IR820 is a non-invasive near-infrared (NIR) fluorescence imaging dye that belongs to the family of the heptamethine dyes and has a rigid cyclohexenyl ring, increasing molecular stability and photostability. IR820 could be used as both an imaging dye and a hyperthermia agent.1
IR820 has a little absorption in the visible range thus exhibit low autofluorescence, tissue absorbance, and scatter at NIR wavelengths (700-900 nm).
Cyanobenzothiazole (CBT) derivatives of the IR820 dye offer the opportunity to develop optimal conjugates. Cyanobenzothiazole reactive groups provide an efficient and convenient way to selectively link IR820 dyes to 1,2-aminothiol, such as Cysteine residue on various substrates (Antibodies, peptides, proteins, nucleic-acid, small molecule drug…). Cyanobenzothiazole are very reactive against 1,2-aminiothiol and also showed in a lesser extent reactivity against 1,2-diamine. Cyanobenzothiazole are non-endogeneous functional groups, thus they are not naturally present on targeting molecules (biomolecules). On the other hand, 1,2-aminothiol is present in nature, being the motif of the rare aminoacid cysteine (Cys). It is noteworthy that endogenous Cys in peptides and proteins would react with CBT derivatives only when it is present at the N-terminal position (since the amino group is needed free for the reaction). The reaction proceeds under aqueous conditions at physiological temperatures and pressures. The CBT/1,2-aminothiol combination is thus a bioorthogonal reaction.