In vitro evaluation of graphene oxide nanosheets on immune function.

HYPOTHESIS: Graphene oxide (GO) has attracted the scientific community attention due to its novel properties and wide range of potential applications including hyperthermia cancer therapy. However, little is known about the GO effects on the immune function which involves both innate and adaptive defence mechanisms through the activation of different cell populations and secretion of several cytokines. The effect of different GO nanosheets designed for hyperthermia cancer therapy on macrophage and lymphocyte function should be determined before using GO for this application. EXPERIMENTS: The effects of GO nanosheets with 1 (1-GOs) and 6 arms (6-GOs) of polyethylene glycol on RAW-264.7 macrophages and primary splenocytes (as approximation to the in vivo situation) were evaluated through the proinflammatory cytokine secretion and the modulation of cell proliferation in the presence of specific stimuli for either T-lymphocytes (concanavalin A, anti-CD3 antibody) or B-lymphocytes/macrophages (lipopolysaccharide). FINDINGS: 6-GOs significantly increased the secretion of TNF-α by RAW-264.7 macrophages without alteration of IL-6 and IL-1ß levels. The treatment of primary splenocytes with 1-GOs and 6-GOs in the presence of concanavalin A, anti-CD3 antibody and lipopolysaccharide, produced significant dose-dependent decreases of cell proliferation and IL-6 levels, revealing weak inflammatory properties of GOs which are favourable for hyperthermia cancer therapy.

Odours stimulate neuronal activity in the dorsolateral area of the hippocampal formation during path integration.

The dorsolateral area of the hippocampal formation of birds is commonly assumed to play a central role in processing information needed for geographical positioning and homing. Previous work has interpreted odour-induced activity in this region as evidence for an 'olfactory map'. Here, we show, using c-Fos expression as a marker, that neuronal activation in the dorsolateral area of the hippocampal formation of pigeons is primarily a response to odour novelty, not to the spatial distribution of odour sources that would be necessary for an olfactory map. Pigeons exposed to odours had significantly more neurons activated in this area of the brain than pigeons exposed to filtered air with odours removed. This increased activity was observed only in response to unfamiliar odours. No change in activity was observed when pigeons were exposed to home odours. These findings are consistent with non-home odours activating non-olfactory components of the pigeon's navigation system. The pattern of neuronal activation in the triangular and dorsomedial areas of the hippocampal formation was, by contrast, consistent with the possibility that odours play a role in providing spatial information.

Triggering cell death by nanographene oxide mediated hyperthermia.

Graphene oxide (GO) has been proposed as an hyperthermia agent for anticancer therapies due to its near-infrared (NIR) optical absorption ability which, with its small two-dimensional size, could have a unique performance when compared to that of any other nanoparticle. Nevertheless, attention should be given to the hyperthermia route and the kind of GO-cell interactions induced in the process. The hyperthermia laser irradiation parameters, such as exposure time and laser power, were investigated to control the temperature rise and consequent damage in the GOs containing cell culture medium. The type of cell damage produced was evaluated as a function of these parameters. The results showed that cell culture temperature (after irradiating cells with internalized GO) increases preferentially with laser power rather than with exposure time. Moreover, when laser power is increased, necrosis is the preferential cell death leading to an increase of cytokine release to the medium.

A biorefinery from Nannochloropsis sp. microalga--extraction of oils and pigments. Production of biohydrogen from the leftover biomass.

The microalga Nannochloropsis sp. was used in this study, in a biorefinery context, as biomass feedstock for the production of fatty acids for biodiesel, biohydrogen and high added-value compounds. The microalgal biomass, which has a high lipid and pigment content (mainly carotenoids), was submitted to supercritical CO2 extraction. The temperature, pressure and solvent flow-rate were evaluated to check their effect on the extraction yield. The best operational conditions to extract 33 g lipids/100 g dry biomass were found to be at 40 °C, 300 bar and a CO2 flow-rate of 0.62 g/min. The effect of adding a co-solvent (ethanol) was also studied. When supercritical CO2 doped with 20% (w/w) ethanol was used, it was possible to extract 45 g lipids/100 g dry biomass of lipids and recover 70% of the pigments. Furthermore, the remaining biomass after extraction was effectively used as feedstock to produce biohydrogen through dark fermentation by Enterobacter aerogenes resulting in a hydrogen production yield of 60.6 mL/g dry biomass.

Cell uptake survey of pegylated nanographene oxide.

Graphene and more specifically, nanographene oxide (GO) has been proposed as a highly efficient antitumoral therapy agent. Nevertheless, its cell uptake kinetics, its influence in different types of cells and the possibility of controlling cellular internalization timing, is still a field that remains unexplored. Herein, different cell types have been cultured in vitro for several incubation periods in the presence of 0.075 mg ml(-1) pegylated GO solutions. GO uptake kinetics revealed differences in the agent's uptake amount and speed as a function of the type of cell involved. Osteoblast-like cells GO uptake is higher and faster without resulting in greater cell membrane damage. Moreover, the dependence on the commonly used PEG nature (number of branches) also influences the viability and cell uptake speed. These facts play an important role in the future definition of timing parameters and selective cell uptake control in order to achieve an effective therapy.

Direct nucleation of silver nanoparticles on graphene sheet.

Silver (Ag) nanoparticles were synthesized on the surface of graphene sheet by the simultaneous reduction of Ag+ and graphene oxide (GO) in the presence of simple reducing agent, hydrazine hydrate (N2H4 x H2O). Both the Ag+ and GO were reduced and Ag+ was nucleated onto graphene. GO flakes were prepared by conventional chemical exfoliation method and in the presence of strong acidic medium of potassium chlorate. Silver nanoparticles were prepared using 0.01 M AgNO3 solution. The reduced GO sheet decorated with Ag is referred as G-Ag sample. G-Ag was characterized by FTIR (Fourier transform infrared) spectroscopy using GO as standard. An explicit alkene peak appeared around 1625 cm(-1) was observed in G-Ag sample. Besides, the characteristic carbonyl and hydroxyl peaks shows well reduction of GO. The FTIR therefore confirms the direct interaction of Ag into Graphene. SEM (scanning electron microscopy) and TEM (transmission electron microscopy) analysis were performed for morphological probing. The average size of Ag nanoparticles was confirmed by around 5-10 nm by the high-resolution TEM (HRTEM). The Ag quantum dots incorporated nanocomposite material could become prominent candidate for diverse applications including photovoltaic, catalysis, and biosensors etc.

Inorganic plasma with physiological CO2/HCO3- buffer.

The substitution of tris/HCl buffer by CO(2)/HCO(3)(-) buffer in inorganic plasma was studied. An appropriate gas mixture of CO(2)/N(2) was continuously bubbled in Kokubo's SBF solution prepared without addition of Tris/HCl. This method enables buffering the solution within the 7.3-7.4 pH interval and, at the same time, reaching a HCO(3)(-) concentration between 24 and 27 mmol dm(-3), which are the normal concentrations reported for blood plasma. Mineralisation studies on calcium phosphate ceramics using this solution showed that, in the presence of such hydrogencarbonate concentrations, the formation of a mineralisation layer on the ceramic occurs via a carbonated octacalcium phosphate, that evolves to carbonated hydroxyapatite. The results suggest that mineralisation studies in this new carbonate-containing simulated inorganic plasma mimic biomineralisation more closely than traditional SBF.

The fluorapatite-anorthite system in biomedicine.

Glasses and glass ceramics of fluorapatite-anorthite (eutectic composition) were produced and characterized in order to evaluate their potential application in biomedicine. Bio-reactivity was determined by in vitro tests by immersion of powders in simulated plasma liquids as well as by in vivo experiments by implantation in rabbits. According to the results, the investigated materials are bio-acceptable since no toxic or other harmful evidence was detected. Glass-ceramics showed remarkable inertness, whereas glasses spontaneously dissolved in SBF and after 1 week moderate formation of apatite was observed, that however ceased within a month.

Mineralisation of two phosphate ceramics in HBSS: role of albumin.

The role of albumin in the mineralisation process of commercial hydroxyapatite (HAp) and synthesised biphasic (HAp-tricalcium phosphate) ceramics in a bufferless simulated inorganic plasma (HBSS) was investigated by conventional in vitro tests and static and dynamic wettability measurements. Albumin was either pre-adsorbed or solubilised in HBSS. It was found that calcium complexation by albumin plays a key role in early mineralisation kinetics, so that mineralisation is favoured when albumin is pre-adsorbed and hindered when it is dissolved in HBSS. In the biphasic ceramic this picture is complicated by the fact that albumin, in solution, seems to promote the dissolution of tricalcium phosphate, and simultaneously compete for calcium with the ceramic. It also appears that albumin has a stabilising effect of octacalcium phosphate present in deposits on commercial HAp. The same effect may be present in the case of the biphasic ceramic, at earlier mineralisation times, when octacalcium phosphate appears as a precursor of HAp. Octacalcium phosphate formation on commercial apatite is accompanied by carbonate substitution in phosphate positions.

Acid tolerance and survival of Escherichia coli O157:H7 inoculated in fruit pulps stored under refrigeration.

The adaptation of Escherichia coli O157:H7 cells to acid conditions has been reported. This study showed the behavior of three strains of E. coli O157:H7 in two different physiological stages (acid shocked and control cells), inoculated in five fruit pulps stored at 4 degrees C for up to 30 days. The three strains of E. coli O157:H7 inoculated in grape pulp could be recovered up to day 30. E. coli O157:H7 strains survived for 4 days in all fruit pulps tested with different pH values (2.51 to 3.26), with the exception of acid-shocked cells of E. coli O157:H7 strain 933, which did not survive in "cajá" (Spodias lutea L.) pulp. The results clearly indicated that acid resistance can persist for long periods during storage at 4 degrees C. The protection conferred by acid adaptation suggests that acid-resistant organisms will be better equipped to outlast these acid challenges. The survival of E. coli O157:H7 in fruit pulps with a low pH, stored under refrigeration, is of extreme importance due to the high virulence of this microorganism. The viability of microorganisms was dependent on the viscosity index of fruit pulps. Less viscous pulps supported the bacteria survival longer than more viscous fruit pulps.