Cobalt Chloride as a Hypoxia Mimicking Agent Induced HIF-1α and mTOR Expressions of Human Umbilical Cord Mesenchymal Stem Cells

ABSTRACT Objective: To assess the effects of cobalt chloride (CoCl2) as a hypoxia mimicking agent on human umbilical cord mesenchymal stem cells (hUCMSCs) expression of HIF-1α and mTOR for use in regenerative dentistry. Material and Methods: Human umbilical cord mesenchymal stem cells were isolated and then cultured. The characteristics of stemness were screened and confirmed by flow cytometry. The experiment was conducted on hypoxia (H) and normoxia (N) groups. Each group was divided and incubated into 24-, 48-, and 72-hours observations. Hypoxic treatment was performed using 100 µM CoCl2 on 5th passage cells in a conventional incubator (37°C; 5CO2). Then, immunofluorescence of HIF-1α and mTOR was done. Data was analyzed statistically using One-way ANOVA and Tukey's HSD. Results: Significant differences were found between normoxic and hypoxic groups on HIF-1α (p=0.015) and mTOR (p=0.000) expressions. The highest HIF-1α expression was found at 48 hours in the hypoxia group, while for mTOR at 24 hours in the hypoxia group. Conclusion: Hypoxia using cobalt chloride was able to increase human umbilical cord mesenchymal stem cells expression of HIF-1α and mTOR.

Thermal expansion and corrosion resistance of cobalt-chromium alloys fabricated by contemporary manufacturing processes: an in vitro study / Expansión térmica y resistencia a la corrosión de aleaciones de cobalto-cromo fabricadas mediante procesos de abricación contemporáneos: un estudio in vitro

In Purpose: The fabrication technique can influence the mechanical properties of Cobalt-Chromium (Co-Cr) dental alloys. Hence, the present study aims to determine the corrosion resistance and thermal expansion of alloys manufactured using three contemporary techniques. Material and Methods: A total of nine specimens of Co-Cr alloy were prepared according to ISO 22674 by each one of the three manufacturing processes (three in each process); conventional casting, direct metal laser sintering (DMLS) and milling (MIL). All these specimens were tested for coefficient of thermal expansion and corrosion resistance. The data was tabulated and analyzed statistically. Results: The difference in the thermal expansion of alloys fabricated using three techniques was non-significant at almost all the temperatures from 50 ºC to 950 ºC (p>0.05), except 450 ºC and 600 °C. The polarization resistance of specimens manufactured using the conventional method was more compared to DMLS and MIL at pH 5 (Conventional>MIL>DMLS) (p<0.001). Conclusion: The thermal expansion behavior of alloys manufactured using the three selected techniques were similar, whereas, at acidic pH, the corrosion resistance of conventional and MIL were better than the DMLS.

Antecedentes: La técnica de fabricación puede influir en las propiedades mecánicas de las aleaciones dentales de cobalto-cromo (Co-Cr). Por lo tanto, el presente estudio tiene como objetivo determinar la resistencia a la corrosión y la expansión térmica de aleaciones fabricadas con tres técnicas contemporáneas. Material y Métodos: Se prepararon un total de nueve probetas de aleación de Co-Cr según ISO 22674 por cada uno de los tres procesos de fabricación (tres en cada proceso); fundición convencional, sinterización directa de metal por láser (DMLS) y fresado (MIL). Todos estos especímenes fueron probados para determinar el coeficiente de expansión térmica y la resistencia a la corrosión. Los datos fueron tabulados y analizados estadísticamente. Resultados: La diferencia en la dilatación térmica de las aleaciones fabricadas con las tres técnicas no fue significativa en casi todas las temperaturas desde 50ºC hasta 950ºC (p>0,05), excepto 450ºC y 600ºC. La resistencia a la polarización de las muestras fabricadas con el método convencional fue mayor en comparación con DMLS y MIL a pH 5 (Convencional>MIL>DMLS) (p<0, 0 01). Conclusión: El comportamiento de expansión térmica de las aleaciones fabricadas con las tres técnicas seleccionadas fue similar, mientras que, a pH ácido, la resistencia a la corrosión de la convencional y la MIL fue mejor que la de la DMLS.

Two novel Co(II) complexes with two different Schiff bases: inhibiting growth of human skin cancer cells

Using two flexible Schiff bases, H2L1 and H2L2, two new cobalt II (Co(II))-coordination compounds, namely, Py3CoL1 (1) and Py3CoL2 (2) (Py=pyridine, L1=3,5-ClC6H2(O)C=NC6H3(O)-4-NO2, L2=3,5-BrC6H2(O)C=NC6H3(O)-4-NO2) have been synthesized under solvothermal conditions. Single crystal X-ray structural analysis revealed that compounds 1 and 2 are both six-coordinate in a distorted octahedral geometry, and the 1D chain structure was formed by the π…π and C-H…O interactions or C-H…Cl interaction. The in vitro antitumor activities of 1, 2 and their corresponding organic ligands Py, L1, and L2 were studied and evaluated, in which three human skin cancer cell lines (A-431, HT-144 and SK-MEL-30) were used in the screening tests.

Are bovine teeth a suitable substitute for human teeth in in vitro studies to assess endotoxin load in root canals?

The present study aimed to determine the feasibility of using bovine teeth as a suitable alternative for human teeth, in experiments involving in vitro endotoxin contamination. Twenty bovine central incisors and 20 human single-root premolars had their dental crowns removed and root lengths set at 16 mm. Root canals were prepared up to #60 K-file size and sterilized with cobalt-60 gamma irradiation (20 kGy, 6 h). The teeth were randomly divided into four groups: G1-bovine teeth (bovine negative control, n = 10), G2-human teeth (human negative control, n = 10), G3-bovine teeth, inoculated withEscherichia coli (055:B55) LPS, and G4-human teeth inoculated with E. coli LPS. The G1 and G2 groups were exposed to apyrogenic water. After the teeth had been incubated at 37 °C and atmospheric humidity for 24 h, the samples of solutions in the main canals were collected with apyrogenic absorbent paper tips. LPS levels were quantified using Limulus Amebocyte Lysate assay. The data obtained were statistically analyzed using one-way ANOVA, with a significance level of 5%. A high amount of endotoxin was detected in the inoculated human teeth (G4) when compared to the sterilized teeth (G2), as well as in the inoculated bovine teeth (G3) when compared to the inoculated human teeth (G4). However, there was no statistical difference between bovine teeth before and after the E. coli endotoxin inoculation. Therefore, under the mentioned experimental conditions, the use of bovine teeth should not be a choice for laboratory research on endotoxin contamination.

A new spectrophotometric method for quantification of potassium solubilized by bacterial cultures.

A new spectrophotometric method was developed for the quantification of potassium in the culture broth supernatant of K-solubilizing bacteria. The standard curve of potassium with the new method, which is based on the measurement of cobalt, showed a regression coefficient (R2) of 0.998. The quantification values of potassium obtained with flame photometric method and the newly developed method showed a significant correlation (r) of 0.978. The new method depends on the precipitation of sodium cobaltinitrite with solubilized potassium in liquid medium as potassium sodium cobaltinitrite, which develops bluish green colour by the addition of conc. HCl. The intensity of developed colour can be recorded at 623 nm. This method involves less number of steps, is easy and time saving, and can be used for the reliable estimation of available potassium in culture broth supernatant of K-solubilizing bacteria.

Molecular cloning, purification and characterization of thermostable -1,3-1,4 glucanase from Bacillus subtilis A8-8.

A gene encoding a -1,3-1,4-glucanase (CelA) belonging to family 5 of glycoside hydrolases was cloned and sequenced from the Bacillus subtilis A8-8. The open-reading-frame of celA comprised 1499 base pairs and the enzyme was composed of 500 amino acids with a molecular mass of 55 kDa. The recombinant -1,3-1,4 glucanase was purified by GST-fusion purification system. The pH and temperature optima of the enzyme were 8.0 and 60oC, respectively. The enzyme was stable within pH 6.0-9.0. It was stable up to 60oC and retained 30% of its original activity at 70oC for 60 min. It hydrolyzed lichenan, CMC, xylan, laminarin, avicel and pNPC, but was inactive towards cellobiose. The enzyme activity was markedly activated by Co2+ and Mn2+, but was strongly inactivated by Fe3+. The truncated gene, devoid of cellulose-binding domain (CBD) showed 60% of activity and bound to avicel.

Tensile bond strength of composite luting cements to metal alloys after various surface treatments.

Aims: To evaluate the effects of two different surface treatments and bonding agents on tensile bond strength between a Co-Cr and a Ni-Cr cast alloy and two resin-luting cements. Materials and Methods: Two hundred and forty alloy samples were cast and subjected to surface treatments such as sandblasting, chemical etching, and sandblasting plus chemical etching. Panavia F and CandB cement were used as cementing mediums. The etching qualities were examined by a stereooptic microscope. Failure surfaces were examined throughout scanning electron microscopy. The data were evaluated using statistical methods, namely analysis of variance and multiple comparison test (Tukey HSD). Results: Significant differences were found in the bonding provided by the various cements (P < 0.001) and also type of surface treatments (P < 0.001). For all groups, sandblasted surfaces showed the highest bond strength values. There was no significant difference between the Cr-Co and the Cr-Ni alloys (P > 0.05). Conclusions: Panavia F showed higher tensile strength and the sandblasted samples possessed higher tensile strength.

Synthesis, characterization and catalytic activity of copper [II], nickel [II] and cobalt [II] complexes derived from novel hydrazone drivatives of oxamic hydrazide

A series of new coordination complexes of Cu[II], Ni[II] and Co[II] with omaxic hydrazide [L[1]], N,N' - [salicylidene]- oxamic hydrazide [L[2]] and N,N' - bis [naphthalidene] - oxamic hydrazide [L[3]] have been synthesized and characterized by elemental analysis, magnetic moment, IR, UV - Vis spectra nd molar conductance. The thermal behavior of the complexes was investigated by TG A and DTA techniques. The catalytic activity of the complexes to decolorize the Allura-Red [food dye] in presence of H[2]O[2] was studied

Synthesis and characterization of Co[3]O[4]/CeO[2] nanocomposite

Ceria based nanocoomposite oxides containing different amounts of cobalt [4, 8, 15, 21, 26, 30 wt% ad Co[3]O[4]] were prepared by impregnation method at various calcinations temperatures. The effect of both heat treatment and loading on the structural, textural and morphological properties of the as prepared nanocomposites was determined. The combined effect of cobalt oxide and ceria, at different compositions, strongly influences the properties of the nanocomposite oxide, by dispersing the Co[3]O[4] phase and promoting the efficiency of the Co[3+]-Co[2+] and Ce[4+] - Ce[3+] redox couples. The heat treatment and loading influenced the interaction between cobalt and CeO[2] evidently. The incorporation of Co ions into CeO[2] crystal lattice resulted in weaker interaction between cobalt and ceria on composite surface. Cobalt loading of sample heated at 500 [degree sign]C led to a progressive decrease in the crystallite size, lattice constant and unit cell volume of cerium and cobalt oxides. Co[3]O[4] loading at 500 [degree sign]C brought about a significant increase in the surface area of the investigated system. Opposite behavior was observed by increasing the calcinations temperature from 400 to 600 [degree sign] C. However, the sintering activation energies of cerium and cobalt oxides were evaluated to be 8 and 11 kJ/mol, respectively

Kinetics of oxidation of [N-isopropylidene - hydrazine-s-methyldithiocarboxylate] cobalt [II] complex by N-bromosuccinimide and N-bromophthalimide in non polar solvent

The kinetics of oxidation of [N-isopropylidene - hydrazine-s-methyldithio-carboxylate] cobalt [II] complex by N-bromosuccinimide [NBS] and N-bromophthalimide [NBP] in benzene solvent were studied spectrophotometrically at lambda = 300 - 310 nm and at 281-297 K for a range of complex and oxidant concentrations. The reaction exhibited a first order dependence on both reactants. The detection of the initial cobalt [III] products which are slowly converted to the final cobalt [III] supports an inner-sphere mechanism for the oxidation of the complex by both oxidants. Under identical experimental conditions, the extent of oxidation using the oxidizing agents is in the order: NBS > NBP. GC-MS analysis for the reaction mixture after completion of the oxidation reaction indicates the presence of both succinimide and phthalimide as side products of the oxidation process

Surface and antitumor activity of some novel metal-based cationic surfactants.

The development of anticancer metal-based drugs was attempted by reacting dodecyl amine with selenious acid to produce a quaternary ammonium salt which was then converted to copper and cobalt cationic complexes via complexing the first compounds with copper (II) or cobalt (II) ions. The surface properties of these surfactants were investigated. The surface properties studied included critical micelle concentration (CMC), maximum surface excess (Gamma max ), and minimum surface area (A min ). Free energy of micellization (Delta G degree mic ) and adsorption (Delta G degree ads ) were calculated. Antitumor activity was tested by using Ehrlich ascites carcinoma (EAC) as a model system of mice cell tumor. The compounds were also tested in vitro on five human monolayer tumor cell lines: MCF 7 (breast carcinoma), HEPG 2 (liver carcinoma), U 251 (brain tumor), HCT 116 (colon carcinoma), and H 460 (lung carcinoma). FTIR spectra, elemental analysis, and H 1 NMR spectra were performed to insure the purity of the prepared compounds.

Shear bond strenght between metal alloy and a ceramic system, submitted to different thermocycling immersion times

El objetivo de este estudio fue evaluar la resistencia a cizallamiento de aleaciones metálicas de Co-Cr y Ni-Cr; con un mismo tipo de cerámica, sometidos a diferentes tiempos de inmersión en el termociclaje. Sesenta especímenes fueron confeccionados de forma standarden formato cilindrico. Tres condiciones de termociclaje fueron evaluadas: sin termociclaje, 3000 ciclos (5ºC/55ºC±1) con 30s y 3.000 ciclos (5ºC/55ºC±1) con 60s de tiempo de inmersión. El ensayo de cizallamiento fue realizado en una máquina universal usando un dispositivo para concentrar la tensión en la interfase metalocerámica durante el test. La carga fue aplicada hasta que ocurra la fractura de los especimenes. La información fue estadísticamente analizada por ANOVA(two-way) y el test de Tukey (p<0,05). Los resultados no mostraron diferencia estadísticamente significante entre las combinaciones metal-porcelana. Sin embargo, ambas combinaciones metalocerámicas sometidas a 60s de tiempo de inmersión mostraron valores más bajos en comparación con los especimenes del grupo sin termociclaje. Fue concluido que el tiempo de inmersión de termociclaje de 1 minuto afectó los valores de resistencia de cizallamiento en los grupos de Ni-Cr/porcelana y Cr-Co/porcelana.

Electrical conductance of cobalt [III] complexes of acetylpyridinethiosemicarbazone halides in ethanol at 25C

The conductance in ethanol solution of cobalt [III] complexes of acetylpyridinethiosemicarbazone halides has been measured at 25C and analyzed using the Fuoss-Onsager equation in an attempt to obtain accurate values of the molar specific conductivity at infinite dilution lambda degree, the closest distance of approach a degree and the association constant KA. From the study of the anion solvation, association was found to decrease with increasing the anionic radius. The relation between KA and the solvent separated-iron pair model was discussed. The electrostatic Stoke's radii R+ and R- were calculated

Isoionic association of cobalt [III] complexes of pyridinealdehyde-thiosemicarbazone halides in water, methanol and ethanol

The ion-pair association of cobalt [III] complexes of pyridinealdehydethiosemicarbazone halides in water, methanol, and ethanol at 25 degree from conductance measurements was found to depend on the solvation of the anion and decreased with increasing anion crystallographic radius. The association constant KA increased with increasing anionic in water while the contrary was observed in the case of methanol and ethanol. The association constant KA is analyzed on the basis of solvent separated -ion pair model

Extrathermodynamic analysis on the rate of equation of chloropentaminecobalt [III] ion in 10 acetone decarboxylate solution / acetone dicarboxylate solution

The rate of aquation of [Co[NH[3]][5]C1[2+]ion in aqueous dicarboxylate media of 10% [v/v] acetone has been studied in the temperature range, 30-60°C for six different types of dicarboxylate ions namely, succinate, malate, tartrate, malonante, maleate and phthalate. The ion-pair rate coefficient [k[ip]] has been estimated according to Wyatt and Davies treatment. The thermodynamic parameters delta G[ip] and delta S[ip]have been correlated with delta G o/ip and delta So/ip respectively, in a linear free energy and linear entropy relationships. Besides, the isokinetic relationship analysis reveals the existence of an entropy effect