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PREPARATION OF BIODEGRADABLE CHITOSAN ACETATE SHEET AND ITS APPLICATION TO MICRONEEDLE M. Suzuki 1* , T. Sawa 1 , T. Takahashi 1 , and S. Aoyagi 1 1 Kansai University, JAPAN ABSTRACT Considering that mosquito’s proboscis consists of chitin and protein, biodegradable chitosan acetate microneedle is prepared for fabricating a microneedle imitating the mosquito’s proboscis. Chitosan powder was dissolved by diluted acetic acid. Then, the solution was defoamed, followed by spin-coating and baking to fabricate a sheet. This chitosan acetate sheet is far stiffer than widely used poly lactic acid. A microneedle was fabricated from the chitosan acetate sheet by cutting, of which the length, width and thickness are 2 mm, 150 μm and 100 μm, respectively. This microneedle was able to be inserted to a silicone rubber sheet without buckling. KEYWORDS: Microneedle, Chitosan acetate, Biodegradable polymer, Stiffness test INTRODUCTION Biodegradable polymer is used for low-invasive medical treatment, since it could be a scaffold for helping tissue regeneration, which finally dissolves and disappears in human body. Poly lactic acid (PLA) is expensive owing to its chemical synthetic process, and it dissolves in air exposed to water vapor before inserted inside the body. Chitin and its deacetylated compound chitosan are economical due to its tissue- derived nature; for example, chitin is ingredient of crab carapace, and it dissolves due to enzyme in the body, i.e., does not dissolve before insertion. We are developing a painless microneedle imitating mosquito proboscis [1]. We previously developed a PLA needle [2], considering that it would be safely dissolved even if it is broken inside the body. The mosquito proboscis is a structured chitin plate, which is backed by protein of resillin [3]. We intend to apply chitin-based material, i.e., chitosan, instead of PLA to the microneedle. Chitosan is commercially available as solid powder; however, injection molding of it is difficult, since it is not melted but burned when applied heat over 100°C due to its polysaccharide nature. To address this problem, utilizing that chitosan is chemically dissolved to acetic acid to form solution [4], a sheet is obtained by drying the solution, followed by cutting it to a needle shape. EXPERIMENTAL Chitosan powder (KIMICA Corp.) was thrown into diluted (1%) acetic acid and stirred to form chitosan acetate solution (Fig. 1(a)). The resultant viscous solution was further stirred and defoamed by a centrifugal mixing system (THINKY Corp.) using planetary motion in 10 min (Fig. 1(b)). The solution was further defoamed in a vacuum desiccator in 1~2 hrs. (Fig. 1(c)), followed by spin-coating it on a glass substrate (Fig. 1(d)). The effect of defoaming is shown in Fig. 2. The cross section of fabricated chitosan acetate sheet without foam is shown in Fig. 3. Thickness ranging from 30 to 100 μm was obtained by changing the rotational speed of spin-coating. Figure 1: Process flow for preparing chitosan acetate sheet. Chitosan (9 g) Acetic acid (2 %, 100 ml) Beaker Stick Rotation Revolution Chitosan in vessel (a) Dissolution of chitosan in acetic acid (b) First defoaming of chitosan solution by centrifugal mix- ing system (d) Spin-coating of chitosan solution to fabricate chitosan acetate film. (c) Defoaming and drying in vacuum desiccator Chitosan 3 times repetition of following condition: rotational speed; 700 rpm, time; 30 s. Glass substrate Exhaust Chitosan solution Vacuum desiccator 978-0-9798064-7-6/μTAS 2014/$20©14CBMS-0001 1172 18th International Conference on Miniaturized Systems for Chemistry and Life Sciences October 26-30, 2014, San Antonio, Texas, USA
