Herein, a dual-responsive insulin delivery device by integrating glucose- and HO-responsive polymeric vesicles (PVs) with transcutaneous microneedles (MNs) has been designed. This novel microneedle delivery device achieves a goal of fast response, excellent biocompatibility, and painless administration. The PVs are self-assembled from a triblock copolymer including poly(ethylene glycol), poly(phenylboronic acid) (glucose-sensitive block), and poly(phenylboronic acid pinacol ester) (HO-sensitive block). After loading with insulin and glucose oxidase (GO ), the drug-loaded PVs display a basal insulin release as well as a promoted insulin release in response to hyperglycemic states. The insulin release rate responds quickly to elevated glucose and can be further promoted by the incorporated GO , which will generate the HO at high glucose levels and further break the chemical links of phenylboronic acid pinacol ester group. Finally, the transdermal delivery of insulin to the diabetic rats ((insulin + GO )-loaded MNs) presents an effective hypoglycemic effect compared to that of subcutaneous injection or only insulin-loaded MNs, which indicates the as-prepared MNs insulin delivery system could be of great importance for the applications in the therapy of diabetes.

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Two ionic block copolymers with different lengths of hydrophilic segments, polystyrene‐b‐poly(quaternized 4‐vinylpyridine)/ethyl bromide, are prepared by sequential reactions. They are originally self‐assembled into so‐called “large compound micelles” in aqueous solution. After ion exchange of Iˉ, SCN,ˉ and PF6ˉ for Brˉ, morphological transitions are controlled by a competition of solvation and size effects of the newly introduced counterions. The solvation effect is dominated in a relatively short corona‐forming block. Thus, sphere‐to‐wormlike particles, sphere‐to‐vesicle, and sphere‐to‐precipitate transitions are observed. In contrast, due to a long corona‐forming block, size effects become more profound after adding SCNˉ, thereby no morphological transition occurs. A morphological transition is characterized after partial exchange of Iˉ for Brˉ for both diblocks. A sphere‐to‐wormlike particles transition is observed only after most Brˉ is replaced by Iˉ. This work extends the understanding of morphological regulation through simple ion exchange and encourages rational design of nano‐assemblies.

A Cl− and I− ion‐containing amphiphilic diblock copolymer [PEO‐b‐P(qVBC‐co‐St)], IBCP, which comprises the poly(ethylene oxide) block and poly(quaternized 4‐vinylbenzyl chloride‐co‐styrene) is prepared by sequence reactions. Then the counterion‐mediated self‐assembly behavior in aqueous solution is investigated in detail. The hydrophilicity of anion containing units (qVBC) is controlled by the nature of the different counterions after ion exchange, which is crucial in regulating the self‐assembly process. The addition of Br−, I−, and SCN− counterions (based on the Hofmeister series) results in the formation of tighter ion‐pairs with cations (i.e., more hydrophobic as the qVBC units), which triggers spheres to vesicles, micro‐meter long cylinders and “branched wormlike” aggregates, respectively. Moreover, addition of different amounts of Cl− also causes morphological transition from spheres to long cylinders. And this morphological transition is totally reversible after removing additional Cl−. The adhesive collisions of spherical particles may contribute to the observed sphere‐to‐cylinder morphological transition.