No abstract

Gold nanoparticles (AuNPs) or gold nanorods (AuNRs) are loaded in polyacrylamide hydrogels cooperatively cross-linked by bis-acrylamide and nucleic acid duplexes or boronate ester–glucosamine and nucleic acid duplexes. The thermoplasmonic properties of AuNPs and AuNRs are used to control the stiffness of the hydrogels. The irradiation of the AuNP-loaded (λ = 532 nm) or the AuNR-loaded (λ = 808 nm) hydrogels leads to thermoplasmonic heating of the hydrogels, the dehybridization of the DNA duplexes, and the formation of hydrogels with lower stiffness. By ON/OFF irradiation, the hydrogels are switched between low- and high-stiffness states. The reversible control over the stiffness properties of the hydrogels is used to develop shape-memory hydrogels and self-healing soft materials and to tailor thermoplasmonic switchable drug release. In addition, by designing bilayer composites of AuNP- and AuNR-loaded hydrogels, a reversible thermoplasmonic, light-induced bending is demonstrated, where the bending direction is controlled by the stress generated in the respective bilayer composite.

Photoresponsive hydrogels crosslinked by trans-azobenzene/β-cyclodextrin and duplex DNA or K+-G-quadruplex are described. The hydrogels reveal shape-memory functions and self-healing properties.

Photoresponsive nucleic acids attract growing interest as functional constituents in materials science. We review the recent exciting developments of this field and identify the opportunities and challenges to be addressed by future research efforts.

No abstract

Carboxymethyl cellulose (CMC) chains are functionalized with self-complementary nucleic acid tethers and electron donor or electron acceptor functionalities. The polymer chains crosslinked by the self-complementary duplex nucleic acids and the donor-acceptor complexes as bridging units, yield a stiff stimuli-responsive hydrogel. Upon the oxidation of the electron donor units, the donor-acceptor bridging units are separated, leading to a hydrogel of lower stiffness. By the cyclic oxidation and reduction of the donor units, the hydrogel is reversibly transformed across low and high stiffness states. The controlled stiffness properties of the hydrogel are used to develop shape-memory hydrogels. In addition, CMC hydrogels crosslinked by donor-acceptor complexes and K + -stabilized G-quadruplexes reveal stimuliresponsive properties that exhibit dually triggered stiffness functions. While the hydrogel bridged by the two crosslinking motifs reveals high stiffness, the redox-stimulated separation of the donor-acceptor complexes or the crownether-stimulated separation of the G-quadruplex bridges yields two alternative hydrogels exhibiting low stiffness states. The control over the stiffness properties of the dually triggered hydrogel is used to develop shape-memory hydrogels, where the donor-acceptor units or G-quadruplex bridges act as "memories", and to develop triggered self-healing process of the hydrogel.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201803111.hydrogel-to-solid [29] or hydrogel-to-liquid [30] transitions attract growing interest, and different triggers, such as pH, [31] heat, [32] light, [33][34][35][36] or magnetic field [37,38] are used to reversibly transform the hydrogels between the different states. For example, the mixture of trans-azobenzene-functionalized acrylamide polymer chains and β-cyclodextrin-modified acrylamide polymer chains yielded a photoresponsive hydrogel via crosslinking of the chains by trans-azobenzene/β-cyclodextrin hostguest complexes. [33][34][35][36] The photoisomerization of the trans-azobenzene units to cis-azobenzene units, that lack affinity toward β-cyclodextrin, resulted in the separation of the crosslinking units and the transition of the hydrogel into a solution of the polymer chains. Within the broad class of stimuli-responsive supramolecular hydrogels, deoxyribonucleic acid (DNA)-crosslinked hydrogels provide a rich arsenal of functional materials and, specifically, of stimuli-triggered hydrogel matrices. [39][40][41] Besides the possibility to reconfigure nucleic acid duplexes by fuel/antifuel strands, [42] the pH-stimulated transitions of cytosine-rich strands into i-motif structures, [43][44][45][46] the self-assembly of pH-induced formation and separation of C-G·C + or T-A·T triplexes, [47] the K + -ion-stimulated assembly of G-quadruplexes and their separation by crown ethers or cryptate, [48] the cooperative stabilization of duplex nucleic structures by metal-ion bridges [49] (e.g., THg...

Biocatalytic control over the stiffness of pH-responsive hydrogels is applied to develop shape-memory, self-healing and controlled release matrices.

Microcapsules consisting of hydrogel shells cross‐linked by glucosamine–boronate ester complexes and duplex nucleic acids, loaded with dyes or drugs and functionalized with Au nanoparticles (Au NPs) or Au nanorods (Au NRs), are developed. Irradiation of Au NPs or Au NRs results in the thermoplasmonic heating of the microcapsules, and the dissociation of the nucleic acid cross‐linkers. The separation of duplex nucleic acid cross‐linkers leads to low‐stiffness hydrogel shells, allowing the release of loads. Switching off the light‐induced plasmonic heating results in the regeneration of stiff hydrogel shells protecting the microcapsules, leading to the blockage of release processes. The thermoplasmonic release of tetramethylrhodamine‐dextran, Texas Red‐dextran, doxorubicin‐dextran (DOX‐D), or camptothecin‐carboxymethylcellulose (CPT‐CMC) from the microcapsules is introduced. By loading the microcapsules with two different drugs (DOX‐D and CPT‐CMC), the light‐controlled dose release is demonstrated. Cellular experiments show efficient permeation of Au NPs/DOX‐D or Au NRs/DOX‐D microcapsules into MDA‐MB‐231 cancer cells and inefficient uptake by MCF‐10A epithelial breast cells. Cytotoxicity experiments reveal selective thermoplasmon‐induced cytotoxicity of the microcapsules toward MDA‐MB‐231 cancer cells as compared to MCF‐10A cells. Also, selective cytotoxicity towards MDA‐MB‐231 cancer cells upon irradiation of the Au NPs‐ and Au NRs‐functionalized microcapsules at λ = 532 or 910 nm is demonstrated.