3D Electrospun Scaffolds for Vascular Graft Applications: Fine Tuning of Properties by Plasma-Assisted Etching and Coating

摘要

Primary requirements for synthetic vascular prostheses are biocompatibility, bioactivity, and favorable morphological and mechanical properties. In this research electrospinning, plasma etching and plasma polymerization (PP) were combined to fulfill those criteria. More particularly, we aimed to create scaffolds for subsequent cell-seeding that possess optimal mechanical, morphological and surface-chemical properties in the luminal and media layers. The first set of scaffolds were random electrospun poly (ethylene terephthalate) (ePET) nano-fiber mats, which mimic the morphological and mechanical properties of the extracellular matrix of native blood vessels' lumen. Amine-rich thin PP coatings, deposited via capacitively coupled radio-frequency (r.f.) plasma, enabled confluent monolayer pre-endothelialization of the lumen. Regarding the media layer, ePET nano-fibers were radially highly oriented; in order to bring their mechanical properties in line with those of natural blood vessels, a substantial reduction in Young's modulus had to be attained. For this purpose three different plasma etching techniques were investigated: (ⅰ) atmospheric pressure ("HP") corona discharge in air; low-pressure (ⅱ) r.f. discharge; and (ⅲ) discharge in a microwave plasma asher, the latter two in pure oxygen (O_2), or O_2 mixture with Ar or CF_4. By far the best results were achieved using (ⅲ): without visible damage to the fibers, changes in surface composition and drastically improved wettability resulted in improved adhesion and growth of smooth muscle cells.