Calcium phosphate cement reinforcement by polymer infiltration and in situ curing: a method for 3D scaffold reinforcement.

This study describes a novel method of calcium phosphate cement reinforcement based on infiltrating a pre-set cement with a reactive polymer and then cross-linking the polymer in situ. This method can be used to reinforce 3D calcium phosphate cement scaffolds, which we demonstrate using poly(ethylene glycol) diacrylate (PEGDA) as a model reinforcing polymer. The compressive strength of a 3D scaffold comprised of orthogonally intersecting beams was increased from 0.31 +/- 0.06 MPa to 1.65 +/- 0.13 MPa using PEGDA 600. In addition, the mechanical properties of reinforced cement were characterized using three PEGDA molecular weights (200, 400, and 600 Da) and three cement powder to liquid (P/L) ratios (0.8, 1.0, and 1.43). Higher molecular weight increased reinforcement efficacy, and P/L controlled cement porosity and determined the extent of polymer incorporation. Although increasing polymer incorporation resulted in a transition from brittle, cement-like behavior to ductile, polymer-like behavior, maximizing polymer incorporation was not advantageous. Polymerization shrinkage produced microcracks in the cement, which reduced the mechanical properties. The most effective reinforcement was achieved with P/L of 1.43 and PEGDA 600. In this group, flexural strength increased from 0.44 +/- 0.12 MPa to 7.04 +/- 0.51 MPa, maximum displacement from 0.05 +/- 0.01 mm to 1.44 +/- 0.17 mm, and work of fracture from 0.64 +/- 0.10 J/m(2) to 677.96 +/- 70.88 J/m(2) compared to non-reinforced controls. These results demonstrate the effectiveness of our novel reinforcement method, as well as its potential for fabricating reinforced 3D calcium phosphate cement scaffolds useful for bone tissue engineering.