An flavin adenine dinucleotide (FAD) aptamer-based sensor was constructed with gold nanoparticles (AuNPs) as the main body, and methanobactin (Mb) and FAD as the ligands. Mb was used to wrap AuNPs, which has a strong adsorption capacity for Mb, to form a stable Mb-AuNPs structure. The Mb-AuNPs structure was used to modify the surface of the bare gold electrode by the drip-coating method, and FAD was introduced into the Mb-AuNPs structure, in which the‒COOH groups could firmly bind to FAD, to improve the ability to recognize glucose. As a result, a novel aptamer biosensor with glucose oxidase-like activity could be constructed. Cyclic voltammetry and the time-current curve method were used to explore the feasibility of its application in glucose detection. At 25 ℃ and pH 7.2, there was a good linear relationship between glucose concentration in the range of 10–200 μmol/L and the response current of the biosensor, with a correlation coefficient (R²) of 0.99791, and the detection limit was 4.22 × 10^-8 mol/L (R_SN = 3). The aptamer-based sensor has several advantages such as simple preparation, low price, easy operation and rapid detection.

In this study, a methanobactin (Mb)-coupled lipase biosensor was constructed based on the fact that Mb can specifically capture Cu²⁺. Lipase immobilized on gold nanoparticles (Lipase@AuNPs) was successfully prepared and its structure and morphology were characterized by fluorescence, ultraviolet-visible (UV-vis) and Fourier transform infrared spectroscopy (FTIR) and scanning transmission electron microscopy (STEM). The biosensor could monitor the response of electrical signals during the hydrolysis of triolein by lipase. Cu²⁺ specifically combined with Mb and was enriched around lipase, which inhibited the catalytic activity of lipase and significantly reduced the current intensity, thus allowing rapid qualitative and ultra-trace reverse quantitative detection of Cu²⁺. The results showed that the optimal detection conditions, as determined by differential pulse voltammetry (DPV), were as follows: substrate concentration 2 g/100 mL and buffer pH 7.5. The sensor current difference had a good linear relationship with Cu²⁺ concentration in the range of 1–100 nmol/L. The regression equation was as follows: y = 0.228x + 0.7748, with a correlation coefficient (R²) of 0.9950, and the detection limit of this method was 0.03 nmol/L (R_SN = 3). Therefore, the new lipase biosensor has high sensitivity, specificity and stability, which lays a research foundation for the detection of trace and ultra-trace heavy metals in foods.