STRONG AND TOUGH MINERALISED PLGA NANOFIBRES FOR TENDON-TO-BONE SCAFFOLDS

Engineering complex tissues such as the tendon-to-bone insertion sites requires a strong and tough biomimetic material system that incorporates both mineralised and unmineralised tissues with different strengths and stiffnesses. However, increasing strength without degrading toughness is a fundamental challenge in materials science. A promising nanofibrous polymer-hydroxyapatite system, in which a continuous fibrous network must function as a scaffold for both mineralised and unmineralised tissues is presented. The high toughness of this material system could be maintained without compromising the strength with the addition of hydroxyapatite. Individual electrospun poly (lactide-co-glycolide) (PLGA) nanofibres demonstrated outstanding strain-hardening behaviour and ductility when stretched uniaxially, even in the presence of surface mineralisation. This highly desirable hardening behaviour which results in simultaneous nanofibre strengthening and toughening was shown to depend on the initial cross-sectional morphology of the PLGA nanofibres. For pristine PLGA nanofibres, it was shown that ellipsoidal cross-sections provided the largest increase in fibre strength by almost 200% compared to bulk PLGA. This exceptional strength accompanied by 100% elongation was retained for thin and strongly bonded conformal mineral coatings, which were preserved on the nanofibre surface even for such very large extensions.