A stable water-soluble tetramethylbenzidine-2-hydroxypropyl-beta-cyclodextrin inclusion complex and its applications...

Area of Science:

• Analytical Chemistry
• Biochemistry
• Materials Science

Background:

• 3,3',5,5'-Tetramethylbenzidine (TMB) is a widely used chromogen in enzyme-linked assays.
• TMB's hydrophobicity and limited stability pose challenges in aqueous assay systems.
• Horseradish peroxidase (HRP) is a common enzyme label in immunoassays and other bioanalytical methods.

Purpose of the Study:

• To enhance the solubility and stability of TMB for improved performance in bioassays.
• To characterize the complex formed between TMB and 2-hydroxypropyl-beta-cyclodextrin (hp-beta-CyD).
• To evaluate the utility of the TMB-hp-beta-CyD complex in enzymatic assays for clinically relevant metabolites.

Main Methods:

• Formation of a water-soluble inclusion complex between TMB and hp-beta-CyD.
• Characterization of the TMB-hp-beta-CyD complex using cyclic voltammetry and absorbency measurements.
• Development and validation of enzyme assays utilizing the TMB-hp-beta-CyD/HRP system for D-glucose, lactate, and glutamate detection.

Main Results:

• TMB solubility increased up to 40 mM, and stability was maintained for at least 2 months at room temperature.
• Cyclic voltammetry confirmed a 1:1 complex formation between TMB and hp-beta-CyD with a formation constant of 1.6 M-1.
• Enzyme assays demonstrated high sensitivity (limit < 10 µM) and excellent agreement with standard methods for metabolite quantification in food and clinical samples.

Conclusions:

• Complexation with hp-beta-CyD significantly improves TMB solubility and stability, overcoming limitations of the free chromogen.
• The TMB-hp-beta-CyD/HRP system is a robust and sensitive platform for enzymatic metabolite detection.
• This approach offers a valuable tool for various food and clinical diagnostic applications.