The genotyping of a single-nucleotide polymorphism (SNP) is addressed through methods based on loop-mediated isothermal amplification (LAMP) combined with user-friendly optical read-outs to cover the current demand for point-of-care DNA biomarker detection. The modification of primer design and reaction composition improved the assay selectivity yielding allele-specific results and reducing false-positive frequency. Furthermore, the reduced cost, ease of use and effectiveness of colorimetric detection (solution and hybridisation chip formats) were availed for the image capture by a smartphone, reching high sensitivity. In order to evaluate their discriminating capacities, LAMP-based methods were applied to human samples to genotype a SNP biomarker (rs1954787) located in the GRIK4 gene and related to the treatment response to anti-depressants drugs. Sensitive (limit of detection: 100 genomic DNA copies), reproducible (< 15% error), fast (around 70 min) and low-cost assays were accomplished. Patient subgroups were correctly discriminated, agreeing with reference sequencing techniques. The achieved analytical performances using the developed amplification-detection principles confirmed the approach potential for point-of-care optical DNA testing.

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Sensitive precise measurements were taken (high signal-to-noise ratios, 10-Pm image 24 resolution, 99% scan-to-scan reproducibility). These features confirmed their potential as 25 analytical tools, are a competitive alternative to fluorescence scanners, and incorporate additional advantages, such as user-friendly interface and connectivity for telemedicine needs.The analytical performances of the integrated platform (assay and reader) in the human samples were also excellent, with a low detection limit (100 genomic DNA copies), and reproducible (<15%) and cheap assays (< 10 €/test). The correct genotyping of a genetic biomarker (singlenucleotide polymorphism located in the GRIK4 gene) was achieved as the assigned genotypes agreed with those determined by using sequencing. The portability, favourable discriminating and read-out capabilities reveal that the implementation of mass-produced low-cost devices into minimal-specialised clinical laboratories is closer to becoming a reality.

Until the 1970s, determining a DNA sequence was very difficult and laborious. However, in 1976-1977, two different rapid sequencing methods were simultaneously developed. The first one, developed by A. Maxam and W. Gilbert, was based in the chemical modification of the target DNA, followed by cleavage in specific positions (161). The other technique, created