A novel pH-responsive aptamer-molecularly imprinted hydrogel for efficient identification and separation of ampicillin in complex matrices.

Hybrids of molecular imprinting-aptamers have been used for environmental analysis; however, the weak selectivity and stability inhibited their applications in complex matrices. In this paper, the nano-scale pH-responsive aptamer-molecularly imprinted interpenetrating hydrogels (FeO@Apt-MIH) were prepared in one step by the modified sol-gel method based on the preparation principle of interpenetrating network hydrogels, with FeO as the carrier, aminopropyltriethoxysilane and methyltrimethoxysilane as functional monomers, polyethyleneimine (PEI) as the pH-responsive components, and tetraethoxysilane (TEOS) and glutaraldehyde (GA) as dual cross-linking agents. After optimizing the polymerization and extraction conditions, the pH response performance, extraction capacity and reusability of the material with highly magnetism were investigated, which could achieve magnetic separation within 5 s. The SiO coating hydrolyzed by TEOS provided a rigid backbone for interpenetrating hydrogels, which could improve the acid resistance of PEI by adjusting the isoelectric point of FeO@Apt-MIH and assist in target identification. Selectivity research showed that aptamers and functional monomers have a highly effective synergistic recognition effect on ampicillin, with the imprinting factor of 6.90 and the synergistic recognition factor of 1.48. This solid-phase microextraction material coupled to high-performance liquid chromatography with the linear range of 10-1000 μg/L and the detection limit of 7.67 μg/L enabled the selective separation and detection of ampicillin in milk and honey, with minimal sample matrix interference and recovery between 95.2 and 102 %.