Tracing Phosphate Ions Generated during Loop-Mediated Isothermal Amplification for Electrochemical Detection of...

Traditionally, amplified DNA detection in a loop-mediated isothermal amplification (LAMP) was carried out in a complicated gel electrophoresis or with expensive fluorescence-based methods. Here, instead of direct detection that relies on amplified DNA, the indirect detection based on tracing phosphate ions (Pi) generated during LAMP by using an electrochemical method has been proposed for sensitive nucleic acid detection. Pyrophosphate (PPi) as the byproduct of nucleic acid polymerization reaction in LAMP was hydrolyzed into Pi by the preaddition of thermostable inorganic pyrophosphatase (PPase). Thus, the total amount of Pi in the LAMP-amplified sample was proportional to the amount of starting DNA templates. The obtained Pi could then react with acidic molybdate to form the molybdophosphate precipitates on the electrode surface, which serve as redox mediators to give a readily measurable electrochemical signal. The practicality of this strategy has been further demonstrated by employing it for sensitive and accurate quantification of Nosema bombycis genomic DNA PTP1. The electrochemical method allowed the quantitative analysis for target genomic DNA with a detection limit of 17 fg/μL. Thus, we suppose that the novel method proposed in this work with superior sensitivity and specificity, as well as the simple feature, can be easily established for quantitative analysis of many other kinds of nucleic acids in the assistance of LAMP.