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Magnetic particles, as well as molecularly imprinted polymers, have revolutionized separation and bioanalytical methodologies in the 1980s due to their wide range of applications. Today, biologically modified magnetic particles are used in many scientific and technological applications and are integrated in more than 50,000 diagnostic instruments for the detection of a huge range of analytes. However, the main drawback of this material is their stability and high cost. In this work, we review recent advances in the synthesis and characterization of hybrid molecularly imprinted polymers with magnetic properties, as a cheaper and robust alternative for the well-known biologically modified magnetic particles. The main advantages of these materials are, besides the magnetic properties, the possibility to be stored at room temperature without any loss in the activity. Among all the applications, this work reviews the direct detection of electroactive analytes based on the preconcentration by using magnetic-MIP integrated on magneto-actuated electrodes, including food safety, environmental monitoring, and clinical and pharmaceutical analysis. The main features of these electrochemical sensors, including their analytical performance, are summarized. This simple and rapid method will open the way to incorporate this material in different magneto-actuated devices with no need for extensive sample pretreatment and sophisticated instruments., (© 2021. Springer-Verlag GmbH Germany, part of Springer Nature.)

A new electrochemical magnetoimmunosensor (EMIS) has been developed for the screening of residues of sulfonamide antimicrobials in honey samples. The immunosensor is able to detect up to ten different sulfonamide congeners at levels below the action points established in some European countries (25 μg kg(-1)) after a hydrolysis step in which the sulfonamides are released from the corresponding conjugates formed in samples of this type. In spite of the complexity of the sample after the hydrolysis procedure, the EMIS could perform quantitative measurements, directly in these samples, without any additional sample cleanup or extraction step. For example, sulfapyridine, used as a reference, can be detected in hydrolyzed honey with a limit of detection (IC90) of 0.1 ± 0.03 μg kg(-1). Considering that the use of antibiotics for bee treatment is prohibited in the European Union, the immunosensor presented here could be an excellent screening tool. Moreover, several samples can be processed in parallel, which facilitates the analysis, reducing the necessity to use more costly confirmatory methods for just screening. As a proof of concept, a set of blind honey samples (spiked and incurred) were analyzed and the results were compared with those obtained by high-performance liquid chromatography-tandem mass spectrometry, demonstrating the potential of the EMIS as a screening tool.

An electrochemical magneto immunosensor for the detection of low concentrations of paraquat (PQ) in food samples has been developed and its performance evaluated in a complex sample such as potato extracts. The immunosensor presented uses immunoreagents specifically developed for the recognition of paraquat, a magnetic graphite-epoxy composite (m-GEC) electrode and biofunctionalized magnetic micro-particles (PQ1-BSAMP) that allow reduction of the potential interferences caused by the matrix components. The amperometric signal is provided by an enzymatic probe prepared by covalently linking an enzyme to the specific antibodies (Ab198-cc-HRP). The use of hydroquinone, as mediator, allows recording of the signal at a low potential, which also contributes to reducing the background noise potentially caused by the sample matrix. The immunocomplexes formed on top of the modified MP are easily captured by the m-GEC, which acts simultaneously as transducer. PQ can be detected at concentrations as low as 0.18 ± 0.09 μg L(-1). Combined with an efficient extraction procedure, PQ residues can be directly detected and accurately quantified in potato extracts without additional clean-up or purification steps, with a limit of detection (90% of the maximum signal) of 2.18 ± 2.08 μg kg(-1), far below the maximum residue level (20 μg kg(-1)) established by the EC. The immunosensor presented here is suitable for on-site analysis. Combined with the use of magnetic racks, multiple samples can be run simultaneously in a reasonable time.