Enzyme-based detectors

The M256A1 kit includes enzyme-based detector "tickets," which change color to indicate low concentrations of cyanide, vesicant, and nerve agents in vapor form. The tests take approximately 15 minutes. Sensitivity is such that the tickets may provide a negative reading at concentrations below that immediately dangerous to life and health (IDLH) but still... 

Electrochemical biosensors have been divided into two basic types enzyme-based sensor and electrochemical probe-based sensor. Alkaline phosphatase (ALP) and horse radish peroxidase (HRP) have been often employed for enzyme-based biosensors using p-nitrophenyl phosphate (PNP), a-naphtyl phosphate, 3-3, 5,5 -tetramethylbenzidine (TMB) and 2,2 -azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as substrates of electrochemically active species, and ferrocene (Fc) and methylene blue as the electrochemical mediators. In general, enzymatic amplification of electrochemical signals enables highly sensitive detection of analytes. On the other hand, a direct detection of analytes by using electrochemical probes allows a more rapid time-response onto the detector surface and needs no enzymatic reaction. Based on the reason, a direct detection of analytes by using electrochemical probes has been... 

Development of an Enzyme-Based Photoluminescent Porous Silicon Detector for Chemical Warfare Agents, Chapter 3... 

The ultimate goal of this project is to design enzyme-based PL PSi detectors for toxic chemical detection therefore, the selection of enzymes active towards these types of target molecules is critical. Table I shows activity parameters of some enzymes in solution that have hydrolysis activity toward G-type nerve agents. OPAA-2 was selected for immobilization because it has relatively high activity towards GB and GD, as well as towards surrogates such as DFP, and /7-nitro-phenyl-soman (20-23). The products from the enzymatic action would be a phosphonic acid and HF. 

Tab. S Examples of some bioanalytically useful potentiometric enzyme-based biosensors that can be prepared for monitoring important biomolecules using appropriate immobilized enzymes and ISE or gas sensing detectors...

Another approach to enzyme-based biosensor arrays has been reported by Moser et al. [40]. This flow-based detector, produced with a sealed glass-plate gold-modified counter electrode, has a total internal volume of less than 10 pL, and includes glass-supported elements for the quantitation of glucose, lactate, glutamine, and glutamate in whole blood samples or fermentation broths. Crosstalk and stability issues were successfully addressed. 

Classical low values for the mammalian enzyme that have appeared in the literature are the result of enzyme inactivation by hydrogen peroxide when measurements were carried out with peroxide levels in excess of 10 mM over time scales of 10 minutes or longer. The rapid sampling/titration method of Bonnichsen overcame the inactivation problem and permitted a satisfactory correlation of the overall catalytic measurements and Chance s observations on the intermediate complex (compound 1). Eventually, the introduction of the UV detector/spectrophotometer and the consequent assay based upon the UV absorbance of peroxide (35) further simplified the process by eliminating the discontinuous titrimetric assay. 

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