Electrochemical Detection for Isothermal Loop-Mediated Amplification of Pneumolysin Gene of Streptococcus pneumoniae Based on the Oxidation of Phenol Red Indicator

A highly sensitive electrochemical methodology for end-point detection of loop-mediated isothermal nucleic acid amplification reactions was developed. It is based on the oxidation process of phenol red (PR), commonly used as a visual indicator. The dependence of its redox process on pH, which changes during amplification, allows performing quantitative measurements. Thus, the change in the oxidation potential of PR during the amplification is used, for the first time, as the analytical signal that correlates with the number of initial DNA copies. As a proof-of-concept, the amplification of the pneumolysin gene from Streptococcus pneumoniae, one of the main pathogens causing community-acquired pneumonia, is performed. Combination of isothermal amplification with electrochemical detection, performed on small-size flexible electrodes, allows easy decentralization. Adaptation to the detection of other pathogens causing infectious diseases would be very useful in the prevention of future epidemics.

Automated summary

A highly sensitive electrochemical methodology was developed to detect the end-point of loop-mediated isothermal nucleic acid amplification reactions. The methodology utilizes the oxidation process of phenol red as a visual indicator and quantifies the pH changes during amplification. The change in oxidation potential of phenol red serves as a novel analytical signal correlating with the number of initial DNA copies. In the proof-of-concept study, amplification of the pneumolysin gene from Streptococcus pneumoniae was successfully achieved. The combination of isothermal amplification with electrochemical detection on small flexible electrodes allows for easy decentralization and could be adapted for the detection of other pathogens causing infectious diseases, which is of great importance in preventing future epidemics.