MDEB, a new fluorescent label for carbohydrate nanomaterial in vivo studies

Abstract Typical studies of gastral toxicity of nanoparticles are conducted using radio labeling. This tends to be quite expensive and difficult owing to the required protocols for working with these materials and the expense of both the chemical reagents and dedicated instrumentation. A possible alternative is fluorescence labeling. Fluorescence is just as sensitive as scintillation, given that scintillation is itself a fluorescence measurement and subject to the same limitations. However, most fluorophores are sensitive to changes in pH and hydrolysis reactions present in most mammalian digestive tracts. Here we report the synthesis of a new pH insensitive and hydrolitically stable fluorophore, 10-(4-(3,5-dichlorophenoxy)phenyl)-2,8-diethyl-5,5-difluoro-1,3,7,9-tetramethyl-5H-4l4,5l4-dipyrrolo[1,2-c:2',1'-f][1, 3, 2]diazaborinine (mDTEB). This fluorophore is based on the high quantum yield Boron-dipyrromethene (BODIPY) fluorescent center and is equipped with a reactive handle for convenient attachment to polysaccharides. We validate its effectiveness by labelling cellulose nano fibers (CNFs), where the importance of removing reactive lignin to prevent quenching enables preparation of homogeneously labelled bright mDTEB-CNFs for toxicity studies.