Nonlinear optical response of graphene oxide quantum dots fabricated from electrospun polyacrylonitrile fibers.

The nonlinear optical response of graphene oxide quantum dots (GOQDs) fabricated by the carbonization and exfoliation of electrospun polyacrylonitrile (PAN) fibers is reported. Electrospun and carbonized fibers were characterized by SEM and XPS. SEM micrograph confirmed the formation of PAN fibers of 153.44 ± 6.44 nm, while by XPS the binding energies associated with sp2 and sp3 carbon hybridizations were found, after the carbonization process. On the other hand, the GOQDs obtained were characterized by photoluminescence (PL), UV-Vis, Raman spectroscopy, and High-Resolution Transmission Electron Microscopy (HRTEM). The GOQDs size of 10 nm was estimated by HRTEM. Raman spectroscopy showed the D and G bands associated with the sp2 and sp3 hybridizations of the GOQDs, by PL two energy values of 2.67 and 2.97 eV were calculated. The UV-Vis spectrum showed two absorption bands confirming the presence of GOQDs. The nonlinear characterization was carried out using the P-scan technique, previously photodepositing GOQDs onto an optical fiber, using a coherent radiation source at a wavelength of 1550 nm. The results obtained showed a saturable absorption behavior with a value of ß = - 2.474 × 10 - 4 m / W and a nonlinear susceptibility of χ ( 3 ) ≈ - 7.749 × 10 - 4 ( e s u ) . The results of this work showed that GOQDs obtained can be used for optical switching applications.

High-intensity ultrasound pretreatment influence on whey protein isolate and its use on complex coacervation with kappa carrageenan: Evaluation of selected functional properties.

The aim of this work was to evaluate the influence of high-intensity ultrasound (HIUS) treatment on whey protein isolate (WPI) molecular structure as a previous step for complex coacervation (CC) with kappa-carrageenan (KC) and its influence on CC functional properties. Protein suspension of WPI (1% w/w) was treated with an ultrasound probe (24 kHz, 2 and 4 min, at 50 and 100% amplitude), non HIUS pretreated WPI was used as a control. Coacervation was achieved by mixing WPI and KC dispersions (10 min). Time and amplitude of the sonication treatment had a direct effect on the molecular structure of the protein, FTIR-ATR analysis detected changes on pretreated WPI secondary structure (1600-1700 cm-1) after sonication. CC electrostatic interactions were detected between WPI positive regions, KC sulfate group (1200-1260 cm-1), and the anhydrous oxygen of the 3,6 anhydro-D-galactose (940-1066 cm-1) with a partial negative charge. After ultrasound treatment, a progressive decrease in WPI particle size (nm) was detected. Rheology results showed pseudoplastic behavior for both, KC and CC, with a significant change on the viscosity level. Further, volume increment, stability, and expansion percentages of CC foams were improved using WPI sonicated. Besides, HIUS treatment had a positive effect on the emulsifying properties of the CC, increasing the time emulsion stability percentage. HIUS proved to be an efficient tool to improve functional properties in WPI-KC CC.

Morphological and Optical Characterization of Gold Nanoparticles Decorated Porous Silicon.

In this article, physical characteristics of porous silicon (PS) obtained by electro chemical etching using HAuCl4 in the electrolyte are described. The morphological and optical features of PS decorated with gold-nanoparticles (AuNPs) were analyzed in function of the chemical etching time. The insertion of AuNPs inside the PS were performed simultaneously with the formation of the porous silicon layer. Scanning electron microscopy (SEM) analysis showed the formation and incorporation of AuNPs with an average size of 20 nm in the PS structure, which has a pore size of 1.5 µm. Also, it was possible to observe the loss of Si in function of the etching time. Photoluminescence spectroscopy analysis shows a decreasing of the PL intensity, which can be related to the presence of oxygen in the samples. Raman spectroscopy was used to estimate the size of the Si nanocrystals in the PS structure, which suffers a reduction in size due to the presence of HAuCl4 in the electrolyte.

Componentes Principales mediante Espectroscopia FTIR como Técnica de Caracterización Innovadora durante la Diferenciación de Células Madre Pluripotentes a Células Pancreáticas / Principal Components by FTIR Spectroscopy as Innovative Characterization Technique during Differentiation of Pluripotent Stem Cells to Pancreatic Cells

Resumen: Dos de los grandes retos en la biología de las Células Madre (CM) y la Medicina Regenerativa, son el control en la diferenciación de estas células y asegurar la pureza de las células diferenciadas, por lo que es necesario contar con técnicas rápidas, eficientes y precisas para la caracterización de CM y su diferenciación a diferentes linajes celulares. El objetivo de este trabajo fue analizar Células Madre Pluripotentes (CMP) y Células Pancreáticas Diferenciadas (CPD) mediante espectroscopía Infrarroja por Transformada de Fourier (FTIR) y Análisis de Componentes Principales (ACP). Para ello se diferenciaron CMP a CPD, caracterizando el proceso de diferenciación a los días 0, 11, 17 y 21 mediante microscopía óptica y espectroscopia vibracional. Los espectros FTIR se analizaron con el método multivariado de ACP, utilizando su segunda derivada en las regiones de proteínas, carbohidratos y ribosas. Los resultados indican que el ACP permite caracterizar y discriminar CMP y CPD en sus diferentes etapas de diferenciación en las regiones espectrales analizadas. Con lo anterior concluimos que el ACP permite caracterizar química y estructuralmente CMP y diferentes etapas de su diferenciación en una forma rápida, precisa y no invasiva.

Abstract: Two of the greatest challenges in Stem Cells (SCs) biology and regenerative medicine, are differentiation control of SCs and ensuring the purity of differentiated cells. In this sense, fast, efficient and accurate techniques for SCs characterization and their differentiation into different cell lineages are needed. The aim of this study was to analyse Pluripotent Stem Cells (PSCs) and Differentiated Pancreatic Cells (DPCs) by Fourier Transform Infrared (FTIR) spectroscopy and Principal Component Analysis (PCA). For this purpose, we differentiated PSCs toward DPCs, characterizing the differentiation process at different stages (0, 11, 17 and 21 days) through light microscopy and vibrational spectroscopy. FTIR spectra were analysed with the multivariate method of PCA, using the second derivatives in the protein, carbohydrate and ribose regions. The results indicate that the PCA allows to characterize and discriminate PSCs and DPCs at different stages of differentiation in the analysed spectral regions. From these results, we concluded that the PCA allows the chemically and structural characterization of PSCs and the different stages of their differentiation in a fast, accurate and non-invasive way.

Surface-enhanced Raman scattering of the adsorption of pesticide endosulfan on gold nanoparticles.

The absorption of pesticide endosulfan on the surface of gold nanoparticles results from the formation of micrometric structures (1-10 µm) with irregular shape because of the aggregation of individual particles. Such aggregation of gold nanoparticles after absorption of pesticide shows a surface-enhanced Raman scattering (SERS) spectrum, whose intensity depends on the concentration of endosulfan. In addition, the discoloration of the colloidal solution and a diminishing of the intensity of the surface plasmon resonance absorption from individual particles were observed by UV-visible spectroscopy. At the same time, a second band between 638 and 700 nm confirms the formation of aggregates of gold nanoparticles as the concentration of endosulfan increases. Finally, we used the SERS intensity of the S-O stretching vibration at 1239 cm(-1) from the SO3 group as a measure of concentration of pesticide endosulfan. This method could be used to estimate the level of pollution in water by endosulfan in a simple and practical form.

c-erbB-2 as a possible target for the use of magnetic nanoparticles in breast cancer cells.

Breast cancer (BC) is the most frequent malignancy among women worldwide and has been associated with high mortality because of the late treatment of the disease. Our group has proposed a selective ablation of breast cancer cells by the use of magnetic fields assisted by magnetic nanoparticles. The principle is to increase the conductivity of tumoral tissue by the use of a bioconjugated "nanoparticle-antibody" that recognizes specific antigens on the surface of the cancer cells. The aim of this study was to evaluate the c-erbB-2 antigen in breast cancer cells of type BT-474, MCF-7, and MDA-MB-231 as a possible target for the use of magnetic nanoparticles coupled to a specific Monoclonal Antibody (Mab). Quantitative real-time polymerase chain reaction and flow cytometry were used to estimate the relative expressions of the c-erbB-2 gene and the c-erbB-2 antigen in the cell lines, respectively. A covalent union of magnetic nanoparticles to anti c-erbB-2 Mab was used to develop the bioconjugate. Fluorescence microscopy was used to determine the cells that were tagged by the bioconjugate. The results show a well-differentiated relative expression of c-erbB-2 in the studied cell lines and are qualitatively in agreement with the fluorescent marking by the magnetic nanoparticles. The selected breast cancer cells appear to be suitable for experimental evaluation of selective targeting by magnetic nanoparticles.

Blood lead levels measured prospectively and risk of spontaneous abortion.

Studies of low to moderate level lead exposures have reported mixed findings regarding the risk of spontaneous abortion, despite lead's abortifacient properties at very high doses. To evaluate the risk of spontaneous abortion from low or moderate lead exposures, a nested case-control study was conducted within a cohort of pregnant women in Mexico City, 1994-1996. During their first trimester, 668 women enrolled, were interviewed, and contributed blood specimens. Pregnancies were followed by home visits or telephone calls. Spontaneous abortions before week 21 (n = 35) were matched with pregnancies that survived beyond week 20 (n = 60) on maternal age, hospital, date of enrollment, and gestational age at enrollment. Mean blood lead levels were 12.03 microg/dL for cases and 10.09 microg/dL for controls (p = 0.02). Odds ratios for spontaneous abortion comparing 5-9, 10-14, and > or =15 microg/dL with the referent category of <5 microg/dL of blood lead were 2.3, 5.4, and 12.2, respectively, demonstrating a significant trend (p = 0.03). After multivariate adjustment, the odds ratio for spontaneous abortion was 1.8 (95% confidence interval = 1.1, 3.1) for every 5 microg/dL increase in blood lead. Low to moderate lead exposures may increase the risk for spontaneous abortion at exposures comparable to US general population levels during the 1970s and to many populations worldwide today; these are far lower than exposures encountered in some occupations.

Cadmium levels in maternal, cord and newborn blood in Mexico City.

Blood samples were withdrawn from n = 49 mothers and their children at the moment of birth to assess blood cadmium levels of the mother, the newborn and the cord. A questionnaire was applied to the mothers in order to obtain data about possible sources of cadmium exposure. Maternal blood cadmium was found significantly correlated (r2 = 0.578) with cord blood cadmium levels, while cord blood was correlated (r2 = 0.499) with newborn blood cadmium. Nevertheless, maternal blood cadmium and newborn blood cadmium were not correlated at all (r2 = 0.047). Previous smoking habits of the mother increased maternal blood cadmium concentrations significantly, but it did not modify cadmium concentrations of either the cord or the newborn. The latter result suggests the existence of a placental barrier for cadmium. Birthweight was found to be inversely associated (P < 0.06) only with cord blood cadmium levels. The results of the study suggest that cord blood cadmium holds information about both maternal and newborn cadmium status and also about cadmium effects on birthweight.

Blood lead levels in pregnant women of high and low socioeconomic status in Mexico City.

This study examined the determinants of blood lead (BPb) in 513 pregnant women in Mexico City: 311 from public hospital prenatal clinics, representing primarily women of low socioeconomic status (SES), and 202 from private hospitals, primarily women of high SES. Overall, BPb levels ranged from 1.38 to 29 micrograms/dl, with geometric means of 6.7 and 11.12 micrograms/dl for women from private and public hospitals, respectively. The crude geometric means difference obtained by t-test was 4.42 (p < 0.001). BPb was measured from January 1994 to August 1995 and showed higher levels during fall and winter and lower levels during spring and summer. The main BPb determinants were the use of lead-glazed ceramics in women from public hospitals and season of the year in women from private hospitals. Consumption of tortillas (corn bread rich in calcium) decreased BPb levels in the lower SES group, but the relationship was not statistically significant (p > 0.05). Consumption of milk products significantly (p < 0.05) reduced BPb levels in the higher SES group. In 112 women whose diets were deficient in calcium, taking calcium supplements lowered their blood lead levels about 7 micrograms/dl. A predictive model fitted to these data, using the strongest predictors plus gestational age, showed a difference of 14 micrograms/dl between the best and worst scenarios in women from public hospitals. Avoiding use of lead-glazed ceramics, consuming diets rich in calcium, and, if needed, taking calcium supplements, would be expected to result in substantial lowering of BPb, especially in pregnant women of low socioeconomic status.

Use of lead-glazed ceramics is the main factor associated to high lead in blood levels in two Mexican rural communities.

Two isolated rural communities of Mexico were studied to assess the possible relationship between lead-glazed ceramics use and lead exposure. Women from these communities (n = 98) were asked to participate by filling out a general-purpose and exposure questionnaire in order to assess the individual contribution of ceramics to lead exposure. Blood samples were withdrawn to measure lead in blood and erythrocytic zinc protoporphyrin levels. Results were analyzed by multiple regression in order to find predictors of the dependent variables. Significant association between lead in blood and erythrocytic zinc protoporphyrin levels was identified with the following variables: storage in lead-glazed ceramics, cooking in lead-glazed ceramics, and meat and cheese consumption. The adjusted regression models explained 20-23% of the variance of the dependent variables (lead in blood and erythrocytic zinc protoporphyrin). A significant association (r2 = .38) was observed between lead in blood and lead in food prepared in lead-glazed ceramics in a subsample of 28 women. Results indicate that lead-glazed ceramics use may be the main predictor of lead in blood and erythrocytic zinc protoporphyrin levels in the rural communities studied.