Drug delivery with dissolving microneedles: skin puncture, its influencing factors and improvement strategies

Over the past decades, the use of microneedles, a unique transdermal drug delivery technology, to deliver drugs to the skin for biological effects has been very active, and the interest in dissolving microneedles in this field has also increased rapidly. However, ensuring the effectiveness of microneedles requires attention to several key steps. The microneedle must pierce the stratum corneum first, and then continue to penetrate to a certain depth under the action of applied force, without bending or breaking during the puncture process, to ensure the accurate and controllable delivery of the microneedles. In the process of microneedle penetration, the skin is easily deformed due to its elasticity, and the microneedle often cannot penetrate the skin completely, which reduces the delivery efficiency of the microneedle and limits the application of the microneedle in drug delivery, especially for dissolving microneedles whose mechanical strength is weaker than that of metal and monocrystalline silicon microneedles. The delivery efficiency of the microneedle is mainly related to the penetration depth of the microneedle, which in turn is related to factors such as the mechanical properties of the skin, the structure of the microneedle, and the way of administration. Clearly, there are still many technical challenges to make the effectiveness of dissolving microneedles in line with requirements of clinical medication. Therefore, it is necessary to systematically review the influencing factors of the penetration depth of the dissolving microneedles and the methods to improve the delivery efficiency. Technological improvement strategies suitable for enhancing the drug delivery efficiency of dissolving microneedles will certainly contribute to more accurate delivery of bioactive ingredients to the body and a wider range of medical applications.