Design and Characterisation of Cytocompatible Polyester Substrates with Tunable Mechanical Properties and Degradation Rate

Although it has been repeatedly indicated the importance to develop implantable devices and cell culture substrates with tissue-specific rigidity, current commercially available products, in particular cell culture substrates, have rigidity values well above most tissues in the body. Herein, six resorbable polyester films were synthesised and fabricated using compression moulding with a thermal presser into films with tailored stiffness by appropriately selecting the ratio of their building up monomers (e.g. lactic acid, glycolic acid, trimethylene carbonate, dioxanone, ε-caprolactone). Typical NMR and FTIR spectra were obtained, suggesting that the fabrication process did not have a negative effect on the conformation of the monomers. Surface roughness analysis revealed no apparent differences between the films as a function of monomer ratio or polymer composition. Subject to monomer ratio / polymer composition, polymeric films were obtained with glass transition temperatures from -52 ºC to 61 ºC; contact angles in water from 81 º to 94 º; storage modulus from 108 MPa to 2,756 MPa and loss modulus from 8 MPa to 507 MPa (both in wet state, at 1 Hz frequency and at 37 ºC); ultimate tensile strength from 8 MPa to 62 MPa, toughness from 23 MJ/m 3 to 287 MJ/m 3 , strain at break from 3 % to 278 %, macro-scale Young’s modulus from 110 MPa to 2,184 MPa (all in wet state); and nano-scale Young’s modulus from 6 kPa to 15,019 kPa (in wet state). With respect to in vitro degradation in phosphate buffered saline at 37 ºC, some monomer combinations resulted in polymeric films that started degrading from day 7, whilst for other polymeric films no significant degradation was observed up to 21 days of degradation. In vitro biological analysis using human dermal fibroblasts and a human monocyte cell line (THP-1) showed the potential of the polymeric films to support cell growth and controlled immune response. Evidently, the selected polymers exhibited properties suitable for a range of clinical indications.