Y-type molecular sieve framework for efficient enrichment of urinary serotonin prior to screening for type 2 diabetes by LC-MS/MS.

A distinctive adsorption behavior of serotonin in ultrastable Y-type molecular sieve (USY) has been found in 13 molecular sieves, which is suggestive of a unique capability of USY as a dispersive solid-phase microextraction (D-µSPE) agent. Experimental analysis and GFN2-xTB calculation reveal that the adsorption of serotonin in USY conforms to Langmuir isotherm model, and the electrostatic interactions and the plausible horizontal adsorption mode between serotonin and USY are main factors for efficient adsorption in solution. Under the optimal conditions, the D-µSPE-LC-MS/MS method shows lower instrumental detection limit and method detection limit at around 0.5 and 0.025 µg L-1 for serotonin, with the intra-day and inter-day precision and recoveries in the range of 2.7-5.1% and 98.3-101.3% in real urine quantified by the isotope-labelled standard solutions. Nonparametric test shows that the median concentration of serotonin in urines of type 2 diabetes mellitus (T2DM) patients is remarkably lower than that in healthy volunteers, with tryptophane (Try) showing an opposite trend, and thus the Try/serotonin ratio has a significant advantage in T2DM screening, revealed by the area under the receiver operating characteristic curve (AUC), DeLong's test, 10-fold cross-validation, and multivariate logistic regression analysis. This work not only provides a simple, rapid and efficient detection method for urinary serotonin but also shows a possibility of Try/serotonin as a biomarker index in T2DM screening.