Research in China Yields New DLP 3D Printed Microneedles

Chinese researchers are finding better ways to create microneedles, helping patients avoid some of the pain and discomfort offered by more conventional injection devices. Novel, 3D printed hydrogel microneedles help complete a variety of critical tasks, to include drug delivery, outlined in the recently published ‘3D Printed Multi-Functional Hydrogel Microneedles Based on High-Precision Digital Light Processing.’

The use of microneedles continues to increase due to benefits they offer patients, along with uses such as vaccinations, sensors (for instance, to test for potassium levels), and measurements for everything from glucose levels to that of alcohol. Scientists and medical researchers employ a wide variety of microneedles (usually made from polymers), such as solid, coated, dissolving, and hydrogel-forming:

“Solid MNs are utilized in non-coated quadratic process, by which the micropore is firstly generated on skin and then the drug is delivered through the micropore. Thus, this method is relatively rough and could cause irreversible wound. Coated MNs, which coats the surface of polymer microneedles with drug and penetrates directly through the cuticle of the skin. However, its dosage is difficult to control and quantify. Dissolving MNs use biocompatible polymers to encapsulate drugs such as viral inactivated vaccines, which could penetrate skin and dissolve automatically within minutes,” explain the researchers.

“Recently, Hydrogel-Forming Microneedles are developed because of high-biocompatibility and natural porous structure.”

Microneedles can be controlled with water, used to expand and create in-situ conduits. And while microneedles are excellent vehicles for injection, they can also serve other purposes such as allowing fluorescent substances to be combined with materials for sensing antigens.

Simplified schematic of high-precision digital light processing (H-P DLP) system.

In this study, the scientists were mainly concerned with creating high-performance yet affordable hydrogel microneedles through high-precision digital light processing (H-P DLP). This method is also beneficial as hydrogel MNs can also be fabricated in different shapes. Samples were printed with varying exposure times, and then the authors collected data regarding the resulting mechanical properties.

Measuring the mechanical performance of microneedles (MNs) with universal material testing machine.

Ultimately, the exposure time was the controlling method for precision and stiffness, showing a decline when set over 300ms, but with stiffness increasing simultaneously. Upon completing the study, the authors noted 300ms as the ‘ideal exposure time’ for building MNs.

“Photosensitive resin used in SLA has poor biocompatibility. Combining template driven fabrication with UV curing materials is a complicated process,” concluded the researchers. “Comparing with those microneedles, hydrogel microneedles could be used for drug loading and the drug loading capacity is greatly increased. The fabrication time of biocompatible microneedles is greatly reduced owe to the ordinal fabrication of base and needles. The fabrication of several microneedles could be completed only in few minutes.

“ … the results of drug injection and drug detection were analyzed quantitatively, which may provide a certain reference for micro needle using in biological injection and drug extraction. Due to the low-cost, painless, short manufacturing time, well biocompatibility, and drug delivery performance properties of 3D built MNs, it is exciting to adapt MNs to the market. We expect to apply 3D printed MNs with properties above to clinical usage in the future.”

3D printing continues to be a catalyst for change in the realm of medical devices, and increasingly so for smaller components like microneedles, whether they are being used for transdermal drug delivery, innovative treatments for examples such as diseases of the eye, and other biomedical applications.

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The picture of side face of MNs with different exposure time: (a) 50 ms; (b) 100 ms; (c) 300 ms; (d) 500 ms; (e) 700 ms; and (f) 900 ms. The scale bar is 200 µm.