Microneedle array systems for long-acting drug delivery

The development of microneedles (MNs) assisted drug delivery technologies have been highly active for more than two decades. The minimally invasive and self-administered MN technology bypasses many challenges associated with injectable drug delivery systems, by delivering the therapeutic materials directly into the dermal and ocular space and allowing the release of the active ingredient in a sustained or controlled manner. Different types of MNs (biodegradable solid/dissolving MNs and nanoparticle loaded/coated polymeric MNs or delivery by hollow MNs) have been envisioned for long-acting sustained delivery of therapeutic payloads, with the aim of reducing the side effects and administration frequency to improve the patient compliance. In this review, we covered the different types of MNs loaded with different nano/biotherapeutics for long-acting delivery for a wide range of potential clinical applications. We also outlined the future development scenario of such long-acting MN delivery systems for different disease conditions to achieve improved clinical benefit. Finally, we discussed the challenges lie ahead to realize the full potential of sustained-release long-acting MNs in the clinic.