do ca2+-chelating polysaccharides reduce calcium ion release from gypsum-based biomaterials?

calcium sulphate, a widely used bone filler, may negatively affect human osteoblasts due to release of high quantities of calcium ions. to reduce this effect, an attempt was made to enrich calcium sulphate with ca2+-chelating plant and rhizobial exopolysaccharides (eps).

methodology

incubation of polysaccharide-enriched calcium sulphate composites was performed in dmem/f12 medium. ca2+ (and mg2+ and pi) levels were estimated using standardised, spectrophotometry-based kits. composite surface morphology was tested using sem technique.

results

rhizobial eps was found slightly less effective at ca2+ chelation than sodium alginate. both polysaccharides may be used as gypsum supplements in the form of setting liquids (0.3% total mass), but only sodium alginate may be used as a powder (up to 5% total mass of the composite). polysaccharide-triggered reduction of ca2+ release reached the level of 50% during the first 2.5 h of incubation, then decreased significantly.

conclusions

both tested polysaccharides possess calcium-chelating properties. however, although alginate caused a reduction in ca2+ levels in the media incubated with the gypsum samples, the reduction was too short lived to provide a long-term effect. further modification of the composite content using calcium-deficient hydroxyapatite and low-molecular weight rhizobial eps with higher solubility could bring more satisfactory results.