Elsevier

Materials Letters

Volume 264, 1 April 2020, 127351
Materials Letters

Aligned biomimetic scaffolds based on carbon nanotubes-reinforced polymeric nanofibers for knee meniscus tissue engineering

https://doi.org/10.1016/j.matlet.2020.127351Get rights and content

Highlights

  • Here we fabricated an aligned biomimetic scaffold mixing polycaprolactone and carbon nanotube.

  • Scaffolds with both circumferentially and radially aligned were developed.

  • Dynamic mechanical analysis showed an improvement in the mechanical properties.

  • Mesenchymal stem cells survived when cultivated on produced scaffolds.

Abstract

Many strategies in tissue engineering have been developed in order to provide potential treatments for Knee meniscal injuries since it is a high incidence lesion and without effective treatment available in clinical practice. The success of this approach is directly related to the creation of a scaffold able to reproduce the complex extracellular matrix of the native meniscus with adequate mechanical properties. Here we fabricated an aligned biomimetic scaffold, based on carbon nanotube (CNT)-reinforced polymeric nanofibers. For that, scaffolds with both circumferentially and radially aligned polycaprolactone fibers were developed from a specific electrospinning setup and incorporated with two different concentrations of CNT: 0.05% and 0.10%. Characterization by scanning electron microscopy confirmed the spatial distribution and the alignment of the electrospun nanofibers as well as a decrease in average fiber size with the addition of CNT (the presence of CNT was confirmed by transmission electron microscopy). Dynamic mechanical analysis and biological assays showed an improvement in the mechanical properties related to increased CNT content without influence in mesenchymal stem cells survival. These findings suggest a potential applicability of this nanocomposite for knee meniscus tissue engineering.

Introduction

The high incidence associated with the absence of effective treatment available in clinical practice for meniscal injuries, makes it urgent to develop new therapies in order to adequately stimulate the regeneration of this tissue, in which the field of tissue engineering has become one of the main research interests [1], [2].

Tissue engineering strategies require suitable biomaterial scaffolds and the fabrication of an ideal meniscus scaffold have been facing two major challenges: to mimic the complex extracellular matrix architecture of the native tissue and reproduce its mechanical properties [3]. In a previous study in our research group [4], an important step was taken towards recreating the orientation of the constituent fibers of the extracellular matrix of the knee meniscus from the development of a novel electrospinning setup able to produce scaffolds with both circumferentially and radially aligned polymeric nanofibers. However, no mechanical investigation was performed.

Thus, herein was proposed the evaluation of nanocomposites scaffolds based on the incorporation of low levels of carbon nanotubes (CNT) into polycaprolactone (PCL) nanofibers obtained from recently developed electrospinning setup [4], in order to analyze the effect of CNT reinforcement on the mechanical properties. Because of their exceptional mechanical strength, CNTs can play an important role as nanofiller. The fabrication of nanocomposites formed by biocompatible synthetic polymers and CNTs is a promising approach for load bearing tissue engineering [5], [6].

Additionally, biological assays were performed to assess the cell viability and the potential applicability of this nanocomposite for meniscus regenerative medicine. The mesenchymal stem cells (MSC) were used as a cell source because these cells have been suggested as good source for meniscal repair [7].

Section snippets

Materials and methods

For experiments, solutions of polycaprolactone (PCL, MW 80 kDa, Sigma-Aldrich) were used at 12 wt% with chloroform (Sigma-Aldrich) and dimethylformamide (DMF, Sigma-Aldrich) as solvents (3:1 ratio), incorporated with three different concentrations of CNT: 0 wt% (Group PCL, control with no CNT inclusion), 0.05 wt% (Group PCL/CNT 0.05%) and 0.10 wt% (Group PCL/CNT 0.10%). For this purpose, Multiwall Carbon Nanotubes (MWCNTs), synthetized and functionalized by oxygen plasma [8], [9], were

Results and discussion

As reported in the previous study [4], it is also possible to identify the spatial distribution of the electrospun nanofibers: circumferentially oriented fibers (deepest) and radially (most superficial) (Fig. 1A) according arrangement of the major structural components of the meniscus extracellular matrix [16], [17]. The CNTs embedded within the PCL nanofibers were confirmed by TEM image, showing the presence of CNT agglomerates (Fig. 1B).

Besides the difference of the average diameter between

Conclusions

In conclusion, the present study demonstrated that the PCL scaffolds radially aligned nanofibers (CircAN) with incorporation of two concentration of CNT result in a better mechanical property in terms of yield stress, failure stress and Young's modulus, and also is suitable for MSC survival and maybe cell differentiation. Although further studies are still required, this preliminary investigation demonstrates a great potential for meniscal tissue engineering application.

Author contributions

All authors contributed to the design of the study and the writing of the manuscript. EA and MLR performed the biological in vitro tests. TDS produced and characterized all membranes. GFS performed the mechanical tests. MF and AOL supervised all students. All authors read and approved the final manuscript.

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.

Acknowledgments

This work was supported by the National Council for Scientific and Technological Development (CNPq, #303752/2017-3 and #404683/2018-5).

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