Stiffness‐Switchable, Biocatalytic pH‐Responsive DNA‐Functionalized Polyacrylamide Cryogels and their Mechanical Applications

Abstract

The large‐pore interconnected channels in cryogels, allow convectional flow and rapid mass‐transport of solute constituents between the solution and cryogel polymer framework, as compared to slower, diffusionally‐controlled mass‐transport in small‐pore hydrogels. These features are applied to develop enzyme‐loaded polyacrylamide (pAAm) cryogels, and glucose oxidase (GOx)‐loaded pH‐responsive DNA‐based pAAm cryogels, revealing enhanced biocatalytic transformations, enhanced temporal stiffness changes, and mechanical bending functions, as compared to analog hydrogels. DNA‐based pAAm cryogel/hydrogel matrices, revealing pH‐switchable stiffness properties through reversible reconfiguration of DNA‐bridging units into i‐motif structures, are introduced. Enhanced switchable stiffness changes of DNA‐based pAAm cryogels, as compared to analog hydrogels, are demonstrated upon subjecting the cryogel/hydrogel matrices to auxiliary pH‐changes, or by integration of GOx into the frameworks, and driving pH‐changes through GOx‐catalyzed aerobic oxidation of glucose to gluconic acid. Enhanced stiffness changes of pAAm cryogels represent a major advance to control the mechanical properties of cryogels and are attributed to the convectionally‐controlled mass‐transport in the cryogel matrices. Moreover, bilayer constructs consisting of poly‐N‐isopropylacrylamide (pNIPAM) cryogels and pH‐responsive DNA‐based pAAm cryogel or hydrogel structures are constructed. Enhanced pH/glucose triggered mechanical bending rates of the pNIPAM cryogel/pAAm cryogel or pNIPAM cryogel/GOx‐loaded pAAm cryogel, as compared to analog pNIPAM cryogel/pAAm hydrogel frameworks are demonstrated.

Chemical and Photochemical-Driven Dissipative Fe3+/Fe2+-Ion Cross-Linked Carboxymethyl Cellulose Gels Operating Under Aerobic Conditions: Applications for Transient Controlled Release and Mechanical Actuation

“…The curvature (1/ r ) was evaluated using eq , where r corresponds to the radius of the bent configuration, Y is the distance separating the ends of the curved structure, and X is the maximum height of the curved structure. , r = Y 2 8 X + X 2 …”

“…For details, see Supporting Information, Page S20. In fact, in a previous recent report, the enzyme-catalyzed bending of a bilayer cryogel framework was demonstrated. The novelty of the present system rests, however, on the development of a light-stimulated mechanoresponsive cryogel framework revealing dissipative, transient, and mechanical functions.…”

“…These features lead to substantially faster response times for the stimuli-responsive cryogels as compared to those of analogue hydrogels. 65 Moreover, an important topic in recent materials science development involves the synthesis of out-of-equilibrium, dissipative, transient operating materials. 66−68 Particularly, the development of signal-responsive transient operating chemical systems attracts recent research efforts.…”

“…The interconnected macropores comprising the cryogels yield solvent channels in the framework, introducing significant physical properties as compared to the hydrogel, reflected by material compressibility, , different mechanical strengths, , and most importantly, convection transport of the solute across the channels, , as compared to diffusion-controlled transport of the solute in hydrogel matrices. These features lead to substantially faster response times for the stimuli-responsive cryogels as compared to those of analogue hydrogels …”

3D Printing Silk Fibroin/Polyacrylamide Triple-Network Composite Hydrogels with Stretchability, Conductivity, and Strain-Sensing Ability as Bionic Electronic Skins

“…Synthetic polymers, such as polyacrylamide (PAM), poly­(acrylic acid), and poly N -isopropylacrylamide, are extensively used to prepare hydrogel-based sensors. Compared with synthetic polymers, natural polymers have many advantages, e.g., good biocompatibility, biodegradability, and sustainability.…”