Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
Dermatology Clinic, University Medical Center of the Johannes Gutenberg-University Mainz, Langenbeckstr. 1, 55131 Mainz, Germany.
Biomacromolecules. 2020 Nov 9;21(11):4469-4478. doi: 10.1021/acs.biomac.0c00377. Epub 2020 Jul 10.
Monitoring local temperature inside cells is crucial when interpreting biological activities as enhanced cellular metabolism leads to higher heat production and is commonly correlated with the presence of diseases such as cancer. In this study, we report on polymeric upconversion nanocapsules for potential use as local nanothermometers in cells by exploiting the temperature dependence of the triplet-triplet annihilation upconversion phenomenon. Nanocapsules synthesized by the miniemulsion solvent evaporation technique are composed of a polymer shell and a liquid core of rice bran oil, hosting triplet-triplet annihilation upconversion active dyes as sensitizer and emitter molecules. The sensitivity of the triplet-triplet annihilation upconversion to the local oxygen concentration was overcome by the oxygen reduction ability of the rice bran oil core. The triplet-triplet annihilation upconversion process could thus successfully be applied at different levels of oxygen presence including at ambient conditions. Using this method, the local temperature within a range of 22 to 40 °C could be determined when the upconversion nanocapsules were taken up by HeLa cells with good cellular viability. Thus, the higher cell temperatures where the cells show enhanced metabolic activity led to a significant increase in the delayed fluorescence spectrum of the upconversion nanocapsules. These findings are promising for further development of novel treatment and diagnostic tools in medicine.
当解释生物活性时，监测细胞内的局部温度至关重要，因为增强的细胞代谢会导致更高的热量产生，通常与癌症等疾病的存在相关。在这项研究中，我们报告了用于细胞内局部纳米温度计的上转换纳米胶囊，利用三重态-三重态湮灭上转换现象的温度依赖性。通过 miniemulsion 溶剂蒸发技术合成的纳米胶囊由聚合物壳和米糠油的液体芯组成，作为敏化剂和发射体分子承载三重态-三重态湮灭上转换活性染料。米糠油芯的氧还原能力克服了三重态-三重态湮灭上转换对局部氧浓度的敏感性。因此，即使在环境条件下，也可以成功地在不同氧存在水平下应用三重态-三重态湮灭上转换过程。使用这种方法，当 HeLa 细胞摄取上转换纳米胶囊时，可以在 22 至 40°C 的范围内确定局部温度，并且细胞具有良好的细胞活力。因此，细胞表现出增强的代谢活性的更高细胞温度导致上转换纳米胶囊的延迟荧光光谱显著增加。这些发现为医学中新的治疗和诊断工具的进一步发展提供了希望。
