Elsevier

Materials Letters

Volume 263, 15 March 2020, 127281
Materials Letters

Novel double-layered planar scaffold combining electrospun PCL fibers and PVA hydrogels with high shape integrity and water stability

https://doi.org/10.1016/j.matlet.2019.127281Get rights and content

Highlights

  • A novel double-layered scaffold is introduced.

  • The hybrid structure is based on hydrophilic & hydrophobic biocompatible polymers.

  • The hydrophobic PCL layer maintains the shape of the scaffold after water exposure.

  • The electrospinning conditions were optimized via needleless device NanospiderTM.

Abstract

Novel double-layered materials with different properties of each side were prepared via needleless electrospinning and compared in terms of morphology, wettability, adhesion and proliferation of mouse fibroblasts. The materials consist of hydrophilic poly(vinyl alcohol) fibers with low (PVA_L) or high (PVA_H) degree of hydrolysis, and hydrophobic poly(ε-caprolactone) (PCL) fibrous layer. Although the PVA_L fibers were fully dissolved following a water exposure, the shape of the scaffold was maintained due to water stable PCL layer. Exposing PVA_H based fibrous layer to water created a hydrogel-like structure with shape defined by the PCL layer. According to the MTT assay, the mouse fibroblasts seeded on the scaffold exhibited the greatest proliferative activity on the PCL fibers. These double-layered scaffolds with different features on each side are very promising for many novel medical applications such as wound dressing or abdominal adhesion prevention.

Introduction

Tissue engineering scaffolds based on multiple layers are utilized for many applications, including mimicking of native tissues such as blood vessels or skin [1], [2], as well as for sustainable drug release [3]. Several references have been found in the literature for the production of fibrous multilayers based on combination of hydrophilic and hydrophobic polymers. Askari [3] combined poly(vinyl alcohol) (PVA) and poly(ε-caprolactone) (PCL) layers with medical drugs, resulting in slower drug release compared to monolayers. Furthermore, Trinca [2] fabricated scaffolds made of PCL and a mixture of chitosan and polyethylenoxide to cover skin wounds. However, usual approaches based on scaffold fabrication via needle electrospinning have limited maximal throughput, allowing only laboratory scale production. In contrast, by producing nanofibres along the entire length of a wire, the NanospiderTM technology has significantly increased production capability and potential for well controlled, mass-scale production. We chose to optimize our study for this technology due to these promising properties.

The newly introduced double-layers consist of PVA with low degree of hydrolysis 88% (PVA_L) fibers, respectively PVA with high degree of hydrolysis 98,0 – 98,8% (PVA_H) fibers and poly-e-caprolactone (PCL). Poly-e-caprolactone is a hydrophobic, biocompatible FDA approved polymer with high stability in the aqueous environment. Due to its good mechanical properties, PCL is used for the fabrication of bone [4] or vascular scaffolds [5], among others. Hydrophilic PVA is a synthetic polymer with varying degree of hydrolysis, ranging from a typical value of 80% to over 99% [6]. Although PVA-based scaffolds produced by electrospinning are widely used for tissue engineering, the rapid aqueous solubility of PVA has so far remained a limiting factor for many applications. The combination with the PCL layer creates a shape stable scaffold and prevents further use of cytotoxic cross-linking techniques for water soluble polymers such as glutaraldehyde [7], therefore maintaining the biocompatibility of the scaffolds.

Section snippets

Materials

A solution of PVA_L was prepared from aqueous 16% PVA Moviol® (Mw 130.000 g/mol, 88% hydrolysis, Merck, Germany) in a final concentration of 12% w/w. A 10% w/w PVA_H solution was prepared by dissolving of PVA Mowiol® (Mw 125.000 g/ mol, 98.0–98.8% hydrolysis, Sigma Aldrich, USA) in a solvent system containing ethanol (Penta Chemicals, CZE) and deionized water (DIW) in a 1:4 ratio. The solution of PVA_H was heated to 60 °C to enhance solubility. Poly(ε-caprolactone) (Mw 43.000 g/mol,

Morphology characterization and contact angle measurement

In this work, sequential electrospinning was chosen to fabricate the double-layered planar mats. The same approach was already used in a study by Kharaziha or Kidoaki [1], [8]. The morphology of prepared structures is depicted in the Fig. 1 (A – F) together with graph of fiber diameter (Fig. 1 – G). Microfibers and nanofibers were formed in the layer of PCL_L and PCL_H, resulting in high value of the SD. The SEM picture of PVA_L material shows uniform defect-less fiber morphology with thinner

Conclusion

We developed two forms of planar double-layered materials with different wettability of each side. The materials consist of hydrophobic PCL and hydrophilic PVA with two degrees of hydrolysis. The processing condition were optimized via NanospiderTM, which further allows industrial large scale production. Moreover, these scaffolds exhibit high shape integrity as well as layer adherence and introduce new possibilities for PVA applications in medicine and tissue engineering.

CRediT authorship contribution statement

Marketa Klicova: Conceptualization, Investigation, Writing - original draft, Writing - review & editing, Visualization. Andrea Klapstova: Methodology, Investigation, Formal analysis. Jiri Chvojka: Project administration. Barbora Koprivova: Methodology. Vera Jencova: Methodology, Validation. Jana Horakova: Supervision.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The research was supported by the SGS project Reg. No. 21311, provided by the Ministry of Education, Youth and Sports (CZE) in 2019.

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