Homogeneous fluorescent aptasensor for active tuberculosis diagnosis by direct quantification of circulating TB7.7 based on aptamer beacon with graphene oxide

•Washing-free fluorometric aptasensor for M. tuberculosis biomarker, TB7.7.•TB7.7 aptamer and TB7.7-responsive aptamer beacon were developed for the first time.•Aptamer beacon- and GO-based dual quenching enhances signal-to-background ratio.•Clinical validation of circulating TB7.7 in human serum as a biomarker for active TB.•Simple and cost-effective (<$1/test) molecular diagnostics for active TB.