13g , 20 ] In this system, the shaped hydrogel was stabilized by bridging the acrylamide chains with two types of cooperative crosslinking elements involving duplex DNA and pH-sensitive i-motif units. The pH-stimulated separation of the i-motif dissociated the hydrogel into a quasi-liquid state, where the entanglement of the polymer chains by the residual duplex units provided a temporary memory for restoring the original shape upon reforming the i-motif bridging units. The development of other shape memory hydrogels, and particularly, the conjugation of hybrid shape memory polymers triggered by different stimuli, remains a challenge in materials science. Here we wish to report on the preparation of different pH-responsive shape memory hydrogels composed of acrylamide chains crosslinked by duplex DNA and pH-sensitive triplex DNA crosslinking units. In contrast to the previously reported system, the shape memory hydrogels exist at neutral pH as stable hydrogels, and are dissociated to quasi-liquid states either at acidic pH values (pH = 5.0) or at basic pH values (pH = 10.0). We further demonstrate the integration of two pH-sensitive hydrogels into a hybrid twodomain shaped structure, where each domain can be selectively addressed to undergo hydrogel/quasi-liquid shape memory dictated transitions. A Shape Memory Acrylamide/DNA Hydrogel Exhibiting Switchable Dual pH-ResponsivenessYuwei Hu , Chun-Hua Lu , Weiwei Guo , Miguel Angel Aleman-Garcia , Jiangtao Ren , and Itamar Willner * Shape memory acrylamide/DNA hydrogels include two different crosslinkers as stabilizing elements. The triggered dissociation of one of the crosslinking elements transforms the shaped hydrogel into an arbitrarily shaped (or shapeless) quasi-liquid state. The remaining crosslinking element, present in the quasi-liquid, provides an internal ...

Controlled 3D Shape Transformation Activated by Room Temperature Stretching and Release of a Flat Polymer Sheet

“…A previous work found that the PEO/PAA (80/20, w/w) blend can be stretched at room temperature to a strain beyond 800% and retain most of the elongation after removal of the external stress. 28 However, the sample becomes harder and brittle in relatively dry environments (less than 55% relative humidity). In the present study, the PEO/PAA (80/20) blend was chosen, and in order to increase its tolerance to humidity change and further improve the mechanical properties, tannic acid (TA), a naturally derived polyphenol that can form multiple interactions with a wide range of polymers and small molecules, is added in the blend to form H-bonds with both PEO and PAA.…”

“…We first prepared and studied a series of samples to optimize the mechanical properties and ductility. A previous work found that the PEO/PAA (80/20, w/w) blend can be stretched at room temperature to a strain beyond 800% and retain most of the elongation after removal of the external stress . However, the sample becomes harder and brittle in relatively dry environments (less than 55% relative humidity).…”

Controlled Release in Hydrogels Using DNA Nanotechnology

“…The increase in release time is likely due to the diffusion limitations of the system since the trigger will need to diffuse into the DNA-Gel hydrogel for the strand displacement reaction to occur. The release rate of our system is notably faster than some of the other release systems reported in other studies, which typically have a release time over a few days [54][55][56][57]. However, it is important to note that most of these studies characterized the release behaviors of large biomolecules, such as erythropoietin (~30.4 kDa) and vascular endothelial growth factor (~19-22 kDa), which has a slower diffusive rate within a hydrogel.…”

Programming the Assembly of Oligo-Adenine with Coralyne into a pH-Responsive DNA Hydrogel

“…In the construction of pH-responsive DNA hydrogels, dynamic reconfigurable DNA structures governed by pH variations, such as A-motif, − i-motif, , C + ·G-C and T·A-T triplex, ,, adenine-cyanuric acid (A-CA) triplex, are harnessed as the pivotal cross-linking elements. To facilitate comparisons, the pH responsiveness and conformational transitions of these DNA structures are briefly summarized in Figure .…”