Naked-Eye Colorimetric and Electrochemical Detection of Mycobacterium tuberculosis-toward Rapid Screening for Active Case Finding

Despite recent advances in detection strategies, Tuberculosis (TB) is still a significant global health problem, partly due to a lack of rapid, sensitive, and low cost methodologies. In countries with developing health care systems, there is an urgent need to rapidly screen groups of people identified to have had contact with patients diagnosed with TB in order to halt the spread of the infection in their communities. To this end, we have devised a simple colorimetric assay that utilizes the chemical oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) by isothermally functionalized DNA targets as a sensitive and specific biosensor for the detection of Mycobacterium tuberculosis. As TMB is also electrochemically active, we extended the method to electrochemical detection on cheap disposable electrodes, and compared the characteristics of both sensing methods. Our assays are inexpensive (US$3), rapid (75 min), sensitive (approaching single cell), and highly specific to M. tuberculosis. We believe that our assay could potentially enable public health officials to quickly make important decisions related to the appropriate channeling of precious healthcare resources and form part of the solution to reduce lengthy time-to-diagnosis that is commonly associated with conventional approaches in these settings.