Heparin terminally grafted with a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), was prepared by sequential steps of chemical modification of one terminal group of heparin, leading to its dithiocarbamylation as an iniferter (initiator-transfer agent-terminator), followed by quasi-living photopolymerization, thereby producing PNIPAM with a molecular weight (mol wt) ranging from 2 x 10(3), to 1 x 10(5) g/mol at the terminus of heparin (PNIPAM-heparin). The lower critical solution temperature depended on the mol wt of PNIPAM. Higher-mol-wt PNIPAM-heparin completely precipitated at 34 degreesC. The adsorptivity on the poly(ethylene terephthalate) (PET), poly(styrene) (PST), and segmented polyurethane (PU) films was assessed by wettability measurement and surface chemical compositional analysis using X-ray photoelectron spectroscopy. The temperature-dependent amount of adsorbed PNIPAM-heparin was quantitatively determined by a confocal laser scanning microscope (CLSM) using fluorescence-labeled PNIPAM-heparin. The relative degree of heparin complexation with antithrombin III (ATIII) was assessed based on fluorescence intensity using the avidin-biotinylated enzyme complex assay technique under a CSLM. The results showed that irrespective of the type of polymer films, higher-mol-wt PNIPAM-heparin adsorbed better and was more stable than lower-mol-wt PNIPAM-heparin at 40 and 20 degreesC, an effect which was more enhanced on a hydrophobic surface (PST) than on polar surfaces (PET and PU). The desorption of PNIPAM-heparin did not occur even in the serum-containing medium. In addition, higher complexation capability with ATIII was observed for higher-mol-wt PNIPAM-heparin probably due to its higher adsorption capability. The desorption of PNIPAM-heparin was noted at 20 degreesC. Thus, it is concluded that PNIPAM-heparin exhibits thermoresponsiveness of surface biofunctionality.