High performance fluorescence biosensing of cysteine in human serum with superior specificity based on carbon dots and cobalt-derived recognition

Abstract Elevated levels of cysteine (Cys) have been associated with many diseases and it is of vital importance to discriminate and quantify Cys in human serum. However, analogues of Cys especially homocysteine (Hcy) and glutathione (GSH) possess similar structure, which lead to a big challenge for specific detection of Cys without interference from other coexist biothiols. In this work, we developed a novel sensing approach for highly selective and sensitive determination of Cys by using fluorescence carbon dots (CDs) and cobalt-derived specific recognition. To construct such a sensing platform, cobalt-doped CDs (Co-CDs) were synthesized directly by using folic acid (FA) as precursor and CoCl 2 as dopant. The fluorescence of the Co-CDs can be specifically and intensively suppressed by the addition of Cys due to the combination with cobalt, while Hcy and GSH cannot induce any obvious fluorescence changes. Besides the robust selectivity, this new developed sensing strategy displayed a good correlation with Cys from 0.1 to 100 μM with a limit of detection (LOD) of 80 nM. This sensing platform was successfully applied to detect Cys in human serum samples with some advantages including highly selective and sensitive, convenient and rapid, as well as cost-effective, suggesting its great potential to be used in specific Cys analyzing in biological and bioanalytical applications.