Metallic Microneedles for Transdermal Drug Delivery: Applications, Fabrication Techniques and the Effect of Geometrical Characteristics

Current procedures for transdermal drug delivery (TDD) have associated limitations including poor administration of nucleic acid, small or large drug molecules, pain and stress for needle phobic people. A painless micro-sized device capable of delivering drugs easily and efficiently, eliminating the disadvantages of traditional systems, has yet to be developed. While polymeric-based microneedle (MN) arrays have been used successfully and clinically as TDD systems, these devices lack mechanical integrity, piercing capacity and the ability to achieve tailored drug release into the systemic circulation. Recent advances in micro/nano fabrication techniques using Additive Manufacturing (AM), also known as 3D printing, have enabled the fabrication of metallic MN arrays, which offer the potential to overcome the limitations of existing systems. This review summarizes the different types of MNs used in TDD and their mode of drug delivery. The application of MNs in the treatment of a range of diseases including diabetes and cancer is discussed. The potential role of solid metallic MNs in TDD, the various techniques used for their fabrication, and the influence of their geometrical characteristics (e.g., shape, size, base diameter, thickness, and tip sharpness) on effective TDD are explored. Finally, the potential and the future directions relating to the optimization of metallic MN arrays for TDD are highlighted.

Automated summary

Current procedures for transdermal drug delivery have limitations in administering nucleic acid and small or large drug molecules, and causing pain and stress for needle phobic individuals. The development of a painless micro-sized device for efficient drug delivery is still needed. Recent advances in 3D printing have made it possible to fabricate metallic microneedle arrays, which have the potential to overcome the limitations of traditional systems. This review summarizes the types and modes of drug delivery of microneedles in transdermal drug delivery, discusses their applications in the treatment of diseases, and explores the fabrication techniques and geometrical characteristics of solid metallic microneedles.