title: Ultrasensitive cysteine sensing using citrate-capped CdS quantum dots.
abstract: The importance of cysteine (Cys) in biological systems has stimulated a great deal of efforts in the development of analytical methods for the determination of this amino acid. In this work, a novel fluorescent probe for Cys based on citrate (Cit)-capped CdS quantum dots (QDs) is reported. The Cit-capped CdS QDs fluorescent probe offers good sensitivity and selectivity for detecting Cys. A good linear relationship was obtained from 1.0 × 10(-8)mol L(-1) to 5.0 × 10(-5)mol L(-1) for Cys. The detection limit was calculated as 5.4 × 10(-9)mol L(-1). The proposed method was applied to detect Cys in human urine samples, which showed satisfactory results. This assay is based on both the lability of Cit and the strong affinity of thiols to the surface of CdS QDs. The addition of Cys improved the passivation of the surface traps of CdS QDs and enhanced the fluorescence intensity.
authors.affiliation: School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, PR China. glwang@jiangnan.edu.cn
authors.forename: Guang-Li
authors.initials: GL
authors.lastname: Wang
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Dong
authors.forename: Hong-Xiao
authors.initials: HX
authors.lastname: Yang
authors.forename: Zai-Jun
authors.initials: ZJ
authors.lastname: Li
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical / Q000295:instrumentation*; D002951:Citrates / Q000737:chemistry*; D003545:Cysteine / Q000032:analysis* / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D006801:Humans; D057230:Limit of Detection; D045663:Quantum Dots; D013050:Spectrometry, Fluorescence; D013440:Sulfides / Q000737:chemistry*
chemical_list: D019187:Cadmium Compounds; D002951:Citrates; D005456:Fluorescent Dyes; D013440:Sulfides; C034939:cadmium sulfide; D003545:Cysteine