Conductive nano-gold self-assembled MXene@hemin with high catalytic activity achieved by strong metal-support interactions: A powerful nanozyme for development of electrochemical aptasensor in tuberculosis diagnosis

Despite multiple advances in tuberculosis (TB), there is still a lack of effective methods available for its diagnosis. To this end, we developed a novel nanozyme-mediated electrochemical aptasensor for TB diagnosis. We showed that hemin decorated with multi-layered MXene enhanced the metal-support interaction with nano-gold via charge transfer, resulting in excellent peroxidase-like activity aside from the highly conductive feature. The Km value of hemin functionalized MXene decorated with nano-gold (MXene@hemin-Au) was 0.37 mM and 0.23 mM for H2O2 and TMB, respectively, which was smaller to that of MXene@hemin (4.01 mM and 0.39 mM) or horseradish peroxidase (3.7 mM and 0.434 mM), indicating its high affinity to both substrates, showing improved stability in harsh conditions and excellent biocompatibility. Given these advantages, an ultrasensitive detection method was established based on a typical sandwich format using a combination of specific Mycobacterium tuberculosis (MTB) ESAT-6 antigen aptamers with MXene@hemin-Au as probes for signal amplification and gold nanoparticles supported nitrogen-doped carbon nanotube (N-CNTs-Au) as a sensing platform. It exhibited a wide detection linear for ESAT-6 antigen from 100 fg mL−1 to 50 ng mL−1, with limit of detection and limit of quantification of 2.36 fg mL−1 and 7.87 fg mL−1, respectively. For its diagnostic application, of note, the proposed method outperformed diagnostic performance for TB in contract to a commercial ELISA method in terms of specificity (100% vs. 20.59%) and area under curve (0.987 vs. 0.596), verifying its great potential in clinical practice.