Abstract: A high-efficiency magnetic separation method for Listeria monocytogenes was developed using a capture probe prepared by directly adsorbing an aptamer onto a magnetic metal-organic framework (MOF) composite (Fe3O4@MIL-100(Fe)). Under optimized conditions (7 μL of aptamer solution at 100 μmol/L, coupling time of 120 min, 0.1 mg of Fe3O4@MIL-100(Fe), addition of Ca2+, capture time of 60 min, and bacterial concentration of 103 CFU/mL), the capture efficiency (CE) for L. monocytogenes reached up to (83.87 ± 2.31)%, and the method exhibited good specificity. In the milk matrix, however, the CE decreased to 11.58%. Further analysis of key interfering components in milk (mainly casein, whey protein, and lactose) revealed that the milk matrix reduced the aptamer loading and target affinity of the capture probe through nonspecific adsorption and physical encapsulation, thereby significantly decreasing its magnetic separation efficiency. This study provides a theoretical basis for constructing anti-interference and efficient magnetic separation methods suitable for various food matrices, and offers technical support for the accurate, rapid, and sensitive detection of foodborne pathogens.

Key words: magnetic metal-organic framework composite material; Listeria monocytogenes; magnetic separation; milk matrix; interfering matrix