幾丁聚醣為多功能性的天然多醣類高分子，來源充足，具有許多生化特性：生物相容性、生物可分解性、免疫刺激性等等，因此廣泛應用在農業與生醫工程。然而幾丁聚醣的溶解度很差，故許多學者針對幾丁聚醣結構上進行化學修飾，以改變幾丁聚醣的溶解性質，或作為其他反應的前驅物，擴展幾丁聚醣的應用性。
維他命C磷酸鎂塩，為L-抗壞血酸-2-磷酸酯鎂（Magnesium ascorbyl phosphate，MAP），可被皮膚上豐富的磷酸酶迅速分解成維他命C，研究證實維他命C與維他命C磷酸鎂塩在人類真皮纖維母細胞，影響膠原蛋白的生成量是不分軒輊。本研究之目的在藉由親水性的乙二醇幾丁聚醣，與不同碳鏈長度的脂肪酸（lauric acid、palmitic acid）合成同時具有親水及親脂特性的lauroyl glycol chitosan (GCL)與palmitoyl glycol chitosan (GCP），並以MAP作為模式藥物，評估兩性幾丁聚醣作為經皮吸收載體的可行性。
核磁共振圖譜分析顯示，合成之GCL架接比例為16.3 ± 2.5％、GCP為13.4± 1.8%，並可由紅外線光譜觀測分子結構中，amide Ι 區段C=O吸收波數與alkyl CH2吸收面積明顯地增加。兩性乙二醇幾丁聚醣在高濕度下具有高穩定性，而GCP、GCL水溶液的粘度高於10%乙醇溶液約1.1~1.4倍。兩性幾丁聚醣在一小時內的水合能力最強，GCP在pH 7.4環境下水合作用達14.6倍，在pH 6.0環境下亦有8.5倍；GCL在pH 7.4環境下水合達11.7倍；pH 6.0環境下為6.2倍。以兩性乙二醇幾丁聚醣作為MAP之經皮傳輸載體，隨著濃度的增加，MAP釋出速率隨之降低，且具統計上的差異。在穿皮速率方面，無論在是否添加10%乙醇水溶液中，皆有效地增加MAP的穿皮速率。以純水作為溶劑，相較於水溶液，1% GCL滲透速率增加至2.96倍、1% GCP增加至1.6倍；1 0%乙醇水溶液作為溶劑，相較於10%乙醇，1% GCL滲透速率降低至0.96倍、1% GCP降低至0.79倍，然而隨著GCL、GCP濃度增加，其滲透速率皆為增加的趨勢。比較長短鏈的脂肪酸，架接短鏈脂肪酸的GCL，以純水作溶劑皮膚滲透速率是GCP 1.8倍，10 %乙醇作溶劑皮膚滲透速率是GCP 1.2倍。比較相同濃度兩性凝膠影響穿皮速率，1 %GCL為GCP1.22 倍、3 %GCL為GCP 1.08倍。綜合研究結果顯示，以脂肪酸修飾之兩性乙二醇幾丁聚醣劑型，可以增加親水性MAP之經皮吸收，具有應用於皮膚外用劑型之潛力。

Chitosan, a polysaccharide, is obtained by partial deacetylation of chitin, the second most abundant polymer. It has been receiving a great deal of interest for medical and pharmaceutical applications due to its intrinsic properties, including biocompatibility, biodegradability, non-antigenicity and so on. However, the solubility of chitosan is very poor. Many works have attempted to modify its structure and chemistry.
Magnesium ascorbyl phosphate (MAP), an ascorbic acid derivative, is rapidly converted to ascorbic acid by phosphatases in the skin. Studies have demonstrated MAP was equivalent to ascorbic acid in stimulating collagen synthesis in dermal fibroblasts. The objectives of the studies were to modify the water-soluble chitosan derivative – glycol chitosan, by the use of pendant hydrophobic groups to achieve non-covalent cross-linking with lauric and palmitic acid, and to evaluate the potential of the amphiphilic hydrogels as topical delivery carrier for the hydrophilic model compound, MAP.
The levels of lauroylation and palmitoylation in the polymers, as determined by proton neutron magnetic resonance spectroscopy, were 16.3 ± 2.5 % and 13.4 ± 1.8%, respectively. The molecular structures of the amphiphilic polymers were characterized by their FT-IR spectra. They were also shown to be highly stable at high-humidity environment. The viscosity of the polymer was higher with palmitoyl cross-linkage, and hydration was better under neutral than acidic conditions.
The effects of amphiphilic glycol chitosan on the skin penetration of MAP were evaluated through nude mice skin. MAP release from the hydrogel was significantly decreased with increasing amount of amphiphilic glycol chitosan in the formulations. Regardless of the addition of 10% ethyl alcohol, skin penetration of MAP prepared in amphiphilic glycol chitosan was effectively increased. In aqueous vehicle, MAP flux was increased 2.96 and 1.6 fold with 1% GCL and GCP, respectively, while in 10% ethanol, it was decreased to 0.96 and 0.79 fold. Nevertheless, skin flux of MAP was increased when the amount of hydrogel was increased. The increase of skin penetration was more prominent with GCL, which is cross-linked with the shorter chain length of lauric acid, than GCP.
In conclusion, the studies demonstrated physically cross-linked chitosans with lauric and palmitic acids increased the skin penetration of MAP. Both GCL and GCP can potentially be applied as topical delivery carriers to improve percutaneous absorption of hydrophilic drugs.

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