Department of Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom.
Jerzy Haber Institute of Catalysis and Surface Chemistry Polish Academy of Sciences, Krakow PL-30329, Poland.
J Photochem Photobiol B. 2018 Oct;187:131-135. doi: 10.1016/j.jphotobiol.2018.08.018. Epub 2018 Aug 18.
Protein encapsulated gold nanoclusters have received much attention due to the possibility of using them as a non-toxic fluorescent probe or marker for biomedical applications, however one major disadvantage currently is their low brightness and quantum yield in comparison to currently used fluorescent markers. A method of increasing the fluorescence emission of Human Serum Albumin (HSA) encapsulated gold nanoclusters (AuNCs) via a Polyallylamide hydrochloride (PAH) coating is described. PAH molecules with a molecular weight of ~17,500 Da were found to enhance the fluorescence emission of HSA-AuNCs by 3-fold when the protein/polymer concentration ratio is 2:1 in solution. Interestingly, the fluorescence lifetime of the AuNCs was found to decrease while the native tryptophan (TRP) fluorescence lifetime also decreased during the fluorescence emission intensity enhancement caused by the PAH binding. Coinciding with the decrease in fluorescence lifetime, the zeta potential of the system was observed to be zero during maximum fluorescence intensity enhancement, causing the formation of large aggregates. These results suggest that PAH binds to the HSA-AuNCs acting as a linker; causing aggregation and rigidification, which results in a decrease in separation between native TRP of HSA and AuNCs; improving Förster Resonance Energy Transfer (FRET) and increasing the fluorescence emission intensity. These findings are critical to the development of brighter protein encapsulated AuNCs.
由于有可能将其用作生物医学应用的无毒荧光探针或标记物，因此，包裹蛋白质的金纳米团簇受到了广泛关注，然而目前存在的一个主要缺点是与当前使用的荧光标记物相比，其亮度和量子产率较低。本文描述了一种通过聚烯丙基盐酸盐（PAH）涂层来提高人血清白蛋白（HSA）包裹的金纳米团簇（AuNCs）荧光发射的方法。当溶液中蛋白质/聚合物浓度比为 2:1 时，分子量约为 17500 Da 的 PAH 分子可将 HSA-AuNCs 的荧光发射强度提高 3 倍。有趣的是，发现 AuNCs 的荧光寿命在荧光发射强度增强过程中随着天然色氨酸（TRP）荧光寿命的降低而降低，这是由于 PAH 结合所致。与荧光寿命的降低相吻合的是，在最大荧光强度增强时，体系的 zeta 电位观察到为零，导致大聚集体的形成。这些结果表明，PAH 作为连接体结合到 HSA-AuNCs 上，导致聚集和僵化，从而导致 HSA 的天然 TRP 与 AuNCs 之间的分离减少，从而改善Förster 共振能量转移（FRET）并增加荧光发射强度。这些发现对于开发更亮的蛋白质包裹的 AuNCs 至关重要。
