Industrial perspectives for personalized microneedles

Abstract

Microneedles and, subsequently, microneedle arrays are emerging miniaturized medical devices for painless transdermal drug delivery. New and improved additive manufacturing methods enable novel microneedle designs to be realized for preclinical and clinical trial assessments. However, current literature reviews suggest that industrial manufacturers and researchers have focused their efforts on one-size-fits-all designs for transdermal drug delivery, regardless of patient demographic and injection site. In this perspective article, we briefly review current microneedle designs, microfabrication methods, and industrialization strategies. We also provide an outlook where microneedles may become personalized according to a patient's demographic in order to increase drug delivery efficiency and reduce healing times for patient-centric care.

Keywords: 3D printing; microfabrication; microneedles; personalized medicine; transdermal drug delivery; two-photon polymerization.

Figure 1

Conical microneedles with varying heights were printed via two-photon polymerization on a “Quantum X shape” lithography system, and the 10 × 10 microneedle array was printed in 130 min. The scale bar is 1 mm in both images. (A) Scanning electron microscopy image of microcones. (B) Optical microscopy image of transparent microcones.

Figure 2

Various solid and hollow microneedle designs printed via two-photon polymerization on a “Quantum X shape” lithography system. (A) Scanning electron microscopy image of a 4 × 4 array consisting of both solid and hollow microneedles. The designs were inspired by Mizuno et al. [32] and Cordeiro et al. [29]. The scale bar is 500 μm. (B) Optical microscopy image of a large 2 cm × 2 cm array with 1746 individual microneedles. The microneedles are 1200 μm tall, 250 μm wide at the base, and spaced 500 μm apart. The large microneedle array was printed in 18 h. The scale bar is 1 mm.

Figure 3

Simple twisted microneedles inspired by snake fangs and Bae et al. [39]. The microneedle array was printed via two-photon polymerization on a “Quantum X shape” lithography system. All scale bars are 500 μm. (A) Zoomed-out image of the microneedle array. (B) Closer inspection of optically transparent twisted microneedles. (c) Top-down view of the twisted microneedle array.

Figure 4

A graphical plot comparing the light-based printing microfabrication techniques SLA, DLP, and 2PP. This relationship plot compares the smallest feature sizes in the XY plane and the Z axis of commercial instruments. The bubble size represents the approximate cost of the instrument. We see a trend that when small feature sizes of the order of micrometers need to be obtained, the cost of the instrument substantially increases.