Development of theranostic agent for imaging-guided photothermal therapy has been of great interest in the field of nanomedicine.In this work,our synthesized near-infiared (NIR) dye,IR825,is bound with human serum albumin (HSA),forming a HSA-IR825 complex with greatly enhanced fluorescence under 600 nm excitation by as much as 100 folds compared to that of free IR825,together with a rather high absorhance at 808 nm.The unique optical behavior of HSA-IR825 enables imaging and photothermal therapy at separated wavelengths both with optimized performances.As revealed by in vivo fluorescence imaging,HSA-IR825 upon intravenous injection shows high tumor uptake together with low levels of retentions in other organs.While HSA is an abundant protein in human serum,IR825 is able to be excreted by renal excretion as evidenced by high-performance liquid chromatography (HPLC) [1].