Mycobacterium tuberculosis piezoelectric sensor based on AuNPs-mediated enzyme assisted signal amplification

Rapid diagnosis of tuberculosis disease (TB) still remained a pressing need for TB control efforts all over the world. However, the existing detection approaches cannot satisfy demand of rapid detection of clinical Mycobacterium tuberculosis (M. tuberculosis) because of the long detection time and high cost. Herein, we proposed a new M. tuberculosis piezoelectric sensor based on AuNPs-mediated enzyme assisted signal amplification. A hairpin-shaped DNA duplex with a protrusion of the 3' end was designed. In the presence of specific 16 S rDNA fragment of M. tuberculosis, the hairpin probe was opened, which triggered the selective cleavage of hairpin probe by Exonuclease III (Exo III), resulting in the release of uncut DNA probe and target DNA. The released target DNA hybridized with another hairpin-shaped DNA duplex, and a new digestion cycle was started, thus generating large amounts of uncut DNA probes. The uncut DNA was pulled to the electrode surface by the hybridization with capture probe modified on the electrode. Subsequently detection probe labeled AuNPs was hybridized with uncut DNA and entered between the two electrodes. The AuNPs linked to hybridized detection probe were grown in the HAuCl₄ and Nicotinamide adenine dinucleotide (NADH) solution and offered the conductive connection between the gaps of electrode. The changes were monitored by the piezoelectric sensor. The piezoelectric biosensor could achieve a detection of M. tuberculosis (10²-10⁸ CFU mL^-1) within 3 h, the detection limit (LOD) was 30 CFU mL^-1. The methodology could be transformed into different microbial targets, which is suitable for further development of small portable equipment and multifunctional detection.