A novel nano-trapping matrix for enrichment and analysis of crotonaldehyde in smoker saliva

Crotonaldehyde is a harmful ingredient in cigarette smoke and poses serious health risks due to irritation of the mucous membranes and systemic toxicity, which are associated with respiratory illnesses and cancer. Thus, developing rapid detection methods for crotonaldehyde levels in biofluids is essential for effective monitoring and management. In this work, we designed a novel nano-trapping matrix for the sensitive analysis of crotonaldehyde in saliva. This nano-trapping matrix is constructed by assembling a platinum inlaid metal–organic framework (MOF) shell on a magnetic Fe₃O₄ core through a simple one-pot process and serves a dual purpose as follows. One function is as an efficient nano-trapper for enriching target analytes via π–π interactions, thereby reducing matrix interference. Another function is serving as an effective matrix for direct matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) detection. This function leverages the synergistic properties of the π-electron system in MOFs and the conductivity and high UV absorption of Fe₃O₄, along with the photoelectric abilities of Pt nanoparticles to improve ionization efficiency and enhance MS signal intensity. Thus, the traditional elution process was avoided and a simple yet sensitive analytical method was established, achieving a detection limit of 1 ng mL⁻¹. The method demonstrated good applicability by successfully capturing and detecting crotonaldehyde from saliva samples of three smokers, including one cigarette user and two e-cigarette users. Our approach offers an effective analytical tool for crotonaldehyde biomonitoring and provides a referenceable design strategy for integrated nanomaterials for the capture and direct analysis of small molecules.