Dextran T3 (Dextran 3; Dextran T3(MW 2400-3600)) is a neural tracer and intestinal permeability probe that can move anterogradely and retrogradely in neuronal axons by passive diffusion. Dextran T3 (MW 3,000) is able to permeate across the intestinal epithelial cell membrane in the presence of cholera toxin-induced cytoskeletal disturbance. Dextran T3 (MW 3,000) is used as a fluorescent marker to rapidly label developing neurons (such as Xenopus retinal ganglion cells) and to assess intestinal barrier function. It can be used to study axonal transport in neuroanatomy and permeability changes in intestinal pathophysiology. The Dextran series of compounds are also natural polysaccharide drug carriers that can be connected to drugs through covalent bonding methods such as ester bonds, amide bonds or click chemistry, or self-assembled to form carriers such as nanoparticles and hydrogels. Dextran is biodegradable and biocompatible, and can achieve targeted delivery and controlled release of drugs. Dextran derivatives can prolong the half-life of drugs, increase local concentrations, and reduce the activity of immune clearance.