Faculty of Chemistry, University of Warsaw, Pasteura 1, 02-093 Warsaw, Poland.
Laboratory of Electron and Confocal Microscopy, Faculty of Biology, University of Warsaw, Miecznikowa, 02-096 Warsaw, Poland.
J Colloid Interface Sci. 2019 Apr 15;542:317-324. doi: 10.1016/j.jcis.2019.02.004. Epub 2019 Feb 2.
Reported poly(N-isopropylacrylamide) (poly(NIPAM)) thermoresponsive systems do not preserve their structure and shape regardless applied temperature. Poly(NIPAM) modified with lipophilic units of butylacrylate (BA) is expected to form spontaneously nanospheres stable at a broad range of temperature. Moreover, it should be possible to introduce solvatochromic dyes to the spheres for optical evaluation of the system and designing thermometers at the nanoscale. In this study, poly(NIPAM-BA) polymer used in nanoprecipitation process formed stable nanospheres, as shown by scanning transmission electron microscopy (STEM), dynamic light scattering (DLS), and zeta potential analysis. As a model compound, Nile Red was introduced to the structures allowing fluorometric investigation and confocal imaging. The nanoparticles were stable in solution both below and above polymer transition temperature. However, as expected for thermoresponsive polymer, the diameter of nanospheres changed from about 30 nm at 10 °C to about 150 nm at 20 °C. For dye loaded spheres this process was coupled with pronounced change in emission. For low temperatures nanostructures existed as ultra-small highly lipophilic particulates, whereas at higher temperatures their diameter and hydrophilicity increased. In consequence the dye was extruded from spheres at low temperatures as a shell layer, this process was fully reversible within the temperatures range from 5 to 30 °C. Freezing of the nanospheres resulted in irreversible change in morphology allowing monitoring of transient sample freezing. Forming poly(NIPAM-BA) spheres loaded with solvatochromic dyes were found as a facile technique for designing optical nanothermometer.
据报道，聚 N-异丙基丙烯酰胺（poly(NIPAM)) 温度响应系统无论施加的温度如何都不能保持其结构和形状。用丁基丙烯酸盐 (BA) 修饰的聚 (NIPAM) 有望自发形成在较宽温度范围内稳定的纳米球。此外，应该可以向球体中引入溶剂致变色染料，用于系统的光学评估和纳米尺度温度计的设计。在这项研究中，用于纳米沉淀过程的聚 (NIPAM-BA) 聚合物形成了稳定的纳米球，如扫描透射电子显微镜 (STEM)、动态光散射 (DLS) 和zeta 电位分析所示。作为模型化合物，尼罗红被引入到结构中，允许荧光研究和共聚焦成像。纳米粒子在聚合物转变温度以下和以上的溶液中均稳定。然而，正如对温度响应聚合物的预期，纳米球的直径从 10°C 时的约 30nm 变化到 20°C 时的约 150nm。对于负载染料的球体，这个过程伴随着发射的明显变化。对于低温纳米结构存在于超小的高亲脂性颗粒中，而在较高温度下，其直径和亲水性增加。结果，在低温下，染料从球体中挤出作为壳层，该过程在 5 至 30°C 的温度范围内是完全可逆的。纳米球的冻结导致形态的不可逆变化，允许监测瞬态样品冻结。负载溶剂致变色染料的聚 (NIPAM-BA) 球体的形成被发现是设计光学纳米温度计的一种简便技术。
