Date of Award:

5-2011

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biological Engineering

Committee Chair(s)

Soonjo Kwon

Committee

Soonjo Kwon

Committee

Tapas Kar

Committee

David Britt

Abstract

Carbon nanotubes (CNTs) are one of the most popular nanomaterials. There has been increasing interest in the development and applications of carbon nanotubes due to their huge potential in industrial and medical applications. Recent applications of carbon nanotubes include development of scaffolds and drug delivery systems. Despite rapidly emerging applications of CNTs, little is known about the impact of CNTs on cellular processes, especially mesenchymal stem cell (MSC)'s differentiation. Also, the effects of nanoparticle exposure under different conditions on cellular responses have not been well characterized yet.

To characterize the effects of CNTs on creating nanoscale scaffolds for tissue engineering, we incorporated multi-walled CNTs (MWCNTs) into reconstituted type I collagen, and evaluated proliferation, differentiation, mineralization and inflammatory response of MSC on those scaffolds. MWCNTs were homogeneously distributed in collagen matrix, and strongly entrapped in collagen at the concentrations below 100 ppm. Alkaline phosphatase (AP) activity and mineralized nodules of extracellular matrix (ECM) were monitored as osteogenic differentiation markers. AP activity was significantly increased in 12 days after being replaced by differentiating media. Collagen enhanced AP activity, and MWCNT-collagen scaffolds induced additional increase in AP activity. The MSC released a significantly higher level of AP on MWCNT-collagen scaffolds than the plastic surface did at day 16. An increasing percentage of ECM mineralization was seen at day 16 after being replaced by differentiating media in the presence of MWCNT-collagen scaffolds. This study indicated the possibility of enhancement in MSC differentiation in the MWCNT-collagen scaffolds. The increased level of differentiation markers was due to the increased stiffness of the scaffolds for MSC. Our data indicated that the collagen-MWCNT scaffolds might have the potential application to create nanoscale scaffold materials for tissue engineering.

To illustrate the effects of interleukin-8 (IL-8) expression in human alveolar epithelial cells (A549) under various exposure conditions of CNT, we measured the level of IL-8 expression in the presence and absence of serum following exposure of SWCNTs. The results demonstrated that the IL-8 expression was enhanced in the presence of serum. The IL-8 expression kept increasing at low concentration even after removing SWCNTs from the media. Further studies are required to characterize biological functions and toxicological potentials of nanomaterials.

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Comments

This work made publicly available electronically on May 11, 2011.

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