Impact of electrolyte solution on electrochemical oxidation treatment of Escherichia coli K-12 by boron-doped diamond electrodes.

We studied the disinfection efficacy of boron-doped electrodes on Escherichia coli-contaminated water-based solutions in three different electrolytes, physiological solution (NaCl), phosphate buffer (PB), and phosphate buffer saline (PBS). The effect of the electrochemical oxidation treatment on the bacteria viability was studied by drop and spread plate cultivation methods, and supported by optical density measurements. We have found that bacterial suspensions in NaCl and PBS underwent a total inactivation of all viable bacteria within 10 min of the electrochemical treatment. By contrast, experiments performed in the PB showed a relatively minor decrease of viability by two orders of magnitude after 2 h of the treatment, which is almost comparable with the untreated control. The enhanced bacterial inactivation was assigned to reactive chlorine species, capable of penetrating the bacterial cytoplasmic membrane and killing bacteria from within.

Coating Ti6Al4V implants with nanocrystalline diamond functionalized with BMP-7 promotes extracellular matrix mineralization in vitro and faster osseointegration in vivo.

The present study investigates the effect of an oxidized nanocrystalline diamond (O-NCD) coating functionalized with bone morphogenetic protein 7 (BMP-7) on human osteoblast maturation and extracellular matrix mineralization in vitro and on new bone formation in vivo. The chemical structure and the morphology of the NCD coating and the adhesion, thickness and morphology of the superimposed BMP-7 layer have also been assessed. The material analysis proved synthesis of a conformal diamond coating with a fine nanostructured morphology on the Ti6Al4V samples. The homogeneous nanostructured layer of BMP-7 on the NCD coating created by a physisorption method was confirmed by AFM. The osteogenic maturation of hFOB 1.19 cells in vitro was only slightly enhanced by the O-NCD coating alone without any increase in the mineralization of the matrix. Functionalization of the coating with BMP-7 resulted in more pronounced cell osteogenic maturation and increased extracellular matrix mineralization. Similar results were obtained in vivo from micro-CT and histological analyses of rabbit distal femurs with screws implanted for 4 or 12 weeks. While the O-NCD-coated implants alone promoted greater thickness of newly-formed bone in direct contact with the implant surface than the bare material, a further increase was induced by BMP-7. It can be therefore concluded that O-NCD coating functionalized with BMP-7 is a promising surface modification of metallic bone implants in order to improve their osseointegration.

Great Variety of Man-Made Porous Diamond Structures: Pulsed Microwave Cold Plasma System with a Linear Antenna Arrangement.

Synthetic diamond films are routinely grown using chemical vapor deposition (CVD) techniques. Due to their extraordinary combination of intrinsic properties, they are used as the functional layers in various bio-optoelectronic devices. It is a challenge to grow the dimensional layers or porous structures that are required. This study reviews the fabrication of various porous diamond-based structures using linear antenna microwave plasma (LAMWP) chemical vapor deposition (CVD), a low-cost technology for growing diamond films over a large area (>1 m2) at low pressure (<100 Pa) and at low temperature (even at 350 °C). From a technological point of view, two different approaches, i.e., templated diamond growth using three different prestructured (macro-, micro-, and nanosized) porous substrates and direct bottom-up growth of ultra-nanoporous diamond (block-stone and dendritelike) films, are successfully employed to form diamond-based structures with controlled porosity and an enhanced surface area. As a bottom-up strategy, the LAMWP CVD system allows diamond growth at as high as 80% CO2 in the CH4/CO2/H2 gas mixture. In summary, the low-pressure and cold plasma conditions in the LAMWP system facilitate the growth on three-dimensionally prestructured substrates of various materials that naturally form porous self-standing diamond structures.

Uptake and intracellular accumulation of diamond nanoparticles - a metabolic and cytotoxic study.

Diamond nanoparticles, known as nanodiamonds (NDs), possess several medically significant properties. Having a tailorable and easily accessible surface gives them great potential for use in sensing and imaging applications and as a component of cell growth scaffolds. In this work we investigate in vitro interactions of human osteoblast-like SAOS-2 cells with four different groups of NDs, namely high-pressure high-temperature (HPHT) NDs (diameter 18-210 nm, oxygen-terminated), photoluminescent HPHT NDs (diameter 40 nm, oxygen-terminated), detonation NDs (diameter 5 nm, H-terminated), and the same detonation NDs further oxidized by annealing at 450 °C. The influence of the NDs on cell viability and cell count was measured by the mitochondrial metabolic activity test and by counting cells with stained nuclei. The interaction of NDs with cells was monitored by phase contrast live-cell imaging in real time. For both types of oxygen-terminated HPHT NDs, the cell viability and the cell number remained almost the same for concentrations up to 100 µg/mL within the whole range of ND diameters tested. The uptake of hydrogen-terminated detonation NDs caused the viability and the cell number to decrease by 80-85%. The oxidation of the NDs hindered the decrease, but on day 7, a further decrease was observed. While the O-terminated NDs showed mechanical obstruction of cells by agglomerates preventing cell adhesion, migration and division, the H-terminated detonation NDs exhibited rapid penetration into the cells from the beginning of the cultivation period, and also rapid cell congestion and a rapid reduction in viability. These findings are discussed with reference to relevant properties of NDs such as surface chemical bonds, zeta potential and nanoparticle types.

Nanodiamond as promising material for bone tissue engineering.

The adhesion, growth and differentiation of human osteoblast-like MG 63 cells were investigated in cultures grown on nanostructured nanocrystalline diamond (NCD) films with either low surface roughness (rms of 8.2 nm) or hierarchically organized surfaces made of low roughness NCD films deposited on Si surfaces with the original microroughness (rms of 301.0 nm and 7.6 nm, respectively). The NCD films were grown using a microwave plasma-enhanced CVD method in an ellipsoidal cavity reactor. The films were treated in oxygen plasma to enhance the hydrophilic character of the diamond surface (water drop contact angle approx. 20 degrees). The samples were then sterilized by 70% ethanol, inserted into 12-well polystyrene multidishes (diameter 2.2 cm), seeded with human osteoblast-like MG 63 cells (40,000 cells/dish, 10,530 cells/cm2) and incubated in 2 ml of DMEM medium with 10% of fetal bovine serum. On day 3 after seeding, the cell numbers were significantly higher on the nanostructured NCD films (72,020 +/- 6540 cells/cm2) and also on the hierarchically micro- and nanostructured films (60200 +/- 6420 cells/cm2) than on the control polystyrene culture dish (40750 +/- 2,530 cells/cm2). The cells on hierarchically micro- and nanostructured diamond substrates also adhered over a significantly larger area (3730 +/- 180 microm2 compared to 2740 +/- 130 microm2 on polystyrene). The cell viability, measured by a LIVE/DEAD viability/cytotoxicity kit, reached 98% to 100% on both types of NCD films. The XTT test showed that the cells on both nanodiamond layers had significantly higher metabolic activity than those on the control polystyrene dish (approx. 2 to 3 times). Immunofluorescence staining of the cells on both NCD films revealed talin-containing focal adhesion plaques and beta-actin filaments, well apparent particularly at the cell periphery, as well as the presence of considerable amounts of osteocalcin, i.e., a marker of osteogenic cell differentiation. These results suggest that nanocrystalline diamond films give good support for adhesion, growth and differentiation of osteogenic cells and could be used for surface modification of bone implants in order to improve their integration with the surrounding bone tissue.