Abstract
Intrinsic nanocrystalline diamond (NCD) films have been proven to be promising substrates for the adhesion, growth and osteogenic differentiation of bone-derived cells. To understand the role of various degrees of doping (semiconducting to metallic-like), the NCD films were deposited on silicon substrates by a microwave plasma-enhanced CVD process and their boron doping was achieved by adding trimethylboron to the CH4:H2 gas mixture, the B∶C ratio was 133, 1000 and 6700 ppm. The room temperature electrical resistivity of the films decreased from >10 MΩ (undoped films) to 55 kΩ, 0.6 kΩ, and 0.3 kΩ (doped films with 133, 1000 and 6700 ppm of B, respectively). The increase in the number of human osteoblast-like MG 63 cells in 7-day-old cultures on NCD films was most apparent on the NCD films doped with 133 and 1000 ppm of B (153,000±14,000 and 152,000±10,000 cells/cm2, respectively, compared to 113,000±10,000 cells/cm2 on undoped NCD films). As measured by ELISA per mg of total protein, the cells on NCD with 133 and 1000 ppm of B also contained the highest concentrations of collagen I and alkaline phosphatase, respectively. On the NCD films with 6700 ppm of B, the cells contained the highest concentration of focal adhesion protein vinculin, and the highest amount of collagen I was adsorbed. The concentration of osteocalcin also increased with increasing level of B doping. The cell viability on all tested NCD films was almost 100%. Measurements of the concentration of ICAM-1, i.e. an immunoglobuline adhesion molecule binding inflammatory cells, suggested that the cells on the NCD films did not undergo significant immune activation. Thus, the potential of NCD films for bone tissue regeneration can be further enhanced and tailored by B doping and that B doping up to metallic-like levels is not detrimental for cells.
Highlights
Nanostructured materials, i.e. materials characterized by dimensions of less than 100 nanometres, are promising for a wide range of advanced technologies, including nanomedicine
Conclusions and further perspectives We found that both the intrinsic nanocrystalline diamond (NCD) films and the borondoped NCD films accelerated the proliferation of human osteoblast-like MG 63 cells in cultures on these films in the early exponential phase of growth, increased their numbers and enhanced their differentiation towards the osteogenic cell phenotype, manifested by increased concentration of osteocalcin and collagen I per mg of cellular protein in comparison with cells grown on standard polystyrene dishes
These beneficial effects can be explained by the nanoroughness of NCD films and their wettability, and they were further enhanced by boron doping of these films
Summary
Nanostructured materials, i.e. materials characterized by dimensions of less than 100 nanometres, are promising for a wide range of advanced technologies, including nanomedicine. In this novel interdisciplinary scientific field, nanostructured materials are developed or applied as carriers for targeted drug and gene delivery, as tracers for bioimaging, tools for nanoscale surgery, components of nanoelectronic biosensors, and as cell carriers for tissue engineering, i.e. for constructing bioartificial replacements for irreversibly damaged tissues and organs. The cells have to bridge the irregularities or to spread only in a limited space in the grooves among the prominences, which reduces the cellsubstratum contact area, proliferation activity, viability and functioning of the cells, e.g., the activity of alkaline phosphatase in osteoblasts, necessary for bone tissue mineralization [2,3,4,5]
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