Simultaneous electrochemical determination of nuc and mecA genes for identification of methicillin-resistant Staphylococcus aureus using N-doped porous carbon and DNA-modified MOF

Abstract

The detection of Staphylococcus aureus specific gene in combination with the mecA gene is vitally important for accurate identification of methicillin-resistant Staphylococcus aureus (MRSA). A homogeneous electrochemical DNA sensor was fabricated for simultaneous detection of mecA and nuc gene in MRSA. Metal-organic framework (type UiO-66-NH₂) was applied as nanocarrier. Two electroactive dyes, methylene blue (MB) and epirubicin (EP), were encapsulated in UiO-66-NH₂, respectively, and were locked by the hybrid double-stranded DNA. Based on the target-response electroactive dye release strategy, once target DNA exists, it completely hybridizes with displacement DNA (D_EP and D_MB). So D_EP and D_MB is displaced from the MOF surface, causing the release of electroactive dyes. Co-Zn bimetallic zeolitic imidazolate framework-derived N-doped porous carbon serves for electrode modification to improve electrocatalytic performance and sensitivity. The differential pulse voltammetry peak currents of MB and EP were accurately detected at - 0.14 V and - 0.53 V versus the Ag/AgCl reference electrode, respectively. Under the optimal conditions, the detection limits of mecA gene and nuc gene were 3.7 fM and 1.6 fM, respectively. Combining the effective application of MOFs and the homogeneous detection strategy, the sensor exhibited satisfactory performance for MRSA identification in real samples. The recovery was 92.6-103%, and the relative standard deviation was less than 5%. Besides, MRSA and SA can also be distinguished. This sensor has great potential in practical applications.

Keywords: Co-Zn bimetallic ZIF; Differential pulse voltammetry; Electrochemical DNA sensor; Foodborne bacteria; Modified electrode; UiO-66.