A bioinspired glucose-responsive insulin delivery system for self-regulation of blood glucose levels is desirable for improving health and quality of life outcomes for patients with type 1 and advanced type 2 diabetes. Here we describe a painless core–shell microneedle array patch consisting of degradable cross-linked gel for smart insulin delivery with rapid responsiveness and excellent biocompatibility. This gel-based device can partially dissociate and subsequently release insulin when triggered by hydrogen peroxide (H2O2) generated during the oxidation of glucose by a glucose-specific enzyme covalently attached inside the gel. Importantly, the H2O2-responsive microneedles are coated with a thin-layer embedding H2O2-scavenging enzyme, thus mimicking the complementary function of enzymes in peroxisomes to protect normal tissues from injury caused by oxidative stress. Utilizing a chemically induced type 1 diabetic mouse model, we demonstrated that this smart insulin patch with a bioresponsive core and protective shell could effectively regulate the blood glucose levels within a normal range with improved biocompatibility.

Nanomaterials are regularly added to crosslinkable polymers to enhance mechanical properties; however, important effects related to gelation behavior and crosslinking kinetics are often overlooked. In this study, we combine cellulose...

Ionic liquids (ILs) containing reactive groups provide a tunable medium for bulk polymerization and network formation with potential applications as 3D-printable materials. In this study, dynamic rheology and real-time Fourier transform infrared spectroscopy are used to monitor the in situ photopolymerization and gelation of coordinated ILs containing varying molar ratios of 1-vinylimidazole (Vim) to lithium bistriflimide (LiTf2N). Three distinct regimes are observed: (1) at low [LiTf2N], samples increase in complex shear modulus (G*) and conversion faster with increasing [LiTf2N] and behave as solutions; (2) at intermediate [LiTf2N], G* growth and conversion achieve local maxima, and samples undergo sol-to-gel transitions during polymerization; (3) at high [LiTf2N], G* growth and conversion slow with [LiTf2N], and samples exhibit viscoelastic material behavior. Gelation is attributed to Li+ coordination with imidazole pendant groups to form physical cross-links between polymer chains, while the three regimes reflect the interplay of competing effects of increased polymer content and coordination-induced cross-linking. Rheological dark curing is also observed at high [LiTf2N] due to continued physical cross-linking by Li+ after cessation of UV light.

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As the need for high-refractive-index materials escalates to meet the growing demands for antireflective coatings and various photonic devices with robust mechanical properties, elastomeric polymer nanocomposites containing a high loading level of zirconia nanoparticles afford tremendous promise. In this study, the interactions between two functionalized zirconia nanoparticles, one reactive and the other passive, with a short-chain, UV-curable poly­(dimethylsiloxane) in solvent are systematically examined by dynamic rheology. The effects of surface functionality, as well as UV light intensity and nanoparticle loading, on the cross-linking behavior are elucidated, and both filled systems are observed to form cross-linked networks at loading levels of up to 85 wt % zirconia. The time required to achieve dynamic modulus crossover (indicating network formation) exhibits a power-law dependence on the UV light intensity for both systems at all zirconia contents. At high loading levels of the passive nanofiller (75 wt % zirconia), the resulting films appear opaque, possessing significantly higher turbidity than those containing reactive nanoparticles, which conversely yield films with low turbidity and high optical clarity at loading levels as high as 80 wt % zirconia. Reactive zirconia is more strongly incorporated into the polymer network than passive zirconia, as evidenced by values of the ultimate gel moduli, zirconia leaching from solvent-swelled films, and the topologies of cross-fractured surfaces.