The influence of different pH values between assembly and application environment on the surface properties of layer-by-layer assembled heparin and chitosan multilayer films was investigated.The high adsorption amount of cationic dye and high wettability on the chitosan terminated multilayer films at high environment pH may indicate the excess of free sulfate group existed on the chitosan surface.Since the ionization degree of chitosan decreased with increasing of pH,the multilayer films assembled at low pH will lead to some excess free unpaired sulfate group in higher pH application environment,which paired with ionized amino group under prepared conditions.The blood-compatibility tests performed with these films clearly demonstrated that the good anticoagulant activity of low pH assembled heparin/chitosan even on the chitosan-terminated surface.Such an easy and controlled processing by the difference of pH values between assembly and application environment may have a good potential for fabrication of biomedical device coating.
