Novel Biosensors Based on Water-Soluble Fluorescent Silver Nanoclusters for Selectively Detection of Thiol-Amino Acid

Noble metal (Au, Ag, Pt) nanoclusters, due to the attractive properties (such as brightness, photostability and biological compatibility), has recently become the subject of intense research and widely used in single-molecule studies, sensing, biolabeling, and biological fluorescence imaging. Numerous studies have shown that metal nanoclusters are excellent for detecting the poisonous metal ions (Hg)1 and amino acid (cysteine, homocysteine)2. It would be significant to achieve detecting special amino acid in vivo or even intracellular. Herein water-soluble fluorescent silver nanoclusters with red emission band have been designed and successfully synthesized under UV photoreduction by using Poly (methacrylic acid) (PMAA) and other ligands as the scaffolds. The effects of reaction parameters, including UV irradiation time, pH, the initial ratio of COO-/Ag+, ageing time, and the type of scaffold, on the fluorescence of silver nanoclusters were studied. We have proposed a ligand-to-metal charge transfer (LMMCT) mechanism to explain the fluorescence from AgNCs.3 Since the thiol group can coordinate with Ag+, causing the quenching of fluorescence, we design a probe to detect the amino acid containing the thiol group, such as cysteine and glutathione. The detection limit can approach micro-mole concentration. The results should stimulate additional experimental and theoretical research on the molecular-level design of luminescent nano probes in biophotonics and other applications.Reference:(1) Tao, Y.; Lin, Y.; Huang, Z.; Ren, J.; Qu, X. Talanta 2012, 88, 290.(2) Zhu, J.; Song, X.; Gao, L.; Li, Z.; Liu, Z.; Ding, S.; Zou, S.; He, Y. Biosensors & bioelectronics 2014, 53, 71.(3) Chen, Y.; Yang, T.; Pan, H.; Yuan, Y.; Chen, L.; Liu, M.; Zhang, K.; Zhang, S.; Wu, P.; Xu, J. J Am Chem Soc 2014, 136, 1686.