Discriminatory Detection of Cysteine and Homocysteine Based on Dialdehyde-Functionalized Aggregation-Induced Emission Fluorophores

• Published in: Chemistry : a European journal Vol. 19; no. 2; pp. 613 - 620
• Main Authors: Mei, Ju, Wang, Yijia, Tong, Jiaqi, Wang, Jian, Qin, Anjun, Sun, Jing Zhi, Tang, Ben Zhong
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 07.01.2013; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: aggregation; Aldehydes; Aldehydes - chemistry; Amino acids; Buffers; Chemistry; Chemistry Techniques, Analytical - instrumentation; Cysteine; Cysteine - analysis; Cysteine - blood; Cysteine - chemistry; Dimethyl Sulfoxide - chemistry; Discrimination; Emission; Fluorescence; fluorescence spectroscopy; Fluorescent Dyes - chemistry; fluorescent probes; Homocysteine; Homocysteine - analysis; Homocysteine - blood; Homocysteine - chemistry; Humans; Isomerism; Reaction kinetics; Solubility; Spectrometry, Fluorescence
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201202969

We demonstrate a concept‐proof work of using fluorescence (FL) “turn‐on” probes for the discriminatory detection of cysteine (Cys) over homocysteine (Hcy). The fluorogens are provided with aggregation‐induced emission (AIE) characteristic and functionalized with two aldehyde‐groups (DMTPS‐ALD and TPE‐ALD). All the detections were carried out in a biocompatible medium (10 mM HEPES buffer and DMSO, pH 7.4). In principle, the formation of thiazinane/thiazolidine through the chemical reaction of aldehydes on the probe molecules and the residue of Cys/Hcy determines the selective recognition of Cys and Hcy over other amino acids and glucose. The FL responses originate from the AIE property of thiazinane/thiazolidine resultants, which have low solubility and precipitate (aggregate) in the detection medium. The discrimination between Cys and Hcy comes from the difference in reaction kinetics of TPE‐ALD/DMTPS‐ALD with Cys and Hcy, thereby the FL responses show different time courses and intensity enhancement. It is worth noting that TPE‐ALD outshined the other two probes in performance with fast response, a high FL enhancement up to 16‐fold, high sensitivity, and good specificity and selectivity. Moreover, its FL response threshold at 250 μM is very close to the lower limit of the normal level of Cys in human plasma, which implies that TPE‐ALD could be applied as a potential indicator of Cys deficiency. Aldehyde‐functionalized fluorogens with aggregation‐induced emission (AIE) characteristics have been used as fluorescence “turn‐on” probes for the discriminatory detection of cysteine (Cys) over homocysteine (Hcy; see figure). The underlying mechanism for the discrimination is the kinetic difference of the reactions and the solubility difference between the fluorogens and the probe–analyte adducts. This proof‐of‐concept study indicates that this mechanism may be common to all the dialdehyde‐substituted AIE‐active molecules.