A review of recent advances in microneedle technology for transdermal drug delivery

Transdermal devices are used to deliver drugs through the skin. However, limitations such as molecular weight and hydrophilicity of the molecules prevent its wider use. Microneedle technology offers an enhanced drug delivery option. Depending on the delivery, different types of microneedles such as solid, hollow, dissolving and coated are discussed. While solid microneedles create micropores in the skin, hollow microneedles provide a channel into the dermis. Dissolving microneedles have been explored for vaccine delivery while coated microneedles use a drug dispersion to effectively load drugs. This review also focuses on the techniques involved in fabrication of microneedles. Several methods using various solvent techniques, electromechanical systems, laser ablation and additive manufacturing are discussed. The nature of material used impacts the method used for fabrication. Various degradable and non-degradable materials used for fabrication are discussed. Microneedles can be made from metals, silicone, ceramics, synthetic as well as biodegradable polymers like carbohydrates. Each material has its own advantages and disadvantages. Stainless steel demonstrates good biocompatibility but are highly corrosive while silicones are easy to fabricate but brittle. Microneedle technology possesses a tremendous potential considering the variations in types and materials it offers with ease of fabrication and are the next generation therapeutics.