Fucoidan, FSD Fluor™ 680 is a fluorescence labeled biopolymer that fucoidan (~30 KDa) is covalently conjugated with FSD Fluor 680.  Fucoidan is a highly sulfated polysaccharide from various species of brown algae and seaweed and known to have nanomolar affinity to P-selectin which is overexpressed on the various cancers, endothelium overlying active atherosclerotic plaques, and activated platelet. FSD 680 is the new generation of bright red dye, developed by BioActs’ cutting-edge technology, that displaying excellent optical property comparing to spectrally similar dyes. FSD 680 might be excited using the 633 nm laser line and the emission occurs at biological tissue permeable NIR region. Fucoidan, FSD Fluor™ 680 can be applicable in fluorescence imaging of various biological studies such as P-selectin overexpression in tumor cells, angiogenic blood vessels in tumors and inflammatory lesions, vulnerable atherosclerotic plaques, platelet-rich thrombus, heart ischemia, etc.