Design of bioresorbable calcium phosphate cement with high porosity via the addition of bioresorbable polymers

Novel calcium phosphate cements (CPCs) that can be resorbed into the human body need to be developed. One approach for improving bioresorbability is reducing the content of calcium phosphate in CPCs; however, this may induces difficulties in setting the cement and increases the risk of decay. Adding bioresorbable polymers to a liquid solution can shorten the setting time and inhibit decay during setting. A novel bioresorbable polymer, phosphorylated pullulan (PPL), was recently reported. The effect of adding PPL to α-tricalcium phosphate (α-TCP)-based CPCs was examined and compared to that of adding bioresorbable polymers such as collagen, chitosan, and alginate. Collagen did not significantly inhibit the conversion of α-TCP to hydroxyapatite (HA), and its combination with calcium phosphate decreased the setting time and suppressed decay; chitosan decreased the setting time when combined with calcium phosphate; and alginate inhibited the conversion of α-TCP to HA and contributed to suppressing the decay. In contrast, PPL slightly inhibited the conversion of α-TCP to HA; however, its combination with calcium phosphate decreased the setting time. Thus, selecting bioresorbable polymers can help effectively control the properties of CPCs.