A novel biosensor based on ball-flower-like Cu-hemin MOF grown on elastic carbon foam for trichlorfon detection

In this study, ball-flower-like Cu-hemin MOFs microstructures supported by flexible three-dimensional (3D) nitrogen-containing melamine carbon foam composites (denoted as Cu-H MOFs/NECF) were constructed. They were used for the immobilization of acetylcholinesterase (AChE) to detect trichlorfon, a widely applicable organophosphorus pesticide (OP). The formation of Cu-H MOFs/NECF was confirmed by scanning electron microscopy, X-ray powder diffraction and energy-dispersive X-ray spectroscopy. The results indicated that ball-flower-like Cu-hemin MOF microstructures were evenly grown on the fibers of 3D-NECF via a simple room temperature mixing method, which could greatly increase the effective surface area. The Cu-H MOFs/NECF composites also overcome the disadvantages of carbon foam materials such as too large pore diameters that always lead to the stacking of the protease and poor conductivity. Moreover, the composites contain nitrogen elements not only from melamine but also from hemin, which is bound to greatly increase the biocompatibility. The composites were directly used to immobilize a large number of AChE to prepare integrated AChE/Cu-H MOFs/NECF electrodes. Simultaneously, the integrated electrode showed better performance for trichlorfon detection. The sensor exhibited good stability and toughness, wide linear range (0.25-20 ng mL^-1) and low detection limit (0.082 ng mL^-1). Hence, the AChE/Cu-H MOFs/NECF trichlorfon sensor could be a valuable platform for the pesticide residues field testing.