Construction of pH-Triggered DNA Hydrogels Based on Hybridization Chain Reactions

As a novel type of bio-functional material,DNA hydrogels have attracted more and more attention due to their successful applications in 3D cell culturing and tissue engineering for the designable and programmable responsiveness.Herein,we have developed a pH-triggered DNA hydrogel based on a clamped hybridization chain reaction(C-HCR).In this system,a DNA switch was designed,which can release the initiator strand in a controllable way via the formation of the C-G-C4 triplex under the pH stimuli.While the pre-gelation solution is stable in neutral environment,the C-HCR will trigger the sol-gel transition as the pH decreased to 5.0.This strategy has endowed the DNA hydrogel with good controllability for triggering,which also shows potential in intellectual responsiveness to certain stimuli.

Dual stimuli-responsive polyurethane-based hydrogels as smart drug delivery carriers for the advanced treatment of chronic skin wounds

The design of multi-stimuli-responsive vehicles for the controlled and localized release of drugs is a challenging issue increasingly catching the attention of many research groups working on the advanced treatment of hard-to-close wounds.In this work,a thermo-and pH-responsive hydrogel(P-CHP407)was prepared from an ad hoc synthesized amphiphilic poly(ether urethane)(CHP407)exposing a significant amount of-COOH groups(8.8±0.9 nmol/g_(polymer)).The exposure of acid moieties in P-CHP407 hydrogel led to slightly lower initial gelation temperature(12.1◦C vs.14.6◦C,respectively)and gelation rate than CHP407 hydrogel,as rheologically assessed.Nanoscale hydrogel characterization by Low Field NMR(LF-NMR)spectroscopy suggested that the presence of carboxylic groups in P-CHP407 caused the formation of bigger micelles with a thicker hydrated shell than CHP407 hydrogels,as further proved by Dynamic Light Scattering analyses.In addition,P-CHP407 hydrogel showed improved capability to change its internal pH compared to CHP407 one when incubated with an alkaline buffer(pH 8)(e.g.,pH_(change_5min)=3.76 and 1.32,respectively).Moreover,LF-NMR characterization suggested a stronger alkaline-pH-induced interaction of water molecules with micelles exposing-COOH groups.Lastly,the hydrogels were found biocompatible according to ISO 10993 and able to load and release Ibuprofen:delivery kinetics of Ibuprofen was enhanced by P-CHP407 hydrogels at alkaline pH,suggesting their potential use as smart delivery systems in the treatment of chronic infected wounds.