Aptamer-functionalized magnetic blade spray coupled with a nucleic acid dye-based mass tag strategy for miniature mass spectrometry analysis of endoglin.

Ambient ionization mass spectrometry (AIMS) allows rapid analysis of targets, while its overall selectivity is somewhat limited due to the lack of chromatographic separation. Recently, magnetic blade spray (MBS) has enhanced AIMS by incorporating immunomagnetic beads instead of the traditional coated blade spray (CBS) coating, thereby improving selectivity and sensitivity by targeted analyte detection and reducing background interference. In this study, an aptamer-functionalized and nucleic acid dye (GelRed)-loaded MS probe (AGMP) was developed and employed with MBS-based miniature mass spectrometer. Specifically, AGMP was assembled using aptamer-functionalized magnetic nanoparticles loaded with GelRed as mass tags for highly sensitive analysis of endoglin (CD105). For the preparation of AGMP, the CD105 binding aptamer of End-A2 was first selected through three rounds of capillary electrophoresis (CE)-SELEX with an optimal affinity of 62.3 pM. After optimizing the critical parameters that affected adsorption, desorption, and ionization efficiency, this method displayed satisfactory sensitivity with detection and quantitation limits of 0.2 and 1 ng/mL, respectively, as well as reliable recoveries of 90.1-106.8 % with relative standard deviations of 1.6-5.4 %. Besides, the method effectively mitigated the matrix effects with a slope deviation of 10.03 %, and exhibited good selectivity and environmental friendliness. Furthermore, this AGMP-based MBS strategy was successfully applied for CD105 detection in serum samples, demonstrating its potential for sensitive and on-site biomolecule analysis in complex matrices.