New generation poly(ε-caprolactone)/gel-derived bioactive glass composites for bone tissue engineering: Part I. Material properties

Poly(epsilon-caprolactone) (PCL) based composite films containing 12 and 21 vol.% bioactive glass (SBG) microparticles were prepared by solvent casting method. Two gel-derived SBGs of SiO2-CaO-P2O5 system differing in SiO2 and CaO contents were applied (mol%); S2: 80SiO(2), 16CaO, 4P(2)O(5) and A2: 40SiO(2), 54CaO, 6P(2)O(5). The surfaces of the films in contact with Petri dish and exposed to the gas phase during casting were denoted as GS and AS, respectively. Both surfaces of films were characterised in terms of their morphology, micro- and nanotopography as well as wettability. Also mechanical properties (tensile strength, Young's modulus) and PCL matrix crystallinity (degree of crystallinity, crystal size) were evaluated. Degradation behaviour was examined by incubation of materials in UHQ-water at 37 degrees C for 56 weeks. The crystallinity, melting temperature and mass loss of incubated materials and pH changes of water were monitored. Furthermore, proliferation of MG-63 osteoblastic cells by direct contact and cytotoxic effect of obtained materials were investigated. Results showed that opposite surfaces of the same polymer and composite films differ in studied surface parameters. The addition of SBG particles into PCL matrix improves nano- and micro-roughness of both surfaces, enhances the hydrophilicity of GS surfaces (similar to 67 degrees for 21A2-PCL compared to similar to 78 degrees for pure PCL) and also makes AS surface more hydrophobic (similar to 94 degrees for 21S2-PCL compared to similar to 86 degrees for pure PCL). The nucleation density of PCL was increased with increasing content of SBG particles, which results in the large number of fine spherulites on composite AS surfaces observed using polarized optical (POM), scanning electron (SEM), and atomic force (AFM) microscopies. Higher content of SBG particles causes a notable increase of Young's modulus (from 038 GPa for pure PCL, 0.90 GPa for 12A2-PCL to 131 GPa for 21A2-PCL), which also depends on SBG chemical composition. After 56-week degradation test, considerably higher crystallinity increase (Delta chi c similar to 148% for 21S2-PCL, similar to 81% for 21A2-PCL) and weight loss (similar to 17% for both) were found for composite materials, depending on SEC composition, in contrast to value variations for pure PCL film (Delta chi c similar to 43%, weight loss similar to 1.6%). Furthermore, it seems that both SBG could neutralize acidic degradation by-products of PCL at later incubation stages. Obtained SBG-PCL composites show excellent biocompatibility, support cell proliferation also may modulate cell response depending on the glass composition. The results indicate the possibility to use different contents and/or chemical compositions of SBG to obtain composite materials with various, but controlled, surface and mechanical properties as well as degradation kinetics. (C) 2015 Elsevier BM. All rights reserved.