Síntese, caracterização e atividade antimicrobiana de nanofibras de policaprolactona - nistatina produzidas por eletrofiação / Synthesis, characterization and antimicrobial properties of nanofibers polycaprolactane - nystatin produced by electrospinning

O objetivo desse estudo foi sintetizar um scaffold de nanofibras (NFs) de Policaprolactona (PCL) com adição de nistatina (NYS), caracterizar e avaliar a atividade antimicrobiana. NFs foram sintetizadas pela técnica da eletrofiação, utilizando-se solução de PCL puro e PCL adicionado de NYS. Para a síntese das NFs de PCL, o polímero foi dissolvido em Dimetilformamida (DMF) e 1,1,2,2 Tetracloroetano (TCE), logo após foram adicionadas três concentrações de NYS (Grupos A, B e C). As amostras foram analisadas em Microscopia Eletrônica de Varredura (MEV), Espectroscopia por energia dispersiva (EDS), Análise de molhabilidade, Análise de Difratometria de Raios-X (DRX) e Espectroscopia de Infravermelho por Transformada de Fourier (FTIR). Após a análise em MEV foi realizada a média dos diâmetros das fibras com Software ImageJ. As atividades antimicrobianas foram avaliadas por meio dos testes de concentração inibitória mínima (CIM) e concentração microbicida mímica (CMM). As NFs de PCL com NYS (A) apresentaram diâmetro de 0,99µm ±0,29, o padrão do grupo B apresentou uma média de diâmetro de 1,3µm ±0,56 e o grupo C 1,24µm ±0,48. O DRX e o EDS comprovaram a presença de PCL e de NYS nas amostras. A CIM e a CMM comprovaram a ação fungicida e fungistática das NFs A, B e C(AU)

The aim of this study was to synthesize a scaffold of policaprolactane (PCL) nanofibers (NFs) with addition of nystatin (NYS), to characterize and evaluate the antimicrobial activity. NFs were synthesized by the electro-spinning technique, using pure PCL and NYS and PCL solutions. For the synthesis of PCL NFs, the polymer was dissolved in Dimethylformamide (DMF) and 1,1,2,2- Tetrachloroethane (TCE), after which three concentrations of NYS (Groups A, B and C) were added. The samples were analyzed in Scanning Electron Microscopy (SEM), Dispersive Energy Spectroscopy (EDS), Goniometer, X-ray Diffraction Analysis (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). After SEM analysis, the mean fiber diameter was performed with ImageJ Software. The antimicrobial activities were evaluated through the tests of minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC).The NFs of PCL with NYS (A) had a diameter of 0.99 µm ± 0.29, the standard of group B presented a mean diameter of 1.3 µm ± 0.56 and group C 1.24 µm ± 0.48. The DRX and the EDS verified the presence of PCL and NYS in the samples. CIM and CMM proved the fungicidal and fungistatic action of NFs A, B and C(AU)

Viability of mesenchymal stem cells during electrospinning

Tissue engineering is a technique by which a live tissue can be re-constructed and one of its main goals is to associate cells with biomaterials. Electrospinning is a technique that facilitates the production of nanofibers and is commonly used to develop fibrous scaffolds to be used in tissue engineering. In the present study, a different approach for cell incorporation into fibrous scaffolds was tested. Mesenchymal stem cells were extracted from the wall of the umbilical cord and mononuclear cells from umbilical cord blood. Cells were re-suspended in a 10 percent polyvinyl alcohol solution and subjected to electrospinning for 30 min under a voltage of 21 kV. Cell viability was assessed before and after the procedure by exclusion of dead cells using trypan blue staining. Fiber diameter was observed by scanning electron microscopy and the presence of cells within the scaffolds was analyzed by confocal laser scanning microscopy. After electrospinning, the viability of mesenchymal stem cells was reduced from 88 to 19.6 percent and the viability of mononuclear cells from 99 to 8.38 percent. The loss of viability was possibly due to the high viscosity of the polymer solution, which reduced the access to nutrients associated with electric and mechanical stress during electrospinning. These results suggest that the incorporation of cells during fiber formation by electrospinning is a viable process that needs more investigation in order to find ways to protect cells from damage.

Voltammetric determination of trace metals Zn2+, Cd2+, Pb2+, Cu2+, Co+2 and Ni+2 in some medicinally important plants from Western Ghats, Karnataka State, India.

Trace metal levels in selected medicinal plant leaves from Western Ghats, Karnataka, India were studied A method for the determination of Zinc, Copper, Lead and Cadmium simultaneously in the pH of 4.5 in citrate buffer, and Cobalt and Nickel simultaneously in the pH 9.2 in ammonia buffer medium has been optimized. Electrochemical method, Differential Pulse Anodic Stripping Voltammetry (DPASV) has been used for quantification. The optimized procedure has been successfully applied for the determination of the above-mentioned metal ions in some medicinally important plant leaves from Western Ghats, Karnataka, India. The concentrations of trace metals in the medicinal plant samples were found to be in the ranges: 15.61-20.71 mg g(-1) for copper, 0.056-0.10 mg g(-1) for cadmium, 0.91-1.81 mg g(-1) for lead, 0.42-0.96 mg g(-1) for nickel, 1.21-1.97 mg g(-1) for cobalt and 23.29-32.52 mg g(-1) for zinc. The effect of pH, deposition time and potential has been studied and optimized. The study reveals that all the trace metals are well within the maximum permissible limits, therefore, medicinal plants of this region are very much suitable for medicinal use. The results are compared with the data obtained by atomic absorption spectroscopy.

Batch adsorption studies for chromium removal.

The adsorption of hexavalent chromium (Cr (VI)) on pongamia (Pongamia pinnata) leaf powder was investigated in the present study. Crude pongamia leaf powder (CPLP) and nitric acid treated pongamia leaf powder (APLP) were used as adsorbents. CPLP did not show remarkable adsorption efficiency but APLP had good adsorption capacity and adsorption removal efficiency. The parameters studied included the contact time, initial solute concentration and pH. The optimum pH for removal of chromium was found to be 2 for both CPLP and APLP. The best contact time for maximum chromium adsorption was 165 minutes for CPLP and APLP. CPLP and APLP showed good adsorption capacity and adsorption removal efficiency at an initial chromium concentration of 5 mg/L. The adsorption was found to follow Langmuir and Freundlich isotherms for CPLP and APLP but they showed good curve fit for Freundlich isotherm.

Electrogeneration of hydrogen peroxide applied to the peroxide-mediated oxidation of (R)-limonene in organic media

Horse radish peroxidase (HRP) from Armoracia rusticana catalyses the oxidation of (R)-limonene into the oxidized derivatives carveol and carvone. This study compares the direct addition (DA) of hydrogen peroxide with its continuous electrogeneration (EG) during the enzymatic oxidation of (R)-limonene. Reaction mixtures containing HRP, (R)-limonene as substrate, and hydrogen peroxide, added directly or electrogenerated, in 100 mM sodium-potassium phosphate buffer pH 7.0, at 25ºC were studied. Two electrochemical systems for the hydrogen peroxide electrogeneration were evaluated, both containing as auxiliary electrode (AE) a platinum wire and saturated calomel electrode (SCE) as reference. Reticulated vitreous carbon foam (RVCF) and an electrolytic copper web (CW) were evaluated as working electrodes (WE). Results were compared in terms of hydrogen peroxide electrogeneration, (R)-limonene residual concentration or conversion and product selectivity. Best results in terms of maximum H2O2 concentration (1.2 mM) were obtained using the CW electrode at -620 mV SCE, and continuous aeration. Use of the EG system under optimized conditions, which included the use of acetone (30% v/v) as a cosolvent in a 3 hrs enzymatic reaction, lead to a 45% conversion of (R)-limonene into carveol and carvone (2:1). In comparison to the results obtained with DA, the use of EG also improved the half-life of the enzyme.

Hydrogen production by photosynthetic green algae.

Oxygenic photosynthetic organisms such as cyanobacteria, green algae and diatoms are capable of absorbing light and storing up to 10-13% of its energy into the H-H bond of hydrogen gas. This process, which takes advantage of the photosynthetic apparatus of these organisms to convert sunlight into chemical energy, could conceivably be harnessed for production of significant amounts of energy from a renewable resource, water. The harnessed energy could then be coupled to a fuel cell for electricity generation and recycling of water molecules. In this review, current biochemical understanding of this reaction in green algae, and some of the major challenges facing the development of future commercial algal photobiological systems for H2 production have been discussed.

Microfiltración apical de tres cementos selladores a base de hidróxido de calcio: Apexit, CRCS y Sealapex / Apical microleakage of three calcium hidroxide-based sealers: Apexit, CRCS and Sealapex

El propósito de este estudio fue evaluar la microfiltración apical de tres cementos selladores a base de hidróxido de calcio: Sealapex, Apexit y CRCS, usando el método electroquímico. Se utilizaron 30 raíces de dientes unirradiculares humanos; las coronas anatómicas fueron removidas, dejando 16 mm de longitud radicular y una preparación crown down fue realizada con limas tipo K Flex y se irrigó con hipoclorito de sodio al 5.25 por ciento. Las raíces fueron divididas al azar en tres grupos de 10 dientes, cada uno de los cuales se obturó con la técnica de condensación lateral usando uno de los tres cementos selladores: grupo 1 Sealapex, grupo C CRCS y grupo 3 Apexit. Posteriormente se desobturaron con fresa Peeso Nº2 hasta dejar 5 mm de remanente de gutapercha. Después, los especímenes fueron colocados en cloruro de sodio al 1 por ciento a 37ºC y una humedad relativa del 100 por ciento durante 30 días. La microfiltración se midió a los 15 y 30 días. El análisis estadístico Kruskal Wallis y Mann Whitney mostró diferencias significativas en el grado de microfiltración de los tres cementos a los 15 y 30 días, dando mejores resultados el Apexit, seguido de Sealapex y por último el CRCS

Construcción y caracterización de un sensor electroquímico de interés médico y farmacológico / Construction and characterization of a electrochemical sensor of interest medical and pharmacologic

La necesidad en la detección de elementos trazas en los fluidos biológicos y en determinados medicamentos ha incrementado la demanda de técnicas cada vez más sensibles y selectivas para tal fin. En la actualidad se requiere de técnicas de análisis que además de ser sensibles y selectivas abaraten el costo del análisis clínico. La técnica electroquímica de Voltometría de Redisolución Anódica (VRA) ha mostrado ser una técnica bastante adecuada para este propósito, si se utilizan sensores electroquímicos específicos. Iones metálicos como Pb²+, Cu²+ y Zn²+ presentes en muestras de orina y semen previamente pretratadas, así como, iones Pb²+ y Cu²+ en preparaciones farmacéuticas fueron detectados simultáneamente utilizado la técnica VRA con un sensor electroquímico construido de carbón vítreo y modificado electroquímicamente con una película delgada de mercurio en el laboratorio

Complexing behaviour of naphthylidene sulfamethazine schiff base ligand towards some metal ions

Mn [II], Co [II], Ni [II] and Cu [II] complexes of the Schiff base derived from 2-hydroxy-1-naphthaldehyde and sulfamethazine were prepared by both chemical and electrochemical methods. The structure of the complexes was investigated by chemical microanalysis, conductance and magnetic moment measurements as well as spectral methods. The results indicated that the Schiff base ligand behaved as tetradentate dibasic for 1:2 [L:M] complexes and bidentate monobasic for 1:1 and 2:1 [L:M] complexes. The thermal behavior of the complexes was studied using TGA and DTA. The energy of activation [Ea] for the decomposition process was calculated. The values of Ea of binuclear complexes were higher than those of the mononuclear complexes. For the 1:1 complexes, Ea increased as the ionic radii of metal ion increased

Aplicación de métodos electroquímicos de análisis en el campo microbiológico: una revisión / Application of electrochemical methods of analysis in the microbiological field: a review

This article presents a review on the application of electrochemical methods of analysis in the microbiological field. The main features of potentiometry, voltammetry and amperometry are discussed including a chronological description of the systems that have been developed so far.

Thin molecular films of supramolecular porphyrins

A relevant series of symmetric supramolecular porphyrins has been obtained by attaching four [RuII(bipy)2Cl] groups to the pyridyl substituents of meso-tetra(4-pyridyl)porphyrin and its metallated derivatives. These compounds display a rich electrochemistry and versatile catalytic, electrocatalytic and photochemical properties, associated with the ruthenium-bipyridine and the porphyrin complexes. These properties can be transferred to the electrodes by attaching thin molecular films of the compounds, by dip-coating, electrostatic assembly or electropolymerization. In this way, the interesting properties of those supermolecules and supramolecular assemblies can be used to prepare molecular devices and sensors

Importancia de la electroquímica en investigaciones médicas y farmacológicas / Electrochemical importance in medical and pharmacology research

Algunos aspectos de la aplicación de técnicas electroquímicas en la detección de ciertas drogas e iones metálicos presentes en fluidos biológicos, así como en la detección de ciertos compuestos liberados por neuronas son investigados. Consideraciones respecto al uso de estas técnicas electroquímicas con determinados electrodos modificados son analizadas

Dielectric relaxation study of glycine and valine in water mixture using picosecond time domain reflectometry.

The complex permittivity of glycine and valine in water mixture for various temperatures and concentrations have been measured as a function of frequency between 10 MHz and 10 GHz using (TDR) time domain reflectometry technique. Dielectric parameters ie. static dielectric constant and relaxation time were obtained from the complex permittivity spectra using nonlinear least square fit method. From the values of relaxation time, thermodynamic parameters were determined.

Electrochemical fixation techniques: I. Electrochemical fixation of human brain

An electrochemical brain fixation procedure (EBFP) to treat brains excised from human cadavers is described thoroughly. It is as precise as any other similar method currently available. However, it takes only as much as 36 h to completion instead of the much longer lapses required by immersion in formaldehyde. Actions were taken to secure that it is not a source of artifacts of any kind, neither neurons nor glia or blood vessels. It is, therefore, amenable to be used as a valuable research and teaching tool. Other advantages are that it does not pose any health hazard, is money- and time-saving, and cuts down on equipment and facilities

Behavior of long-term dantrolene sodium-treated rat skeletal muscles: histochemical and electromechanical aspects

Histochemical and electrochemical studies were carried out on skeletal rat muscles treated with dantrolene sodium (DS) for 60 days. Histochemical experiments revealed a conversion from fast twitch (type II) to slow twitch (type I) fibers for soleus (S), gastrocnemius (GM), and extensor digitorum longus (EDL) muscles. However, a significant decreased of muscle contractility was not observed in these chronically treated rat muscles in opposition to both those directly exposed in vitro as the muscles obtained from only 1-h DS-treated animals

Electrochemical fixation techniques: II. Electrochemical dog body fixation. Histological study

This is the first attempt to harden all organs of a body together without excising them. This process was accomplished in bottom-belted, gastrointestinal (GI) or intravenously (IV) catheterized dog cadavers so as to influx en electrolytic solution containing formaldehyde (ESF). The IV influx of ESF was found to be the best perfusion pathway. After 48 h of immersion in ESF, 24 h current time of 17.5 A of current intensity, 24º to 56ºC, we ended up with thoroughly fixed dog cadavers that were wrapped with ethyl alcohol:glycerol gauzes and stored in plastic bags at room temperature. Optical microscopy of every sliced tissue showed normal blood vessels, neurons, glial and Purkinje cells and their nuclei of brain and cerebellum, respectively. Cardiac muscle fibers were of normal appearance. Kidney Bowman's capsule and space were found to be normal excepto for vacuolarly degenerated tubules. Small intestine showed normal epithelial cells andcrypts of Lieberkühn. In liver, sinusoids were normally arrayed but showed vacuolar cell degeneration. Herin a method to attain an electrochemical whole body fixation is described