Thermoregulated extraction of luteolin under neutral conditions using oligo(ethylene glycol)-based magnetic nanoparticles with Wulff-type boronate affinity

Boronic acid-functionalized magnetic porphyrin-based covalent organic framework for selective enrichment of cis-diol-containing nucleosides

In this study, a novel boronic acid-functionalized magnetic porphyrin-based covalent organic framework (COF) with a core-shell structure was designed and synthesized for the selective enrichment and detection of nucleosides. Firstly, brominated porphyrin-based COF was in situ grown on Fe3O4-NH2 nanospheres (denoted as Fe3O4@Br-COF), then a post-synthetic modification strategy was used to introduce boronic acid into the framework via Suzuki-Miyaura cross-coupling reaction to obtain boronic acid functionalized magnetic COF (denoted as Fe3O4@BA-COF). Suzuki-Miyaura cross-coupling possesses the advantages of mild synthesis conditions, high tolerance to functionalities, and ease of handling and separation, which is considered as a promising candidate for functionalizing COF. It is worth mentioning that the porphyrin-based COF possesses a unique nitrogen-rich skeleton and "trap" structure formed by four pyrrole rings, which can provide hydrogen bond and make it more suitable for trapping analytes than other types of COF. The boronic acid group provides boronate affinity, which enables better selective enrichment of cis-diol-containing nucleoside. The morphology and structure of the prepared Fe3O4@BA-COF was characterized by various methods. Based on the Fe3O4@BA-COF, a facile magnetic solid phase extraction coupled with high performance liquid chromatography method (MSPE-HPLC) was used to extract and detect adenosine, guanosine, uridine, and cytidine in urine samples. This work not only provides a mild and feasible post-synthetic modification method for fabrication of boronic acid-functionalized magnetic COF, but also provides an efficient and rapid method to selectively enrich and detect hydrophilic nucleosides.

Design, Preparation, and Application of Magnetic Nanoparticles for Food Safety Analysis: A Review of Recent Advances

This review (with 126 references) aims at providing an updated overview of the recent developments and innovations of the preparation and application of magnetic nanoparticles for food safety analysis. During the past two decades, various magnetic nanoparticles with different sizes, shapes, and surface modifications have been designed, synthesized, and characterized with the prospering development of material science. Analytical scientists and food scientists are among the ones who bring these novel materials from laboratories to commercial applications. Powerful and versatile surface functional groups and high surface to mass ratios make these magnetic nanoparticles useful tools for high-efficiency capture and preconcentration of certain molecules, even when they exist in trace levels or complicated food matrices. This is why more and more methods for sensitive detection and quantification of hazards in foods are developed based on these magic magnetic tools. In this review, the principles and superiorities of using magnetic nanoparticles for food pollutant analysis are first introduced, like the mechanism of magnetic solid phase extraction, a most commonly used method for food safety-related sample pretreatment. Their design and preparation are presented afterward, alongside the mechanisms underlying their application for different analytical purposes. After that, recently developed magnetic nanoparticle-based methods for dealing with food pollutants such as organic pollutants, heavy metals, and pathogens in different food matrices are summarized in detail. In the end, some humble outlooks on future directions for work in this field are provided.