title: Effects of Stirring and Fluid Perfusion on the In Vitro Degradation of Calcium Phosphate Cement/PLGA Composites.
abstract: In vitro degradation rates of calcium phosphate bioceramics are investigated using a large variation of soaking protocols that do not all match the dynamic conditions of the perfused physiological environment. Therefore, we studied the effect of stirring and fluid perfusion on the in vitro degradation rate of apatitic calcium phosphate cements (CPC) containing poly(lactic-co-glycolic acid) (PLGA) microspheres. The composites were soaked in phosphate-buffered saline up to 6 weeks under unstirred, stirred, or perfused conditions followed by analysis of mass loss, compression strength, porosity, crystal phase composition, and morphology of the cement composites. The results showed that fluid perfusion reduced the decrease in pH and corresponding degradation rates, while nonperfused soaking conditions (i.e., stirred and unstirred conditions) resulted into more extensive acidification, the rate of which increased with stirring. After 2 weeks, the formation of a secondary brushite phase was observed for cement composites soaked under nonperfused (i.e., stirred and unstirred) conditions, whereas this phase was not detected in cements soaked under perfused conditions. The degradation rate of cement composites decreased in the order unstirred>stirred>perfused, as evidenced by quantification of mass loss, compression strength, and pore morphology. To summarize, we have demonstrated that soaking conditions strongly affected the in vitro degradation process of CPCs. As a consequence, it can be concluded that the experimental design of current in vitro degradation studies does not allow for correlation to (pre-)clinical studies.
authors.affiliation: Department of Biomaterials, Radboud University Medical Center , Nijmegen, The Netherlands .
authors.forename: Jie
authors.initials: J
authors.lastname: An
authors.affiliation: Department of Biomaterials, Radboud University Medical Center , Nijmegen, The Netherlands .
authors.forename: Sander C G
authors.initials: SC
authors.lastname: Leeuwenburgh
authors.affiliation: Department of Biomaterials, Radboud University Medical Center , Nijmegen, The Netherlands .
authors.forename: Joop G C
authors.initials: JG
authors.lastname: Wolke
authors.affiliation: Department of Biomaterials, Radboud University Medical Center , Nijmegen, The Netherlands .
authors.forename: John A
authors.initials: JA
authors.lastname: Jansen
mesh_terms: D001843:Bone Cements / Q000737:chemistry*; D002130:Calcium Phosphates / Q000737:chemistry*; D019245:Compressive Strength; D006863:Hydrogen-Ion Concentration; D021621:Imaging, Three-Dimensional; D019344:Lactic Acid / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008970:Molecular Weight; D010477:Perfusion; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D014961:X-Ray Diffraction; D055114:X-Ray Microtomography
chemical_list: D001843:Bone Cements; D002130:Calcium Phosphates; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C020243:calcium phosphate