Electrospun Tube Application

Electrospinning is a very simple method of obtaining nanofibers. Although membrane is the most commonly derived form from electrospinning, tubular structures made out of nanofibers may also be easily constructed using electrospinning. The electrospun fibrous tube has been explored for various applications although most of them are in the biomedical field due to numerous studies on its biocompatibility and mimicry to natural extracellular matrix (ECM).

Vascular graft is one of the most widely investigated applications of electrospun tubes. For successful clinical application, several physical properties of the constructed vascular graft needs to be addressed. A physical factor to consider is the non-kinking after it has been implanted. Commercially available grafts are mostly rigid and easily kink when implanted. Matsushita et al (2020) formed corrugation on a tube made of co-electrospun electrospun poly(L-lactide-co-caprolactone)/poly-ε-caprolactone (PCL/PLCL) nanofibers so that the corrugated tube is able to resist kinking. Such corrugation was formed by wrapping a monofilament around the electrospun tube, longitudinally compressed and allowing it to set for 24 h before the tube was relaxed and the filament removed. The electrospun graft was implanted in a sheep model. There was no significant kinking in the grafts and endothelial cells were observed in the grafts 1 month after the surgeries.

A, Image of EXXCEL SOFT vascular graft (Maquet Cardiovascular, Wayne, NJ) that exhibits kinking upon a 180° bend. B, The TEVG graft that has corrugations to maintain flexibility and conformability upon a 180° bend. Scale bar = 10 mm. C, Close-up of the TEVG graft corrugations. Scale bar = 1 mm. D, A comparison of the kink radius for the non-corrugated and corrugated grafts [Matsushita et al 2020].

Since the fibers produced by electrospinning are in the nano to micrometer diameter level, it can easily produce tubes of a few millimetres diameter. Material and structural versatility has made electrospinning an attractive process for manufacturing peripheral nerve regeneration scaffolds. Beyond the wide range of materials that can be electrospun, drugs, growth factors and other additives may also be incorporated into the electrospun fibers. a wide range of materials may be used for electrospinning depending on the required property. Man-made biodegradable polymers such as poly(lactic acid) has been electrospun with bioactive molecules such as peptides [Schaub et al 2015] collagen [Koh 2009] and laminin [Leach et al 2013] added for better biocompatibility. Various growth factors have also been blended into electrospun fibers to improve its performance [Dinis et al 2014]. To imitate electrical signaling in natural nerves,conductive [Ghasemi-Mobarakeh et al 2009] and piezoelectric [Biazar et al 2013] materials have also been electrospun and the resultant scaffold has been shown to be suitable for nerve regeneration.

Catheter for insertion into the body during surgery to create a passage for fluid or entry of surgical devices is another application where electrospun tubes can be used. Wang et al (2020) constructed a liquid gating membrane-based catheter (LGMC) using electrospun tube as the main structural support. This catheter uses a porous membrane with a liquid filling up the pores in the membrane (gating liquid) to create a continuous wall. It is important that the affinity between the gating liquid and the porous membrane is strong so that the liquid does not leak out from the pores. Increasing the thickness of the tube wall by having a longer electrospinning duration increases the pressure threshold. However, increasing the solution concentration which increases the fiber diameter decreases the pressure thresholds exponentially. This may be due to larger pore sizes of larger diameter fibers. Wang et al (2020) showed that electrospun polyvinylidene fluoride (PVDF) porous tube with perfluorodecalin, Krytox 100, Krytox 103, and silicone oil 500 as gating liquid were able to resist coagulation and clot formation better than bare PVDF tube. The gating liquid may also be used as a carrier for drugs to be released at the surgical site.

Design and preparation of bioinspired LGMC. (A) Electrospinning method is used to fabricate the microporous membrane-based catheter, after which the liquid design is carried out to form the LGMC with specific stability and functionality. HV, high voltage. (B) Inspired by blood vessels, which have adaptive tube sizes and with special mass transfer pathways on vascular walls, the LGMC is designed with the unique ability of the gating liquid to deform and reconfigure in situ to respond to the capillary pressure. Thus, the LGMC can be tunable in sizes with the changes of environmental pressures. The anticoagulation property is realized by the persistent lining of gating liquid at the surfaces. In addition, positionally drug release with tunable adding positions is actualized by the liquid gating microporous membrane-based structures [Wang et al 2020].