Cytotoxic evaluation of cubic boron nitride in human origin cultured cells

Investigation of cytotoxic antiproliferative and antiapoptotic effects of nanosized boron phosphate filled sodium alginate composite on glioblastoma cancer cells

BACKGROUND

The effects of nanosized boron phosphate-filled sodium alginate composite gel (SA/BP) on the biological characteristics of three types of glioblastoma multiforme (GBM) cells (C6, U87MG and T98G) were examined in this study. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay was used to determine the cytotoxicity of the composite gel on GBM, which was then compared to L929 healthy cells. Furthermore, wound healing, apoptosis, and colony formation capacities were evaluated. The investigation revealed that the SA/BP composite gel was successful in all GBM cells and could be used as a treatment agent for GBM and/or other invasive cancer types.

METHODS AND RESULTS

According to the results, the SA/BP composite gel had no effect on healthy fibroblast cells but had a lethal effect on all glioblastoma cells. Additionally, the wound healing method was used to examine the effect of the SA/BP composite gel on cell migration. It was discovered that the wound closed in 24 h in untreated control group cells, while the SA/BP composite gel closed up to 29.62%, 26.77% and 11.31% of the wound for C6, U87MG and T98G cell lines respectively. SA/BP significantly reduced cell migration in cancer cells. The effect of the generated SA/BP composite gel on cell colony development was assessed using a colony formation assay, and the cells reduced colony formation for all GBMs. It was roughly 45% for 24 h and 30% for 48 h when compared to the control group for C6 cells, 33%(24 h) and 40%(48 h) for U87MG cells, 40%(24 h) and 43%(48 h) for T98G cells. DAPI(4',6-Diamidino-2-phenylindole) and JC-1(5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine, iodide) staining to evaluate apoptosis revealed that the SA/BP composite gel dramatically enhanced the frequency of all GBMs undergoing apoptosis.

CONCLUSIONS

In line with experimental findings, it was observed that the SA/BP composite gel system did not affect healthy fibroblast cells but had a cytotoxic effect on glioblastoma cells, significantly reduced cell migration and colony-forming capacity of cells, and significantly increased apoptosis and depolarization of cell membranes. Based on all these findings, it can be said that SA/BP composite gel has cytotoxic, antiproliferative and antiapoptotic effects on different glioblastoma cells.

Sub-toxic levels of cobalt ions impair chondrocyte mechanostranduction via HDAC6-dependent primary cilia shortening

Cobalt ions are the main wear particles associated with orthopaedic implants, causing adverse complications due to cytotoxicity and inflammatory mediators. Recent studies have shown that sub-toxic levels of cobalt ions regulate matrix synthesis and inflammation, but the influence of cobalt ions on mechanotransduction remains unclear. Previously, we reported that sub-toxic levels of cobalt ions modulated primary cilia, which are crucial for mechanotransduction. This study therefore aimed to investigate the effect of cobalt ions on chondrocyte mechanosensation in response to cyclic tensile strain and the association with primary cilia. Sub-toxic levels of cobalt ions impaired chondrocyte mechanosensation and affected the gene expression of aggrecan, collagen II and MMP-13. Moreover, cobalt ions induced HDAC6-dependent primary cilia disassembly, which was associated with either cytoplasmic or ciliary α-tubulin deacetylation. Pharmaceutical HDAC6 inhibition with tubacin restored primary cilia length and mechanotransduction, whereas chemical depletion of primary cilia by chloral hydrate prevented mechanosignalling. Thus, sub-toxic levels of cobalt ions impaired chondrocyte mechanotransduction via HDAC6 activation, which was associated with tubulin deacetylation and primary cilia shortening.

Sub-toxic levels of Co2+ are anti-inflammatory and protect cartilage from degradation caused by IL-1β

BACKGROUND

Cobalt ions from some orthopaedic implants induce a dose-dependent cytotoxic and pro-inflammatory response. Recent studies show that sub-toxic levels of cobalt influence actin organisation regulating fibroblasts and macrophages behaviour. However little is known about the influence of sub-toxic levels of cobalt on articular cartilage biology and biomechanics. Previously, we have reported that IL-1β signalling in chondrocytes, is regulated by primary cilia and associated intraflagellar transport. Since primary cilia expression is modulated by actin organisation, we set out to test the hypothesis that sub-toxic levels of cobalt regulate cilia expression and IL-1β signalling thereby influencing articular cartilage degradation.

METHODS

Isolated chondrocytes and bovine cartilage explants were subjected to Co²⁺ in the presence and absence of IL-1β. Primary cilia were monitored by confocal immunofluorescence. Nitric oxide and PGE₂ release were used to monitor IL-1β signalling. Degradation of cartilage matrix was assessed by the release of sGAG and the biomechanical properties of the tissue in uniaxial unconfined compression.

FINDINGS

Sub-toxic levels of Co²⁺ (50 μM) blocked IL-1β-induced primary cilia elongation in isolated chondrocytes. This was associated with disruption of pro-inflammatory signalling in both isolated chondrocytes and cartilage explants, and inhibition of cartilage matrix degradation and loss of biomechanical properties.

INTERPRETATION

This study reveals that low levels of cobalt ions are anti-inflammatory, preventing cartilage degradation in response to IL-1β. This mechanism is associated with regulation of primary cilia elongation. These observations provide new insight into the potential beneficial role of cobalt and may lead to novel mechanisms for controlling cartilage inflammation.

Deposition of boron doped DLC films on TiNb and characterization of their mechanical properties and blood compatibility

Diamond-like carbon (DLC) material is used in blood contacting devices as the surface coating material because of the antithrombogenicity behavior which helps to inhibit platelet adhesion and activation. In this study, DLC films were doped with boron during pulsed plasma chemical vapor deposition (CVD) to improve the blood compatibility. The ratio of boron to carbon (B/C) was varied from 0 to 0.4 in the film by adjusting the flow rate of trimethylboron and acetylene. Tribological tests indicated that boron doping with a low B/C ratio of 0.03 is beneficial for reducing friction (μ = 0.1), lowering hardness and slightly increasing wear rate compared to undoped DLC films. The B/C ratio in the film of 0.03 and 0.4 exhibited highly hydrophilic surface owing to their high wettability and high surface energy. An in vitro platelet adhesion experiment was conducted to compare the blood compatibility of TiNb substrates before and after coating with undoped and boron doped DLC. Films with highly hydrophilic surface enhanced the blood compatibility of TiNb, and the best results were obtained for DLC with the B/C ratio of 0.03. Boron doped DLC films are promising surface coatings for blood contacting devices.

Cytotoxicity Analysis of Apatites Modified with Divalent Metals

Hydroxyapatite (HA) and apatite based biomaterials are important for bone replacement. Different apatites could be produced by substituting calcium, phosphate or hydroxyl groups, resulting in new materials with different physical, chemical and biological properties. In this work we investigate the biological compatibility of apatites modified by divalent cations in cultured mammalian cells using Balb/c 3T3 fibroblasts cell line. Modified apatites, Ca9.5M0.5(PO4)6(OH)2 (M=Fe, Zn, Cu, Co, Sr, V e Pb) and Ca10(VO4)6(OH)2 were produced and characterized by FTIR, XRD and XRF. Extracts of each metal-modified apatites (0.1mg/mL of Dulbeco Modified Eagle Medium – DMEM without serum) were obtained. Cells (3x104) were exposed for 24 h/37C to the pure extract (100%). Afterwards, the number of viable cells was determined in a hemocitometer. The number of viable cells in the absence of any extract was taking as 100%. SHA didn’t present any toxicity while phenol killed 82% of the cells. In the presence of pure extract of Fe-HA or Sr- HA an increase of 70% and 20%, respectively, in the number of relative cells was observed. On the other hand, the number of residual cells after treatment with the pure extract of Pb+2, Zn+2, Co+2, and (VO4)3- was73, 65, 48, and 21%, respectively. In conclusion, cells response was strongly dependent on the metal that substitutes calcium or phosphate. Further studies are required to better understand the biological effect of these substitutions.