Adsorption of glycosaminoglycans onto coral—a new possible implant biomaterials for regeneration therapy

The adsorption of glycosaminoglycans (heparin, heparan sulfate, dermatan sulfate, highly sulfated chondroitin sulfate, chondroitin sulfate, and hyaluronan) onto coral has been investigated. Granules of natural coral of specific diameter, between 100 and 500 μm, having high content of calcium (>98%) and a homogeneous surface adsorb glycosaminoglycans with different capacity. Heparin (maximum adsorption 1.29±0.10 mg/20 mg of coral, 6.45% w/w) is adsorbed more than highly sulfated chondroitin sulfate species (maximum adsorption of 0.90±0.06 mg/20 mg of coral, 4.50% w/w), chondroitin sulfate (maximum adsorption of 0.72±0.06 mg/20 mg of coral, 3.60% w/w), dermatan sulfate (maximum adsorption of 0.70±0.06 mg/20 mg of coral, 3.50% w/w) and heparan sulfate (maximum adsorption of 0.72±0.07 mg/20 mg of coral, 3.60% w/w). Hyaluronan is not adsorbed onto granules of coral. The percentage adsorption of polyanions onto coral depends mainly on their charge density, with sulfate groups being more important than carboxyl groups. This study found no evidence that iduronic acid is more important than glucuronic acid and no role of molecular mass on the adsorption of polysaccharides onto coral was found. The adsorption of glycosaminoglycans is driven by electrostatic interactions with calcium sites of coral that are dependent on pH and blocked in the presence of large amounts of salt. Due to these peculiar properties, the combination of granules of natural coral with glycosaminoglycans makes this material potentially useful in osseointegration in bone metabolism or periodontal therapy.