The amine reactive succinimidyl ester of MB (methylene blue) can be conjugated to peptides, proteins, drugs, polymeric materials and biomolecules with primary amine groups. ?The conjugates has a blue color that are able to complex with nucleic acids. ?Methylene blue is a well known redox dye which can be reversibly reduced to its colorless leuco form. ?Upon oxidation, the blue color of the dye is recovered.