Simultaneous measurement of different substances from a single sample is an emerging issue for achieving efficient and high-throughput detection in several fields of application. Although immunoanalytical techniques have well-established and prevailing advantages over alternative screening analytical platforms, one of the incoming challenges for immunoassay is exact multiplexing. Lateral flow immunoassay (LFIA) is a leading immunoanalytical technique for onsite analysis, thanks to its simplicity, rapidity, and cost-effectiveness. Moreover, LFIA architecture is adaptable to multiplexing, and is therefore a possible answer to the pressing demand of multiplexing point-of-need analysis. This review presents an overview of diverse approaches for multiplex LFIA, with a special focus on strategies based on new types of magnetic, fluorescent, and colored labels.

Mycotoxins are toxic metabolites of certain fungi that growth on a variety of crops, pre-harvest, during and post-harvest. Because of their toxicity, maximum admissible levels of mycotoxins are regulated worldwide and monitoring of their occurrence in several commodities is mandatory for assuring food safety and consumers' health protection. Analytical methods for mycotoxins include immunochemical-based techniques that principally apply for routinely controls and rapid, on-site detection, and chromatographic-based techniques that provide sensitive, accurate and selective determination of known mycotoxins, besides identification of new or modified compounds through tandem mass spectrometric detectors.

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Natural toxin (for example mycotoxin and phycotoxin) contamination of food is of safety and economic concern, so much effort is devoted to the development of screening methods which enable the toxins to be continuously and widely monitored in food and feed. More generally speaking, rapid and non-instrumental assays for detection of a variety of food contaminants are generating ever-increasing scientific and technological interest because they enable high-throughput, economical, on-site monitoring of such contaminants. Among rapid methods for first-level screening of food contaminants, lateral-flow immunoassay (LFIA), also named immunochromatographic assay or immune-gold colloid immunoassay, has recently attracted scientific and industrial interest because of its attractive property of enabling very rapid, one-step, in-situ analysis. This review focuses on new aspects of the development and optimization of lateral-flow devices for mycotoxin and phycotoxin detection, including strategies for management of matrix interference and, particularly, for investigation of the improvements achieved by signal-enhancing strategies or by application of non-gold nanoparticle signal reporters.

In the current paradigm about molecular imprinting, the imprinted binding sites exist as a consequence of the polymerization process around templates, and the properties of non-imprinted polymers (NIPs) has been largely overlooked. Thus, nothing can be affirmed a priori on the binding properties of NIPs. We propose an alternative view where the imprinting effect is due to the presence of a template molecule which enhances the pre-existing binding properties of a polymer. If a NIP shows no binding properties towards a target molecule the corresponding imprinted polymer (MIP) will show a weak imprinting effect. On the other hand, if a NIP shows binding properties towards a target molecule, the corresponding MIP will show a significant imprinting effect. To verify this hypothesis we prepared a 96-member combinatorial polymeric library in the absence of any template molecule. This library was screened for several potential ligands and, with no exceptions, the composition of the best binding NIP produced a MIP with excellent binding properties, whereas a low binding NIP formulation produced a MIP with comparable low binding. To validate these results the binding properties towards naproxen and ibuprofen were measured for two combinatorial libraries of polymers, prepared in the presence (MIP-library) and the absence (NIP-library) of the template molecule. The experiment's results showed a correlation between the apparent affinity constant measured for the NIP-and the MIP-library, confirming the proposed hypothesis. Moreover, for closely related molecules, it was shown that binding selectivity is an emergent property derived from the imprinting process, and not a property of NIPs.

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Silver nucleation on gold has been exploited for signal amplification and has found application in several qualitative and quantitative bio-sensing techniques, thanks to the simplicity of the method and the high sensitivity achieved. Very recently, this technique has been tentatively applied to improve performance of gold-based immunoassays. In this work, the exploitation of the signal amplification due to silver deposition on gold nanoparticles has been first applied to a competitive lateral flow immunoassay (LFIA). The signal enhancement due to silver allowed us to strongly reduce the amount of the competitor and of specific antibodies employed to build a LF device for measuring ochratoxin A (OTA), thus determining the attainment of the high sensitive assessment of OTA contamination, with a sensitive gain of more than 10-folds compared to the gold-based LFIA that used the same immunoreagents and to all previously reported LFIA for measuring OTA. In addition, a less sensitive "quantitative"-LFIA could be established, by suitably tuning competitor and antibody amounts, which was characterized by reproducible and accurate OTA determinations (RSD% 6-12%, recovery% 82-117%). The quantitative system allowed a reliable OTA quantification in wines and grape musts at the μg/l level requested by the European legislation, as demonstrated by agreeing results obtained through the "quantitative" silver enhanced-LFIA and a reference HPLC-FLD on 30 samples.

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