Chimie et Photonique Moléculaire (CNRS, UMR 6510), Université de Rennes 1, 35042 Rennes, France.
Small. 2011 Nov 18;7(22):3219-29. doi: 10.1002/smll.201100726. Epub 2011 Oct 4.
Two related triphenylamine-based dipolar and octupolar fluorophores are used to prepare aqueous suspensions of fluorescent organic nanoparticles (FONs) via the reprecipitation method. The obtained spherical nanoparticles (30-40 nm in diameter) are fluorescent in aqueous solution (up to 15% fluorescence quantum yield) and exhibit extremely high one- and two-photon brightness, superior to those obtained for quantum dots. Despite the two chromophores showing similar fluorescence in solution, the fluorescence of FONs made from the octupolar derivative is significantly red-shifted compared to that generated by the dipolar FONs. In addition, the maximum two-photon absorption cross section of the FONs made from the octupolar derivative is 55% larger than that of the dipolar derivative FONs. The experimental observations provide evidence that the different molecular shape (rodlike versus three-branched) and charge distribution (dipolar versus octupolar) of the two chromophores strongly affect the packing inside the nanoparticles as well as their spectroscopic properties and colloidal stability in pure water. The use of these FONs as probes for biphotonic in-vivo imaging is investigated on Xenopus laevis tadpoles to test their utilization for angiography. When using FONs made from the octupolar dye, the formation of microagglomerates (2-5 μm scale) is observed in vivo, with subsequent lethal occlusion of the blood vessels. Conversely, the nanoparticles of the dipolar dye allow acute imaging of blood vessels thanks to their suitable size and brightness, while no toxic effect is observed. Such a goal cannot be achieved with the dissolved dye, which permeates the vessel walls.
两种相关的三苯胺基偶极和八极荧光团被用于通过再沉淀法制备荧光有机纳米粒子（FONs）的水悬浮液。所得到的球形纳米粒子（直径为 30-40nm）在水溶液中是荧光的（高达 15％的荧光量子产率），并且表现出极高的单光子和双光子亮度，优于量子点获得的亮度。尽管两种生色团在溶液中表现出相似的荧光，但八极衍生的 FONs 的荧光与偶极 FONs 产生的荧光相比显著红移。此外，八极衍生的 FONs 的最大双光子吸收截面比偶极衍生的 FONs 的大 55％。实验观察结果表明，两种生色团的不同分子形状（棒状与三分支）和电荷分布（偶极与八极）强烈影响纳米粒子内部的堆积以及它们在纯水中的光谱性质和胶体稳定性。使用这些 FONs 作为双光子体内成像的探针在非洲爪蟾（Xenopus laevis）蝌蚪上进行了研究，以测试它们在血管造影中的应用。当使用八极染料制成的 FONs 时，体内观察到微聚集体（2-5μm 规模）的形成，随后血管发生致命性阻塞。相反，偶极染料的纳米粒子由于其合适的尺寸和亮度允许对血管进行急性成像，而没有观察到毒性作用。由于溶解的染料可以渗透血管壁，因此无法实现这种目标。
