Cellulose phosphates as biomaterials. II. Surface chemical modification ofregenerated cellulose hydrogels

Cellulose regenerated by the viscose process was previously investigated as an implantable material in orthopedic surgery. It was envisaged to take ad vantage not only of its good matching with mechanical properties of bone bu t also of its hydroexpansivity, therefore allowing a satisfactory fixation to hard tissue. Both the osteoconduction and the lack of osteoinduction of this material were demonstrated. Grafting of phosphate groups was then envi saged as the means to render cellulose more suitable for orthopedic applica tions by enhancing its bioactivity. In the present work, the previously opt imized phosphorylation reaction was successfully adapted to the surface mod ification of regenerated cellulose. Modified materials were characterized b y XPS, FTIR, and P-31 MAS NMR spectroscopic studies, and contact angle meas urements, revealing the chemical bond between phosphate groups and cellulos e, as well as the hydrophilic nature of phosphorylated materials, which inc reases with increasing phosphate contents. Water swelling and resistance to gamma sterilization were assessed as well, showing that phosphorylated mat erials swell considerably in water and were not affected when sterilization was carried out under a nitrogen atmosphere. The increase in surface rough ness attributed to chemical modification was demonstrated through laser rug osimetry measurements. (C) 2001 John Wiley & Sons, Inc.