The role of regioselectively sulfated and acetylated polysaccharide coatings of biomaterials for reducing platelet and plasma protein adhesion

A brief survey is given about the role of natural polysaccharides such as h eparin (HE), heparan sulfate (HS), chondroitin sulfate (CS), and dermatan s ulfate (DS) in reducing blood coagulation and their potential use as athrom bogenic coatings in the development of tailor-made athrombogenic biomateria ls. Furthermore, known literature and new results about platelet adhesion o n regioselectively modified polysaccharides such as HE, chitosan with HE-li ke functional groups, and sulfated cellulose are presented in two different perfusion systems at different shear rates. Regioselectively modified poly saccharides were tested as coatings of two polymers. The strongest influenc e on platelet adhesion was observed when the three regioselectively modifie d polysaccharides contained 6-O-sulfo- groups. No or little influence was s een with 3-O-sulfo- groups. A variable effect on platelet adhesion was foun d in position 2. N-sulfo- groups in HE induced a medium platelet adhesion, and O-sulfo- groups of iduronic acid moiety in HE induced none. Cellulose c ontaining 2-O-sulfo- groups induced little platelet adhesion, and 2-N-sulfo - groups in chitosan induced a variable platelet adhesion response, dependi ng on the N-SO3/NAc ratio. Preliminary plasma protein adhesion measurements on immobilized HE derivatives with four different fluorescence-labeled pla sma proteins showed a regioselective influence with serum albumin and fibri nogen. 6-O-desulfated HE gave the strongest reduction in protein adsorption followed by N-desulfation and 2-O-desulfation; the lowest reduction was ob served with 3-O-desulfation. Tailor-made athrombogenic coatings of HE shoul d not carry high amounts of 6-O-sulfo- groups or of N-sulfo- groups. Regios electively modified cellulose and chitosan may become suitable for tailor-m ade athrombogenic biomaterials when regioselective reactions are further op timized.