Rapid amperometric verification of PCR amplification of DNA

Amplification of an 800-base template was verified in a 10-min test on a 2-μL sample of the PCR product solution. For verification, digoxigeninylated primers and biotinylated d-UTP-16-biotin were added to the amplification solution. The resulting amplified product was digoxigenin-labeled at its 3'- end and was also labeled with multiple biotin functions along its chain. The detecting electrode was coated with an electron-conducting redox hydrogel to which anti-digoxin monoclonal antibody was covalently bound. The amplified DNA was captured by the electrode through conjugation of its 3'-digoxigenin with the antibody. Exposure to a solution of horseradish peroxidase-labeled avidin led to capture of the enzyme and switched the redox hydrogel from a noncatalyst to a catalyst for H₂O₂ electroreduction. The switching resulted in an H₂O₂ electroreduction current density of 2.1 ± 0.9 μA cm^-2 in 10^-4 M H₂O₂ at Ag/AgCl potential and at 25 °C.