To simplify the preparation process of a glucose-responsive microneedle patch, a cross-linking-density changeable microneedle patch was designed. The microneedle patch was made up of a hydrogel formed by phenylboronic acid-grafted polyallylamine and poly(vinyl alcohol) (PVA). The gel was cross-linked by boronate ester bonds between phenylboronic acid groups and PVA. It still had fluidity and could be filled into a mold to prepare microneedle patches. Moreover, insulin could be directly loaded into the microneedle patch by mixing with the gel. The boronate ester bond would be broken in the presence of glucose, resulting in a decrease in the cross-linking density. Therefore, the gel could achieve a greater swelling degree and insulin could be released faster. In addition, PVA chains were crystallized by repeatedly freezing and thawing to improve the mechanical strength of the microneedle patch. In terms of glucose-dependent insulin release, the gel showed good glucose-responsive insulin-release ability. Through additional ion cross-linking, the microneedle patch could also control the insulin release according to glucose concentration. In the hypoglycemic experiment of diabetic rats, the microneedle patch effectively pierced the skin and slowly released insulin.

中文翻译：

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由葡萄糖响应水凝胶制备的用于胰岛素输送的交联密度可变微针贴片

为了简化葡萄糖响应微针贴片的制备过程，设计了一种交联密度可变的微针贴片。微针贴片由苯基硼酸接枝的聚烯丙胺和聚乙烯醇（PVA）形成的水凝胶组成。凝胶通过苯基硼酸基团和 PVA 之间的硼酸酯键交联。它仍然具有流动性，可以填充到模具中以制备微针贴片。此外，胰岛素可以通过与凝胶混合直接加载到微针贴片中。硼酸酯键在葡萄糖存在下会断裂，导致交联密度降低。因此，凝胶可以达到更大的溶胀度，胰岛素可以更快地释放。此外，PVA 链通过反复冻融结晶，以提高微针贴片的机械强度。在葡萄糖依赖性胰岛素释放方面，凝胶显示出良好的葡萄糖响应性胰岛素释放能力。通过额外的离子交联，微针贴片还可以根据葡萄糖浓度控制胰岛素的释放。在糖尿病大鼠的降血糖实验中，微针贴片有效刺穿皮肤，缓慢释放胰岛素。