Porous copolymers of ε-caprolactone as scaffolds for tissue engineering
Tang M., Purcell M., Steele JAM., Lee KY., McCullen S., Shakesheff KM., Bismarck A., Stevens MM., Howdle SM., Williams CK.
A series of random copolymers were synthesized via the copolymerization of a carbohydrate lactone, acetic acid 5-acetoxy-6-oxotetrahydropyran-2-yl methyl ester (1), and ε-caprolactone. The copolymers were characterized by nuclear magnetic resonance (NMR) spectroscopy, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Copolymers (P1-P4) were produced with typical carbohydrate ester compositions of 1-4 mol %. These copolymers are semicrystalline and can be processed into thin films with Young's moduli of 300-420 MPa, values that exceed that for polycaprolactone (PCL). The copolymers were processed using supercritical carbon dioxide (scCO2, 35 C, 200 bar) into foamed, porous scaffolds, which were characterized by dynamic mechanical thermal analyses (DMTA), mercury porosimetry, and scanning electron microscopy (SEM). The copolymer foams showed increased pore size with increasing carbohydrate ester content. The average pore size increased from 71 μm (PCL) to 319 μm (P4). The foamed scaffolds have normalized storage moduli ranging from 37 MPa cm3g-1 (P4) to 109 MPa cm3g-1 (P1). A representative copolymer foamed scaffold, tested according to ISO 10993-5 criteria, was cytocompatible for cell culture. MC3T3 cells cultured on a film of this copolymer showed increased relative metabolic activities compared to cells cultured on a PCL film. When primary bovine chondrocytes were cultured on the foamed scaffolds, increased cell penetration into the random copolymer foam was observed compared to PCL foams. © 2013 American Chemical Society.