In vitro studies on the effect of delaminated a-C:H film fragments on bone marrow cell cultures

Influence of surface roughness of carbon materials on human osteoblast-like cell growth

This article presents a study of the dependence of the biocompatibility of a carbon-based material, namely a 2D C/C composite, on mechanical and chemical surface modifications. The mechanical modifications were surface grinding and polishing, and chemical modifications were made by depositing thin layers of pyrolytic carbon, titanium-carbon and DLC layers. Human osteoblast-like MG 63 cells were cultivated on these materials. The densities of the cells after one-day cultivation and after four-day cultivation, and the average cell spreading area after one-day cultivation, were evaluated in dependence on particular surface roughness parameters. The minima of the cell density on pyrolytic carbon and titanium-carbon layers were found; they were connected with the maxima of the average cell area. For DLC, the cell area decreased as the roughness parameter Ra increased in the range 0.1-10 µm, although the minimum appeared for the density of the cells. Using a multivariate test, the dependences of the biocompatibility parameters on the layer material and on surface grinding were statistically significant. The results suggest that the optimal roughness parameters for MG 63 cell on carbon based surface were Ra ∼ 3.5 µm, RSm ∼0.03-0.08 mm, Rsk ∼0 or negative and Rku ∼ 20, DLC being the best material choice. These values of roughness were obtained by simple mechanical grinding of substrate and coating by DLC layer.

Adhesion, Growth and Differentiation of Osteoblasts on Surface-Modified Materials Developed for Bone Implants

This review briefly outlines the history and possibilities of bone reconstruction using various types of artificial materials, which allow interaction with cells only on the surface of the implant or enable ingrowth of cells inside the material. Information is also provided on the most important properties of bone cells taking part in bone tissue development, and on diseases and regeneration. The most common cell types used for testing cell-material interaction in vitro are listed, and the most commonly used approaches to this testing are also mentioned. A considerable part of this review is dedicated to the physical and chemical properties of the material surface, which are decisive for the cell-material interaction, and also to modifications to the surface of the material aimed at integrating it better with the surrounding bone tissue. Special attention is paid to the effects of nanoscale and microscale surface roughness on cell behaviour, to material surface patterning, which allows regionally-selective adhesion and growth of cells, and also to the surface chemistry. In addition, coating the materials with bioactive layers is examined, particularly those created by deposition of fullerenes, hybrid metal-fullerene composites, carbon nanotubes, nanocrystalline diamond films, diamond-like carbon, and nanocomposite hydrocarbon plasma polymer films enriched with metals.

Tribological behavior of DLC-coated articulating joint implants

Coatings from diamond-like carbon (DLC) have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the total joint replacement field, layer performance, stability and adhesion in realistic physiological setups are quintessential and these aspects have not been consistently researched. In our team's efforts to develop long-term stable DLC implant coatings, test results gained from a simplified linear spinal simulator setup are presented. It is shown that metal-on-metal (MoM) pairs perform well up to 7 million loading cycles, after which they start to generate wear volumes in excess of 20 times those of DLC-coated implants. This is attributed to the roughening observed on unprotected metal surfaces. Furthermore, we illustrate that in contrast to DLC-on-DLC, MoM tribopairs require protein-containing media to establish low-friction conditions. Finally, results of defect monitoring during testing are presented, showing catastrophic failure of layers whose interfaces are too weak with respect to the stress-corrosion-cracking mechanism encountered in vivo.

Osteoblast interaction with DLC-coated Si substrates

Diamond-like carbon (DLC) coating is a convenient means of modifying material surfaces that are sensitive to wear, such as titanium and silica substrates. This work aims to evaluate the osteoblast-like cells' response to DLC-coated Si (Si-DLC), which was treated under different conditions. DLC and deuterated DLC films were deposited by plasma-enhanced chemical vapor deposition to obtain a 200-nm-thick layer on all the samples. Three types of precursor gas were applied for deposition: pure methane (CH(4)), pure deuterated methane (CD(4)) and their half/half mixture. All surface treatments were performed under two different self-bias voltages (V(sb)): -400 and -600V. The modified surfaces were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, Rutherford backscattering spectroscopy, elastic recoil detection analysis, X-ray reflectometry and the sessile-drop method. MC3T3-E1 osteoblasts were cultured on the Si-DLC wafers for 3 and 6 days. Biological tests to measure cell proliferation, cell vitality, cell morphology and cell adhesion were performed. All DLC coatings produced a slightly more hydrophobic state than non-treated Si. Certain types of amorphous DLC coating, such as the surface treated under the V(sb) of -600V in pure methane (600CH(4)) or in pure deuterated methane (600CD(4)), offered a significantly higher cell proliferation rate to Si substrate. Scanning electron microscopy observations confirmed that the optimal cell adhesion behavior, among all the treated surfaces, occurred on the surface of the 600CH(4) and 600CD(4) groups, which showed increased amounts of filopodia and microvilli to enhance cell-environment exchange. In conclusion, DLC coating on Si could produce better surface stability and improved cellular responses.

Biological response to micron- and nanometer-sized particles known as potential wear products from artificial hip joints: Part I: Selection and characterization of model particles

The aim of this work was to select and characterize model particles, which correspond to real wear products from artificial hip joints, and to investigate the dispersing behavior of these powders. Commercially available nano and microparticles of corundum, graphite, and chromium oxide were selected or alternatively self-produced by milling. These powders were characterized regarding density, specific surface area, crystalline phases, particle size distributions and shape. Volume-based particle size distributions Q(3)(d) were measured after dispersing in water, water with dispersant, Ringers solution, and cell culture solution (Dulbecco's Modified Eagle's Medium (DMEM)) by laser diffraction and ultrasonic spectroscopy. Nanopowders formed agglomerates in the micrometer range in cell culture solutions. The micropowders showed only a marginal agglomeration. The median diameters of the dispersed nanopowders were even bigger than those of micropowders. Calculations of the number-based size distribution Q(0)(d) showed that in spite of the agglomeration the predominant number of the nano and microparticles is in the sub micrometer range, with only one exception, the micrographite powder.