| Summary: | 碩士 === 國立中山大學 === 化學系研究所 === 105 === (a) Surfen-Assembled Graphene Oxide for Fluorescence Turn-On Detection of Sulfated Glycosaminoglycans in Biological Matrix
Sulfated glycosaminoglycans (GAGs) not only serve as biomarker for mucopolysaccharidoses disease but also participate in various biological processes, such as blood clot medication (heparin) and signal transduction (heparan sulfate). However, few fluorescent sensors, such as 1,9-dimethylmethylene blue, have been developed for the detection of sulfated GAGs in the real world. Herein, we fabricated a surfen/few-layer graphene oxide (FLGO) nanocomplex for sensing sulfated GAGs in biological fluids. Surfen molecules are self-assembled onto the surface of FLGO through electrostatic attraction and their fluorescence was then quenched by the creation of the FLGO-surfen complex (static quenching),and partially combined with the energy transfer from surfen to FLGO (dynamic quenching). The presence of sulfated GAGs resulted in the fluorescence recovery through the formation of the surfen-GAGs complex, which exhibits weak binding to FLGO and keeps surfen molecules away from the FLGO surface. Because FLGO efficiently reduced the fluorescence background from surfen and competed with sulfated GAGs for binding to surfen, surfen-assembled FLGO exhibited higher sensitivity andbetter selectivity for sulfated GAGs than surfen. The aforementioned strategy was exemplified by the analysis of heparin in human plasma and sulfated GAGs in artificial cerebrospinal fluid; the limits of detection at a signal-to-noise ratio of 3 for heparin, dermatan sulfate, and heparin sulfate were determined to be 30, 30 and 60 ng/mL, respectively.
(b) Boosted Peroxidase-Like Activity in Gold Nanoparticles by Incorporating Adenosine Diphosphate: Application to Sulfated Glycosaminoglycans Sensing
Gold-based nanomaterials as a mimic peroxidase are of great interest in the development of biosensors. However, they suffer from low catalytic activity, resulting in poor detection sensitivity toward a target of interest. Herein, this study presents that the modification of citrate-capped gold nanoparticles with adenosine diphosphate (ADP) is capable of boosting their catalytic activity for the oxidation reaction of hydrogen peroxide (H2O2) and amplex ultrared (AU). The improved activity resulted from: (1) the attachment of ADP onto the surface of the AuNPs allows them to stabilize in the catalytic condition and (2) ADP mimics as a distal histidine residue of horseradish peroxidase for activating H2O2. Compared to citrate-capped AuNPs, the Michaelis constant of ADP-modified AuNPs (ADP-AuNPs) was lowered to be 4.4-fold and their maximum velocity was enhanced to be 2.5-fold. Cationic surfen molecules were found to be efficient to induce the aggregation of ADP-AuNPs, thereby inhibiting their catalytic activity for the AU-H2O2 reaction. Since heparin specifically binds to surfen through strong electrostatic attraction between them, the presence of heparin disassembled the aggregation of ADP-AuNPs. As a result, the fluorescence of the oxidized AU linearly increased with an increase in the concentration of heparin from 1 to 8 nM. The proposed system was successfully applied for the determination of heparin in plasma.
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