Stability immobilized heparin

Fig. 10. Kinetics of stabilized fibrin lysis by the (heparin + trypsin)-con-taining polymer. The arrow marks the addition of the polymer containing immobilized heparin only 1371...

Stability of Immobilized Heparin. The amount of heparin eluting from the gel beads was calculated from the amount of heparin found in the wash solvent at any time (determined using the toluidine blue technique) and the amount of heparin initially present in the heparin-PVA solution. After the first 50 h of washing, the rate of elution decreased rapidly to a low, relatively constant value of 1.67 x 10-2 xg/g wet gel min. A similar elution rate was obtained in plasma using 35S-heparin (27). Assuming a particle diameter of 180 xm and a gel density of 1.05 g/cm3, this release rate corresponds to 5.3 X 10"5 (xg/cm2 min. The rate is comparable to the release rate... 

Surface block-graft-copolymerization, based on the photochemistry of N, AT-diethyldithiocarbamate has been applied to precisely design biocompatible and functional surfaces (patterns of immobilized heparin or proteins), as well as block-grafted surfaces on polystyrene [83]. Polystyrene surfaces have also been patterned by immobilization of poly(Af-isopropylacrylamide) by photolithography, and subsequently used for regiospecific cell attachment [84]. Surface modification of polydimethylsiloxane microfluidic devices by UV induced polymer grafting improved the stability of the electroosmotic mobility and improved electrophoretic resolution of peptides [85]. 

The stability of heparin-amine complexes depends to a large extent on the structure of the constituent amine. The best results were obtained for dimethylaniline and pyridine (Table 6) 65). The amount of bound heparin is, as is seen, proportional to the amount of immobilized amine, while the molar ratio amine/heparin is predetermined by the structure of the surface. Microscopically rough surfaces were shown to prevent association between heparin and amine as the portion of the amine is sterically inaccessible for the macromolecules of heparin. 

Chymotrypsin has been successfully immobilized by carbodi-imide-mediated reaction with heparin.Catalytic properties of the modified enzyme, which is of potential importance therapeutically, were unchanged while the enzyme s thermal stability was improved. 

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