Previous resear
ch from our group has demonstrated that bromoalkylation of polyurethane elastomers via basemediated a
ctivation of the urethane-hard segment nitrogen groups
can be used to either atta
ch bisphosphonategroups to
confer
cal
cifi
cation resistan
ce or append
cholesterol to promote endothelial
cell adhesion. In the presentstudies we further explore the potential of this
chemi
cal approa
ch by investigating bulk
carboxylation ofpolyurethanes via bromoalkylation to enable surfa
ce heparinization for thromboresistan
ce. Thus, polyurethane(PU) was modified with pendant 7-
carboxy-5-thiaheptyl groups using a polymer-analogous rea
ction ofbromobutylated PU with tetrabutylammonium 3-mer
captopropionate in mild
conditions. The grafting ofpolyallylamine (PAA) onto the surfa
ce of
carboxylated PU via dire
ct
coupling of amino and
carboxy groupsresulted in high levels of PAA (up to 8
![](/images/entities/mgr.gif)
g/
cm
2). The surfa
ce-aminated PU was further
covalently modified withunfra
ctionated heparin as
confirmed by FTIR. Fluores
cen
ce labeling of PAA hydro
chloride and heparin withBODIPY-FL was used to quantify the extent of surfa
ce modifi
cations. Heparin was
covalently bound at a highlevel (1.11 ± 0.06
![](/images/entities/mgr.gif)
g/
cm
2) and was shown to be a
ctive, with demonstrable Fa
ctor Xa inhibition and plateletfa
ctor IV binding. It is
con
cluded that surfa
ce amination of bulk-
carboxylated PU represents a novel approa
ch forheparinizing PU;
carboxylation followed by surfa
ce amination represents another important dimension of bromo-alkyl a
ctivation of polyurethane hard segments, thereby enabling heparinization.