Yasaman Alinejad

Preosteoblasts behavior in contact with single‐walled carbon nanotubes synthesized by radio frequency induction thermal plasma using various catalysts

The influence of single‐walled carbon nanotubes (SWCNTs) produced by radio frequency (RF) induction thermal plasma with three catalyst mixtures (Ni‐Co‐Y2O3, Ni‐Y2O3 and Ni‐Mo‐Y2O3) was evaluated on the behavior of murine MC3T3‐E1 preosteoblasts. After analyzing SWCNTs properties, mitochondrial enzymatic (MTS) and lactate dehydrogenase (LDH) activities as well as neutral red (NR) uptake were measured to assess the cellular viability. To ascertain that the cytotoxicity was not merely as a result of the mechanical disturbance, either SWCNTs were added on the attached cells or cells were seeded on the SWCNT‐covered plates. Regardless of the catalyst mixtures used for their production, SWCNTs added on the attached cells reduced cell viability drastically in a dose‐dependent manner. However, the viability of cells seeded on SWCNTs even on those produced with Ni‐Co‐Y2O3 was slightly decreased at 24 h and besides cells could proliferate within 48 h. Furthermore, cells were able to organize normal filamentous actin cytoskeleton and no apoptotic cells were detected in the cultures. Thus except mechanical disturbance, thermal plasma grown SWCNTs seem to induce no severe cytotoxicity on MC3T3‐E1 preosteoblasts and therefore are considered promising CNTs to be studied more deeply for future applications in bone tissue engineering. Copyright

Induction thermal plasma process modifies the physicochemical properties of materials used for carbon nanotube production, influencing their cytotoxicity.

Abstract The effect of radio frequency induction thermal plasma (RFITP) process on the cytotoxicity of materials used for single-walled carbon nanotube production remains unknown. In this study, the influence of RFITP process on physicochemical and cytotoxic properties of commercial Co, Ni, Y2O3, Mo catalysts and carbon black was investigated. The cytotoxic assays (MTS, LDH, neutral red, TUNEL) revealed the strongest effect of commercial Co on murine Swiss 3T3 fibroblasts affecting their viability in a dose-dependent manner within 24 h. The cells contained also less actin stress fibres. Although RFITP affects the properties of each catalyst (size, morphology, chemistry), only cytotoxicity of Ni catalyst was increased. The plasma-treated Ni induced apoptosis. Comparing Ni particles before and after RFITP process with commercial nanoparticles of Ni revealed that the particles with similar surface area have different cytotoxicities. Interestingly, the observed toxicity of the catalysts was not mainly due to the release of ions.The effect of radio frequency induction thermal plasma (RFITP) process on the cytotoxicity of materials used for single-walled carbon nanotube production remains unknown. In this study, the influence of RFITP process on physicochemical and cytotoxic properties of commercial Co, Ni, Y₂O₃, Mo catalysts and carbon black was investigated. The cytotoxic assays (MTS, LDH, neutral red, TUNEL) revealed the strongest effect of commercial Co on murine Swiss 3T3 fibroblasts affecting their viability in a dose-dependent manner within 24 h. The cells contained also less actin stress fibres. Although RFITP affects the properties of each catalyst (size, morphology, chemistry), only cytotoxicity of Ni catalyst was increased. The plasma-treated Ni induced apoptosis. Comparing Ni particles before and after RFITP process with commercial nanoparticles of Ni revealed that the particles with similar surface area have different cytotoxicities. Interestingly, the observed toxicity of the catalysts was not mainly due to the release of ions.

A Longitudinal Low Dose μCT Analysis of Bone Healing in Mice: A Pilot Study.

Low dose microcomputed tomography (μCT) is a recently matured technique that enables the study of longitudinal bone healing and the testing of experimental treatments for bone repair. This imaging technique has been used for studying craniofacial repair in mice but not in an orthopedic context. This is mainly due to the size of the defects (approximately 1.0 mm) in long bone, which heal rapidly and may thus negatively impact the assessment of the effectiveness of experimental treatments. We developed a longitudinal low dose μCT scan analysis method combined with a new image segmentation and extraction software using Hounsfield unit (HU) scores to quantitatively monitor bone healing in small femoral cortical defects in live mice. We were able to reproducibly quantify bone healing longitudinally over time with three observers. We used high speed intramedullary reaming to prolong healing in order to circumvent the rapid healing typical of small defects. Bone healing prolongation combined with μCT imaging to study small bone defects in live mice thus shows potential as a promising tool for future preclinical research on bone healing.

Synthesis of single-walled carbon nanotubes using induction thermal plasma technology with different catalysts: thermodynamic and experimental studies

The effects of the type and quantity of three catalyst mixtures (i.e. Ni-Y2O3, Ni-Co-Y2O3, and Ni-Mo-Y2O3) on single-walled carbon nanotubes (SWCNT) synthesis by induction thermal plasma process have been examined in order to evaluate their individual influences on SWCNT production. Thermodynamic calculations, in gas and particularly in liquid solution phases, have also been performed to better understand the effects of the catalysts on the production of SWCNT. Characterization of the synthesized SWCNT by different techniques including Raman spectroscopy, high resolution scanning electron microscopy (HRSEM) imaging and thermogravimetric analysis (TGA) clearly indicated that the best quality of SWCNT was achieved using Ni-Co-Y2O3 catalyst mixture in the feedstock.

In situ removal of amorphous carbon from single-walled carbon nanotubes synthesized by induction thermal plasma

In this work, a simple, efficient and cost-effective in situ purification method has been developed based on gas-phase oxidation, in an effort to increase purity of single-walled carbon nanotubes (SWNT) in the course of SWNT synthesis by induction thermal plasmas. This newly developed purification method has the following advantages compared with the conventional off-line gas-phase oxidation techniques; 1) residual heat carried by plasma gases from the reactor can be utilized as a heat source for the thermal oxidation reaction; 2) oxidizing reactants can pass through the SWNT soot collected on the surface of metallic filters, resulting in more uniform and effective etch of amorphous carbons; 3) this one-step process is basically continuous and easy to be scaled up. In the purification experiments, for the thermal oxidation of the SWNT soot, pre-heated oxygen is injected into the collection chamber during the SWNT synthesis with three different oxygen flow rates of 5, 7.5 and 10 vol% 02, and then subsequent changes in the SWNT soot are analyzed by various material characterization techniques, such as thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. The results clearly show that the major by-product of amorphous carbons can be successfully eliminated by this method and the purity of the SWNT has been increased approximately from 35 wt% to 60 wt% due to preferential removal of amorphous carbons. The parametric study on the effect of the flow rate also suggests that the most effective flow rate of the oxidizing gas is around 10 vol%. However, the diameter distribution of the SWNT samples has been narrowed during the in situ thermal oxidation process because of a significant loss of thin nanotubes.