Fänger Christian, Wack Holger, Ulbricht Mathias
Fraunhofer Institut für Umwelt-, Sicherheits- und Energietechnik UMSICHT, 46047 Oberhausen, Germany.
Macromol Biosci. 2006 Jun 16;6(6):393-402. doi: 10.1002/mabi.200600027.
Poly(N-isopropylacrylamide) (PNIPA) hydrogels with varied degree of crosslinking (DC) were synthesized by using poly(ethylene glycol) (PEG) as an additive. A phase separated ("macroporous") morphology was formed when using PEG contents of > or = 20 wt.-%. Temperature-dependent degrees of swelling had been measured, and average mesh sizes of the swollen polymer network had been calculated. The loading of the hydrogels with labelled dextrans with various molar masses and bovine serum albumin (BSA)-via swelling of the shrunken gel in a cold solution-and their subsequent unloading-via immersion in hot water-were studied in detail. The loading efficiencies were close to zero for PNIPA prepared at PEG contents of < or = 10 wt.-%, and they increased sharply to about 100% for PNIPA prepared with PEG contents of > or = 20 wt.-%. A complete unloading was achieved as well. For macroporous PNIPA prepared at 40 wt.-% PEG content, the loading efficiency was a function of the DC, and the "cut-off" observed as a function of dextran or protein size correlated with the mesh size of the hydrogel. The function of these "smart" hydrogels can be explained by the temperature-induced "pumping" of the solution into the gel bulk via the permanent pores, along with an uptake into the adjacent hydrogel network. Those materials could be used as matrices for the efficient and reversible immobilization of (bio)macromolecules.
以聚乙二醇（PEG）为添加剂合成了具有不同交联度（DC）的聚（N-异丙基丙烯酰胺）（PNIPA）水凝胶。当PEG含量≥20 wt.-%时，形成了相分离的（“大孔”）形态。测量了温度依赖性溶胀度，并计算了溶胀聚合物网络的平均网孔尺寸。详细研究了通过在冷溶液中使收缩的凝胶溶胀，用不同摩尔质量的标记葡聚糖和牛血清白蛋白（BSA）对水凝胶进行负载，以及随后通过浸入热水进行卸载的过程。对于PEG含量≤10 wt.-%制备的PNIPA，负载效率接近零，而对于PEG含量≥20 wt.-%制备的PNIPA，负载效率急剧增加至约100%。同时也实现了完全卸载。对于PEG含量为40 wt.-%制备的大孔PNIPA，负载效率是交联度的函数，观察到的作为葡聚糖或蛋白质大小函数的“截止”与水凝胶的网孔尺寸相关。这些“智能”水凝胶的功能可以通过温度诱导溶液通过永久孔“泵入”凝胶本体，并同时吸收到相邻水凝胶网络中来解释。这些材料可用作有效且可逆固定（生物）大分子的基质。
