Abstract
From large scale construction of houses and boats, through to smaller scale bioprinting of living tissue and cells - 3D printing is revolutionising manufacturing. Since its inception in 1981, the technology has come a long way, and is expected to continue to improve, finding new applications across numerous industries. While there are still challenges and limitations with this technology, the future of 3D printing looks promising. In this present thesis, the 3D printability of solid and hollow microneedles through polymer based stereolithography 3D printing was investigated, aiming at establishing a foundation of understanding and flexible methodology for various applications within healthcare.Microneedles of varying geometries were designed, and 3D printed in an optimisation process using various types of 3D printing. The effects of printing type, printing parameters and post-processing on print quality and usability were explored. For stereolithography printing, tilt angle was found to directly impact tip diameter and following post-processing, all stereolithography based 3D printed microneedles were mechanically strong and safely penetrated skin ex vivo.
The key to successfully 3D print hollow microneedles stemmed from tilt angle, tilt position, and bore diameter. Hollow microneedles were developed into uniquely designed platforms allowing for easy incorporation of lateral flow assays towards blood-free point-of-care diagnostics. Surface modification through PEGylation created a long-lasting hydrophilic coating crucial for passive collection of sample fluids. The device was evaluated for skin penetration ex vivo, and in vitro simultaneous detection of two inflammation markers at clinically relevant concentrations. Cytotoxicity to skin cells was tested showing the hollow microneedles to be non-cytotoxic with no leachable hazardous materials.
Developed 3D printed solid microneedles were used in a micro-moulding process to fabricate hydrogel-forming microneedles. The swell and de-swell ability of hydrogels was manipulated to capture heat sensitive antibiotics within the polymeric network. The captured antibiotic was demonstrated to be re-released through a controllable swelling process. Exposure to bacteria highlighted the antimicrobial properties of the drug-loaded hydrogel-forming microneedles.
Overall, it would be anticipated that the key findings of the presented research will contribute by demonstrating the use of desktop polymer 3D printing for microneedle fabrication and two possible applications. The overall goal was to help bridge the gap between areas of high- and areas of low-resource, through point-of-care diagnostics and transdermal drug delivery, all through low-cost 3D printed microneedles.
| Date of Award | 13 Sept 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Hannah Leese (Supervisor) & Pedro Estrela (Supervisor) |