Biodegradable polymer microneedle (MN) arrays are an
emerging class of transdermal drug delivery devices that promise a painless and
sanitary alternative to syringes; however, prototyping bespoke needle
architectures is expensive and requires production of new master templates.
Here, we present a new microfabrication technique for MNs using fused
deposition modeling (FDM) 3D printing using polylactic acid, an FDA approved,
renewable, biodegradable, thermoplastic material. We show how this natural
degradability can be exploited to overcome a key challenge of FDM 3D printing,
in particular the low resolution of these printers. We improved the feature
size of the printed parts significantly by developing a post fabrication
chemical etching protocol, which allowed us to access tip sizes as small as 1
μm. With 3D modeling software, various MN shapes were designed and printed
rapidly with custom needle density, length, and shape. Scanning electron
microscopy confirmed that our method resulted in needle tip sizes in the range of
1 – 55 µm, which could successfully penetrate and break off into porcine skin.
We have also shown that these MNs have comparable mechanical strengths to
currently fabricated MNs and we further demonstrated how the swellability of
PLA can be exploited to load small molecule drugs and how its degradability in
skin can release those small molecules over time.
Mathematical Modelling, Simulation and Optimisation of Microneedles for Transdermal Drug Delivery: Trends and Progress
