Thrombin Biosensor Based on Rare Earth Ion Mediated Fluorescence Switch of Graphene Quantum Dots / 分析化学

A label-free method for sensitive and selective detection of thrombin ( Tb) was constructed based on rare earth ion mediated fluorescence switch of graphene quantum dots ( GQDs) . Rare earth ion ( Er3+) can assemble onto the surface of GQDs through the coordination interaction between Er3+ ions and the carboxylate groups located on the surface or edge of the GQDs, resulting in the aggregation of the GQDs and thereby decrease of the fluorescence of the GQDs. In the presence of Tb, the oxygen and nitrogen-donor atoms in Tb can coordinate with Er3+ ions and compete with the carboxylate groups on GQDs to coordinate Er3+ ions, thus the interaction between GQDs and Er3+ ions is reduced, which lead to the restoration of the GQDs fluorescence. In this study, the sensing mechanism was demonstrated by transmission electron microscopy, atomic force microscope, Fourier transform infrared spectroscopy, UV-Vis absorption and fluorescence spectroscopy. The limit of detection for Tb assay was as low as 0. 049 nmol/L. Moreover, this assay was successfully applied to the selective determination of Tb in real samples.

Synthesis of A Novel Fluorescence Switch Conjugated Polymers and Its Discrimination Ability Toward S-Adenosylmethionine / 分析化学

A novel fluorescent switch was constructed based on poly 3-{[ 1-( 2-hydrazino-2-oxoethyl ) piperidin-4-ylidene] methyl}thiophene ( PMTH ) in the presence of Pb2﹢ or S-adenosylmethionine ( SAM ) . The switch turned off in the presence of Pb2﹢owing to complex effect, and the fluorescence intensity of PMTH solution was efficiently quenched by Pb2﹢ ions. Upon adding SAM to the Pb2﹢-PMTH solution, which was stronger Pb2﹢ chelators, it could form more stable SAM-Pb2﹢, the Pb2﹢ ion was displaced from PMTH and the fluorescence of PMTH was recovered. By triggering the turn-on signal of PMTH, a new discrimination ability toward SAM method for the determination of SAM was established. The effects of the interaction on the fluorescence spectral characteristics of these Pb2﹢-PMTH and Pb2﹢-SAM complexes in H2 O-CH3 CH2 OH(4:1, V/V) solution, suitable reaction conditions and influencing factors were investigated. This method offered good sensitivity and selectivity for detecting SAM in the presence of amino acids and metal ions. Under optimum conditions, the concentration of SAM in the range from 1. 0 × 10-8-2. 0 × 10-6 mol/L exhibited a linear relationship with the relative fluorescence intensity. The regression equation was △I = 68. 51﹢72. 32c (μmol/L), the correlation coefficient r=0. 9982. The limit of detection was 8. 72×10-9 mol/L. The system was successfully applied for detecting SAM in human serum, urine and injection samples.