Redox Dyes – and Electron Mediators

Enzymatic assay is a homogeneous assay method widely used to selectively determine the concentration of analytes in biological samples such as blood, urine, serum and plasma. In the field of clinical diagnostics, measuring the concentration of glucose in blood samples plays an important role in the management of diabetes and is performed by the combination of glucose oxidase/dehydrogenase and chemical reactions (Fig. 1). Dojindo offers a variety of chromogenic dyes that generate intense color in the presence of hydrogen peroxide or NADH.

Fig.1
New Trinder's ReagentsOxidative Chromogen DyesTetrazolium SaltsElectron Mediators

New Trinder’s Reagents are stable enough to use in both solution and test strip detection systems. They form highly stable purple or blue dyes through an oxidative coupling reaction with 4-Aminoantipyrine(4-AA) in the presence of hydrogen peroxide and peroxidase. The table below shows the maximum wavelength and molar absorptivity of each oxidized New Trinder’s Reagent complex with 4-AA.

Product Nameλmax(nm), pH Molar absorptivity
ADOS542, 5.5-9.5 2.72 x 104
ADPS 540, 5.9-9.52.79 x 104
ALPS 561, 6.5-7.54.13 x 104
DAOS 593, 5.5-9.5 1.75 x 104
HDAOS 583, 5.5-9.51.73 x 104

Product Name λmax(nm), pH Molar absorptivity
MADB630, 5.5-9.5 1.65 x 104
MAOS 630, 5.5-9.5 2.25 x 104
TODB 550, 5.5-9.5 3.80 x 104
TOOS 555, 5.5-9.5 3.92 x 104
TOPS 550, 5.5-9.5 3.74 x 104

Benzidine derivatives (e.g. TMBZ or SAT-3) are well known to be oxidized with peroxidase and one molecule of hydrogen peroxide.Since the amount of the yielded dye is directly proportional to the concentration of hydrogen peroxide, benzidine derivatives are applied for diagnostic analyses or enzyme immuno-assays as good indicators of hydrogen peroxide.

ProductAbsorbance Max (nm)
KN-dyes (contact)666
DAB465
SAT-3675
TMBZ655
TMBZ-HCl655

Tetrazolium Salts are unique compounds with a slightly yellow color that generate intense orange to purple formazan dyes when reduced. This chemical property makes it possible to apply tetrazolium salts into a wide range of applications, for example, metabolism enzymatic assays, staining, cell viability monitoring and immunoassays in conjunction with an electron mediator. Below are the optical properties of formazan dyes of each tetrazolium salt.

Product Name λmax(nm), pH Molar absorptivity
WST-1 438 2.72 x 104
WST-3 433 2.79 x 104
WST-4 530 4.13 x 104
WST-5 550 1.75 x 104
WST-9 490 1.73 x 104
Product Name λmax(nm), pH Molar absorptivi
INT 490 1.65 x 104
MTT 570 2.25 x 104
Nitro-TB(NBT) 530 3.80 x 104
TB 525 3.92 x 104

Electron mediators have been used in various analysis based on redox reactions. 1-Methoxy PMS is widely used as one of the most common electron mediator which is a small molecule. The newly developed electron mediator, 1-Methoxy PES shows an excellent solution stability even in a mildly alkaline solution. Amine-reactive PES is a novel electron mediator for the modification of enzymes. The mediator can be linked to enzymes such as glucose dehydrogenase by a covalent bond and are expected to be applied to next generation biosensors.

Product NameRedox Potential
1-Methoxy PMS168.0 mV
1-Methoxy PES169.5 mV
Amine-reactive PES173.0 mV

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