Highly active nisin coated polycaprolactone electrospun fibers against both Staphylococcus aureus and Pseudomonas aeruginosa.

In this study, a wound dressing of electrospun polycaprolactone (PCL) fibers incorporating the antimicrobial peptide (AMP) nisin was fabricated. Nisin was physically adsorbed to the PCL fibers and tested for antibacterial activity against both Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa). The PCL fibers had an average diameter of 1.16 µm ± 0.42 µm and no significant change in diameter occurred after nisin adsorption. X-ray photoelectron spectroscopy (XPS) analysis of the fibers detected nitrogen indicative of adsorbed nisin and the signal was used to quantify the levels of coverage on the fiber surfaces. In vitro nisin release studies showed a burst release profile with 80 % of the nisin being released from the fibers within 30 min. Air plasma pre-treatment of the PCL fibers to render them hydrophilic improved nisin loading and release. Antibacterial testing was performed using minimum inhibitory concentration (MIC) and surface attachment assays. The released nisin remained active against both Gram positive S. aureus and Gram negative P. aeruginosa, which has previously been difficult to achieve with single polymer fiber systems. Mammalian cell culture of the nisin coated fibers with L-929 mouse fibroblasts and human epidermal keratinocytes (HEKa) showed that the nisin did not have a significant effect on the biocompatibility of the PCL fibers. The results presented here demonstrate that the physical adsorption, which is a post-treatment, overcomes the potential limitations of harsh chemicals and fabrication conditions of electrospinning from organic solvents and provides a drug loading system having effective antibacterial properties in wound dressings.

Binary Colloidal Crystal (BCC) Substrates for Controlling the Fate of Mouse Embryonic Stem Cells.

Understanding the interactions of stem cells with surface topography can give us an invaluable tool in controlling stemness and fate of stem cells for further use in biomedical applications. In this study, we have fabricated topographical features using a class of cell culture substrates called binary colloidal crystals (BCCs), that are made by self-assembly of mixtures of spherical micron sized silica (Si) and nanometer sized polystyrene (PS) or poly (methyl methacrylate) (PMMA) particles. The substrates formed are arrays of ordered, hexagonally packed large Si particles inter-dispersed with the PS particles that are stabilized by gentle heating, which melts the PS or PMMA forming substrates suitable for cell culture. BCC substrates were used for culture of mouse embryonic stem cells (mESCs). Compared to tissue culture plates, COM1 (Si5-PMMA0.4), COM2 (Si5-PS0.4) and COM4 (Si2-PSC0.22) have shown to provide a better support for mESC proliferation in the presence of the cytokine leukemia inhibitory factor (LIF). The behavior of mESCs with the BCCs in presence and absence of LIF, was further explored and it was found that interaction of mESCs with the culture substrate can be controlled by tuning surface topography and roughness, which is determined by the size and type of particles used in making BCCs. Furthermore, it was shown that limiting cell-surface interactions and controlling colony shape can promote stemness maintenance on COM1 and COM2 substrates as indicated by better proliferation and higher expression of pluripotency genes including Nanog both in presence and in absence of LIF. Together with higher expression of GATA6 gene, it can be stated that these surfaces can be used for endodermic priming of mESCs. Therefore, we believe that these surfaces, especially COM1 and COM2 surfaces can be beneficial as stem cell culture systems for further use in biomedical research.

Antibacterial properties of nanoporous graphene oxide/cobalt metal organic framework.

Metal-organic framework (MOF) based graphene oxide (GO) recently merits of attention because of the relative correspondence of GO with metal ions and organic binding linkers. Furthermore, introducing the GO to the Co-MOF to make a new nanoporous hybrid have are improved the selectivity and stability of the Co-MOF. Here the graphene oxide/cobalt metal organic framework (GO/Co-MOF) was synthesized by a solvothermal process using cobalt salt and terephthalic acid and used for biocidal activity, against the growth of the Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy were confirmed the successful synthesize of metal organic framework and incorporation of Co-MOF in to GO sheets. Scanning electron microscopy was showed the cornflower structure of GO/Co-MOF, and transmission electron microscopy was confirmed, the Co-MOF are decorated on GO. Cytotoxicity study of GO/Co-MOF using 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) cell viability assay showed the biocompatibility to human fibroblasts cell over 72 h. The growth inhibition of the Escherichia coli and Staphylococcus aureus bacteria are reached over 99% for bacteria concentration of 100 µg/mL. The excellent antibacterial activity of GO based Co-MOF is linked to synergistic effect of sharp edges of the GO sheets and the toxic effect of cobalt ions (Co2+) which are released from their surfaces. The GO/Co-MOF radical scavenging assay was measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) antioxidant assay for samples incubated with cells which confirmed the minimum radicals' toxicity on bacteria. This novel graphene oxide based MOF with its intrinsic superior porous structure, highly active metal coordination, and commercial linker, is an excellent promising candidate to use in biological and pharmaceutical applications as high potential sustained bactericidal materials.

Polyethylenimine: A new differentiation factor to endothelial/cardiac tissue.

Among different tissues, endothelial/cardiac types require specific factors to promote myocardial regeneration after occurred injuries. Herein, cardiac stem cells (CSCs) as the major cell population that involved in cardiovascular repair were selected to study the role of polyethyleneimine (PEI) agent on endothelial differentiation. After preparation of electrospun network of PEI with polyacrylonitrile, the related characterizations were carried out including scanning electron microscope (SEM), field-emission SEM, water contact angle, Fourier transform infrared spectroscopy and mechanical properties. Also, the release kinetic of the corresponding agent was studied up to 7 days. The cell differentiation studies were done in the following with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay, Real-time polymerase chain reaction and immunostaining method. The whole obtained results approved the higher differentiation of CSCs into endothelial/cardiac cells. Finally, it is recommended that the PEI delivering increases the healing potency of CSCs and accordingly the regeneration speed of damaged cardiovascular tissue would be improved.

Natural Compounds for Skin Tissue Engineering by Electrospinning of Nylon-Beta Vulgaris.

Natural compounds containing polysaccharide ingredients have been employed as candidates for treatment of skin tissue. Herein, for the first time, electrospinning setup was proposed to fabricate an efficient composite nanofibrous structure of Beta vulgaris (obtained from Beet [Chenopodiaceae or Amaranthaceae]) belonged to polysaccharides and an elastic polymer named nylon 66 for skin tissue engineering. Both prepared scaffolds including noncomposite and composite types were studied by Scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, mechanical assay, and contact angle. Scanning electron microscope examinations have approved the uniform and homogeneous structure of composite nanofibers containing nylon polymer and B. vulgaris extract. FTIR spectroscopy was endorsed the presence of B. vulgaris extract within the interwoven mat of nanofibers. Also, measurement of mechanical property with cell-laden composite scaffolds approved the desirable similarity between corresponding scaffold and native skin tissue. To our surprise, it was found that compared with nylon nanofibrous scaffold, composite sample containing B. vulgaris extract has lower contact angle indicating a higher hydrophilic surface. After cell seeding process of keratinocyte cells on composite and noncomposite scaffolds, SEM and 3[4,5-dimethylthiazoyl-2-yl]-2,5 diphenyltetrazolium bromide (MTT) assays approved higher number of attached cells onto the corresponding composite electrospun membrane. Epidermal gene expression such as involucrin, cytokeratin 10, and cytokeratin 14 was observed through real-time polymerase chain reaction (PCR) technique. Furthermore, immunocytochemistry results (cytokeratin 10 and loricrin) approved that the original property of keratinocytes was strongly preserved using composite scaffold. The corresponding study tries to introduce a new type of natural-based scaffolds for dermal tissue engineering that exhibits an elastic behavior similar to native skin tissue.

Alterations in TSH and Thyroid Hormones following Mobile Phone Use.

OBJECTIVES: In recent years, the widespread use of mobile phones has lead to a public debate about possible detrimental effects on human health. In spite of years of research, there is still a great controversy regarding the possibility of induction of any significant physiological effects in humans by microwave radiations emitted by mobile phones. This study aims to investigate the effects of electromagnetic fields induced by the Global System for Mobile communications (GSM) mobile phones on the Thyroid Stimulating Hormone (TSH) and thyroid hormones in humans. METHODS: 77 healthy university students participated in this study. The levels of T3, T4 and TSH were measured by using appropriate enzyme-linked immunosorbent assay (ELISA) kits (Human, Germany). RESULTS: The average levels of T3, T4 and TSH in students who moderately used mobile phones were 1.25±0.27 ng/ml, 7.76±1.73 µg/dl and 4.25±2.12 µu/l respectively. The levels in the students who severely used mobile phones were 1.18±0.30, 7.75±1.14 and 3.75±2.05 respectively. In non-users, the levels were 1.15±0.27, 8.42±2.72 and 2.70±1.75, respectively. The difference among the levels of TSH in these 3 groups was statistically significant (P<0.05). CONCLUSION: As far as the study is concerned, this is the first human study to assess the associations between mobile phone use and alterations in the levels of TSH and thyroid hormones. Based on the findings, a higher than normal TSH level, low mean T4 and normal T3 concentrations in mobile users were observed. It seems that minor degrees of thyroid dysfunction with a compensatory rise in TSH may occur following excessive use of mobile phones. It may be concluded that possible deleterious effects of mobile microwaves on hypothalamic-pituitary-thyroid axis affects the levels of these hormones.