Nanofiber-microfiber combination

Before electrospinning becomes well known for the construction of nanofiber scaffold, microfibers and textiles have been investigated for use as tissue scaffold due to its superior strength. Suture is an example of microfibers used commonly in clinical setting. Generally, microfiber mesh and textiles have large interfiber pores that allow cell migration and infiltration but the pores of typical electrospun nanofiber membrane is too small for cells to migrate through. A hybrid scaffold consisting of both microfibers and nanofibers have been constructed to take advantage of the benefit of each form. Most combination of micro and nanofibers uses rapid prototyping process to generate the microfibers (See link) for tissue engineering application while electrospun nanofiber deposited on nonwoven microfiber is frequently used filtration application. Nevertheless, researchers have also used electrospun nanofibers deposited on nonwoven microfiber membrane or tube for tissue engineering[Shim et al 2009, Pham et al 2006, Edwards et al 2009]. To construct a thicker scaffold, Tuzlakoglu et al stack layers of microfibers (from wet spinning) coated with nanofibers (from electrospinning) followed by cross-linking [Tuzlakoglu et al 2011].

The limitation of the above mentioned arrangement is that the benefit of nanofibers is not distributed throughout the scaffold. To overcome this limitation, Thorvaldsson et al constructed an electrospinning setup that coat nanofibers on individual microfiber strand [Thorvaldsson et al 2008]. In their scaffold, the structure takes the form of of a tangled fiber mesh. However, it may also be possible to use the coated microfiber to form braids, weaves or other forms. Other researchers have also come out with alternative setup to construct microfiber with nanofiber coating [See Link].

Methods for fabricating non-woven microfibers mesh may also be used together with electrospinning to create a hybrid mesh of micro and nanofibers. Melt blowing is a simple method of fabricating thick microfibous mesh. Electrospinning, melt blowing and particle sputtering of hydroxyapatite has been carried out simultaneously and the resultant hybrid composite mesh collected on a rotating drum [Erben et al 2014]. Osteoblast cultured on the mesh with and without hydroxyapatite particles and nanofibers showed that the composite mesh containing hydroxyapatite particles and nanofibers showed the highest rate of proliferation after 21 days [Erben et al 2014]. In the melt-blowing and electrospinning combination setup by Erben et al (2022), both melt blowing and electrospinning uses multiple spinnerets to produce a 3D poly-ε-caprolactone (PCL) fibers scaffold. In their setup, the electrospinning spinnerets were pointed towards the flight path of the melt blown fibers such that the melt blown fibers caught the electrospun fibers and both fibers were collected using a rotating drum collector. An advantage of this arrangement is that most of the electrospun fibers would be caught and at the same time be evenly distributed throughout the melt blown fibers. The ratio of the fibers may be controlled by the mass flow rate of the polymer passing through the spinnerets. SEM images showed the scaffold with thickness of 6 mm was made of randomly oriented microfibers and nanofibers from melt-blowing and electrospinning respectively.

Scheme of a combination of meltblown and electrospinning technology for the production of a 3D scaffold: 1-extruder, 2-high voltage power supply, 3-multi needle spinner, 4-drum collector [Erben et al 2022].

▼ Reference

▼ Credit and Acknowledgement