BACKGROUND:With unique structure and physicochemical property, carbon nanotubes have promising application prospects in the fields of drug delivery, biosensor and biomaterials. However, carbon nanotubes are highly hydrophobic and trend to aggregate, and thus carbon nanotubes are hard to be dispersed in solution. Furthermore, carbon nanotubes induce blood coagulation and have cytotoxicity, which greatly limit the application of carbon nanotubes. OBJECTIVE:To prepare heparinized single-wal ed carbon nanotubes and to study the effects of heparin-immobilization on the water solubility, stability as wel as biocompatibility of carbon nanotubes. METHODS:By the method of covalent grafting, heparinized single-wal ed carbon nanotubes was fabricated and characterized by Fourier transform infrared spectroscopy and carbazole assay. Transmission electron microscopy was used to investigate the dispersing performance and suspension stability of heparinized single-wal ed carbon nanotubes in aqueous solution. Anti-Xa activity and activated partial thromboplastin time assays were used to measure the anticoagulation activity of heparinized single-wal ed carbon nanotubes. MTT assay was used to evaluate the cytocompatibility of heparinized single-wal ed carbon nanotubes. RESULTS AND CONCLUSION:Heparin was covalently linked to the surface of single-wal ed carbon nanotubes successful y. The amount of heparin on single-wal ed carbon nanotubes was measured to be 257.53 mg/g. Heparinized single-wal ed carbon nanotubes were wel dispersed and stable in an aqueous solution without aggregation. The anti-Xa activity of heparinized single-wal ed carbon nanotubes was measured to be 36.53 U/mg, suggesting a significant anticoagulant activity. Further study of activated partial thromboplastin time assay found that the anticoagulant effect of heparinized single-wal ed carbon nanotubes could be prolonged. MTT assay revealed that heparinized single-wal ed carbon nanotubes had no cytotoxicity and showed good cytocompatibility. Taken together, the immobilization of heparin on single-wal ed carbon nanotubes wil not only improve its solubility and stability in water, but also endow it with excellent biocompatibility.