iFluor® 405–dextran conjugate (average molecular weight ~20,000 Da) is a water-soluble fluorescent probe composed of a 20 kDa dextran polymer covalently labeled with iFluor® 405, a bright blue-emitting fluorophore with excitation and emission maxima at ~403 nm and ~427 nm, respectively. The 20 kDa dextran backbone offers an extended hydrodynamic radius and slower diffusion properties, making it particularly suitable for studies involving macromolecular transport, extracellular diffusion, and vascular permeability. Its larger size compared to 10 kDa dextran enhances retention within extracellular spaces and limits rapid cellular uptake, facilitating its use as an extracellular tracer.

iFluor® 405 is spectrally similar to Pacific Blue® and is well-suited for detection with 405 nm excitation sources commonly available on flow cytometers and fluorescence microscopes. The conjugate demonstrates high photostability, minimal nonspecific binding, and low autofluorescence interference, making it ideal for quantitative and imaging-based applications. Supplied as a lyophilized powder, it can be readily reconstituted in aqueous buffers for use in live-cell imaging, tracer diffusion studies, endocytosis assays, and permeability measurements.