Preparation, characterization and in vitro anticoagulant activity of highly sulfated chitosan

► Sulfation of chitosan was achieved successfully via a trimethylsilylated precursor. ► Highly sulfated chitosan (DS > 2.1) could be obtained under mild reaction conditions. ► Degradation of chitosan could be closely related to free hydroxyl groups. ► Degradation reduced with increasing of degree of silylation during the reaction. ► A high DS (>2.1) was essential for the anticoagulant activity.