State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Bioactive Materials, Ministry of Education, College of Life Sciences, and Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), ‡College of Pharmacy and Tianjin Key Laboratory of Molecular Drug Research, Nankai University , Tianjin 300071, P. R. China.
Anal Chem. 2014 Feb 18;86(4):2193-9. doi: 10.1021/ac4038653. Epub 2014 Feb 4.
The combination of an environment-sensitive fluorophore, 4-nitro-2,1,3-benzoxadiazole (NBD), and peptides have yielded supramolecular nanofibers with enhanced cellular uptake, brighter fluorescence, and significant fluorescence responses to external stimuli. We had designed and synthesized NBD-FFYEEGGH that can form supramolecular nanofibers and emit brighter than its counterpart of NBD-EEGGH without the self-assembling property. The nanofibers of NBD-FFYEEGGH could specifically bind to Cu(2+), leading to the formation of fluorescence quenched elongated nanofibers. This fluorescence quenching property was enhanced in self-assembling nanofibers and could be applied for detection of Cu(2+) in vitro and within cells. In a further step, an enzyme-cleavable DEVD peptide was placed between NBD-FFY and the copper binding tripeptide GGH. The resulting self-assembling peptide NBD-FFFDEVDGGH also showed strong fluorescence quenching to Cu(2+). Upon the enzymatic cleavage to remove the Cu(2+)-binding GGH tripeptide from the peptide, the fluorescence was restored. The cellular uptake of nanofibers was better than that of free molecules because of endocytosis. The supramolecular nanofibers with fluorescence turn-on property could therefore be applied for detection of caspase-3 activity in vitro and within cells. We believe that the combination of environment-sensitive fluorescence and fast responses of supramolecular nanostructures would lead to a useful platform to detect many important analytes.
环境敏感荧光团 4-硝基-2,1,3-苯并恶二唑（NBD）与肽的结合产生了超分子纳米纤维，具有增强的细胞摄取、更亮的荧光以及对外部刺激的显著荧光响应。我们设计并合成了 NBD-FFYEEGGH，它可以形成超分子纳米纤维，并且比没有自组装性质的 NBD-EEGGH 具有更亮的荧光。NBD-FFYEEGGH 的纳米纤维可以特异性结合 Cu(2+)，导致形成荧光猝灭的伸长纳米纤维。这种荧光猝灭性质在自组装纳米纤维中得到增强，可用于体外和细胞内 Cu(2+)的检测。在进一步的步骤中，将酶可切割的 DEVD 肽置于 NBD-FFY 和铜结合三肽 GGH 之间。所得的自组装肽 NBD-FFFDEVDGGH 也对 Cu(2+)表现出强烈的荧光猝灭。当酶切割从肽中去除 Cu(2+)结合的 GGH 三肽时，荧光恢复。由于内吞作用，纳米纤维的细胞摄取量优于游离分子。因此，具有荧光开启特性的超分子纳米纤维可用于体外和细胞内 caspase-3 活性的检测。我们相信，环境敏感荧光和超分子纳米结构快速响应的结合将为检测许多重要分析物提供一个有用的平台。
