PLoS One. 2012;7(8):e44355. doi: 10.1371/journal.pone.0044355. Epub 2012 Aug 31.
Quantum dots (QDs) are very attractive probes for multi-color fluorescence imaging in biological applications because of their immense brightness and reported extended photostability. We report here however that single QDs, suitable for biological applications, that are subject to continuous blue excitation from a conventional 100 W mercury arc lamp will undergo a continuous blue-switching of the emission wavelength eventually reaching a permanent dark, photobleached state. We further show that β-mercaptoethanol has a dual stabilizing effect on the fluorescence emission of QDs: 1) by increasing the frequency of time that a QD is in its fluorescent state, and 2) by decreasing the photobleaching rate. The observed QD color spectral switching is especially detrimental for multi-color single molecule applications, as we regularly observe spectral blue-shifts of 50 nm, or more even after only ten seconds of illumination. However, of significant importance for biological applications, we find that even small, biologically compatible, concentrations (25 µM) of β-mercaptoethanol has a significant stabilizing effect on the emission color of QDs, but that greater amounts are required to completely abolish the spectral blue shifting or to minimize the emission intermittency of QDs.
量子点 (QDs) 由于其极高的亮度和据称延长的光稳定性，在生物应用的多色荧光成像中是非常有吸引力的探针。然而，我们在这里报告称，对于适合生物应用的单个 QD，在受到传统 100 W 汞弧灯持续蓝色激发时，其发射波长会经历连续的蓝色切换，最终达到永久性的黑暗、光漂白状态。我们进一步表明，β-巯基乙醇对 QD 的荧光发射具有双重稳定作用：1）增加 QD 处于荧光状态的时间频率，2）降低光漂白速率。观察到的 QD 颜色光谱切换对于多色单分子应用特别不利，因为我们经常观察到仅在 10 秒的照射后，光谱蓝移 50nm 或更多。然而，对于生物应用来说非常重要的是，我们发现即使是小的、生物相容性的 β-巯基乙醇浓度（25µM）对 QD 的发射颜色也有显著的稳定作用，但需要更大的浓度才能完全消除光谱蓝移或最小化 QD 的发射间歇性。
