藍藻蛋白是一種經生物體合成的天然聚合物。經基因重組後結構以天門冬胺酸(aspartic acid)為主鍊，精氨酸(arginine)與離氨酸(lysine)為側鍊所組成，而離氨酸上含有一級胺容易進行化學修飾。支鍊型聚乙烯亞胺是已知廣泛研究的非病毒型陽離子聚合物基因載體，但當分子量增加、轉染效率提高時會對細胞產生高毒性。
因此本研究以葡萄糖作為交聯劑，接合藍藻蛋白與不同分子量的聚乙烯亞胺合成載體。期望能降低細胞毒性、維持轉染效率並找出最適當合成比例及最適當使用重量比。結果發現當聚乙烯亞胺與葡萄糖為等莫爾比時有最佳轉染效率，而經藍藻蛋白修飾後的聚乙烯亞胺合成載體，在適當比例下能夠有效降低轉染後細胞相對毒性，並維持與PEI25kDa相近的轉染效率。
在物性測試方面複合物表面帶有低於PEI25kDa的正電位，並隨載體中聚乙烯亞胺分子量、莫爾比及複合物中核酸/高分子重量比提高，粒徑下降、表面電位增加；而在強負電環境下載體仍可保有20-50%的核酸含量，與控制組相比有提高穩定性的功效。最後由蛋白質傳遞結果得知S-CGP/1PEI25kDa/1GC與S-CGP/4PEI25kDa/4GC兩組載體都具有良好的蛋白質傳遞效果，未來可改變蛋白質/高分子重量比或是以不同蛋白質對細胞進行傳遞測試提升載體應用範圍。

Cyanophycin is a kind of biopolymers. By genetic recombination, the main chain of cyanophycin is aspartic acid, and the side chain is composed of arginine and lysine. The lysine contains primary amines, and allows chemical modifications. Branched polyethyleneimine (BPEI) is a cationic polymer, and has been extensively studied as a non-viral vector. However, as molecular weight increases and transfection efficiency is enhanced, PEI will produce high cytotoxicity.
In this study, cyanophycin was cross-linked with BPEI of different molecular weights by glucose. It was expected to mitigate cytotoxicity, maintain transfection efficiency, and eventually obtain an optimal mixing ratio and weight ratio. The results suggest that the optimal transfection efficiency occurs when the molar ratio of BPEI monomer and glucose equals to 1. Moreover, BPEI modified with cyanophycin can effectively mitigate cytotoxicity and maintain transfection efficiency which is close to the control group, BPEI25kDa, at the optimal ratio.
From the physical properties tests, the surface of vectors have positive zeta potentials, which are lower than the PEI25kDa. With the increases in molecular weight and the molar ratio of PEI in the vector, the surface zeta potential rises but the hydrodynamic size of the vector decreases. The vectors still retain 20-50% of nucleic acids under negatively charged conditions. Compared with the control group, the vectors increased the stability. Finally, from the results of protein delivery, both S-CGP/1PEI25kDa/1GC and S-CGP/4PEI25kDa/4GC have excellent efficiency. For future studies, changing the weight ratio of protein/polymer or using different proteins will extend the applications of the carrier.

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