Alignment and composition of laminin–polycaprolactone nanofiber blends enhance peripheral nerve regeneration

Abstract

Peripheral nerve transection occurs commonly in traumatic injury, causing deficits distal to the injury site. Conduits for repair currently on the market are hollow tubes; however, they often fail due to slow regeneration over long gaps. To facilitate increased regeneration speed and functional recovery, the ideal conduit should provide biochemically relevant signals and physical guidance cues, thus playing an active role in regeneration. To that end, laminin and laminin–polycaprolactone (PCL) blend nanofibers were fabricated to mimic peripheral nerve basement membrane. In vitro assays established 10% (wt) laminin content is sufficient to retain neurite-promoting effects of laminin. In addition, modified collector plate design to introduce an insulating gap enabled the fabrication of aligned nanofibers. The effects of laminin content and fiber orientation were evaluated in rat tibial nerve defect model. The lumens of conduits were filled with nanofiber meshes of varying laminin content and alignment to assess changes in motor and sensory recovery. Retrograde nerve conduction speed at 6 weeks was significantly faster in animals receiving aligned nanofiber conduits than in those receiving random nanofiber conduits. Animals receiving nanofiber-filled conduits showed some conduction in both anterograde and retrograde directions, whereas in animals receiving hollow conduits, no impulse conduction was detected. Aligned PCL nanofibers significantly improved motor function; aligned laminin blend nanofibers yielded the best sensory function recovery. In both cases, nanofiber-filled conduits resulted in better functional recovery than hollow conduits. These studies provide a firm foundation for the use of natural–synthetic blend electrospun nanofibers to enhance existing hollow nerve guidance conduits.

Interaction of Schwann cells with laminin encapsulated PLCL core–shell nanofibers for nerve tissue engineering

“…The peaks characteristic of laminin was nearly invisible in the spectra produced from PLCL/Lam(B) and PLCL/Lam(CS) nanofibers, where we concluded that the amount of laminin incorporated in PLCL solution was probably too low [PLCL:laminin 1600:1] and thus the concentration of protein on the surfaces of the scaffold was below the determination capability of the equipment. Studies of PCL-laminin blended nanofibers carried out by Neal et al also utilized Fouriertransform infrared spectra where they demonstrated that the peaks representing amide bonds (1564 cm À1 , 1649 -cm À1 ) from laminin are very small for fibers with 0.1 wt% concentration of laminin [34] and the concentration of the protein in PLCL/Lam(B) was much lower with a value of about 0.006 wt%. On the other hand, the application of core-shell nanofibers was quite advantageous since laminin remains encapsulated within the core of the fiber and was not detected on the surface of the fibers, allowing suitable encapsulation of the bioactive factors.…”

Plasma surface functionalization of biodegradable electrospun scaffolds for tissue engineering applications

“…To avoid these surface modifications, some researchers have blended natural polymers and other bioactive molecules with the synthetic polymer solution prior to the electrospinning thus specifically functionalizing the nanofibers for particular TE applications. Collagen, laminin, gelatin, elastin and chitosan have extensively been blended with synthetic polymers to produce nanofibers serving as scaffolds for nerve, blood vessels, skin and bone regeneration together with other TE applications [98][99][100][101][102][103]. Carbon phosphates, serving as bone grafting replacements to fill bone empty spaces and damaged areas, have been blended with polymer solutions to fabricate nanofibers having potentials in osteoconductivity, osteoinductivity and osteointegration [104][105][106].…”

Scaffolds for Peripheral Nerve Regeneration, the Importance of In Vitro and In Vivo Studies for the Development of Cell-Based Therapies and Biomaterials: State of the Art

“…Coating of peripheral nerve conduits can enhance nerve regeneration process and solve longer nerve gaps repair. Resource to extracellular matrix materials, such as fibronectin, laminin and collagen, give naturally hydrophobic scaffolds a hydrophilic surface that promotes cell adhesion [73,116,174]. Collagen Type I conduits coated with laminin and fibronectin have shown improved neural regeneration [175,176].…”