自组装辅助聚合法制备纤维素基温度/pH双敏感性荧光纳米凝胶

通过自组装辅助的一步法制备了具有温度和pH双重响应性的荧光纳米凝胶(FNG). 首先设计制备了一种水溶性含双键的荧光单体5-丙烯酰胺荧光素(5-AAF), 在水溶性纤维素醚——羟丙基纤维素(HPC)主链上引发5-AAF的接枝共聚, 同时由于5-AAF的疏水作用力诱导共聚物发生自组装, 并通过双官能团交联剂亚甲基二丙烯酰胺(MBA)的加入使自组装纳米聚集体交联, 从而一步制得具有环境响应性的FNG, 该过程在水相中进行, 具有高效、 “绿色”的优点. 研究结果表明, 改变合成过程中HPC的分子量可调控所得FNG的环境响应性. 对FNG环境响应性的研究表明, FNG链段上的亲疏水基团及与水分子间的氢键作用是影响凝胶温度响应性的主要因素. 此外, FNG的荧光在中性及碱性溶液中显著加强, 在酸性溶液中迅速猝灭. 由于FNG的荧光信号对温度和pH的显著敏感性, 且具有较低的细胞毒性, 因此在荧光标记生物检测及生物微环境的温度/pH检测等领域具有广泛的应用前景.

Temperature/pH Dual-sensitive Fluorescence Nano-gel Based on Cellulose Through Self-assembly Assisted Polymerization†

Temperature/pH dual-sensitive fluorescence nanogels(FNGs) were synthesized through a self-assembly assisted(SAA) “one-step” method. A hydrophilic fluorescence monomer 5-acrylamide fluorescein(5-AAF) has been fabricated, on this basis, graft copolymerization of 5-AAF from the backbone of hydroxypropyl cellulose(HPC) was initiated using ceric ammonium nitrate(CAN), the self-assembly of 5-AAF graft chains induced by both hydrogen bond and the hydrophobic interaction of fluorescence group proceeded with the polymerization of 5-AAF. Furthermore, N,N'-methylenebisacrylamide(MBA) was applied as crosslinker. As a result, FNGs were synthesized efficiently and environment-friendly with stable temperature/pH sensitivity properties. The environment-sensitivity of resultant FNGs can be tuned by changing molecular weight of HPC, the existence of hydrophobic/hydrophilic group on FNGs as well as the hydrogen bond contributed to FNGs’ temperature-sensitivity. Moreover, FNGs displayed impressive pH-sensitivity under various pH values, the fluorescence intensity can be rapidly enhanced at neutral and alkalic environment, while it quenches at acidic environment. The influence of pH on fluorescence intensity can be reversed without any other recovery process. The cytotoxicity of FNG was preliminarily studied, the results revealed good biocompatibility of FNGs. The temperature/pH responsivity of the FNGs’ fluorescence are of great potential in biomedical detection, such as fluorescence labeling, or temperature/pH sensor for micro-environment.