Rapid screening drug susceptibility test in tuberculosis using sandwich electrochemical immunosensor

Drug susceptibility testing (DST) for Mycobacterium tuberculosis currently faces multiple challenges, including lengthy ineffective standard methods, the expensive cost of molecular tests, and large bulky diagnostic machines. In this work, a disposable MPT64 sensor was developed to rapidly determine drug susceptibility (DS-TB) and multidrug resistant tuberculosis (MDR-TB) using an electrochemical sandwich-immunosensor for the detection of MPT64 as an indicator of Mycobacterium tuberculosis growth. Anti-MPT64 (as capture antibody; cAb) was immobilised on screen printed carbon electrodes to specifically bind with MPT64 target protein. A reporter probe of anti-MPT64 conjugated with horseradish peroxidase (HRP labeled rAb) then completed the sandwich immunocomplex. The current signals were received from the catalytic reaction between 3,3'-5,5'-tetramethylbenzidine (TMB), H₂O₂ and HRP labeled rAb using the chronoamperometric mode on a portable potentiostat. Increasing MPT64 concentration was taken as an indicator of growth, which was measured by the disposable MPT64 sensor. This sensor shows the possibility of determining DST by comparing the signals of DS-TB and MDR-TB growth in drug-free and drug-containing liquid medium. The time required to identify DS-TB and MDR-TB in pure culture MTB and leftover sputum sediments from patients are 3 days and 4-6 days, respectively. Therefore, using this sensor is significantly rapid and inexpensive and has the potential to be used for drug susceptibility testing of tuberculosis in middle to low income countries.