Microneedle (MN) patches enable simple self-administration of drugs via the skin. In this study, we sought to deliver drug-loaded microspheres (MSs) using MN patches and found that the poly(lactic-co-glycolic acid) (PLGA) MSs failed to localize in the MN tips during fabrication, thereby decreasing their delivered dose and delivery efficiency into skin. We determined that surface interactions between the hydrophobic MSs and the poly(dimethylsiloxane) (PDMS) mold caused MSs to adhere to the mold surface during casting in aqueous formulations, with hydrophobic interactions largely responsible for adhesion. Further studies with polystyrene MSs that similarly carry a negative charge like the PLGA MSs demonstrated both repulsive electrostatic interactions as well as adhesive hydrophobic interactions. Reducing hydrophobic interactions by addition of a surfactant or modifying mold surface properties increased MS loading into MN tips and delivery into porcine skin ex vivo by 3-fold. We conclude that surface interactions affect the loading of hydrophobic MSs into MN patches during aqueous fabrication procedures and that their modulation with the surfactant can increase loading and delivery efficiency.

中文翻译：

---

表面相互作用对溶解微针贴片中微球负载的影响

微针 (MN) 贴片可以通过皮肤简单地自我给药。在本研究中，我们试图使用 MN 贴片递送载药微球 (MS)，并发现聚乳酸-乙醇酸）（PLGA）MS 在制造过程中未能定位在 MN 尖端，从而降低了它们向皮肤的递送剂量和递送效率。我们确定疏水性 MS 和聚 (二甲基硅氧烷) (PDMS) 模具之间的表面相互作用导致 MS 在水性配方中的铸造过程中粘附到模具表面，其中疏水相互作用主要负责粘附。对与 PLGA MS 类似地带有负电荷的聚苯乙烯 MS 的进一步研究证明了排斥性静电相互作用和粘性疏水相互作用。通过添加表面活性剂或改变模具表面特性来减少疏水相互作用，将 MS 加载到 MN 尖端和离体递送到猪皮肤中增加了 3 倍。