Multi-stimuli Responsive Hydrogel Research Articles

A multi-stimuli responsive polyoxometalate-guanosine monophosphate hybrid chromogenic smart hydrogel

We propose facile synthesis of POM-GMP supramolecular hydrogel exhibiting chromism in response to multiple stimuli-light, electricity, temperature, stress, iodide, pH and biologically relevant thiols such as cysteine and glutathione.

Multi-stimuli responsive photonic hydrogel based on a novel photonic crystal template containing gold nanorods.

Multi-stimuli responsive photonic hydrogels (MRPHs) fabricated by doping nanoparticles into hydrogels show promising potential value in the fields of visual detection and drug delivery. However, complicated surface chemical modification is selected to improve the compatibility between nanoparticles and a pre-gel solution of hydrogel. Herein, we developed a simple and convenient vertical deposition method to prepare a novel photonic crystal (PC) template containing gold nanorods (Au NRs) (Au NRs/PC template), which could respond to near-infrared (NIR) light due to the conversion capability of Au NRs from NIR light to heat. Additionally, carboxyl groups on the surface of polystyrene (PS) colloids endowed the Au NRs/PC template with pH-stimulus responsiveness. Based on the Au NRs/PC template, MRPH film was fabricated by infiltrating the pre-gel solution of poly(N-isopropylacrylamide) (PNIPAM) hydrogel into the gap of a 'sandwich' structure through capillary forces and then polymerizing at 25 °C for 24 h. The obtained MRPH film could respond to NIR light, pH and temperature. Under the irradiation of NIR light, only the irradiated position lost structural color while the film volume had no distinct change. With the increase of ambient temperature, the whole MRPH film completely lost structural color and shrank significantly, which was greatly different from the phenomenon irradiated by NIR light. Besides, the structural color of the MRPH film exhibited a red shift from green to orange-red as the pH increased. Overall, both the Au NRs/PC template and the MRPH film may have potential applications in visual detection, due to their multi-stimuli responsiveness.

Bacteria-Activated Dual pH- and Temperature-Responsive Hydrogel for Targeted Elimination of Infection and Improved Wound Healing.

Antibacterial treatment that provides on-demand release of therapeutics that can kill a broad spectrum of pathogens while maintaining long-term efficacy and without developing resistance or causing side effects is urgently required in clinical practice. Here, we demonstrate the development of a multistimuli-responsive hydrogel, prepared by cross-linking N-isopropylacrylamide with acrylic acid and loaded with ultrasmall silver nanoparticles (AgNPs), offering the on-demand release of Ag+ ions triggered by changes in the wound microenvironment. We demonstrate that this dual-responsive hydrogel is highly sensitive to a typical wound pH and temperature change, evidenced by the restricted release of Ag+ ions at acidic pH (<5.5) while significantly promoting the release in alkaline pH (>7.4) (>90% release). The pH-dependent release and antibacterial effect show minimal killing at pH 4 or 5.5 but dramatically activated at pH 7.4 and 10, eliminating >95% of the pathogens. The in vivo antibacterial efficacy and safety showed a high potency to clear Staphylococcus aureus wound infection while significantly accelerating the wound healing rate. This multifunctional hydrogel presents a promising bacteria-responsive delivery platform that serves as an on-demand carrier to not only reduce side effects but also significantly boost the antibacterial efficiency based on physiological needs. It offers great potential to improve the way wound infections are treated with direct clinical implications, providing a single platform for long-lasting application in wound management.

Synthesis of Agarose-Based Multistimuli-Responsive Hydrogel Dressing for Accelerated Wound Healing.

Stimuli-responsive hydrogels have drawn increasing research interest in regenerative medicine due to their tunable molecular structures and functional properties for both providing a suitable microenvironment for wound healing and to serve as a sustainable therapeutic. Hence, we developed a stimuli-responsive drug-loaded hydrogel wound dressing for sustained, controlled release of the drug and accelerating wound healing. Hydrogel dressings with stimuli-responsive properties were prepared using carboxymethyl agarose (CMA) with various degrees of substitution and calcium ion crosslinking, followed by the loading of recombinant human epidermal growth factor (Rh-EGF) on the CMA hydrogel. Experimental results indicated that these hydrogel composites showed pH and temperature stimuli-responsive behaviors and released the encapsulated drug sustainedly in various release media. Moreover, the hydrogel dressings exhibited a porous network structure, stable physical properties, and excellent biocompatibility. The investigation in vivo showed that the Rh-EGF-loaded CMA hydrogel dressing significantly enhanced wound healing and reduced inflammatory responses by upregulating the transforming growth factor-beta, vascular endothelial growth factor, and cluster of differentiation 31 (CD31). These results confirm that Rh-EGF-loaded CMA hydrogel dressings possess potential application in accelerating wound healing and tissue regeneration.

A triple-stimuli responsive supramolecular hydrogel based on methoxy-azobenzene-grafted poly(acrylic acid) and β-cyclodextrin dimer

It has been attracted broad interest to construct stimulus responsive supramolecular hydrogels as smart materials over the past few decades; however, the design of multi-stimuli responsive hydrogels remains a formidable challenge. Herein, a multi-stimuli responsive supramolecular hydrogel has been designed on the basis of methoxy-azobenzene-grafted poly (acrylic acid) (PAA-mAzo) and β-CD dimer, which involves the host-guest and electrostatic interactions. Besides the common thermo-responsive behavior, the hydrogel also exhibits reversible sol-gel transition under green and blue light irradiations because of the disassociation and association of host–guest interaction between mAzo and β-CD. In addition, the hydrogel turns into precipitate at low pH due to the decrease of solubility of PAA in aqueous solution. The electrostatic interaction between the negatively charged carboxylic acid groups and hydrated protons at high pH makes the recovery of hydrogel. At last, the release of rhodamine B loaded in the triple-stimuli responsive hydrogel can be accelerated by green light irradiation and low pH, which demonstrates the potential applications in biomedical materials.

Stimuli-Responsive Hydrogels with Antibacterial Activity Assembled from Guanosine, Aminoglycoside, and a Bifunctional Anchor.

Multistimuli-responsive hydrogels with specific functions have attracted great interest for biomedical applications; however, these smart hydrogels usually require the presynthesis of macromolecular building blocks with multiple ligands and the integration of bioactive cargoes into the gels. Here, a multistimuli-responsive hydrogel with potent antibacterial activity by a combination of supramolecular assembly and iminoboronate chemistry is reported. The hydrogel consists of all-small-molecule building blocks including aminoglycoside, guanosine, potassium ion, and a bifunctional anchor bearing both boronic acid and aldehyde groups. Guanosines form quadruplexes in the presence of potassium ions via supramolecular assembly, and the bifunctional anchor connects aminoglycosides, a class of potent antibiotics to cis-diol groups on quadruplexes via dynamic iminoboronate chemistry, yielding a smart hydrogel containing abundant antibiotics. The hydrogel is sensitive to multistimuli such as heat, acids, oxidants, glucose and crown ether, which promote the release of antibiotics from the gels. Moreover, the prepared hydrogels show potent antibacterial activities both in vitro and in vivo. The results provide a new option to prepare antibacterial hydrogels with multistimuli responsiveness via facile chemistry using all-small-molecule building blocks.

Switchable Electrochemical Behavior of Matrine and Sophoridine at Multi-stimuli Responsive Hydrogel Film Electrode and Construction of Logic Gate†

Switchable Electrochemical Behavior of Matrine and Sophoridine at Multi-stimuli Responsive Hydrogel Film Electrode and Construction of Logic Gate†

Pillar[5]arene-based multifunctional supramolecular hydrogel: multistimuli responsiveness, self-healing, fluorescence sensing, and conductivity

A pillar[5]arene-based multi-stimuli responsive supramolecular hydrogel has been constructed. This hydrogel not only could ultra-sensitively detect Fe3+ by fluorescence, but it is also an excellent self-healing and conductive material.

Continuous fabrication of multi-stimuli responsive graphene oxide composite hydrogel fibres by microfluidics

Stimuli responsive graphene oxide composite hydrogel fibres were preparedviaa microfluidic spinning process, and exhibit both thermo-triggered volume-phase transitions and electrically triggered bending behaviours.

Cross-linkable multi-stimuli responsive hydrogel inks for direct-write 3D printing

Triple-stimuli responsive hydrogel can be 3D printed and cross-linked in the presence of a photoradical generator and 365 nm UV light.

Multi-stimuli responsive supramolecular hydrogels based on Fe3+ and diblock copolymer micelle complexation

We report a multi-stimuli responsive supramolecular hydrogel with great potential for biomedical application, which was composed of the micelle-forming diblock copolymer and physically cross-linked by complexation between ferric ions and carboxylic acid groups, exhibiting gel–sol transition caused by UV irradiation, multidentate ligands (EDTA) and redox agents (Na2S2O4).

Multistimuli-responsive Hydrogel Particles Prepared via the Self-assembly of PEG-based Hyperbranched Polymers

Abstract Generally, it is very difficult to obtain multistimuli-responsive hydrogel particles. Here, we introduce a novel method for the preparation of multistimuli-responsive hydrogel particles by adding water into the poly(ethylene glycol) (PEG)-based hyperbranched polymers. The produced PEG-base polymers via reversible addition–fragmentation chain transfer (RAFT) polymerization become temperature-sensitive and less soluble when heated above the lower critical solution temperature (LCST) after directly adding water. Subsequently, the hydrogel particles can be formed via hyperbranch–hyperbranch coupling through disulfide exchange. The resulting hydrogel particles are temperature-, photo-, and redox-responsive.

Multi stimuli-responsive hydrogel microfibers containing magnetite nanoparticles prepared using microcapillary devices.

Extensive research efforts have been devoted to the development of hydrogel microfibers for tissue engineering, because the vascular structure is related to the transport of nutrients and oxygen as well as the control of metabolic and mechanical functions in the human body. Even though stimuli-responsive properties would enhance the potential applicability of hydrogel microfibers for artificial tissue architectures, previous studies of their fabrication have not considered changes in the microfibers in response to external stimuli. In this work, we prepared temperature-responsive poly(N-isopropylacrylamide) (PNIPAm) microfibers with controlled shapes and sizes by the in situ photo-polymerization of aqueous monomers loaded in calcium alginate templates generated from microcapillary devices. We found that the shape and size of the hydrogel microfibers could be controlled by adjusting the injection positions of the solutions and varying the diameters of the inner capillary, respectively. We further fabricated light-responsive materials by incorporating photothermal magnetite nanoparticles (MNPs) within the temperature-responsive PNIPAm hydrogel microfibers. Because the MNPs incorporated into the PNIPAm microfibers generated heat upon the absorption of visible light, we could demonstrate volume changes in the microfibers triggered by both visible light irradiation and temperature.

Magnetically doped multi stimuli-responsive hydrogel microspheres with IPN structure and application in dye removal

Interpenetrating polymer network (IPN) hydrogel microspheres composed of temperature-sensitive crosslinked poly(N-isopropylacrylamide) (PNIPAM) and pH-sensitive crosslinked poly(methacrylic acid) (PMAA) are prepared by sequential polymerization method. The IPN hydrogel microspheres are characterized for their temperature- and pH-responsive behaviors by measuring the variation of hydrodynamic diameters. The results showed that these hydrogel microspheres exhibited both temperature- and pH- sensitive volume phase transitions. The structure and properties are systematically characterized using FTIR, 1H-NMR, transmission electron microscope (TEM), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermo-gravimetric analyses (TGA). IPN hydrogel microspheres are then magnetically doped by in-situ formation of Fe3O4 nanoparticles. The adsorption/desorption of various dyes and subsequent separation of dye loaded magnetic hydrogel microspheres from the aqueous medium are studied under the influence of magnetic field.

Stiff, Multistimuli‐Responsive Supramolecular Hydrogels as Unique Molds for 2D/3D Microarchitectures of Live Cells

Supramolecular hydrogels constructed through molecular self-assembly of small molecules have unique stimuli-responsive properties; however, they are mechanically weak in general, relative to conventional polymer gels. Very recently, we developed a zwitterionic amino acid tethered amphiphilic molecule 1, which gave rise to a remarkably stiff hydrogel comparable with polymer-based agarose gel, retaining reversible thermal-responsive properties. In this study, we describe that rational accumulation of multiple and orthogonal noncovalent interactions in the supramolecular nanofibers of 1 played crucial roles not only in the mechanical reinforcement but also in the multistimuli responsiveness. That is, the zwitterionic amino acid moiety and the C-C double bond unit of the hydrogelator 1 can function as a pH-responsive unit and a light-responsive unit, respectively. We also demonstrated that this stiff and multistimuli-responsive supramolecular hydrogel 1 is applied as a unique mold for 2D and 3D-patterning of various substances. More significantly, we succeeded in the fabrication of a collagen gel for spatial patterning, culturing, and differentiation of live cells by using hydrogel 1 molds equipped with 2D/3D microspace channels (100-200 μm in diameter).