Strong and tough mineralized PLGA nanofibers for tendon-to-bone scaffolds

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

Mineralized poly(lactide-co-glycolide) (PLGA) hydroxyapatite electrospun nanofibers (inset) for tendon-to-bone scaffolds have been shown to possess outstanding toughness and three times the tensile strength of bulk PLGA. Pristine PLGA nanofibers with non-uniform surface morphology surpassed the strength of those with uniform circular cross-section, while nanofibers with ellipsoidal cross-sections resulted in the highest strength (see plots). The exceptional fiber strength and elongation were retained for thin and strongly bonded conformal hydroxyapatite coatings (c), which were preserved on the nanofiber surface even for very large extensions.Figure optionsDownload high-quality image (158 K)Download as PowerPoint slide