ACCUMULATION VOLTAMMETRY OF AVIDIN AND BIOTIN USING A BIOTIN-LABELED WITH NILE-BLUE-A

Avidin and biotin were detected in accordance with an electrochemical procedure using labeling. Biotin labeled with Nile Blue A, an electroa ctive dye, was prepared and used in avidin-biotin assay. The binding o f the biotin part with avidin makes labeled biotin (LB-N) electroinact ive. This is because the part of Nile Blue A is also taken in biotin s ites of avidin. Therefore, the concentration of avidin could be estima ted by measuring the peak current of LB-N. When biotin and LB-N compet ed for the site of avidin, biotin was also determined by the changing of the electrode response. Levels of detection for avidin and biotin w ere 10(-9) M. This method has merit that does not require a separation procedure of the free LB-N from the bound one. On the contrary, an ef fect for length of spacer between Nile Blue A and the biotin part was investigated. It was shown that adsorption of reagent to the electrode increased with increasing the length of the spacer.