Humberto M. Brandão

Ecotoxicological effects of carbon nanotubes and cellulose nanofibers in Chlorella vulgaris.

BackgroundMWCNT and CNF are interesting NPs that possess great potential for applications in various fields such as water treatment, reinforcement materials and medical devices. However, the rapid dissemination of NPs can impact the environment and in the human health. Thus, the aim of this study was to evaluate the MWCNT and cotton CNF toxicological effects on freshwater green microalgae Chlorella vulgaris.ResultsExposure to MWCNT and cotton CNF led to reductions on algal growth and cell viability. NP exposure induced reactive oxygen species (ROS) production and a decreased of intracellular ATP levels. Addition of NPs further induced ultrastructural cell damage. MWCNTs penetrate the cell membrane and individual MWCNTs are seen in the cytoplasm while no evidence of cotton CNFs was found inside the cells. Cellular uptake of MWCNT was observed in algae cells cultured in BB medium, but cells cultured in Seine river water did not internalize MWCNTs.ConclusionsUnder the conditions tested, such results confirmed that exposure to MWCNTs and to cotton CNFs affects cell viability and algal growth.

Ecotoxicological studies of micro- and nanosized barium titanate on aquatic photosynthetic microorganisms

The interaction between live organisms and micro- or nanosized materials has become a current focus in toxicology. As nanosized barium titanate has gained momentum lately in the medical field, the aims of the present work are: (i) to assess BT toxicity and its mechanisms on the aquatic environment, using two photosynthetic organisms (Anabaena flos-aquae, a colonial cyanobacteria, and Euglena gracilis, a flagellated euglenoid); (ii) to study and correlate the physicochemical properties of BT with its toxic profile; (iii) to compare the BT behavior (and Ba(2+) released ions) and the toxic profile in synthetic (Bolds Basal, BB, or Mineral Medium, MM) and natural culture media (Seine River Water, SRW); and (iv) to address whether size (micro, BT MP, or nano, BT NP) is an issue in BT particles toxicity. Responses such as growth inhibition, cell viability, superoxide dismutase (SOD) activity, adenosine-5-triphosphate (ATP) content and photosynthetic efficiency were evaluated. The main conclusions are: (i) BT have statistically significant toxic effects on E. gracilis growth and viability even in small concentrations (1μgmL(-1)), for both media and since the first 24 h; on the contrary of on A. flos-aquae, to whom the effects were noticeable only for the higher concentrations (after 96 h: ≥75 μg mL(-1) for BT NP and =100 μg mL(-1) for BT MP, in BB; and ≥75 μg mL(-1) for both materials in SRW), in spite of the viability being affected in all concentrations; (ii) the BT behaviors in synthetic and natural culture media were slightly different, being the toxic effects more pronounced when grown in SRW - in this case, a worse physiological state of the organisms in SRW can occur and account for the lower resistance, probably linked to a paucity of nutrients or even a synergistic effect with a contaminant from the river; and (iii) the effects seem to be mediated by induced stress without a direct contact in A. flos-aquae and by direct endocytosis in E. gracilis, but in both organisms the contact with both BT MP and BT NP increased SOD activity and decreased photosynthetic efficiency and intracellular ATP content; and (iv) size does not seem to be an issue in BT particles toxicity since micro- and nano-particles produced significant toxic for the model-organisms.

Synthesis, Vibrational Spectroscopic and Thermal Properties of Oxocarbon Cross‑Linked Chitosan

In this work specimens of chitosan which have been cross-linked covalently and ionically with different oxocarbon and pseudo-oxocarbon anions have been synthesised and characterized using infrared and Raman spectroscopic techniques, solid state 13C nuclear magnetic resonance (NMR) and by thermogravimetry. According to the spectroscopic and thermal results, ionically crosslinked chitosans are obtained with squarate, croconate and rhodizonate ions as crosslinking agents, whereas covalently crosslinked chitosan can be obtained when squaric acid is used as the crosslinking agent; the same products are not observed when the pseudo-oxocarbon anion croconate violet is used, which can be attributed to the low basic strength of the crosslinking species.

Chitosan and Poly(Methyl Methacrylate-Co-Butyl Methacrylate) Bioblends: A Compatibility Study

Chitosan/poly(methyl methacrylate-co-butyl methacrylate) (PMMA-co-BMA) blends were prepared via a solution blending method in the presence of formic acid. The compatibility of the bioblends was studied by different methods, such as Fourier transform infrared and Raman spectroscopy, micro-Raman imaging, thermogravimetric analyses, differential scanning calorimetry and scanning electron microscopic analysis. According to the obtained results, it has been concluded that the PMMA-co-BMA/chitosan bioblends are compatible in all the studied compositions. Specific interactions between carbonyl and methyl groups of the PMMA-co-BMA structure and methyl, amine and amide groups of chitosan are responsible for the observed compatibility.

Efficient delivery of DNA into bovine preimplantation embryos by multiwall carbon nanotubes.

The pellucid zone (PZ) is a protective embryonic cells barrier against chemical, physical or biological substances. This put, usual transfection methods are not efficient for mammal oocytes and embryos as they are exclusively for somatic cells. Carbon nanotubes have emerged as a new method for gene delivery, and they can be an alternative for embryos transfection, however its ability to cross the PZ and mediated gene transfer is unknown. Our data confirm that multiwall carbon nanotubes (MWNTs) can cross the PZ and delivery of pDNA into in vitro-fertilized bovine embryos. The degeneration rate and the expression of genes associated to cell viability were not affected in embryos exposed to MWNTs. Those embryos, however, had lower cell number and higher apoptotic cell index, but this did not impair the embryonic development. This study shows the potential utility of the MWNT for the development of new method for delivery of DNA into bovine embryos.

Direct and indirect toxic effects of cotton-derived cellulose nanofibres on filamentous green algae

Recently, cellulose nanofibers (CNFs) have attracted considerable attention as natural, abundant polymers with excellent mechanical properties and biodegradability. CNFs provide a new materials platform for the sustainable production of high-performance nano-enable products for various applications. Given the increasing rates of CNF production, the potential for their release to the environment and the subsequent impact on ecosystem is becoming an increasing concern that needs to be addressed. Here, we used the Klebsormidium flaccidum as a bioindicator organism of terrestrial and freshwater habitats pollution using a battery of biomarkers. Our results show that cotton CNFs inhibit the proliferation of algae and induce morphological changes in them. The two main toxicity mechanisms induced by cotton CNFs are: (i) a direct contact of CNFs with the cell wall and cellular membrane and (ii) an indirect effect through the generation of reactive oxygen species (ROS).

Biocompatibility assessment of fibrous nanomaterials in mammalian embryos.

Currently there is a growing interest in the use of nanotechnology in reproductive medicine and reproductive biology. However, their toxic effects on mammalian embryos remain poorly understood. In this work, we evaluate the biocompatibility of two fibrous nanomaterials (NMs): cotton cellulose nanofibers (CNF) and carboxylated multiwalled carbon nanotubes (MWCNT-COOH), by performing an investigation of the embryonic development, gene expression (biomarkers focused on cell stress, apoptosis and totipotency) and in situ apoptosis in bovine embryos. Exposure to NMs did not interfere in preimplantation development or in the incidence of apoptosis in the bovine embryo, but they did affect the gene expression. The results presented are important for an understanding of the toxicity of cotton CNF and MWCNT-COOH on mammalian embryos. To our knowledge, we report the first evaluation of biocompatibility between these NMs on preimplantation embryos, which may open a new window for reproductive biomedical applications.

Encapsulated Brucella ovis Lacking a Putative ATP-Binding Cassette Transporter (ΔabcBA) Protects against Wild Type Brucella ovis in Rams.

This study aimed to evaluate protection induced by the vaccine candidate B. ovis ΔabcBA against experimental challenge with wild type B. ovis in rams. Rams were subcutaneously immunized with B. ovis ΔabcBA encapsulated with sterile alginate or with the non encapsulated vaccine strain. Serum, urine, and semen samples were collected during two months after immunization. The rams were then challenged with wild type B. ovis (ATCC25840), and the results were compared to non immunized and experimentally challenged rams. Immunization, particularly with encapsulated B. ovis ΔabcBA, prevented infection, secretion of wild type B. ovis in the semen and urine, shedding of neutrophils in the semen, and the development of clinical changes, gross and microscopic lesions induced by the wild type B. ovis reference strain. Collectively, our data indicates that the B. ovis ΔabcBA strain is an exceptionally good vaccine strain for preventing brucellosis caused by B. ovis infection in rams.

Economia de escala no processo de resfriamento do leite

Objetivou-se, neste artigo, estimar os custos envolvidos no processo de resfriamento do leite cru, tipo B, apos a implantacao da Instrucao Normativa 51 e a verificacao das possiveis fontes de economias de escala nesse processo. A partir dos conceitos da engenharia economica calculou-se o custo uniforme liquido equivalente de investimento do processo de resfriamento do leite, que somado ao custo operacional, resultou no custo uniforme liquido total por litro de leite. Concluiu-se que existe forte tendencia a economia de escala nessa atividade devido aos retornos crescentes no custo de investimento e operacional, conforme aumenta-se a capacidade dos tanques de resfriamento.

Cytotoxicity and Compatibility of Polymeric Blend: Evaluation of the Cytotoxicity in Fibroblast Bovine Cells and Compatibility of Poly(ɛ-Caprolactone)/Poly(Methyl Methacrylate-co-Butyl Methacrylate) Blend Films

ABSTRACT Blends between poly(ϵ-caprolactone) and poly(methyl methacrylate-co-butyl methacrylate) were prepared by solution blending in the presence of dichloromethane as solvent. The compatibility of the blends was studied by Fourier-transform infrared spectroscopy, Raman spectroscopy, micro-Raman imaging, and thermogravimetric analysis. Cytotoxicity assays were also performed to assess the feasibility of using such materials in veterinary devices. Based on results, we conclude that poly(ϵ-caprolactone) and poly(methyl methacrylate-co-butyl methacrylate)-form compatible blends owing to specific interactions between carbonyl groups of poly(methyl methacrylate-co-butyl methacrylate) and hydrogens present in the polymeric chain of poly(ϵ-caprolactone). Furthermore, these materials were not toxic to bovine fibroblasts, which supports their possible use in cattle veterinary devices. GRAPHICAL ABSTRACT