Immobilization of zeolitic imidazolate framework-90 onto modified stainless steel wire via covalent bonding for solid-phase microextraction of biomarkers in exhalation of lung cancer patients

The improvement of the strong force between the coating and the substrate is important to make the coating for solid-phase microextraction with good stability, durability, and reproducibility during thermal and solvent desorption. In this paper, zeolitic imidazolate frameworks-90 coating was immobilized on the stainless-steel fiber via the chemical-bonded method with the help of polydopamine. The fiber was used for the solid-phase microextraction of lung cancer biomarkers prior to gas chromatography-mass spectrometry analysis. Several extraction and desorption conditions were optimized. Under the optimized conditions, the established method exhibited high enrichment factors (434–7560), low limits of detection (2.6–4.2 ng/L), wide linear ranges (0.02–30 μg/L), good repeatability (3.46%–9.37% for intra-day, 4.11%–9.18% for inter-day, n = 6) and reproducibility (5.37%–7.02%, n = 3). Moreover, the coated fiber is thermally stable and can be reused at least 100 cycles of extraction/desorption/conditioning without significant loss of extraction efficiency and precision. Eventually, the self-made coated fiber combined with gas chromatography-mass spectrometry was successfully applied to the extraction and detection of five biomarkers of lung cancer from real breath samples with a satisfactory recovery (96.6%–117.6%).