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Title: Nanostructured Fiber Materials and Composites for Tissue Engineering
Journal: Tampere University of Technology
Author: 1. Mohammad Kazemi Pilehrood
Year: 2016
Address: Tampere University of Technology, Finland
Abstract: The demand for organ transplantation is increased day by day, highlighting the necessity for the
development of tissue engineering as a part of strategic solution in medical treatments.
Nanotechnology has brought a possibility to introduce materials, architectures and specific
topographies required for the closet analogies in extracellar matrix (ECM) in native tissue. Among
different nanostructured materials, electrospun nanofibers are recommended as an appropriate
scaffold for tissue engineering due to their structural, biomedical and biophysical properties.
The aim of this thesis was to study the properties of electrospun nanofibers as scaffolds in tissue
engineering. To this end, we first studied electrospinning mechanism as a nanofabrication method
for the preparation of electrospun nanofibers. Secondly, the structural characteristics of electrospun
nanofibers in different morphological conditions were observed by image analysis. In the third step,
the comparative study was established between these structural characteristics and the viability of
cells. And finally, the effects of nanofiber coating in viability, proliferation and differentiation of
mesenchymal stem cells were discussed.
Polyacrylonitrile (PAN) nanofibers and carbon nanotube (CNT) reinforced PAN nanofibers were
electrospun successfully. A polymer plasticiser, ethylene carbonate (EC), was added into the
PAN/CNT solutions. It was observed that increasing the polymer concentration led to a reduction of
beads density and an increase in the diameter of the PAN nanofibers. The fiber diameters also
increased as a result of the addition of CNTs below the electrical percolation threshold. It was found
that the inclusion of EC permits changes in the morphological characteristics of the PAN/CNT
nanocomposite fiber regardless of the effects of its conductivity and viscosity.
3D nanofibrous chitosan-polyethylene oxide (PEO) scaffolds were fabricated by electrospinning
using different processing parameters. The structural characteristics, such as pore size, overall
porosity, pore interconnectivity, and scaffold percolative efficiency (SPE), were observed by using
detailed image analysis. Mouse fibroblast cells (L929) were cultured in RPMI for 2 days in the
presence of various samples of nanofibrous chitosan/PEO scaffolds. Cell attachment and the
corresponding mean viability were enhanced from 50% to 110% compared to that of a control even
at packed morphologies of scaffolds constituted from pores with nanoscale diameter. To elucidate
the correlation between structural characteristics within the depth of the scaffolds’ profile and cell
viability, a comparative analysis was proposed. This analysis revealed that larger fiber diameters
and pore sizes can enhance cell viability. On the contrary, increasing the other structural elements
such as overall porosity and interconnectivity due to a simultaneous reduction in fiber diameter and
pore size through the electrospinning process can reduce the viability of cells. In addition, it was
found that manipulation of the processing parameters in electrospinning can compensate for the effects of packed morphologies of nanofibrous scaffolds and can thus potentially improve the
infiltration and viability of cells.
We present a new hybrid scaffold constructed by coating electrospun chitosan/polyethylene oxide
(PEO) nanofibers on commercial BioTek polystyrene (PS) scaffold obtained from Sigma Aldrich.
The viability and proliferation rate of mesenchymal stem cells (MSCs) seeded on micro-nano
structured hybrid scaffold (MNHS) and commercial PS scaffolds were analyzed using the MTT
assay. The results of the MTT assay revealed a higher degree of viability and proliferation rate in
MSCs seeded on MNHS compared with the commercial PS scaffold. DAPI images also confirmed
the higher degree of attachment and viability of MSCs seeded on MNHS. Moreover, MSCs on both
scaffolds differentiated to osteoblasts and adipocytes cells, as reflected by the images obtained from
Alizarin Red and Oil Red-O staining. Alkaline phosphatase activity (ALP) and calcium content
assays revealed that the MNHS has a higher potential for osteogenic differentiation than the
commercial scaffold. To quantify the osteoblast and adipocyte gene expression, quantitative RTPCR
was carried out for MNHS, commercial scaffold and Tissue culture polystyrene (TCPS). It
was found that MNHS can express a higher level of Runt-related transcription factor 2 (Runx2),
osteonectin and osteocalcin in osteogenic differentiation as well as increased expression of PPARγ
and UCP-1 in adipogenic differentiation. The enhancement of the attachment, viability and
proliferation as well as bi-lineage differentiation may result from the biochemical and structural
analogies of MNHS to native ECM. Furthermore, it was observed that biocompatible MNHS
scaffold can potentially be utilized as a suitable scaffold for bone and connective tissue engineering.
Keywords:
Application: Tissue Engineering
Product Model 1: Electroris
Product Model 2:
URL: https://tutcris.tut.fi/portal/files/9122871/pilehrood_1432.pdf#="https://tutcris.tut.fi" & "/portal/files/9122871/pilehrood_1432.pdf"#