Nanocatalizadores de platino soportados sobre un sistema proteína de capa-s/partículas poliméricas : obtención, caracterización y comportamiento en la reacción de reduccción de p-nitrofenol

En este trabajo se prepararon y caracterizaron bionanocatalizadores de platino soportados sobre un template formado por proteínas de capa-S y nanopartículas poliméricas. Las proteínas de capa-S utilizadas fueron aisladas de L. kefiri y las nanopartículas poliméricas fueron a base de poliuretano y acrílico, sintetizados mediante el método del prepolímero y por polimerización en emulsión, respectivamente. Una vez obtenidos los catalizadores, se lo redujo con H2 gaseoso a temperatura ambiente. Todos los sistemas fueron caracterizados por FTIR y microscopía electrónica de transmisión para evaluar la eficiencia de la síntesis de las nanopartículas poliméricas, la morfología del template proteína de capa-S/nanopartículas poliméricas y la distribución de tamaños de las partículas metálicas. Los catalizadores se emplearon en la reacción de reducción del p-nitrofenol con NaBH4, la cual fue seguida espectrofotométricamente, midiendo la absorción del reactivo a 400 nm. Se obtuvieron conversiones de entre 80 y 100% para tiempos de reacción de entre 1 y 1.5 h, obteniéndose los mejores resultados con el catalizador soportado sobre el template capa-S de L. kefiri 83111/acrílico. La excelente performance alcanzada se asigna a la capacidad del template proteínas de capa-S/nanopartículas poliméricas de actuar como guía del crecimiento y ensamblaje de las nanopartículas de platino.Fil: Huggias, Sofía . Universidad Nacional de La PlataFil: Bolla; Patricia A.. Universidad Nacional de La PlataFil: Serradell;María A.. Universidad Nacional de La PlataFil: Peruzzo, Pablo J.. Universidad Nacional de La PlataFil: Casella, Mónica L.. Universidad Nacional de La Plat

Caracterización y actividad catalítica de bionanocatalizadores de platino soportados sobre sistemas proteínas de capa-s/poliuretano

Las subunidades de proteínas de capa-S poseen la capacidad de autoensamblarse sobre distintas superficies formando arreglos en la escala nanométrica. Este aspecto disparó el interés por el empleo de estas proteínas en la construcción biomolecular con prometedoras aplicaciones nanobiotecnológicas

Functional Induction of the Cystine-Glutamate Exchanger System Xc- Activity in SH-SY5Y Cells by Unconjugated Bilirubin

We have previously reported that exposure of SH-SY5Y neuroblastoma cells to unconjugated bilirubin (UCB) resulted in a marked up-regulation of the mRNA encoding for the Na+ -independent cystine∶glutamate exchanger System Xc− (SLC7A11 and SLC3A2 genes). In this study we demonstrate that SH-SY5Y cells treated with UCB showed a higher cystine uptake due to a significant and specific increase in the activity of System Xc−, without the contribution of the others two cystine transporters (XAG− and GGT) reported in neurons. The total intracellular glutathione content was 2 folds higher in the cells exposed to bilirubin as compared to controls, suggesting that the internalized cystine is used for gluthathione synthesis. Interestingly, these cells were significantly less sensitive to an oxidative insult induced by hydrogen peroxide. If System Xc− is silenced the protection is lost. In conclusion, these results suggest that bilirubin can modulate the gluthathione levels in neuroblastoma cells through the induction of the System Xc−, and this renders the cell less prone to oxidative damage

Encapsulation of Clay within Polymer Particles in a High-Solids Content Aqueous Dispersion

By using a two-step polymerization process, it was possible to encapsulate clay platelets within polymer particles dispersed in water. First, seed polymer particles with chemically bonded clay were obtained by batch miniemulsion polymerization. Then, the clay was buried within the particles by the addition of neat monomer in a second step. The final stable dispersions can have a solids content of up to 50 wt %. Transmission electron microscopy images clearly show the presence of clay platelets inside the polymer colloids, although they are not totally exfoliated. The obtained nanocomposites showed an increase in both the storage modulus in the rubbery state and the water resistance as the clay content increases. The approach presented here might be useful for encapsulating other high-aspect ratio nanofillers

Response to H₂O₂ oxidative stress of SH-SY5Y cells pretreated with bilirubin and GSH intracellular levels of the cells before H₂O₂ treatment.

<p>SH-SY5Y cells were exposed to two successive treatments: the first with 140 nM Bf (control with 0.6% DMSO medium) for 24 h. After this treatment, cells were released in growth medium for 156 h. Immediately after exposure to UCB (column A) and 156 h (column B) of release, cells were incubated, as second treatment, with different concentrations of H₂O₂ for 60 min and viability evaluated by MTT. At each time viability is expressed as a percentage of the controls considered as 100%. At each time viability results are compared with GSH intracellular levels of the cells before H₂O₂ treatment. Results are expressed as media ± SD of four different experiments.</p

Effect of bilirubin on mRNA expression levels of genes involved in cystine uptake.

<p>SH-SY5Y cells exposed to free medium (untreated), 0.6% DMSO medium or 140 nM Bf medium were collected after 1, 4 and 24 h of treatment. Specific mRNA expressions was analysed by qPCR. mRNA expression is shown as mean ± SD of 3 experiments relative to 1 h untreated control set at 1.0. **p<0.001 and *p<0.01 versus DMSO or untreated controls.</p

List of primer sequences designed for the quantification of specific mRNAs by qPCR.

<p>List of primer sequences designed for the quantification of specific mRNAs by qPCR.</p

Response to H₂O₂ oxidative stress in xCT silenced SH-SY5Y cells pre-treated with bilirubin.

<p><u>Panel A</u>: Protein expression of xCT (55 kDa and 35 kDa) was analyzed by Western blot after siRNA and Bf treatment. Lane 1: MOCK and 0.6% DMSO; lane 2: NT and 0.6% DMSO; lane 3: anti-xCT and DMSO 0.6%. Lane 4: MOCK and Bf 140 nM; lane 5: NT and Bf 140 nM ; lane 6: anti-xCT and Bf 140 nM. <u>Panel B</u>: Quantification of bands shown in lanes from 1 to 6 of panel A. xCT 35 kDa and 55 kDa bands normalized by actin and expressed as relative to MOCK . <u>Panel C</u>) H₂O₂ dose-response by MTT test was evaluated in untransfected (MOCK – left), transfected with not targeting siRNA (NT – middle) and transfected with siRNA against SLC7A11 gene (anti-xCT - right) SH-SY5Y cells. After silencing, and before 1 h H₂O₂ treatment, SH-SY5Y cells were exposed for 24 h to 0.6% DMSO or Bf 140 nM as indicated in the legend of each picture.</p

Sodium –dependent and independent L-[¹⁴C] cystine transport in SH-SY5Y cells.

<p>Transport activity was measured in control (0.6% DMSO, 24 h) and treated (Bf 140 nM, 24 h) cells. L-[¹⁴C] cystine (0.8 µM) uptake was measured after 10 min incubation at 37°C in the presence and absence of sodium ions. L-quisqualate (500 µM) was used as a specific inhibitor for System X_c⁻. Each point represents the mean ± SD of three plates of cells (** p<0.001).</p