可自我修復之新穎多聚醣混成雙重結構凝膠於生物醫學應用之研究

Abstract

幾丁聚醣、藻酸鈉兩者皆為天然性的多糖類高分子，具有相當優異的生物相容性可應用於各種生醫材料上，本實驗中藉由研究兩種材料形成的複合結構水膠在物理性質及生物性質上的表現來改善各種生醫材料的應用。在本實驗中，成功的將兩性幾丁聚醣(CHC)與藻酸鈉(SAL)均勻混合溶液調配出來，而不會如過去的研究般互相聚集凝結。藉由藻酸鈉會與兩價正離子如鈣離子產生作用力進而生成特殊的蛋盒(egg-box)結構的特性，將幾丁聚醣/藻酸鈉的混合溶液浸泡於氯化鈣水溶液內得到雙重結構高水含量的水膠體。實驗中我們使用小瓶傾斜法(vial tilting)來測定溶液的凝膠時間，從結果中發現每種組成的凝膠時間都非常地快速，凝膠過程大都發生於幾秒內或接觸瞬間。此外複合雙重結構水膠的澎潤吸水率經過冷凍乾燥維持結構處理後，浸泡於欲吸收的溶液中一天測量其飽和吸水程度。而保水力則利用達最大吸水率的水膠置於常溫下測定。其結果顯示出此複合水膠具有很高的吸水率及良好的保水能力。不同組成的水膠的動態機械性質(流變性質)使用流變儀來測定。結果顯示此種雙重結構的水膠在高剪切力造成水膠結構暫時分離後，消除外加剪切力時，其水膠網狀結構具有可逆性，可回復回原本的狀態，此性質稱之為搖變性(thixotropic)。另外也發現當兩塊高甘油比例組成的水膠個別截開得到新斷面後，立刻貼附在一起一段時間後，兩個個別的水膠斷面監會生成新的作用力將兩個水膠連接在一起，此性質我們稱之為可自我修復。利用兩性幾丁聚醣於水中有形成微胞的能力來包覆脂溶性藥物(維他命A)，並利用藻酸鈉的特性來形成水膠體，進而達成雙步驟的藥物釋放效果。一開始沒被包覆及吸附在微胞表面的藥物分子會快速釋放，迅速使藥物血液濃度達到有效濃度，而被包覆的藥物分子則在之後達到緩慢釋放的效果，藉而維持血液中的藥物濃度，達到長時間的療效。細胞存活率使用人類皮膚纖維母細胞(WS1)來進行測試，結果顯示相當好的存活率，代表此水膠具有優異的生物相容性。另外皮膚敏感性測試也顯示在動物實驗中不會有任何刺激性的反應出現。搖變性及自我修復的性質使此種複合結構水膠能應用在注射系統上，且雙重結構的長時間釋放效果使其具備用於慢性疾病的長時間治療的潛力。而高吸水率、高保水力及對皮膚無刺激性也在傷口敷材上具有相當好的應用。

In this study, we combine two excellent nature polysaccharide materials to acquire a dual-structure hydrogel for biomedical uses due to their high biocompatibility, good physical properties, and the novel dual-structure in drug delivery system. A new unique dual-structure hydrogel composed of nanostructures of amphiphilic chitosan (CHC) dispersed in a sodium alginate matrix (SAL) is presented. The successful creation of the composite is based on combining chitosan and sodium alginate without precipitation or agglomeration, which has not been previously reported. The CHC/SAL composite gels presents a number of properties making them attractive for biomedical applications, in particular as implantable depot gels or in dermal applications. The gels are shown to form rapidly upon exposure of the combination solution to Ca2+ containing gelation medium. The formed gels have storage moduli similar to soft tissue and displays shear reversible gelation with fast recovery of mechanical properties, in addition to self-healing capability at certain compositions. The gels exhibit moderate swelling in deionized water and low swelling in simulated body fluid and cell culture media. Furthermore, the water retention of the gels is good. The drug release from the composite gels is demonstrated using the hydrophobic drug all-trans retinoic acid, which is used in cancer and skin disorder therapies. The drug release initially occurs through a Fickian mechanism for a fraction of the loaded drug, where the fraction released during this process depends on release media and gel composition. However, a large fraction of loaded drug can be retained for long term depot drug delivery. Furthermore, the CHC/SAL gels are determined to have low toxicity and skin irritation. Those results showed superior physical properties such as high ESD, excellent water retention, shear recovery and self-healing properties and outstanding biocompatibility such as low cytotoxicity and no irritation reaction. Those great characters enabled improving in biomedical applications such as wound dressing and injectable long-term therapeutic mechanism.