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The precision and versatility of CRISPR-based techniques, combined with the advantages of nucleic acid-based nanotechnology, hold great promise in transforming the landscape of molecular diagnostics. While significant progress has been made, current CRISPR-based platforms primarly focus on nucleic acid detection. To expand the applicability and fully leverage the advantages offered by CRISPR-based diagnostics, ongoing efforts explore molecular strategies to develop CRISPR sensors capable of detecting a diverse range of analytes beyond nucleic acids. In addition, challenges still persist in the adaptation of CRISPR platforms for point-of-care (POC) applications, involving concerns such as portability and automation, as well as the complexities associated with multiplexing. Here, we provide a detailed classification and comprehensive discussion of molecular strategies facilitating the conversion of non-nucleic acid target binding into CRISPR-powered outputs with an emphasis on their corresponding design principles. Furthermore, the second part of the review outlines current challenges and potential solutions for seamlessly integrating these strategies into user-friendly platforms and rapid tests specifically tailored for point-of-care (POC).

Standard methods for chemical food safety testing in official laboratories rely largely on liquid or gas chromatography coupled with mass spectrometry. Although these methods are considered the gold standard for quantitative confirmatory analysis, they require sampling, transferring the samples to a central laboratory to be tested by highly trained personnel, and the use of expensive equipment. Therefore, there is an increasing demand for portable and handheld devices to provide rapid, efficient, and on-site screening of food contaminants. Recent technological advancements in the field include smartphone-based, microfluidic chip-based, and paper-based devices integrated with electrochemical and optical biosensing platforms. Furthermore, the potential application of portable mass spectrometers in food testing might bring the confirmatory analysis from the laboratory to the field in the future. Although such systems open new promising possibilities for portable food testing, few of these devices are commercially available. To understand why barriers remain, portable food analyzers reported in the literature over the last ten years were reviewed. To this end, the analytical performance of these devices and the extent they match the World Health Organization benchmark for diagnostic tests, i.e., the Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end-users (ASSURED) criteria, was evaluated critically. A five-star scoring system was used to assess their potential to be implemented as food safety testing systems. The main findings highlight the need for concentrated efforts towards combining the best features of different technologies, to bridge technological gaps and meet commercialization requirements.

Standard methods for chemical food safety testing in official laboratories rely largely on liquid or gas chromatography coupled with mass spectrometry. Although these methods are considered the gold standard for quantitative confirmatory analysis, they require sampling, transferring the samples to a central laboratory to be tested by highly trained personnel, and the use of expensive equipment. Therefore, there is an increasing demand for portable and handheld devices to provide rapid, efficient, and on-site screening of food contaminants. Recent technological advancements in the field include smartphone-based, microfluidic chip-based, and paper-based devices integrated with electrochemical and optical biosensing platforms. Furthermore, the potential application of portable mass spectrometers in food testing might bring the confirmatory analysis from the laboratory to the field in the future. Although such systems open new promising possibilities for portable food testing, few of these devices are commercially available. To understand why barriers remain, portable food analyzers reported in the literature over the last ten years were reviewed. To this end, the analytical performance of these devices and the extent they match the World Health Organization benchmark for diagnostic tests, i.e., the Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Deliverable to end-users (ASSURED) criteria, was evaluated critically. A five-star scoring system was used to assess their potential to be implemented as food safety testing systems. The main findings highlight the need for concentrated efforts towards combining the best features of different technologies, to bridge technological gaps and meet commercialization requirements. View Full-Text

Gold nanostars (GNST), gold nanospheres (GNP) and carbon black (CB) are chosen as alternative nanomaterials to modify carbon screen-printed electrodes (c-SPEs). The resulting three kinds of modified c-SPEs (GNP-SPE, CB-SPE and GNSP-SPE) were electrochemically and microscopically characterized and compared with standardized c-SPEs after pretreatment with phosphate buffer by pre-anodization (pre-SPE). The results show outstanding electrochemical performance of the carbon black-modified SPEs which show low transient current, low capacitance and good porosity. A competitive chronoamperometric immunoassay for the shellfish toxin domoic acid (DA) is described. The performances of the CB-SPE, GNP-SPE and pre-SPE were compared. Hapten-functionalized magnetic beads were used to avoid individual c-SPE functionalization with antibody while enhancing the signal by creating optimum surface proximity for electron transfer reactions. This comparison shows that the CB-SPE biosensor operated best at a potential near − 50 mV (vs. Ag/AgCl) and enables DA to be determined with a detection limit that is tenfold lower compared to pre-SPE (4 vs. 0.4 ng mL−1). These results show very good agreement with HPLC data when analysing contaminated scallops, and the LOD is 0.7 mg DA kg−1 of shellfish.

Nowadays there is a high demand for cost-effective and user-friendly on-site screening tools in the food safety industry. Electrochemical sensors are the perfect candidates for this purpose since they combine the qualities of being miniaturized and relatively cheap at the same time. The use of carbon-based screen-printed electrodes (SPEs) is particularly ideal for on-site analysis, because of their well known low production cost, which drastically decreases the costs of the analysis. Furthermore, these SPEs can easily be modified with nanomaterials, which can result in a significant increase of their performance. In this study a characterization of in-house SPEs modified with CB and their application for the detection of different pesticides is described. Different materials have been investigated during the printing process and the working electrode has been modified with nanoparticles directly in the ink or by dropcasting either manually or using the Biodot dispenser. After an electrochemical characterization, the best performing SPE has been selected and its performance has been evaluated by using it either directly as a platform for the indirect competitive immunoassay or just as a transducer when the assay was performed using magnetic beads (MBs) as a platform for an Enzyme-Linked-Immunomagnetic-Electrochemical (ELIME) format. Both of the approaches have shown similar LOD and comparable sensitivity despite the fact that different enzymes (horseradish peroxidase and alkaline phosphatase) and different electrochemical techniques (Chronamperometry and Differential Pulse Voltammetry respectively) were applied, from which the latter approach also allows for multiplexation. Thus, the described system is a promising candidate for the development of a portable smartphone-connected device for on-site analysis.

Food contaminants monitoring is conducted in an intensive manner yet, there are still food safety scandals related to various chemical compounds. This fact highlights the need to review the requirements posed by the current legal framework on analytical methods performance and evaluate its application in published studies. Herein, we present an inventory including more than 470 publications on screening and confirmatory methods, which were used to control hazardous compounds such as pesticides, antibiotics, mycotoxins, aquatic toxins and allergens. Analytical performance characteristics, trends and state of the art, both merits and shortcomings, are critically discussed and summarized in excel tabulations. This repository highlights the ever-increasing use of screening methods and the necessity to confirm their performance by applying confirmatory methods. In conclusion, more effort is needed on validation and benchmarking, especially of newly developed technology such as smartphone-based methods, to avoid false-negative results and ensure that methods fit for purpose. © 2019 The Authors