Center of Physical Sciences and Technology, Saulėtekio av. 3, Vilnius, LT-10257, Lithuania.
Phys Chem Chem Phys. 2020 Apr 28;22(16):8296-8303. doi: 10.1039/c9cp06865a. Epub 2020 Feb 27.
Viscosity is the key parameter of many biological systems as it influences passive diffusion, affects the lipid raft formation and plays a significant role in several diseases on a cellular level. Consequently, determination of precise viscosity values is of great interest and viscosity-sensitive fluorescent probes offer a convenient solution for this task. One of the most frequently used viscosity-sensitive probes is BODIPY-C. Yet despite its regular use, BODIPY-C remains insufficiently investigated. In this work, we explored how the polarity, hydrogen bonding abilities of the solvent and the presence of macromolecules affect the viscosity-sensing qualities of BODIPY-C. In addition, we investigated the relaxation pathway of BODIPY-C with the help of femtosecond transient absorption and time-dependent DFT calculations. Our results show that while BODIPY-C is not affected by protic solvents, accurate quantitative determination of viscosity is possible only if BODIPY-C is calibrated in the same polarity environment as in the sample of interest, and the size of the surrounding molecules is not larger than the size of BODIPY-C. The latter limitation is likely to apply to all molecular rotors.
粘度是许多生物系统的关键参数，因为它影响被动扩散，影响脂筏的形成，并在细胞水平上对几种疾病起着重要作用。因此，精确测量粘度值非常重要，而对粘度敏感的荧光探针为此提供了一种便捷的解决方案。其中最常用的粘度敏感探针之一是 BODIPY-C。然而，尽管它经常被使用，但 BODIPY-C 的研究仍然不够充分。在这项工作中，我们研究了溶剂的极性、氢键能力以及大分子的存在如何影响 BODIPY-C 的粘度感应性质。此外，我们还借助飞秒瞬态吸收和含时密度泛函理论计算研究了 BODIPY-C 的弛豫途径。研究结果表明，虽然 BODIPY-C 不受质子溶剂的影响，但只有在与感兴趣的样品具有相同极性环境中对 BODIPY-C 进行校准，并且周围分子的大小不大于 BODIPY-C 的大小时，才能对粘度进行准确的定量测定。后一个限制可能适用于所有分子转子。
