Magnetic borate-modified Mxene: A highly affinity material for the extraction of catecholamines

A novel magnetic borate-modified MXene composite was prepared by in situ growth of Fe₃O₄ particles onto the surface of phenylboronic acid modified Ti₃C₂T_x nanosheets. The magnetic composite possesses highly selective recognition properties to catecholamines, and high adsorption capacity (up to 319.6 μmol g^-1) for dopamine. Besides, the adsorption of urinary catecholamines can be accomplished within 2.0 min. The excellent adsorption performance can be assigned to its unique 2D layered structures, which helps to shorten the diffusion path and facilitate molecular transport. In addition, the multilayer adsorption and the synergetic interactions of borate affinity, van der Waals forces, hydrogen bonding and π-π stacking also contribute to the adsorption. By coupling the magnetic boronate affinity composites with high-performance liquid chromatography-fluorescence detection, a sensitive method for the determination of catecholamines in urine samples was proposed. The validation results revealed it can offer good linearities (correlation coefficients higher than 99%). The method detection limits were 0.06, 0.16, 0.03 and 0.14 ng mL^-1 for norepinephrine, epinephrine, dopamine and isoprenaline, respectively, and relative recoveries for these catecholamines were in the range of 98.56-108.1%, 92.56-110.0%, 98.79-112.3% and 88.14-97.81%, respectively. The proposed method was successfully applied to analyze the catecholamines in the urine samples from 15 healthy volunteers and 16 patients with Alzheimer's disease. The results indicated that the magnetic borate-modified Mxene composite possesses superior extraction performance, and can be used as an outstanding candidate for the extraction of catecholamines in pre-clinical or clinical studies.