Handheld isothermal amplification and electrochemical detection of DNA in resource-limited settings

Abstract

This paper demonstrates a new method for electrochemical detection of specific sequences of DNA present in trace amounts in serum or blood. This method is designed for use at the point-of-care (particularly in resource-limited settings). By combining recombinase polymerase amplification (RPA)— an isothermal alternative to the polymerase chain reaction — with an electroactive mediator, this electrochemical methodology enables accurate detection of DNA in the field using a low-cost, portable electrochemical analyzer (specifically designed for this type of analysis). This handheld device has four attributes: (1) It uses disposable, paper-based strips that incorporate screen-printed carbon electrodes; (2) It accomplishes thermoregulation with ±0.1 °C temperature accuracy; (3) It enables electrochemical detection using a variety of pulse sequences, including square-wave and cyclic voltammetry, and coulometry; (4) It is operationally simple to use. Detection of genomic DNA from Mycobacterium smegmatis (a surrogate for M. tuberculosis—the main cause of tuberculosis), and from M. tuberculosis itself down to ∼0.040 ng/μL provides a proof-of-concept for the applicability of this method of screening for disease using molecular diagnostics. With minor modifications to the reagents, this method will also enable field monitoring of food and water quality.