A general strategy for generating gradients of bioactive proteins on electrospun nanofiber mats by masking with bovine serum albumin

Abstract

Electrospun nanofibers are widely used in tissue engineering owing to their capability to mimic the structures and architectures of various types of extracellular matrices. However, it has been difficult to incorporate a biochemical cue into the physical cue provided by the nanofibers. Here we report a simple and versatile method for generating gradients of bioactive proteins on nanofiber mats. We establish that the adsorption of bovine serum albumin (BSA) onto nanofibers is a time- and concentration-dependent process. By linearly increasing the volume of BSA solution introduced into a container, a gradient in BSA is readily generated across the length of a vertically oriented strip of nanofibers. Next, the bare regions uncovered by BSA can be filled with the bioactive protein of interest. In demonstrating the potential application, we examine the outgrowth of neurites from dorsal root ganglion (DRG) isolated from chick embryos and then seeded on aligned polycaprolactone nanofibers covered by nerve growth factor (NGF) with a uniform coverage or in a gradient. In the case of uniform coverage, the neurites extending from DRG show essentially the same length on either side of the DRG cell mass. For the sample with a gradient in NGF, the neurites extending along the gradient (i.e., increase of NGF concentration) were significantly longer than the neurites extending against the gradient.

Ultraviolet Functionalization of Electrospun Scaffolds to Activate Fibrous Runways for Targeting Cell Adhesion

“…For example, it was reported that the introduction of oxygen and nitrogen functional groups onto the surface of electrospun scaffolds could lead to an enhanced proteins/biomolecules adsorption and consequently to a larger number of anchoring points for cells, influencing their attachment, spreading and shape (Qiu et al, 2017; Babaei et al, 2018). In this context, it is possible to shape linear (Tanes et al, 2017) and circular (Wu et al, 2018) chemical gradients by creating concentration and time dependent graded masks of inert bovine serum albumin (BSA) able to block the plasma induced chemical groups from selected zones, potentiating counter current functionalized regions of the selected bioactive agent. However, this surface modification strategy depends on a vacuum system and can often damage the electrospun fibers, especially following prolonged exposure that is often needed to improve its otherwise limited penetration depth (Hasan et al, 2014; Duque Sánchez et al, 2016).…”

Engraving the Surface of Electrospun Microfibers with Nanoscale Grooves Promotes the Outgrowth of Neurites and the Migration of Schwann Cells

“…By varying the PCL to PVP mass ratio and the flow rates for inner and outer fluids,t he dimensions of the grooves can be optimized to maximize the guidance for the extension of neurites and migration of glial cells.F or the aligned microfibers engraved with grooves of 239 AE 54 nm in width, together with at hickness of 301 AE 56 nm for the ridges,w eo btained the best performance in terms of neurite extension and Schwann cell migration. Such aligned microfibers can be directly used to construct NGCs and further integrated with gradients in terms of proteins and/or growth factors [40,41] to augment the efficacyofn erve repair.…”

Promoting Cell Migration and Neurite Extension along Uniaxially Aligned Nanofibers with Biomacromolecular Particles in a Density Gradient

“…[27,28] With the integration of gradients in chemical cues, the directional extension of neurites can be further augmented. [14,15] Compared with other types of ECM components, laminin can effectively enhance axonal regrowth for some sensory neurons. [39] As such, we added laminin into collagen particles to investigate the combined effect of topographic and hypotactic cues on the extension of neurites.…”

“…[3] As for the repair of periphery nerve injury, it requires not only the recruitment of glial cells to the defect site but also the promotion of neurite extension and axon nanofibers, offering a haptotactic cue to further improve the guidance efficacy. [15,[29][30][31] For example, a gradient of proteins was generated on a mat of aligned nanofibers by varying the contact time between the bioactive agents and the fibers. [15,[29][30][31] In other studies, chemical reactions such as surface-initiated atom transfer radical polymerization have been used to produce a gradient of peptides on the surface of fibers.…”

“…[15,[29][30][31] For example, a gradient of proteins was generated on a mat of aligned nanofibers by varying the contact time between the bioactive agents and the fibers. [15,[29][30][31] In other studies, chemical reactions such as surface-initiated atom transfer radical polymerization have been used to produce a gradient of peptides on the surface of fibers. [32][33][34] These methods, however, typically involve the use of multiple steps and custom-made reagents, limiting their capability and versatility.…”