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Lithium administration is a commonly prescribed treatment for some mental disorders, e.g. bipolar disorder. However, Li+ level must be regularly monitored to maintain therapeutical effect and avoid adverse side effects. Currently, it is determined in blood, using complex instrumentation, which excludes self-monitoring of lithium concentration by patients themselves. That creates a need for simple, reliable and fast sensors for Li monitoring in biological fluids. In this paper, we introduced a microfluidic thread-based analytical device for optical determination of lithium in saliva. Lithium ion recognition was achieved by incorporating of chromoionophore- ionophore chemistry onto thread. To ensure appropriate selectivity over other alkaline metal ions, it was necessary to include an efficient lithium extractant in the sensing cocktail, alongside its usual components. After optimization of cocktail composition, the developed sensors allowed for lithium determination in a range from 8.8⋅10−4 to 0.95 mol L−1 with remarkable precision of 0.3% (at 10−2 mol L−1) and within a very short time of ca. 10 s. The analytical usefulness of the developed sensors was tested with saliva samples, which were analyzed without any prior processing. A comparison of the obtained results with a reference method revealed high ac- curacy (relative error < ±20% in most cases)., This work was founded by Spanish “Ministerio de Economía y Competitividad” (Projects PID2019-103938RB-I00) and Junta de Andalucía (Projects B-FQM-243-UGR18 and P18-RT-2961). The projects were partially supported by European Regional Development Funds (ERDF). These investigations were also supported by Polish National Science Centre (Project PRELUDIUM no. 2021/41/N/ST4/00299).

Supplementary data to this article can be found online at https://doi. org/10.1016/j.bios.2023.115268, The COVID-19 pandemic has highlighted the need for innovative approaches to its diagnosis. Here we present CoVradar, a novel and simple colorimetric method that combines nucleic acid analysis with dynamic chemical labeling (DCL) technology and the Spin-Tube device to detect SARS-CoV-2 RNA in saliva samples. The assay includes a fragmentation step to increase the number of RNA templates for analysis, using abasic peptide nucleic acid probes (DGL probes) immobilized to nylon membranes in a specific dot pattern to capture RNA fragments. Duplexes are formed by labeling complementary RNA fragments with biotinylated SMART bases, which act as templates for DCL. Signals are generated by recognizing biotin with streptavidin alkaline phosphatase and incubating with a chromogenic substrate to produce a blue precipitate. CoVradar results are analysed by CoVreader, a smartphone-based image processing system that can display and interpret the blotch pattern. CoVradar and CoVreader provide a unique molecular assay capable of detecting SARS-CoV-2 viral RNA without the need for extraction, preamplification, or pre-labeling steps, offering advantages in terms of time (similar to 3 h/test), cost (similar to epsilon 1/test manufacturing cost) and simplicity (does not require large equipment). This solution is also promising for developing assays for other infectious diseases., FEDER/Junta de Andalucia-Consejeria de Economia y Conocimiento CV20-77741, A-FQM-760-UGR20, PID 2019-110987RB-I00, PID 2019-103938RB-I00, Spanish MCIN/AEI P18-RT-2961, P18-TP-4160, FEDER/Junta de Andalucia-Consejeria de Salud y Familias PIP-0232-2021, European Commission, MCIN/AEI PTQ 2020-011388, IJC 2020-043307-I, European Union NextGenerationEU/PRTR PTQ 2020-011388, IJC 2020-043307-I