Environment-sensitive fluorescent supramolecular nanofibers for imaging applications.
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.
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.
Yanbin
Y
Cai
Yang
Y
Shi
Huaimin
H
Wang
Jingyu
J
Wang
Dan
D
Ding
Ling
L
Wang
Zhimou
Z
Yang
D004777:Environment; D005456:Fluorescent Dyes / Q000737:chemistry*; D006367:HeLa Cells; D006801:Humans; D057139:Nanofibers / Q000737:chemistry*; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence / Q000379:methods*
D005456:Fluorescent Dyes