Advances in the Application of Microneedles in the Treatment of Local Organ Diseases.

In recent years, microneedles (MNs) have attracted a lot of attention due to their microscale sizes and high surface area (500-1000 µm in length), allowing pain-free and efficient drug delivery through the skin. In addition to the great success of MNs based transdermal drug delivery, especially for skin diseases, increasing studies have indicated the expansion of MNs to diverse nontransdermal applications, including the delivery of therapeutics for hair loss, ocular diseases, and oral mucosal. Here, the current treatment of hair loss, eye diseases, and oral disease is discussed and an overview of recent advances in the application of MNs is provided for these three noncutaneous localized organ diseases. Particular emphasis is laid on the future trend of MNs technology development and future challenges of expanding the generalizability of MNs.