Growth and characterization of Escherichia coli DH5α biofilm on concrete surfaces as a protective layer against microbiologically influenced concrete deterioration (MICD)

Biofilms of selected bacteria strains were previously used on metal coupons as a protective layer against microbiologically influenced corrosion of metals. Unlike metal surfaces, concrete surfaces present a hostile environment for growing a protective biofilm. The main objective of this research was to investigate whether a beneficial biofilm can be successfully grown on mortar surfaces. Escherichia coli DH5α biofilm was grown on mortar surfaces for 8 days, and the structure and characteristics of the biofilm were studied using advanced microscopy techniques such as scanning electron microscopy and confocal laser scanning microscopy in combination with fluorescence in situ hybridization, live/dead, extracellular polymer staining, ATP analysis, and membrane filtration. A biofilm layer with a varying thickness of 20–40 μm was observed on the mortar surface. The distribution of live and dead bacteria and extracellular polymers varied with depth. The density of the live population near the mortar surface was the lowest. The bacteria reached their highest density at three fourths of the biofilm depth and then decreased again near the biofilm–liquid interface. Overall, the results indicated a healthy biofilm growth in the chosen growth period of 8 days, and it is expected that longer growth periods would lead to formation of a more resistant biofilm with more coverage of mortar surfaces.     

Adsorption Properties of Tetracycline onto Graphene Oxide: Equilibrium,Kinetic and Thermodynamic Studies

Graphene oxide (GO) nanoparticle is a high potential effective absorbent. Tetracycline (TC) is a broad-spectrum antibiotic produced, indicated for use against many bacterial infections. In the present research, a systematic study of the adsorption and release process of tetracycline on GO was performed by varying pH, sorption time and temperature. The results of our studies showed that tetracycline strongly loads on the GO surface via π–π interaction and cation–π bonding. Investigation of TC adsorption kinetics showed that the equilibrium was reached within 15 min following the pseudo-second-order model with observed rate constants of k₂ = 0.2742–0.5362 g/mg min (at different temperatures). The sorption data has interpreted by the Langmuir model with the maximum adsorption of 323 mg/g (298 K). The mean energy of adsorption was determined 1.83 kJ/mol (298 K) based on the Dubinin–Radushkevich (D–R) adsorption isotherm. Moreover, the thermodynamic parameters such as ΔH°, ΔS° and ΔG° values for the adsorption were estimated which indicated the endothermic and spontaneous nature of the sorption process. The electrochemistry approved an ideal reaction for the adsorption under electrodic process. Simulation of GO and TC was done by LAMMPS. Force studies in z direction showed that tetracycline comes close to GO sheet by C₈ direction. Then it goes far and turns and again comes close from amine group to the GO sheet.     

A comparison between osteogenic differentiation of human unrestricted somatic stem cells and mesenchymal stem cells from bone marrow and adipose tissue

To evaluate the potential of three stem cells for cell therapy and tissue engineering applications, the biological behavior and osteogenic capacity of the newly introduced cord-blood-derived, unrestricted somatic stem cells (USSC) were compared with those of mesenchymal stem cells isolated from bone marrow (BM-MSC) and adipose tissue (AT-MSC). There was no significant difference between the rates of proliferation of the three stem cells. During osteogenic differentiation, alkaline phosphatase (ALP) activity peaked on day 7 in USSC compared to BM-MSC which showed the maximum value of ALP activity on day 14. However, BM-MSC had the highest ALP activity and mineralization during osteogenic induction. In addition, AT-MSC showed the lowest capacity for mineralization during differentiation and had the lowest ALP activity on days 7 and 14. Although AT-MSC expressed higher levels of collagen type I, osteonectin and BMP-2 in undifferentiated state, but these genes were expressed higher in BM-MSC during differentiation. BM-MSC also expressed higher levels of ALP, osteocalcin and Runx2 during induction. Taking together, BM-MSC showed the highest capacity for osteogenic differentiation and hold promising potential for bone tissue engineering and cell therapy applications.     

Regional left ventricular myocardial contractility and stress in a finite element model of posterobasal myocardial infarction

Recently, a noninvasive method for determining regional myocardial contractility, using an animal-specific finite element (FE) model-based optimization, was developed to study a sheep with anteroapical infarction (Sun et al., 2009, "A Computationally Efficient Formal Optimization of Regional Myocardial Contractility in a Sheep With Left Ventricular Aneurysm," ASME J. Biomech. Eng., 131(11), p. 111001). Using the methodology developed in the previous study (Sun et al., 2009, "A Computationally Efficient Formal Optimization of Regional Myocardial Contractility in a Sheep With Left Ventricular Aneurysm," ASME J. Biomech. Eng., 131(11), p. 111001), which incorporates tagged magnetic resonance images, three-dimensional myocardial strains, left ventricular (LV) volumes, and LV cardiac catheterization pressures, the regional myocardial contractility and stress distribution of a sheep with posterobasal infarction were investigated. Active material parameters in the noninfarcted border zone (BZ) myocardium adjacent to the infarct (T(max_B)), in the myocardium remote from the infarct (T(max_R)), and in the infarct (T(max_I)) were estimated by minimizing the errors between FE model-predicted and experimentally measured systolic strains and LV volumes using the previously developed optimization scheme. The optimized T(max_B) was found to be significantly depressed relative to T(max_R), while T(max_I) was found to be zero. The myofiber stress in the BZ was found to be elevated, relative to the remote region. This could cause further damage to the contracting myocytes, leading to heart failure.     

Analysis of microRNA signatures using size-coded ligation-mediated PCR

The expression pattern and regulatory functions of microRNAs (miRNAs) are intensively investigated in various tissues, cell types and disorders. Differential miRNA expression signatures have been revealed in healthy and unhealthy tissues using high-throughput profiling methods. For further analyses of miRNA signatures in biological samples, we describe here a simple and efficient method to detect multiple miRNAs simultaneously in total RNA. The size-coded ligation-mediated polymerase chain reaction (SL-PCR) method is based on size-coded DNA probe hybridization in solution, followed-by ligation, PCR amplification and gel fractionation. The new method shows quantitative and specific detection of miRNAs. We profiled miRNAs of the let-7 family in a number of organisms, tissues and cell types and the results correspond with their incidence in the genome and reported expression levels. Finally, SL-PCR detected let-7 expression changes in human embryonic stem cells as they differentiate to neuron and also in young and aged mice brain and bone marrow. We conclude that the method can efficiently reveal miRNA signatures in a range of biological samples.     

A comparison of DNA damage induced by aflatoxin B1 in hepatocyte-like cells, their progenitor mesenchymal stem cells and CD34(+) cells isolated from umbilical cord blood

This study compared the sensitivity of differentiated hepatocyte-like cells, their progenitor mesenchymal stem cells (MSCs) and CD34(+) stem cells to DNA damage and toxicity induced by aflatoxin B1 (AFB1). The hepatocyte-like cells and their progenitor cells (isolated from umbilical cord blood (UCB)) were each treated with AFB1 on day 15 of differentiation. Cell toxicity and genotoxicity effects were assessed using MTT and alkaline comet assays. AFB1 treatment resulted in a dose- and time-dependent inhibition of cell growth. The IC(50) values of AFB1 for hepatocytes differentiated from CD34(+) and MSCs were within the same range (44.7-46.8μM). The IC(50) calculated for non-differentiated MSCs and CD34(+) cells was slightly lower (42.0-43.4μM) than that calculated for their differentiated counterparts. However, the extent of DNA damage was different in differentiated and non-differentiated cells. The percentages of DNA (% DNA) in comet tails measured in hepatocytes differentiated from MSCs exposed to AFB1 (0, 2.5, 10 and 20μM) for 24h were ～15, 55, 65 and 70%, respectively. In comparison, hepatocytes from CD34(+) cells were more resistant to AFB1-induced DNA damage. Hepatocyte-MSCs were most sensitive to DNA damage, followed by UCB-CD34(+) cells, then UCB-MSCs and finally hepatocyte-CD34(+) cells. These results clearly showed that stem cells from different sources have different sensitivities to DNA damaging agents. These differences can be assigned to the expression levels of cytochrome P450 (CYP) particularly CYP3A4 in non-differentiated and differentiated cells. These data are useful in better understanding the susceptibility/resistance of stem cells in the process of differentiation to environmental toxicants.     

An efficient method for isolation of murine bone marrow mesenchymal stem cells

Mesenchymal stem cells (MSCs) have been isolated based on the ability of adherence to plastic surfaces. The potential of these cells to differentiate along multiple lineages is the key to identifying stem cell populations in the absence of molecular markers. Here we describe a homogenous population of MSCs from mouse bone marrow isolated using a relatively straightforward and novel approach. This method is based on the combination of frequent medium change (FMC) and treatment of the primary cultures with trypsin. Cells isolated using this method demonstrated the MSCs characteristics including their ability to differentiate into mesenchymal lineages. MSCs retained the differentiation potentials in expanded cultures up to 10 passages. Isolated MSCs were reactive to the CD44, Sca-1, and CD90 cell surface markers. MSCs were negative for the hematopoietic surface markers such as CD34, CD11b, CD45, CD31, CD106, CD117 and CD135. The data presented in this report indicated that this method can result in efficient isolation of homogenous populations of MSCs from mouse bone marrow.