Hyaluronic Acid

Chemical derivatization of HA - HylansA general method to cross-link HA chains is based on the reaction of formaldehyde(or other agents, such as dimethylurea, dimethylolethyleneurea, ethylene oxide,polyaziridine, or polyisocyanate) and HA at a neutral pH, which involvespolysaccharide hydroxyl groups and protein amino or imino groups. The protein linksof the HA chains are reflected by the jelly behavior of the solution. Under properreaction conditions, two to eight HA molecules are connected. The MW of hylans,prepared by this method, varies between 8 10 6 and 24 10 6 Da. The protein contentis from 0.4 to 0.8%. Another method used the reaction between divinyl sulfone (DVS)and the hydroxyl groups of HA. DVS reacts readily with HA in aqueous alkalinesolutions at room temperature to provide cross-linked HA gels. The reaction is veryfast, and strong gels are obtained within minutes.29