Provided is a method of continuous glucose monitoring (CGM) comprising using an FAD-GDH. The FAD-GDH is capable of retaining initial activity over a certain period of time. Also provided is a method for screening for an FAD-GDH suitable for use in CGM as well as a CGM device comprising an FAD-GDH.

An aqueous composition includes (i) glutamate dehydrogenase from a bacterium of the Clostridium genus, (ii) a stabilizing compound that is a carboxylic acid having a carbon-based chain of at least three carbon atoms and comprising at least two —COOH groups, or a salt thereof, and (iii) any of a monosaccharide polyol, disaccharide polyol, or polymeric macromolecule in addition to the glutamate dehydrogenase. A process for stabilizing the glutamate dehydrogenase in order to maintain antigenic properties of the glutamate dehydrogenase includes stabilizing the glutamate dehydrogenase in the aqueous composition and maintaining the antigenic properties of the glutamate dehydrogenase during storage of the aqueous composition.

Provided herein are methods for selection of circular aptamers using a circular nucleic acid library. Also provided are circular aptamers, circular aptamer probes, biosensor systems, and the methods for their use in detecting a microorganism target, or a target molecule present on or generated from a microorganism or a virus in a test sample, including C. difficile glutamate dehydrogenase and methods for determining whether a subject has a C. difficile infection.

An aqueous composition includes (i) glutamate dehydrogenase from a bacterium of the Clostridium genus, (ii) a stabilizing compound that is a carboxylic acid having a carbon-based chain of at least three carbon atoms and comprising at least two COOH groups, or a salt thereof, and (iii) any of a monosaccharide polyol, disaccharide polyol, or polymeric macromolecule in addition to the glutamate dehydrogenase. A process for stabilizing the glutamate dehydrogenase in order to maintain antigenic properties of the glutamate dehydrogenase includes stabilizing the glutamate dehydrogenase in the aqueous composition and maintaining the antigenic properties of the glutamate dehydrogenase during storage of the aqueous composition.

A class of compounds of monosulfonic phenyltetrazole, with the structure of 2-(R1 phenyl)-5 (2-sulfonic phenyl)-2H-tetrazole. The 2-sulfonic phenyl tetrazolium salt of this invention has advantages of low toxicity, short synthetic route, easy control of purity and quality. As the 2-sulfonic phenyl tetrazolium salts has almost no absorption at 450 nm where the reduzate has greater absorption, spectrophotometry can simply and rapidly determine the activity of glutamate dehydrogenase, or the content of NADH/NADPH.

A process for stabilizing glutamate dehydrogenase (GDH) from a bacterium of the Clostridium genus, in an aqueous solution, in order to maintain the antigenic properties thereof, includes the step of mixing the glutamate dehydrogenase and a stabilizing composition which is a carboxylic acid having a carbon-based chain of at least 3 carbon atoms and comprising at least 2 COOH groups, or a salt thereof. GDH compositions thus stabilized and a method of detecting the presence of bacteria of the Clostridium genus are also disclosed.

Provided is a method of continuous glucose monitoring (CGM) comprising using an FAD-GDH. The FAD-GDH is capable of retaining initial activity over a certain period of time. Also provided is a method for screening for an FAD-GDH suitable for use in CGM as well as a CGM device comprising an FAD-GDH.

Clostridium difficile disease involves a range of clinical presentations ranging from carrier status with other causes of symptoms to mild and self-limiting diarrhea to life-threatening pseudomembranous colitis and megacolon. Cases of C. difficile are treated differently depending on the presence and then the severity of disease. Patients that are carriers may not receive treatment with concern of causing the disease. Mild to moderate cases may be treated with metronidazole while severe and relapsing cases are often treated with vancomycin or fidaxomicin. Current molecular assays are highly sensitive for detecting toxigenic C. difficile and cannot rule out carrier status. Utilization of a biomarker panel that includes C. difficile antigen (GDH), toxins A and B, and fecal lactoferrin allows clinicians to differentiate between a carrier state and active state of C. difficile and allows for monitoring to evaluate the effectiveness of treatment.

A class of compounds of monosulfonic phenyltetrazole, with the structure of 2-(R1 phenyl)-5 (2-sulfonic phenyl)-2H-tetrazole. The 2-sulfonic phenyl tetrazolium salt of this invention has advantages of low toxicity, short synthetic route, easy control of purity and quality. As the 2-sulfonic phenyl tetrazolium salts has almost no absorption at 450 nm where the reduzate has greater absorption, spectrophotometry can simply and rapidly determine the activity of glutamate dehydrogenase, or the content of NADH/NADPH.

An analytical apparatus is disclosed for detecting at least one analyte in a sample, where in an analyte measurement at least an electrical or optical property changeable by presence of the analyte at least one test chemical of a test element is recorded, and where the analytical apparatus also can perform at least one quality measurement on the at least one test chemical such as an intrinsic luminescence, which is recorded and from the intrinsic luminescence a conclusion is drawn on a quality of the test chemical and thus the test element. Methods also are disclosed for detecting at least one analyte in a sample that include a quality measurement of the at least one test chemical of the test strip.