Direct and rapid detection of serum amino acid and monoamine neurotransmitters to assist the diagnosis of panic disorder

The measurement of amino acid and monoamine neurotransmitters (NTs) in serum plays a central role in the identification and monitoring of clinical panic disorder (PD). However, the strong polarity and chemical heterogeneity of NTs make direct extraction and rapid detection extremely challenging. Herein, we developed a strategy that integrated solid phase extraction based on magnetic Fe₃O₄ coated with polydopamine (Fe₃O₄@PDA) and direct analysis of mass spectrometry in real time (DART-MS) for quantification of 10 NTs. We systematically investigated the optimal conditions of this strategy to achieve good accuracy and precision. Compared with existing magnetic solid phase extraction methods for NTs detection in biological samples, this strategy could adsorb more targets while having similar adsorption efficiencies, and the total process time was reduced by an average of 69.42%. We rapidly determined the metabolic abnormality of 6 types of NTs in the serum of PD patients and demonstrated their diagnostic accuracy. In addition, an outstanding feature of PD in which tryptophan was more metabolized by the KYN pathway and the 5-hydroxytryptamine pathway was inhibited could be elucidated by this strategy. Our results highlighted the potential ability of Fe₃O₄@PDA coupled with DART-MS to assist in the clinical diagnosis of PD.