A Review of Methylene Blue’s Interactions with DNA and Their Relevance for DNA-Based Sensors

Almost since methylene blue was discovered in the late 19th century, its optical and redox properties have been used in a variety of molecular sensing applications. This review focuses on the properties, interactions, and in vitro uses of methylene blue with double- and single-stranded DNA, particularly within the context of molecular sensing assays. We provide our assessment of how methods based on the interaction of methylene blue and DNA compare to other detection and quantification methods for sensing DNA and other molecules. There are three properties of methylene blue that are particularly salient for assay development. First, methylene blue does not specifically bind DNA, and thus, in complex samples, it is a poor reporter for assays that use the binding properties of methylene blue to drive the assay specificity. Second, methylene blue generates singlet oxygen when it interacts with light between 580 and 700 nm; singlet oxygen is a highly reactive species that may impact the performance and variability of some assay formats over time. Third, despite a voltage potential peak close to that of oxygen reduction, methylene blue is one of the more favorable redox reporters currently described.