The current generation of vascular grafts (VGs) is limited by excessive mechanical stiffness (most particularly, high Young’s modulus) that leads to intimal hyperplasia and ultimately graft failure. Therefore, fine-tuning of the mechanical properties will directly affect performance of an engineered VG after implantation. Those characteristics can be modified by clean, highly reproducible and environmentally benign plasma-based etching, which offers an attractive alternative to wet-chemical methods.
To this end, a Montreal-based research group have replaced conventional woven VGs (DacronR) by aligned electrospun poly(ethylene terephthalate) (ePET) nanofiber mats, which mimic the media layer of arteries. They used three different plasma etching techniques to bring mechanical and surface properties of the mats in line with those of natural blood vessels: i) atmospheric pressure (‘‘HP’’) corona discharge in air; ii) low-pressure radio-frequency plasma (‘‘LP’’) and iii) microwave plasma asher; (ii) and (iii) in pure oxygen (O2), or O2 mixture with Ar or CF4.
The team also investigated the effects of their new procedure on morphology, surface chemistry/wettability, and bioactivity. Among those three etch techniques, plasma ashing (with pure O2) seems to be most advantageous in terms of rapidity, minimal apparent damage to nano-fiber surfaces and efficacy in optimizing the mechanical properties. Thus, the researchers believe that their selected plasma-etching technique enables one to achieve finely-controlled mechanical and surface properties that are required for VG applications.