Substrate-Independent Ag-Nanoparticle-Loaded Hydrogel Coating with Regenerable Bactericidal and Thermoresponsive Antibacterial Properties

We report a Ag-nanoparticle (AgNP)-based substrate-independent bactericidal hydrogel coating with thermoresponsive antibacterial property. To attach the hydrogel coating onto model substrate, we first coated ene-functionalized dopamine on the substrate, and then the hydrogel thin layer was formed on the surface via the UV light initiated surface cross-linking copolymerization of <i>N</i>-isopropylacrylamide (NIPAAm) and sodium acrylate (AANa). Then, Ag ions were adsorbed into the hydrogel layers and reduced to AgNPs by sodium borohydride. The coating showed robust bactericidal ability against <i>Escherichia coli</i> and <i>Staphylococcus aureus</i> toward both contacted bacteria and the bacteria in the surrounding. Upon a reduction of the temperature below the LCST of PNIPAAm, the improved surface hydrophilicity and swollen PNIPAAm could detach the attached dead bacteria. Meanwhile, the long-lasting and regenerable antibacterial properties could be achieved by repeatedly loading AgNPs. By precisely controlling the AgNP loading amounts, the coating showed excellent hemocompatibility and no cytotoxity. Additionally, the coating could be applied to modify cell culture plate, since it could support cell adhesion and proliferation at 37 °C, while detach the cell by changing the temperature below lower critical solution temperature without the treatment of proteases. The study thus presents a promising way to fabricate thermoresponsive and regenerable antibacterial surfaces on diverse materials and devices for biomedical applications

In Situ Synthesis of Magnetic Field-Responsive Hemicellulose Hydrogels for Drug Delivery

A one-pot synthetic methodology for fabricating stimuli-responsive hemicellulose-based hydrogels was developed that consists of the in situ formation of magnetic iron oxide (Fe₃O₄) nanoparticles during the covalent cross-linking of O-acetyl-galactoglucomannan (AcGGM). The Fe₃O₄ nanoparticle content controlled the thermal stability, macrostructure, swelling behavior, and magnetization of the hybrid hydrogels. In addition, the magnetic field-responsive hemicellulose hydrogels (MFRHHs) exhibited excellent adsorption and controlled release profiles with bovine serum albumin (BSA) as the model drug. Therefore, the MFRHHs have great potential to be utilized in the biomedical field for tissue engineering applications, controlled drug delivery, and magnetically assisted bioseparation. Magnetic field-responsive hemicellulose hydrogels, prepared using a straightforward one-step process, expand the applications of biomass-derived polysaccharides by combining the renewability of hemicellulose and the magnetism of Fe₃O₄ nanoparticles

Synthesis and Characterization of Ultrahigh Ion-Exchange Capacity Polymeric Membranes

A universal mold casting approach for the preparation of cation-exchange membranes (CEMs) and anion-exchange membranes (AEMs) with ultrahigh ion-exchange capacities (IECs) is developed based on in situ cross-linking polymerization of acrylic acid (AA) and 2-vinylpyridine (2VP), respectively. This new method produced ultrahigh IECs of 7.88 mequiv g^–1 for CEM and 6.27 mequiv g^–1 for AEM, which are 8.8 and 7.0 times that (0.89 mequiv g^–1) of Nafion 117, respectively. Also, the prepared membranes demonstrate excellent thermal and chemical stability and acceptable conductivity. As a consequence, the membranes show relatively high performance for ion-exchange application and methanol barrier, exhibiting ion permeabilities of 2.06 × 10^–7 cm² s^–1 for Na⁺, 2.57 × 10^–7 cm² s^–1 for Ca²⁺, 1.45 × 10^–7 cm² s^–1 for Cu²⁺ regarding CEMs, and 7.72 × 10^–7 cm² s^–1 for methanol regarding AEMs. These results indicate that the CEMs and AEMs fabricated from the universal mold casting approach are promising candidates for targeting ultrahigh ion-exchange capacity membranes

Facile and Green Approach towards Electrically Conductive Hemicellulose Hydrogels with Tunable Conductivity and Swelling Behavior

A one-pot reaction to synthesize electrically conductive hemicellulose hydrogels (ECHHs) is developed via a facile and green approach in water and at ambient temperature. ECHHs were achieved by cross-linking <i>O</i>-acetyl-galactoglucomannan (AcGGM) with epichlorohydrin in the presence of conductive aniline pentamer (AP) and were confirmed by infrared spectroscopy (IR) and elemental analysis. All hydrogels had macro-porous structures, and the thermal stability of ECHHs was improved by the addition of AP. Hydrogel equilibrium swelling ratios (ESRs) varied from 13.7 to 11.4 and were regulated by cross-linker concentration. The ESRs can also be tuned from 9.6 to 6.0 by changing the AP content level from 10 to 40% (w/w) while simultaneously altering conductivity from 9.05 × 10^–9 to 1.58 × 10^–6 S/cm. ECHHs with controllable conductivity, tunable swelling behavior, and acceptable mechanical properties have great potential for biomedical applications, such as biosensors, electronic devices, and tissue engineering

Reinforced-Concrete Structured Hydrogel Microspheres with Ultrahigh Mechanical Strength, Restricted Water Uptake, and Superior Adsorption Capacity

Functional hydrogels own superior advantages in wastewater purification thanks to their abundant functional groups and porous structure. However, the hydrogels cannot be used as stable adsorbents due to their insufficient mechanical properties and exorbitant swelling ratio. Inspired by the strong mechanical properties of the reinforced-concrete structure, the novel reinforced-concrete structured hydrogel microspheres were prepared, and the structure endowed the hydrogel with superior mechanical properties (the compressive stress was 27.4 MPa with a strain of 80%) and restricted swelling ratio (the water uptake was less than 2.2 g/g under pH = 7) but caused no obviously negative effect on the originally outstanding adsorption ability. The adsorption column filled with the concrete-structured hydrogel microspheres reached stable and efficient removal of the cationic dyes and heavy metal salts (1246 mg/g for MB, 491 mg/g for MV, 1253 mg/g for Cu­(II), 564 mg/g for Ni­(II), 640 mg/g for Cd­(II), and 252 mg/g for Pb­(II)). These results indicated that the microspheres were qualified for the work as stable and efficient adsorbents and, more importantly, the reinforced-concrete structure might accelerate the actual application of the hydrogels in diverse fields to a great extent

Photoresponsive Surface Molecularly Imprinted Poly(ether sulfone) Microfibers

In the present study, photoresponsive surface molecularly imprinted poly­(ether sulfone) microfibers are prepared via nitration reaction, the wet-spinning technique, surface nitro reduction reaction, and surface diazotation reaction for the selectively photoregulated uptake and release of 4-hydrobenzoic acid. The prepared molecularly imprinted microfibers show selective binding to 4-HA under irradiation at 450 nm and release under irradiation at 365 nm. The simple, convenient, effective, and productive method for the preparation of azo-containing photoresponsive material is also applied to the modification of polysulfone and poly­(ether ether ketone). All three benzene-ring-containing polymers show significant photoresponsibility after the azo modification

In Situ Cross-Linking of Stimuli-Responsive Hemicellulose Microgels during Spray Drying

Chemical cross-linking during spray drying offers the potential for green fabrication of microgels with a rapid stimuli response and good blood compatibility and provides a platform for stimuli-responsive hemicellulose microgels (SRHMGs). The cross-linking reaction occurs rapidly in situ at elevated temperature during spray drying, enabling the production of microgels in a large scale within a few minutes. The SRHMGs with an average size range of ∼1–4 μm contain <i>O</i>-acetyl-galactoglucomannan as a matrix and poly­(acrylic acid), aniline pentamer (AP), and iron as functional additives, which are responsive to external changes in pH, electrochemical stimuli, magnetic field, or dual-stimuli. The surface morphologies, chemical compositions, charge, pH, and mechanical properties of these smart microgels were evaluated using scanning electron microscopy, IR, zeta potential measurements, pH evaluation, and quantitative nanomechanical mapping, respectively. Different oxidation states were observed when AP was introduced, as confirmed by UV spectroscopy and cyclic voltammetry. Systematic blood compatibility evaluations revealed that the SRHMGs have good blood compatibility. This bottom-up strategy to synthesize SRHMGs enables a new route to the production of smart microgels for biomedical applications

Reinforced-Concrete Structured Hydrogel Microspheres with Ultrahigh Mechanical Strength, Restricted Water Uptake, and Superior Adsorption Capacity

Functional hydrogels own superior advantages in wastewater purification thanks to their abundant functional groups and porous structure. However, the hydrogels cannot be used as stable adsorbents due to their insufficient mechanical properties and exorbitant swelling ratio. Inspired by the strong mechanical properties of the reinforced-concrete structure, the novel reinforced-concrete structured hydrogel microspheres were prepared, and the structure endowed the hydrogel with superior mechanical properties (the compressive stress was 27.4 MPa with a strain of 80%) and restricted swelling ratio (the water uptake was less than 2.2 g/g under pH = 7) but caused no obviously negative effect on the originally outstanding adsorption ability. The adsorption column filled with the concrete-structured hydrogel microspheres reached stable and efficient removal of the cationic dyes and heavy metal salts (1246 mg/g for MB, 491 mg/g for MV, 1253 mg/g for Cu­(II), 564 mg/g for Ni­(II), 640 mg/g for Cd­(II), and 252 mg/g for Pb­(II)). These results indicated that the microspheres were qualified for the work as stable and efficient adsorbents and, more importantly, the reinforced-concrete structure might accelerate the actual application of the hydrogels in diverse fields to a great extent

Reinforced-Concrete Structured Hydrogel Microspheres with Ultrahigh Mechanical Strength, Restricted Water Uptake, and Superior Adsorption Capacity

Functional hydrogels own superior advantages in wastewater purification thanks to their abundant functional groups and porous structure. However, the hydrogels cannot be used as stable adsorbents due to their insufficient mechanical properties and exorbitant swelling ratio. Inspired by the strong mechanical properties of the reinforced-concrete structure, the novel reinforced-concrete structured hydrogel microspheres were prepared, and the structure endowed the hydrogel with superior mechanical properties (the compressive stress was 27.4 MPa with a strain of 80%) and restricted swelling ratio (the water uptake was less than 2.2 g/g under pH = 7) but caused no obviously negative effect on the originally outstanding adsorption ability. The adsorption column filled with the concrete-structured hydrogel microspheres reached stable and efficient removal of the cationic dyes and heavy metal salts (1246 mg/g for MB, 491 mg/g for MV, 1253 mg/g for Cu­(II), 564 mg/g for Ni­(II), 640 mg/g for Cd­(II), and 252 mg/g for Pb­(II)). These results indicated that the microspheres were qualified for the work as stable and efficient adsorbents and, more importantly, the reinforced-concrete structure might accelerate the actual application of the hydrogels in diverse fields to a great extent