Visualization methods for loop mediated isothermal amplification (LAMP) assays

Recent advances in nucleic acid (NA) detection techniques have significantly enhanced the diagnosis of diseases caused by a range of pathogens. These NA-based methods that target specific gene sequences for identification offer high specificity. Despite the effectiveness of polymerase chain reaction (PCR), its requirement for sophisticated laboratory settings and expensive equipment restricts its accessibility, particularly in resource-limited settings. As an alternative, isothermal nucleic acid amplification methods are highly sought after due to their rapid, sensitive, and specific detection ability. Among these, loop mediated isothermal amplification (LAMP) stands out due to its simplicity, reliability, and cost-effectiveness. LAMP operates without the need for varied temperature cycles, employing a simple heating block to maintain a constant temperature, thus facilitating onsite rapid testing. In LAMP, the detection step is critical as it shows the outcome of the assay. In order to make the LAMP technique user-friendly and applicable for large scale testing, it is critical to have visual detection where the results can be observed with the naked eye. This review focuses on recent developments of LAMP visualization techniques, including the more common fluorescence, turbidity, and gel electrophoresis methods, as well as innovations in colorimetric techniques applying novel transduction methods such as nanoparticles and digital tools. Additionally, various practical applications of LAMP are discussed.