Salvador Claro Neto

Study of the biodegradation of a polymer derived from castor oil by scanning electron microscopy, thermogravimetry and infrared spectroscopy

The aim of this research is to study the biodegradation of a polyurethane derived from castor oil, which contains polyester segment in its molecular structure, thus becoming susceptible to the microorganisms attack. The biodegradation of polyurethane was tested in contact with microorganisms resulting from microbiological grease degrading agents, in appropriate liquid media, with a duration of 156 days. The study was done by using scanning electron microscopy (SEM), thermogravimetry (TG) and Fourier-transform infrared spectroscopy with accessory for attenuated total reflectance (FTIR-ATR). The results suggest that the degradation of polyurethane derived from castor oil occurs. TG curves are used in order to indicate the biodegradation, showing changes between the thermal behavior of the samples that were inoculated with microorganisms and control. In the FTIR-ATR spectra, there are detectable changes between the spectra of control and attacked specimens; this suggests that degradation occurs, with the decreased intensity of the absorption band at 1042 cm -1 , corresponding to the esters links.

Synthetic Phosphoethanolamine Induces Apoptosis Through Caspase-3 Pathway by Decreasing Expression of Bax/Bad Protein and Changes Cell Cycle in Melanoma

Phospholipids are potential antineoplastic agents that are abundant constituents of the cell membrane of eukaryotes and are supposed to be involved in specific intracellular signaling such as cell death. The aim of this study was to assess the in vitro and in vivo antitumor effects of synthetic phosphoethalomanine (PHO-S) on B16F10 murine melanoma cells and normal human fibroblasts. The cytotoxicty was evaluated by MTT assay and PHO-S was cytotoxic in melanoma cells but not in fibroblasts with IC50% of 1.4 mg/ml to melanoma cells. In vivo antitumor activity was evaluated in a mice model subcutaneously injected with B16F10 melanoma cells. The mice treated with PHO-S in all concentrations showed a decrease of the tumor growth and metastasis. Cytometry analysis showed that the PHO-S blocked DNA synthesis, decreased number of melanoma cells in S phase and G2/M, besides increasing number of apoptotic cells, inducing caspase-3 activity and decreasing Bad/Bax protein expression. Histologically, the dorsal tumors in the control group showed pigmented nodular masses with high vascularization and pleomorphic tumor cells. In the treated group, PHO-S reduction vascularization intratumoral with increased of collagen fibers and infiltrates neutrophils. The data indicate that PHO-S is a lipid compound potential with proapoptotic and antiproliferative effects but further work will be necessary to elucidate the antitumor mechanisms.

Biodegradation of polyurethane derived from castor oil

The aim of this research was to study the biodegradation of a polymer derived from castor oil, which is a renewa- ble, natural material that is a practical alternative for the replacement of traditional polyurethane foams. Due to its molecular structure, which contains polyester segments derived from vegetable oil, the polymeric surface is susceptible to microor- ganism attack. This study tested the biological degrading agent that was in contact with the microorganisms resulting from microbiological grease degrading agents, when foam was inoculated. Solid-media agar-plate tests were conducted for their potential to evaluate the biodegradation of polymeric particles by specific strains of microorganisms during 216 hours. The growth rate was defined. This technique provides a way of distinguishing the degradation abilities of microorganisms from the degradability of materials.

Synthetic phosphoethanolamine a precursor of membrane phospholipids reduce tumor growth in mice bearing melanoma B16-F10 and in vitro induce apoptosis and arrest in G2/M phase

Phosphoethanolamine (Pho-s) is a compound involved in phospholipid turnover, acting as a substrate for many phospholipids of the cell membranes, especially phosphatidylcholine. We recently reported that synthetic Pho-s has potent effects on a wide variety of tumor cells. To determine if Pho-s has a potential antitumor activity, in this study we evaluated the activity of Pho-s against the B16-F10 melanoma both in vitro and in mice bearing a dorsal tumor. The treatment of B16F10 cells with Pho-s resulted in a dose-dependent inhibition of cell proliferation. At low concentrations, this activity appears to be involved in the arrest of the cell cycle at G2/M, while at high concentrations Pho-s induces apoptosis. In accordance with these results, the loss of mitochondrial potential and increased caspase-3 activity suggest that Pho-s has dual antitumor effects; i.e. it induces apoptosis at high concentrations and modulates the cell cycle at lower concentrations. In vivo, we evaluated the effect of Pho-s in mice bearing B16-F10 melanoma. The results show that Pho-s reduces the tumoral volume increasing survival rate. Furthermore, the tumor doubling time and tumor delays were substantially reduced when compared with untreated mice. Histological analyses reveal that Pho-s induces changes in cell morphology, typical characteristics of apoptosis, in addition the large areas of necrosis correlating with a reduction of tumor size. The results presented here support the hypothesis that Pho-s has antitumor effects by the induction of apoptosis as well as the inhibition of cell proliferation by arrest at G2/M. Thus, Pho-s can be regarded as a promising agent for the treatment of melanoma.

Effects of Ricinus communis oil esters on salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

This study showed the interference of esters extracted from Ricinus communis in the secretory cycle of salivary glands of Rhipicephalus sanguineus ticks, which consequently caused collateral effects on their feeding process. Ticks attached on hosts which were fed with commercial feed containing different concentrations of R. communis oil esters suffered damages such as cytoplasmic changes in their salivary glands, notably in the acinar cells, impairing the functioning of the acini and accelerating the organs degeneration as a whole. It was found that esters interfered with the activity of cellular secretion by changing the glycoprotein of salivary composition especially in acini II cells. It was also shown that the damages caused by esters in the salivary glands cells of these ectoparasites increased in higher concentrations of the product and degenerative glandular changes were more pronounced.

The effects of fillers on polyurethane resin-based electrical insulators

The increasingly widespread use of polymeric insulators in vehicle distributors and transmission systems has led to an ongoing quest for quality and low costs. This quest has, in turn, resulted in improved performance and cost benefits, brought about by the use of new polymeric and composite resins. Occasionally, however, while some properties are improved, others may show a loss of optimal performance. Therefore, to understand the behavior of fillers, such as carbon black, silica and mica added to castor oil-derived polyurethane resins, several thermal, mechanical and electrical tests were conducted on samples and insulators produced specifically for this purpose, using these new materials. The results of these tests clearly demonstrated that this type of resin and its composites can be used to manufacture indoor electrical insulators and that the fillers analyzed in this study improve or maintain the characteristics of the pure resins.

Potential antitumor activity of novel DODAC/PHO-S liposomes

In recent studies, we showed that synthetic phosphoethanolamine (PHO-S) has a great potential for inducing cell death in several tumor cell lines without damage to normal cells. However, its cytotoxic effect and selectivity against tumor cells could increase with encapsulation in cationic liposomes, such as dioctadecyldimethylammonium chloride (DODAC), due to electrostatic interactions between these liposomes and tumor cell membranes. Our aim was to use cationic liposomes to deliver PHO-S and to furthermore maximize the therapeutic effect of this compound. DODAC liposomes containing PHO-S (DODAC/PHO-S), at concentrations of 0.3–2.0 mM, prepared by ultrasonication, were analyzed by scanning electron microscopy (SEM) and dynamic light scattering. The cytotoxic effect of DODAC/PHO-S on B16F10 cells, Hepa1c1c7 cells, and human umbilical vein endothelial cells (HUVECs) was assessed by MTT assay. Cell cycle phases of B16F10 cells were analyzed by flow cytometry and the morphological changes by SEM, after treatment. The liposomes were spherical and polydisperse in solution. The liposomes were stable, presenting an average of ∼50% of PHO-S encapsulation, with a small reduction after 40 days. DODAC demonstrated efficient PHO-S delivery, with the lowest values of IC50% (concentration that inhibits 50% of the growth of cells) for tumor cells, compared with PHO-S alone, with an IC50% value of 0.8 mM for B16F10 cells and 0.2 mM for Hepa1c1c7 cells, and without significant effects on endothelial cells. The Hepa1c1c7 cells showed greater sensitivity to the DODAC/PHO-S formulation when compared to B16F10 cells and HUVECs. The use of DODAC/PHO-S on B16F10 cells induced G2/M-phase cell cycle arrest, with the proportion significantly greater than that treated with PHO-S alone. The morphological analysis of B16F10 cells by SEM showed changes such as “bleb” formation, cell detachment, cytoplasmic retraction, and apoptotic bodies after DODAC/PHO-S treatment. Cationic liposomal formulation for PHO-S delivery promoted cytotoxicity more selectively and effectively against B16F10 and Hepa1c1c7 cells. Thus, the DODAC/PHO-S liposomal formulation presents great potential for preclinical studies.

Caracterização Física e Térmica de Compósito de Poliuretano Derivado de Óleo de Mamona Associado com Partículas de Bambu

Composites of Polyurethane (PU) resin derived from castor oil and bamboo particles (Dendrocalamus giganteus) were prepared by pressing with 10, 15 and 20% weight of PU. The aim of this study was to develop a new application of wastes from bamboo manufacture, minimizing the negative impact to the environment, adding a resin free of volatile organic compounds (COV). The composite characterization was performed with physical and thermogravimetric analysis. The association of PU and bamboo particles produced the expected effects, including a decrease in moisture content, swelling and water absorption as PU percentage increased. The Shore D hardness increased with the percentage of resin PU in the composite.

Gamma radiation effects on mechanical properties and morphology of a polyurethane derivate from castor oil

In this study, an adhesive of a polyurethane derivate from castor oil was irradiated with gamma radiation from a 60Co source, at doses from 0.2 to 25 kGy. This adhesive polyurethane is considered for use in hospital furniture because it does not liberate dangerous solvents. Hardness and elastic modulus were measured by instrumented indentation with a pyramidal Berkovich indenter, using loads from 0.08–40 mN with a nanoindenter XP. The instrumented indentation hardness was 110 MPa for an untreated sample, increasing to 124 MPa after irradiation with 25 kGy, at penetration depths of about 5 μm. The increases in elastic modulus induced by radiation were less pronounced. This polyurethane is naturally cross-linked and the relative modifications in the hardness are attributed to an additional cross-linking process induced by radiation. X-ray diffraction indicates a slight increase in crystallinity. The roughness measured by atomic force microscopy increases after gamma irradiation.

Aplicação de indentação instrumentada na caracterização mecânica de poliuretana derivada de óleo de mamona

The mechanical properties of polyurethane derived from castor oil, obtained by instrumented indentation technique with pyramidal and spherical indenters are reported. The influence of the indenter shape on the values of mechanical properties of the polymer was investigated. The indentations were made with pyramidal Berkovich, cube corner and a spherical indenter with radius of 150 μm in a Nanoindenter XP TM . The applied loads varied between 1 and 200 mN. The penetration depth increases for acute indenters, being higher for the cube corner tip. The hardness and elastic modulus were determined using the method of Oliver and Pharr. It was found that the measured values for hardness are higher for more acute indenters. The hardness with the pyramidal Berkovich tip was 0.14 GPa for small penetrations and 0.12 GPa for higher penetration depths. The values obtained with a cube corner tip were 25 to 30% higher. This is related to the volumes of regions with high plastic deformation in the case of acute indenters compared to the volumes of regions that present viscoelastic deformation. The apparent viscosity determined using the spherical indenter, in tests with applied constant forces, is equal to (22 ± 2) × 10 12 Pa.s.