Fluorescent lateral flow assay strip for Mycobacterium tuberculosis and Mycobacterium smegmatis based on mycobacteriophage tail protein and aptamer

Timely and facile monitoring of Mycobacterium tuberculosis (M. tuberculosis) plays an important role for preventing and controlling tuberculosis infection. Mycobacterium smegmatis (M. smegmatis) has long been employed as a safe surrogate for the investigation of M. tuberculosis. In this work, an aqueous soluble tail protein derived from our previously isolated mycobacteriophage was prepared with a recombinant expression technique and noted as GP89, which shows noticeable binding capacity to Mycobacterium genus. GP89 was sprayed as a capture agent onto a nitrocellulose membrane for forming the test line of a lateral flow assay (LFA) strip. Moreover, an aptamer binding M. tuberculosis and M. smegmatis was labeled with fluorescent microspheres to act as the signal tracer of the LFA method. With the GP89 based LFA, M. tuberculosis and M. smegmatis can be detected with the aid of a handheld UV flashlight or a portable fluorescent strip reader within 10 min. The concentration range for quantitating M. tuberculosis and M. smegmatis are both 1.0 x 10(2) CFU mL(-1) - 1.0 x 10(6) CFU mL(-1), and the detection limits for the two mycobacteria are 2.0 and 24 CFU mL(-1) (S/N = 3), respectively. The test strip was applied to detect M. tuberculosis and M. smegmatis in different samples such as physiological salt solution, urine, and saliva. This study offers a promising screening tool for diagnosing M. tuberculosis infection in resource-limited institutes.