Subject Number : S-16-NM-0063
Support Type : 機器利用
Proposal Title (English) : Microneedles（Prototype of calcium phosphate nanoparticle-encapsulated microneedles for transdermal delivery）
Username (English) : Abigail Magee
Affiliation (English) : Biomedical Engineering, University of Central Oklahoma

1. Summary
Microneedle (MN) technology, a minimally invasive drug delivery system, has the potential to be an alternative to hypodermic needle tech. Generally, MNs are composed of arrays of micro-projections ranging from 25-2000 μm in height, with different tip shapes and tip intervals, being attached to a base support. When applied to skins, they puncture the epidermis and reach the dermis. This technique would allow painless delivery and improve patient compliance. However, MNs for vaccine delivery is still the big challenge to find a safe and efficient delivery system to help genetic materials target to the specific cell.
In the recent past, the incorporation of genetic materials into nanoparticles-based system has been proposed as a novel strategy for transdermal gene delivery. The use of nanoparticles-based systems can aid in the stabilization of genetic materials in vivo, in addition to providing controlled and sustained of release.
Thus, the study we investigates the prototype of MNs by using of Ca2+-phosphate precipitate (CaP) nanoparticles as the delivery agent loaded in gelatin MNs. CaP is the main component found in human bone and teeth, and have been widely used for use as a novel non-viral carrier for targeted gene delivery. Gelatin has been selected as MNs constructed material because it is the FDA-approval polymer and can provide a brittle mechanical strain. The study we demonstrate that CaP-encapsulated MNs can provide the required mechanical strength to effectively penetrate the skin show promise for future nano-carrier for transdermal delivery.

2. Experimental
Briefly, CaP nanoparticles were fabricated by dropping 18.6 μl of CaCl2 solution (2M) one-eighth volume at a time into 150 μl of 2× Hank’s balanced salt solution (HBSS). Then, quickly pipeted the solution several times, followed by incubating it at room temperature for 20 min to form the precipitation of CaP nanoparticles.
To prepare the CaP-encapsulated MNs, CaP solution is first poured onto the silicone mold, followed by centrifuging the samples to compact the CaP solution into mold cavities. Then, gelatin polymer was poured onto the silicone mold and centrifuged for 1 h at 3000 rpm to compact the gelatin polymer into mold cavities. Finially, the prototype of CaP-encapsulated MNs was formed after drying at room temperature overnight and removed by use of an adhesive tape. (Fig. 1)
The prototype of CaP-encapsulated MNs was evaluated using from scanning electron microscopy (SEM; Miniscope TM3000), texture analyser (TA-XT2i) in MMS platform (NIMS).

Fig. 1. Fabrication process of MNs with CaP nanoparticles encapsulated within the needles.

3. Results and Discussion
In this study, we used gelatin to be the MNs’ constructed material. CaP-loaded MNs have been fabricated by dropping CaP solution onto a MN inverse mold and then using centrifugation to force the liquid into mold, followed by the casting of gelatin in the form of a MNs patch (Fig. 1). The constructed of MNs was formed only with gelatin and water without the addition of any excipient or gross-linker. The morphology revealed CaP-loaded MNs was formed in nano-size with uniformed shape, which had similar surface morphology as gelatin MNs (Fig. 2a). EDX results also indicated that Ca and P ions mainly deposited at the tips of MNs (Fig. 2b). In addition, the mechanical strength of MNs showed a mild increased with the additional loading of CaP particles into the gelatin MN tips (Fig. 3). After MNs application, the porcine skin surface showed the array of spots corresponding to the MNs insertion site (Fig. 4). The morphology of MNs following insertion into the porcine cadaver skin showed that the MNs were collapsed with shortened tips during the insertion process. The MNs did not bend and break while in the skin. Overall, the study we demonstrate that CaP-encapsulated MNs can provide the required mechanical strength to effectively penetrate the skin show promise for future nano-carrier for transdermal delivery.

Fig. 2 Comparative surface morphology of gelatin MNs and MNs loaded with 300 μg CaP particles (a). The ionic distribution of calcium and phosphate ions in CaP-loaded MN patch (b).

Fig. 3 Comparative mechanical force of gelatin MNs and MNs with 300 μg CaP particles loaded.

Fig. 4 Skin insertion capability of CaP-loaded MNs patch on porcine cadaver skin for 1 min, and the morphology of MNs patch after insertion.

4. Others
Platform staffs kindly provided assistances and advices to use table top SEM and texture analyser.
This work was financially supported by the NNCI and NIMS Internship program, and by the Nanotechnology Platform Program Japan from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT). The author also thanks Professor N. Hanagata and Dr. M.H. Chen for this study advice and support.
5. Publication/Presentation
N/A

6. Patent
N/A