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Towards precision nanomanufacturing for mechanical design: From individual nanofibers to mechanically biomimetic nanofibrillary vascular grafts
Electrospun nanofibers have high potential to improve properties and performance of biomedical materials due to their biomimetic structure and unique mechanical properties. Despite their potential, use of polymer nanofibers has been limited due to poor control over nanofiber structure and properties and due to lack of advanced design and nanomanufacturing methods. The objective of this work was to improve the understanding of process parameter-structure-property relationships in individual biomedical nanofibers, and to develop an advanced method for mechanically and structurally biomimetic nanofiber-based vascular graft material manufacturing. Mechanical tests of individual biomedical DNA nanofibers show ultrahigh mechanical properties and atypical size-effects, indicating on high molecular orientation and possible fundamentally different molecular alignment mechanisms from synthetic polymer nanofibers. Novel structural characterization methods were developed to study molecular structure and its size-effects in individual DNA nanofibers. The results reveal high molecular orientation in DNA nanofibers, which decreases gradually with increase of diameter. These results are in good agreement with observed mechanical properties and with proposed bottom-up molecular alignment mechanisms during DNA electrospinning. Based on mechanical analysis of individual nanofibers, an advanced method was developed for manufacturing of mechanically biomimetic nanofibrillary vascular graft materials. Different process parameter-property relationships were established to induce biaxial non-linearity and anisotropy. These relationships were studied parametrically and used to mimic the mechanical properties of human carotid artery and pig iliac artery. In-vivo tests of pig iliac artery-mimetic nanofibrillary graft material show improved surgical and biomechanical characteristics compared to the state-of-the-art control material. Histology results reveal that developed biomimetic nanofibrillary vascular graft material also possesses improved healing response manifested by smooth muscle cell infiltration within the graft material and by endothelial cell coverage on the grafted lumen. The results of this study provide new knowledge of manufacturing, structure, and properties of individual nanofibers and nanofibrillary membranes. These results can be used to develop new and improve existing mechanical design principles of nanofibrillary materials for biomedical and other applications.
Maleckis, Kaspars, "Towards precision nanomanufacturing for mechanical design: From individual nanofibers to mechanically biomimetic nanofibrillary vascular grafts" (2017). ETD collection for University of Nebraska - Lincoln. AAI10257211.