Li Hui-Juan, Li Peng-Yun, Li Li-Ying, Haleem Abdul, He Wei-Dong
CAS Key Laboratory of Soft Matter Chemistry, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China.
Fourth Technique Division, Third Institute of China Aerospace Science and Industry Corp, Beijing 100048, China.
Molecules. 2018 Apr 16;23(4):921. doi: 10.3390/molecules23040921.
Narrowly distributed poly(l-lysine---isopropylacrylamide) (PLL--PNIPAM) was prepared through ring-opening polymerization of ε-benzyloxycarbonyl-l-lysine -carboxy-α-amino anhydride and atom transfer radical polymerization of NIPAM, followed with the removal of ε-benzyloxycarbonyl group. Then gold nanoparticles (AuNPs) grafted with PLL--PNIPAM (PNIPAM-PLL-AuNPs) were obtained by the reduction of chloroauric acid with sodium citrate in the presence of PLL--PNIPAM. PNIPAM-PLL-AuNPs and its precursors were thoroughly characterized by proton magnetic resonance spectroscope, Fourier transform infrared spectroscope, UV-vis spectroscope, transmission electron microscopy, dynamic light scattering, thermogravimetric analysis, and circular dichroism. The obtained PNIPAM-PLL-AuNPs exhibited high colloid stability even at strong alkaline (pH = 12) and acidic (pH = 2) conditions. The thermal and pH dual-responsive behaviors of the grafting PLL--PNIPAM chains was observed to be affected by AuNPs, while not for the secondary structure of PLL chains. Correspondingly, the surface plasmon resonance (SPR) of AuNPs was found to be sensitive to both pH value and temperature. A blue shift in the SPR happened both with increasing pH value and increasing temperature. The stimuli-response was reversible in heating-cooling cycles. The gold nanoparticles with both pH and temperature response may have potential applications in biomedical areas and biosensors.
通过ε-苄氧羰基-L-赖氨酸-α-氨基羧基酐的开环聚合反应和N-异丙基丙烯酰胺的原子转移自由基聚合反应，随后除去ε-苄氧羰基，制备了分布狭窄的聚（L-赖氨酸-异丙基丙烯酰胺）（PLL-PNIPAM）。然后，在PLL-PNIPAM存在下，用柠檬酸钠还原氯金酸，得到接枝有PLL-PNIPAM的金纳米颗粒（PNIPAM-PLL-AuNPs）。通过质子磁共振光谱仪、傅里叶变换红外光谱仪、紫外可见光谱仪、透射电子显微镜、动态光散射、热重分析和圆二色性对PNIPAM-PLL-AuNPs及其前体进行了全面表征。所得到的PNIPAM-PLL-AuNPs即使在强碱性（pH = 12）和酸性（pH = 2）条件下也表现出高胶体稳定性。观察到接枝的PLL-PNIPAM链的热响应和pH双响应行为受金纳米颗粒的影响，而PLL链的二级结构不受影响。相应地，发现金纳米颗粒的表面等离子体共振（SPR）对pH值和温度都敏感。随着pH值升高和温度升高，SPR均发生蓝移。在加热-冷却循环中，刺激响应是可逆的。具有pH和温度响应的金纳米颗粒在生物医学领域和生物传感器中可能具有潜在应用。
