No abstract

Bioinspired hydrogels have promising prospects in applications such as wearable devices, human health monitoring equipment, and soft robots due to their multifunctional sensing properties resembling natural skin. However, the preparation of intelligent hydrogels that provide feedback on multiple electronic signals simultaneously, such as human skin receptors, when stimulated by external contact pressure remains a substantial challenge. In this study, we designed a bioinspired hydrogel with multiple conductive capabilities by incorporating carbon nanotubes into a chelate of calcium ions with polyacrylic acid and sodium alginate. The bioinspired hydrogel consolidates self-healing ability, stretchability, 3D printability, and multiple conductivities. It can be fabricated as an integrated strain sensor with simultaneous piezoresistive and piezocapacitive performances, exhibiting sensitive (gauge factor of 6.29 in resistance mode and 1.25 kPa–1 in capacitance mode) responses to subtle pressure changes in the human body, such as finger flexion, knee flexion, and respiration. Furthermore, the bioinspired strain sensor sensitively and discriminatively recognizes the signatures written on it. Hence, we expect our ideas to provide inspiration for studies exploring the use of advanced hydrogels in multifunctional skin-like smart wearable devices.

No abstract

Glucose stimulates insulin secretion from pancreatic ␤ cells by inducing the recruitment and fusion of insulin vesicles to the plasma membrane. However, little is currently known about the mechanism of the initial docking or tethering of insulin vesicles prior to fusion. Here, we examined the role of the SEC6-SEC8 (exocyst) complex, implicated in trafficking of secretory vesicles to fusion sites in the plasma membrane in yeast and in regulating glucose-stimulated insulin secretion from pancreatic MIN6 ␤ cells. We show first that SEC6 is concentrated on insulin-positive vesicles, whereas SEC5 and SEC8 are largely confined to the cytoplasm and the plasma membrane, respectively. Overexpression of truncated, dominant-negative SEC8 or SEC10 mutants decreased the number of vesicles at the plasma membrane, whereas expression of truncated SEC6 or SEC8 inhibited overall insulin secretion. When single exocytotic events were imaged by total internal reflection fluorescence microscopy, the fluorescence of the insulin surrogate, neuropeptide Y-monomeric red fluorescent protein brightened, diffused, and then vanished with kinetics that were unaffected by overexpression of truncated SEC8 or SEC10. Together, these data suggest that the exocyst complex serves to selectively regulate the docking of insulin-containing vesicles at sites of release close to the plasma membrane.

A facile approach of layer-by-layer depositing and hydrolysis of FeCl3 is developed to fabricate 3D-ordered Fe2O3 film. The 3D-ordered Fe2O3 film was characterized by SEM, XRD, and DRUV−vis. It has 3D-ordered interconnecting macropores (340 nm) with nanocrystalline hematite Fe2O3 walls (27.2 nm). The 3D-ordered macroporous nanocrystalline Fe2O3 film exhibits 2.4 times larger photocatalytic activity for the photodegradation of dye in the presence of H2O2 under visible irradiation than the nanocrystalline α-Fe2O3 film without macropores and very good photostability. The much higher photocatalytic activity of the 3D-ordered macroporous nanocrystalline Fe2O3 film than that of the reference Fe2O3 film is attributed to the unique nanostructure and architecture of the 3D-ordered Fe2O3 film, which result in the much greater light harvesting efficiency and efficient mass transport in the former than in the latter due to the existence of 3D-ordered interconnecting macropores. The effect of photonic stop band on the photocatalytic activity of the 3D-ordered Fe2O3 film was studied by angle-dependent solid-state photodegradation experiments with monochromatic irradiation. A slow photon enhancement of photocatalytic activity was achieved by adjusting the red edge of the photonic stop band of the 3D-ordered Fe2O3 film close to the electronic bandgap of Fe2O3. The photodegradation mechanism of crystal violet on the 3D-ordered Fe2O3 photocatalyst in the presence or absence of H2O2 was discussed.