Continuous separation of cells by balanced dielectrophoretic forces at multiple frequencies

We present a particle-sorting device based on the opposition of dielectrophoretic forces. The forces are generated by an array of electrode chambers located in both sidewalls of a main flow channel. Particles with different dielectric response perceive different force magnitudes and are therefore continuously focused to different streamlines in the flow channel. We relate the particles' dielectric response to their output position in the downstream channel. We demonstrate the performance of the device by separating a mixed yeast cell population into pure fractions of viable and nonviable cells. Finally, we use the device to enrich red blood cells infected with Babesia bovis, a major pathogen in cattle and simultaneously confirm the hypothesis that infection with B. bovis causes significant changes in the dielectric response of red blood cells.     

Biocompatibility and structural stability of a laminin biopolymer

Polylaminin (polyLM) is a polymerized form of the extracellular matrix protein laminin obtained upon pH acidification. Here microscopy and spectroscopic tools are used to study the cell compatibility and the structural stability of polyLM, aiming at establishing its robustness as a biopolymer for therapeutic use. PolyLM is cell compatible as judged by the efficiency of attachment and neuritogenesis. It is resistant to low temperature. Addition of urea or an increase in hydrostatic pressure leads to polymer disassembly. PolyLM biofilms remain stable for 48 h in contact with cell culture medium. The sedimented polymer recovered after centrifugation and adsorbed on a glass coverslip preserved its original structure and its biological properties.

     

Macro,minor and trace elements in bovine milk from two Brazilian dairy regions

Brazil started to export dairy products in the early 2000s and since then has slowly consolidated its position in the world dairy market. To ensure the position in the international market by improving the quality of milk produced in the country, the government created a national program and a network of laboratories for milk quality. The Normative Instruction 51 (Instrução Normativa 51—IN51) was introduced within the national program establishing parameters for milk quality and safety. In spite of not being included in the IN51, chemical elements are under thorough discussion as quality parameters for their nutritional and toxicological relevance. This work aimed at evaluating the quality of milk from one of the major dairy regions in Brazil, located in the state of Rio Grande do Sul, by the determination of chemical elements, comparing the results with those previously obtained for milk samples from the main dairy region of the country, in the state of Minas Gerais. Samples were collected from cooling tanks in nineteen dairy farms. After freeze drying, chemical elements were determined by instrumental neutron activation analysis (INAA) and inductively coupled plasma mass spectrometry (ICP-MS). For ten out of sixteen chemical elements determined, there were significant differences between samples from both producing regions (p < 0.01).     

Chemistry of the silica surface: reaction with phosphorus pentachloride

Solid-state 31P and 29Si NMR experiments, with Magic-Angle Spinning (MAS), were used to elucidate the chemistry that occurs when silica gel is treated with phosphorus pentachloride. A low-loading regime (in which the molar ratio of initial PCl5 to surface silanols sites is <1) and a high-loading regime (in which this ratio is approximately 1) were examined. For each regime, the results for limited and intentional exposure to moisture are presented. The occurrence of phosphorus bridging between two adjacent silanols sites is observed. Bridging structures based on Si-O-P-O-P-O-Si linkages are also indicated.     

Production of Lactic Acid from Sucrose: Strain Selection, Fermentation, and Kinetic Modeling

Lactic acid is an important product arising from the anaerobic fermentation of sugars. It is used in the pharmaceutical, cosmetic, chemical, and food industries as well as for biodegradable polymer and green solvent production. In this work, several bacterial strains were isolated from industrial ethanol fermentation, and the most efficient strain for lactic acid production was selected. The fermentation was conducted in a batch system under anaerobic conditions for 50 h at a temperature of 34 °C, a pH value of 5.0, and an initial sucrose concentration of 12 g/L using diluted sugarcane molasses. Throughout the process, pulses of molasses were added in order to avoid the cell growth inhibition due to high sugar concentration as well as increased lactic acid concentrations. At the end of the fermentation, about 90% of sucrose was consumed to produce lactic acid and cells. A kinetic model has been developed to simulate the batch lactic acid fermentation results. The data obtained from the fermentation were used for determining the kinetic parameters of the model. The developed model for lactic acid production, growth cell, and sugar consumption simulates the experimental data well.     

Application of High Temperature High Resolution Gas Chromatography to Crude Extracts of Propolis

The underivatized acetone and hexane fractions from propolis samples (predominant flora Citrus spp. and Vernonia polyanthes) were analyzed by HT-HRGC (high temperature high resolution gas chromatography) and HT-HRGC coupled to mass spectrometry (HT-HRGC-MS). Several compounds, including flavonoid aglycones, phenolic acids, and high molecular weight compounds were characterized in crude extracts by HT-HRGC-MS. HT-HRGC and HT-HRGC-MS were shown to be quick and informative tools for rapid analysis of crude extracts without need for prior derivatization and purification.     

Monoglyceride and Diglyceride Production Through Lipase-Catalyzed Glycerolysis and Molecular Distillation

Distilled glycerides are obtained through distillation of the system mono-diglycerides which is produced from the esterification reaction between a triglyceride with glycerol. In this work, monoglycerides (MG) and diglycerides (DG) are produced through lipase-catalyzed glycerolysis of soybean oil using Candida antarctica B in a solvent-free system. To separate the products of the reaction in order to obtain essentially MG and an oil of DG, it is necessary to use a suitable process in order to preserve the stability of the components and to keep the products free of inappropriate solvents. So, after 24 h of enzymatic reaction, the mixture of acylglycerols and fatty acids was distilled into a centrifugal molecular distiller, since it provides a free solvent and lower temperature environment to increase the desired product concentration. Starting from a material with 25.06% of triglycerides (TG), 46.63% of DG, 21.72% of MG, 5.38% of free fatty acids (FFA), and 1.21% of glycerol, the MG purity in the distillate stream was 80% at evaporator temperature (T _E) equal to 250 °C and feed flow rate (Q) equal to 10.0 mL/min. At these conditions, the MG recovery was 35%. The material collected in the residue stream presented DG-enriched oil with TG unhydrolyzed, residual MG, and low acidity (29.83% of TG, 53.20% of DG, 15.64% of MG, and 1.33% of FFA), which is suitable to replace TG oil in the human diet.     

Frequency upconversion in rare-earth doped fluoroindate glasses

We present recent results on frequency upconversion (UPC) obtained in fluoroindate glasses (FIG) doped with Ho³⁺, Tm³⁺ and Nd³⁺ ions and codoped with Pr³⁺/Nd³⁺ and Yb³⁺/Tb³⁺ ions. The results for the Ho³⁺-doped samples show strong evidence of energy transfer (ET) between Ho³⁺ ions resonantly excited at 640 nm. The origin of the blue-green upconverted fluorescence observed was identified and the dynamics of the signals revealed the pathways involved in the UPC process. In the case of Tm³⁺-doped FIG, the samples were resonantly excited at 650 nm and the main mechanism that contributes for the red-to-blue upconversion is excited-state absorption (ESA). The FIG samples codoped with Pr³⁺/Nd³⁺ were excited at 588 nm in resonance with transitions starting from the ground state of the Nd³⁺ and the Pr³⁺ ions. It was observed that the presence of Nd³⁺ ions enhanced the Pr³⁺ emission at 480 nm by two orders of magnitude. Multiphonon (MP)-assisted upconversion is also discussed for Nd³⁺-doped FIG pumped at 866 nm. Emission at 750 nm with a peculiar linear dependence with the laser intensity was observed and explained. A rate-equation model that includes MP absorption via thermally coupled electronic excited states of Nd³⁺ was developed and describes well the experimental results. The role played by effective phonon modes is clearly demonstrated. MP-assisted UPC process was also studied in Yb³⁺/Tb³⁺-codoped FIG samples excited at 1064 nm, which is off-resonance with electronic transitions starting from the ground state. It was determined that the mechanism leading to Tb³⁺ emission in the blue is due to ET from a pair of excited Yb³⁺ ions followed by ESA in the Tb³⁺ ions.     

Saccharification of Brazilian sisal pulp: evaluating the impact of mercerization on non-hydrolyzed pulp and hydrolysis products

Cultivation of sisal, a plant with a short growth cycle, is highly productive in Brazil. This work is part of extensive research in which sisal is valued. In these studies, sisal fibers are used in the preparation of bio-based composites and in the derivatization of the pulp, including posterior preparation of films. This study aimed to examine the use of sisal pulp in the production of bioethanol, which can potentially be a high efficiency process because of the cellulose content of this fiber. A previous paper addressed the hydrolysis of sisal pulp using sulfuric acid as a catalyst. In the present study, the influence of the mercerization process on the acid hydrolysis of sisal pulp was evaluated. Mercerization was achieved in a 20% wt NaOH solution, and the cellulosic pulp was suspended and vigorously mixed for 1, 2 and 3 h, at 50 °C. The previously characterized mercerized pulps were hydrolyzed (100 °C, 30% H₂SO₄, v/v), and the results are compared with those obtained for unmercerized pulp (described in a companion paper). The starting sample was characterized by viscometry, α-cellulose content, crystallinity index and scanning electron microscopy. During the reactions, aliquots were withdrawn, and the liquor was analyzed by HPLC. The residual pulps (non-hydrolyzed) were also characterized by the techniques described for the initial sample. The results revealed that pretreatment decreases the polyoses content as well as causes a decrease of up to 23% in the crystallinity and up to 21% in the average molar mass of cellulose after 3 h of mercerization. The mercerization process proved to be very important to achieve the final target. Under the same reaction conditions (30% and 100 °C, 6 h), the hydrolysis of mercerized pulp generated yields of up to 50% more glucose. The results of this paper will be compared with the results of subsequent studies obtained using other acids, and enzymes, as catalysts.     

Aggregation behavior of aqueous dioctadecyldimethylammonium bromide/monoolein mixtures: a multitechnique investigation on the influence of composition and temperature

A recently described non-viral gene delivery system [dioctadecyldimethylammonium bromide (DODAB)/monoolein (MO)] has been studied in detail to improve knowledge on the interactions between lamellar (DODAB) and non-lamellar-forming (MO) lipids, as a means to enhance their final cell transfection efficiency. Indeed, the morphology, fluidity, and size of these cationic surfactant/neutral lipid mixtures play an important role in the ability of these systems to complex nucleic acids. The different techniques used in this work, namely dynamic light scattering (DLS), fluorescence spectroscopy, differential scanning calorimetry (DSC), cryogenic transmission electron microscopy (cryo-TEM), light microscopy (LM), and surface pressure-area isotherms, allowed fully characterization of the phase behavior and aggregate morphology of DODAB/MO mixtures at different molar ratios. Overall, the results indicate that the final morphology of DODAB/MO aggregates depends on the balance between the tendency of DODAB to form zero-curvature bilayer structures and the propensity of MO to form non-bilayer structures with negative curvature. These results also show that in the MO-rich region, an increase in temperature has a similar effect on aggregate morphology as an increase in MO concentration.