Solid microneedles (MNs) represent a useful tool for enhancing skin permeability by creating microchannels that provide a drug delivery route. To achieve the solid polymer MNs to become a clinical reality and to be commercialised, it is much essential to understand the skin penetration process. In this work, the effect of polymer MN height and density, drug molecular weight, as well as drug diffusion time on the drug permeability distribution was systemically investigated in vivo. MN with a height of 800 µm was most conductive to enhance the vertical distribution of drug permeation into the skin, while 11 × 11 MN array was most beneficial to promote the horizontal distribution of drug permeation into the skin. In addition, the increasing of drug molecular weight could reduce the drug permeability distribution and Fluorescein isothiocyanate most likely to penetrate into the skin after MNs pre-treatment. With the increase of drug diffusion time, the drug distribution in the subcutaneous gradually weakened until the drug was absorbed by the subcutaneous tissue at 8 h. These results suggest that the solid polymer MNs can penetrate the stratum corneum of the skin for enhancing drug delivery, especially small molecule drugs.

实心微针 (MN) 是一种有用的工具，可通过创建提供药物递送途径的微通道来增强皮肤渗透性。为了使固体聚合物 MNs 成为临床现实并商业化，了解皮肤渗透过程非常重要。本工作系统地研究了聚合物MN高度和密​​度、药物分子量以及药物扩散时间对药物渗透性分布的影响。. 高度为 800 µm 的 MN 最有利于促进药物渗透进入皮肤的垂直分布，而 11 × 11 MN 阵列最有利于促进药物渗透进入皮肤的水平分布。此外，药物分子量的增加会降低药物渗透性分布，使 MNs 预处理后异硫氰酸荧光素最有可能渗透到皮肤中。随着药物扩散时间的增加，药物在皮下的分布逐渐减弱，直至药物在 8 h 被皮下组织吸收。这些结果表明固体聚合物MNs可以穿透皮肤角质层以增强药物递送，尤其是小分子药物。