Cy5.5 carboxylic acid is an un-activated labeling regent which has low aqueous solubility. For biomolecule labeling, the labeling reagent has low aqueous solubility, using of organic co-solvent to dissolve this molecular is necessary for efficient reaction. First, Cyanine dye should be dissolved in organic solvent and then added to a solution of biomolecule in appropriate aqueous buffer.
Cyanine 5.5 carboxylic acid instead of the drug was injected into the tumors in order to visually observe the dye release by using the in vivo imaging system (IVIS). Research show that NIR irradiation could efficiently triggered drug release from the DEPt-PEG/α-CD hydrogel in vivo [1].
Reference:
[1] Wang, X. ; Wang, C.; Zhang, Q.; Cheng, Y. Near Infrared Light-responsive and Injectable Supramolecular Hydrogels for On-demand Drug Delivery. Chemical Communications, 2016, 52, 978–981.