A 3D Multiarm PEG/Aptamer-Engineered Interface with Superior Antifouling and Selectivity for Trace Aflatoxin Profiling

It is challenging to develop a highly selective and antifouling mass spectrometry (MS) ionization interface for the rapid and sensitive detection of trace analytes in complex matrices, such as aflatoxins (AFs) in Traditional Chinese Medicines (TCMs) and milk. In this study, a bifunctional 8-arm PEG derivative (NH2HCl-8armPEG10K-(MTz)7) was engineered to construct a dense hydration layer on a gold-coated stainless steel (SSS) substrate via polydopamine (PDA) chemistry. This multiarm PEG scaffold not only provides superior steric hindrance against nonspecific adsorption but also serves as a robust linker to immobilize streptavidin (SA) via an efficient copper-free click reaction. Subsequently, biotinylated aptamers targeting six AFs were immobilized with high density and specific orientation. The resulting specific ionization element (AP@SSS) exhibits outstanding anticontamination capabilities and highly specific spatial recognition ability, which has been confirmed through molecular dynamics (MD) simulations and density functional theory (DFT) calculations. After simple sample preparation, the AP@SSS can be directly coupled with ambient electrospray ionization MS, achieving a detection time <1 min. The method demonstrated high sensitivity with limits of detection (LODs) of 0.05-0.380 μg/kg and limits of quantitation (LOQs) of 0.16-1.240 μg/kg. At the same time, good accuracy (recoveries 82.1-102.5%) and precision (RSD: 2.36-17.82%) for AFs in milk and TCM matrices were obtained. The functionalized AP@SSS provides a robust and high-throughput tool for the ultrasensitive monitoring of trace toxins in complex samples.