Maturation of osteoblast-like SaoS2 induced by carbon nanotubes

Abstract

Osteogenic maturation of the osteoblast is crucial for bone formation. In this study, multi-walled carbon nanotubes (MWCNTs) and graphite (GP) were pressed as compacts. The greater ability of carbon nanotubes to adsorb proteins, compared with graphite, was shown. Human osteoblast-like SaoS2 cells were cultured and the cell response to the two kinds of compacts was compared in vitro. Meanwhile, we used cell culture on the culture plate as a control. Assays for osteonectin, osteopontin and osteocalcin gene expression, total protein (TP) amount, alkaline phosphatase activity (ALP) and DNA of cells cultured on the samples were done. During the conventional culture, significantly higher osteonectin, osteopontin and osteocalcin gene expression level, ALP/DNA and TP/DNA on carbon nanotubes were found. To confirm the hypothesis that the larger amount of specific proteins adsorbed on the carbon nanotubes was crucial for this, the compacts were pre-soaked in culture medium having additional recombinant human bone morphogenetic protein-2 (rhBMP-2) before cell culture. Compared with GP, osteonectin, osteopontin and osteocalcin gene expression level, ALP/DNA and TP/DNA of the cells tested increased more on the MWCNTs after the compacts were pre-soaked in the culture medium with rhBMP-2. The results indicated that the carbon nanotubes might induce osteogenic maturation of the osteoblast by adsorbing more specific proteins.

Nanocomposite and Nanostructured Carbon-based Films as Growth Substrates for Bone Cells

“…A similar response was found in human osteosarcoma SaOs-2 cells, which attached and proliferated much worse on graphite than on single-and multi-walled carbon nanotube films . In addition, SaOs-2 cells cultured on graphite showed a lower expression of osteonectin, osteopontin and osteocalcin, i.e., markers of osteogenic cell differentiation, and a lower content of alkaline phosphatase and total protein after pre-soaking both graphite and nanotube compacts in the culture medium with BMP-2 (Li et al, 2009b). In our earlier studies, graphite was prepared by pyrolysis, i.e., by a process defined as thermochemical decomposition of organic material at elevated temperatures (above 430 °C) in the absence of oxygen.…”

“…However, despite its electrical conductivity, which is usually associated with the stimulatory effects on cell colonization and functioning, unmodified graphite is rather bioinert, i.e., less adhesive for cells . It is due to a relatively low ability of graphite to adsorb cell adhesionmediating proteins from the serum supplement of the culture medium Li et al, 2009a) and also bone morphogenetic proteins (BMP), such as BMP-2, a factor promoting the osteogenic cell differentiation (Li et al, 2009b). As a result, graphite compacts allowed the attachment of mouse myoblastic C2C12 cells in significantly lower numbers compared to www.intechopen.com Nanocomposite and Nanostructured Carbon-based Films as Growth Substrates For Bone Cells 387 carbon nanotube compacts, which showed a significantly high capability to adsorb proteins.…”

“…Carbon nanotubes deposited on various substrates, such as polycarbonate membranes , glass coverslips (Holy et al, 2009), titanium (Terada et al, 2009), silicone rubber (Matsuoka et al, 2009), or pressed in compacts (Li et al, 2009a) markedly improved the adhesion, proliferation and differentiation of cells in cultures on these films in comparison with the non-coated materials or pure graphite. Similarly as in the composites of carbon nanotubes with polymers and ceramics, these favorable effects were mediated by an increased adsorption of specific proteins promoting cell adhesion, growth and differentiation, such as cell adhesion-mediating proteins from the serum of the culture medium , Li et al, 2009a and bone morphogenetic protein-2 (Li et al, 2009b), and particularly by the electrical activity of carbon nanotubes (Zanello et al, 2006). The electroactivity of carbon nanotube films makes these materials advantageous for tissue engineering applications involving electrically excitable tissues, such as muscles and nerves.…”

Chromatography of carbon nanotubes separated albumin from other serum proteins: a method for direct analysis of their interactions

“…In other words, there arises an urgent need for a good knowledge on the interaction between intact (chemically unmodified) MWCNT and proteins, especially cell-surface proteins [1][2][3] . In this paper, the classical column chromatography methodwhich entailed the use of a MWCNT-packed columnproved to be useful for the separation of serum proteins.…”

“…However, which protein(s) is(are) responsible for this strong adhesion remains an unresolved question 1,2) . To compound the intrigue surrounding the interaction between CNT and proteins, there remains a lack of a definitive tool and approach to investigate the interaction mechanism.…”