Search

Hydrogels are three-dimensional porous polymeric networks prepared by physical or chemical cross-linking of hydrophilic molecules, which can be made into smart materials through judicious chemical modifications to recognize external stimuli; more specifically, this can be accomplished by the integration with stimuli-responsive polymers or sensing molecules that has drawn considerable attention in their possible roles as sensors and diagnostic tools. They can be tailored in different structures and integrated into systems, depending on their chemical and physical structure, sensitivity to the external stimuli and biocompatibility. A panoramic overview of the sensing advances in the field of hydrogels over the past several decades focusing on a variety protocols of hydrogel preparations is provided, with a major focus on natural polymers. The modifications of hydrogel composites by incorporating inorganic nanoparticles and organic polymeric compounds for sensor applications and their mechanisms are also discussed.

A hybrid poly(N-isopropylacrylamide) (PNIPAm)/cellulose nanofibrils (CNFs) hydrogel composite was fabricated by inverted stereolithography 3D printing to provide a new platform for regulating lower critical solution temperature (LCST) properties and thus tuning optical and bioadhesive properties. The phenomena of interest in the as-printed PNIPAm/CNF hydrogels may be attributed to the fiber-reinforced composite system between crosslinked PNIPAm and CNFs. The optical tunability was found to be correlated to the micro/nano structures of the PNIPAm/CNF hydrogel films. It was found that PNIPAm/CNF hydrogels exhibit switchable bioadhesivity to bacteria in response to CNF distribution in the hydrogels. After 2.0 wt% CNF was incorporated, it was found that a remarkable 8°C reduction of the LCST was achieved relative to PNIPAm hydrogel crosslinked by TEGDMA without CNF. The prepared PNIPAm/CNF hydrogels possessed highly reversible optical, bioadhesion, and thermal performance, making them suitable to be used as durable temperature-sensitive sensors and functional biomedical devices., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

To avoid the problem of difficult wound healing caused by diabetes. In this study, zeolite imidazolium ester skeleton-8 (ZIF-8) was loaded with dihydroquercetin (DHQ) in order to improve the slow-release property as well as the biological activity of DHQ, and the mechanism of wound healing action of ZIF-8-loaded hydrogel was investigated by Western blot technique. The results showed that the dynamic light scattering result was 90.54 ± 3.45 nm and the zeta potential was −32.91 mV. In addition, through the synergistic effect of ZIF-8 and DHQ, the hydrogel exhibited excellent in vitro activity, and the in vitro antioxidant results showed that the inhibition rate of DZP hydrogel against the free radicals of ABTS and DPPH was over 90%, and the inhibition rate against Escherichia coli and Staphylococcus aureus was over 90%, respectively, and also promoted cell growth and migration. In addition, the in vitro release assay of DHQ from DZP hydrogel at 24 h showed 61.69 ± 1.93% at pH = 6.0 and 62.42 ± 1.58% at pH = 7.4, which improves the slow-release property of DHQ and is suitable for long-term tissue repair applications. The results of in vivo experiments showed that DZP hydrogel promotes the healing of difficult-to-heal wounds by inhibiting the activation of the IkBα/NF-κB pathway, stimulating skin neovascularisation, and promoting collagen accumulation. Collectively, these properties make DZP a strong candidate for diabetic wound dressings and are expected to play an important role in wound management. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Developed Poly(N-Isopropylacrylamide)-Cellulose Nanocrystal hydrogel films. • Achieved unique thermo-responsivity and tunable optical performance. • Developed a hybrid materials system to modulate LCST and moisture content for thermo-responsivity and optical tunability. • Demonstrated a ∼ 15 °C reduction of the LCST relative to pure PNIPAm hydrogel films. • Below the LCST, PNIPAm/CNC hydrogel films exhibit transparency or semi-transparency. Abstract A hybrid materials system to modulate lower critical solution temperature (LCST) and moisture content for thermo-responsivity and optical tunability was strategically developed by incorporating cellulose nanocrystals (CNCs) into a poly(N -isopropylacrylamide) (PNIPAm) hydrogel matrix. The PNIPAm/CNC hydrogel films exhibit tunable optical properties and wavelength bandpass selectivity as characterized by PROBE Spectroscopy and Dynamic Light Scattering (DLS). Importantly, the micro/nano structures of the PNIPAm/CNC hydrogel films were completely different when dried below and above the LCST. Below the LCST, PNIPAm/CNC hydrogel films exhibit transparency or semi-transparency due to the uniform bonding of hydrophilic PNIPAm and CNC through hydrogen bonds. Above the LCST, the hydrogel films engage in both hydrophobic PNIPAm and hydrophilic CNC interactions due to changes in PNIPAm conformation which lead to light scattering effects and hence opacity. Furthermore, the incorporation of CNC induces a ∼ 15 °C reduction of the LCST relative to pure PNIPAm hydrogel films. [ABSTRACT FROM AUTHOR]