Sterilization of macroscopic poly(l-lactic acid) porous scaffolds withdense carbon dioxide: Investigation of the spatial penetration of thetreatment and of its effect on the properties of the matrix

Abstract

In this work the sterilization with dense carbon dioxide of poly(l-lactic acid) (PLLA) porous scaffoldsintended for tissue engineering applications was investigated with the main objective of confirming thethree-dimensional efficacy of the treatment and of analysing the scaffold properties after CO2treatment.For this purpose the scaffold was contaminated with a conventional bacterium (Escherichia coli) and withspores (Streptomyces coelicolor), a species more fascinating and difficult to inactivate. Contamination wasperformed in such a way to soak the whole matrix with bacteria and spores. The effect of pressure andtreatment time on the efficacy of the sterilization was evaluated. The E. coli was eradicated from thewhole matrix after just 5 min of exposure to supercritical CO2at 10 MPa and 40◦C. The spores requiredmore severe conditions due to their different and very resistant structures since complete inactivationwas obtained after 360 min of exposure at 30 MPa and 40◦C or at 30 MPa and 30◦C after the addition of200 ppm of H2O2to near critical CO2. The treatment with dense CO2did not alter the biocompatibilityand the structure of the scaffold as demonstrated by biological culture tests and calorimetric and SEManalyses.