Methylene blue is one of the oldest organic dyes. It was first prepared in 1876 by H. Caro—BASF’s research director at the time—for use as a cotton dye. In 1880, microbiologist R. Koch established it as a medical stain. It is also used as an indicator for redox reactions, a photosensitizer for generating singlet oxygen, and a drug to treat methemoglobinemia, among other conditions. Until recently, dyestuff-grade methylene blue was used in medicine, but a pharmaceutical grade is now under development.
MOTW update:
February 10, 2025
Methylene blue1 is an organic dye that dates back to 1876 for use on cotton fabrics. It has since been used for other purposes, such as a medical stain, an antifungal agent, a redox reaction indicator, and a photosensitizer for generating singlet oxygen. Last month, Jan A. Mennigen and co-workers at the University of Ottawa reported on the effects of methylene blue on zebrafish (Danio rerio), which are widely used as model organisms in biological research. Zebrafish embryos are typically reared in media containing methylene blue as an antifungal; but the researchers found that the dye can confound behavioral assays on the larval fish. The authors conclude that the use of methylene blue in zebrafish research should be reconsidered.
1. CAS Reg. No. 61-73-4.
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