Electrochemical sensor for discrimination tyrosine enantiomers using graphene quantum dots and β-cyclodextrins composites

An electrochemical sensor using the composites of graphene quantum dots (GQDs) and beta-cyclodextrins ((beta-CDs) functionalized glassy carbon electrode (GCE) was developed for determination and recognition of tyrosine (Tyr) enantiomers which are biomarker of depression. The modified electrode is simple to fabricate and rapid, sensitive, selective to detect the Tyr enantiomers. In order to further validate the feasibility of the electrochemical sensor in real samples, the sensor was applied to the detection of L-Tyr in blood serum samples of healthy people and depression patients, and found that the quantities of L-Tyr of depression patients in serum is less than healthy people. The beta-CDs-GQDs composites were fabricated as modification layer of electrodes. GQDs were used as substrate and functionalized with beta-CDs. The beta-CDs-GQDs composites utilized nanosize of GQDs and enantioselectivity of beta-CDs to realize chiral recognition of Tyr. The beta-CDs-GQDs modified electrode presented significant difference in the oxidation peak current with ratio of L to n-Tyr reaching 2.35. The detection limits of L-Tyr and D-Tyr were 6.07x10(-9) M and 1.03x10(-7) M, respectively and superior to detection limits of the reported methods. In addition, the stability and reproducibility of the prepared modified electrode were investigated, and achieved good results.