Microneedles as the Technique of Drug Delivery Enhancement in Diverse Organs and Tissues

The document from 2018 reviews the use of microneedles for drug delivery across various biological barriers, including skin, ocular, oral mucosal, gastrointestinal, ungual, and vaginal tissues. Microneedles have evolved into different types such as hollow, coated, dissolving, and hydrogel-forming, each with specific drug delivery mechanisms. They are noted for their safety, painlessness, and ability to deliver high molecular weight and hydrophilic drugs. In cosmetology, microneedles have shown effectiveness in skin rejuvenation and hair growth regulation, with specific examples including enhanced delivery of cosmeceuticals and improved effectiveness of minoxidil for treating androgenic alopecia. Dissolving microneedles are promising for cosmetology, with a clinical study showing significant wrinkle improvement using ascorbic acid and retinyl retinoate-loaded hyaluronic acid microneedle patches. For vaccination, microneedles induce stronger immune responses and reduce vaccine doses. They are also less painful and minimize waste. In insulin delivery, microneedles offer a painless alternative to injections, with studies showing effective blood glucose reduction in animal models and one study involving 29 type 1 diabetes subjects showing similar or better pharmacodynamic responses. Microneedles are also promising for ocular drug delivery, offering targeted delivery with reduced pain and tissue damage. For oral and gastrointestinal drug delivery, microneedles can induce robust immune responses and enhance the contrast in optical coherence tomography images. Lastly, a study by Chiu et al. demonstrated that microneedles could significantly increase drug permeation through the nail plate. Despite the potential benefits, further research is needed to address safety concerns and regulatory issues for broader clinical application.