On-line microdialysis assay of l-lactate and pyruvate in vitro and in vivo by a flow-injection system with a dual enzyme electrode

A novel immobilization fluorescence capillary analysis method and its applications

Fluorescence capillary analysis (FCA) realizes trace-level analysis of micro-volume samples; it is easy to operate, extremely low in analytical cost and can significantly lessen environmental pollution from analytical chemistry waste. FCA has the characteristics of green analytical chemistry and has been applied in clinical, biochemical, pharmaceutical, food safety and other fields. FCA basically involves a micro-volume glass capillary, a capillary holder and an ordinary fluorescence detector. The capillary is not only a container for chemical reaction and detection but also functions as a carrier to immobilize enzymes, gene probes or reagents; it can be used repeatedly or can be disposable. In analysis, the capillary which is modified with functional reagents sucks in a measured liquid for the reaction and is then inserted into the holder within the fluorescent detector for measurement. The immobilized FCA method has been successfully used in the determination of reduced coenzyme I, ethanol in liqueur, lactic acid in dairy products, pyruvic acid and glucose in serum, trace-level sulfated bile acid in urine, the ratio of pyruvic/lactic acid in serum, and pyruvic acid in cells as well as in DNA end-labeling and dyeing methods. Further, FCA can also be extended to capillary arrays to complete multipurpose simultaneous determinations and can be combined with mobile phones as fluorescence detectors for use in mobile health analytical technology. FCA will produce considerable social benefits in medicine, pharmacy, fermentation of food, environmental protection and other fields. Therefore, the relevant contents are presented in this tutorial review.

Simultaneous assay of glucose, lactate, L-glutamate and hypoxanthine levels in a rat striatum using enzyme electrodes based on neutral red-doped silica nanoparticles

An electrochemical method suitable for the simultaneous measurement of cerebral glucose, lactate, L-glutamate and hypoxanthine concentrations from in vivo microdialysis sampling has been successfully performed for the first time using a neutral red-doped silica (NRDS) nanoparticle-derived enzyme sensor system. These uniform NRDS nanoparticles (about 50 +/- 3 nm) were prepared by a water-in-oil (W/O) microemulsion method, and characterized by a TEM technique. The neutral red-doped interior maintained its high electron-activity, while the exterior nano-silica surface prevented the mediator from leaching out into the aqueous solution, and showed high biocompability. These nanoparticles were then mixing with the glucose oxidase (GOD), lactate oxidase (LOD), L-glutamate oxidase (L-GLOD) or xanthine oxidase (XOD), and immobilized on four glassy carbon electrodes, respectively. A thin Nafion film was coated on the enzyme layer to prevent interference from molecules such as ascorbic acid and uric acid in the dialysate. The high sensitivity of the NRDS modified enzyme electrode system enables the simultaneous monitoring of trace levels of glucose, L-glutamate, lactate and hypoxanthine in diluted dialysate samples from a rat striatum.