Bone mechanical stimulation with piezoelectric materials

This chapter summarized explores in vivo use of a piezoelectric polymer for bone mechanical stimulatio

Piezoelectric actuators for bone mechanical stimulation: exploring the concept.

Arthroplasty is liable to cause intense changes on strain levels and distribution in the boné surrounding the implant, namely stress shielding. Several solutions have been proposed for this, namely design variations and development of controlled-stiffness implants. A new approach to this problem, with potential application to other orthopaedic problems and other medical fields, would be the development of smart implants integrating systems for bone mechanical stimulation. Ideally, the implant should presente sensing capability and the ability to maintain physiological levels of strain at the implant interface. Piezoelectric materials’ huge potential as a mean to produce direct mechanical stimulation lies on the possibility of producing stimuli at a high range of frequencies and in multiple combinations. The present in vitro and preliminary in vivo studies were a first step towards the validation of the concept

Nanoparticles of titanium dioxide modulate the response to temperature by key enzymes involved in pyruvate availability in cytosol and mitochondria of Saccharomyces cerevisiae BY4741, CICTA 2013

Nanotechnology can be used to obtain materials at nanoscale (<100 nm) with new physicochemical and structural properties which depend on particle size and, probably, may trigger new biological effects. As Saccharomyces cerevisiae is an excellent model for study molecular and cell biology responses is growingly used in the toxicological evaluation of chemicals, such as heavy metals or nanoparticles of metal oxide due increasing use of these materials in consumables as cosmetics and textiles. The malate dehydrogenase (EC 1.1.1.37, MDH2) and malic enzyme (EC 1.1.1.38/39, ME1) of S. cerevisiae catalyze the oxidative decarboxylation of L-malate to pyruvate and CO2 coupled to reduction of NAD(P)+ in NAD(P)H of cytoplasm and mitochondria. These enzymes are part of metabolic crossroads that are implicated in regeneration of pyruvate, thereby contributing to the functionality of the citric acid cycle and generation of reducing equivalents as NADPH or NADH, required for de novo fatty acid biosynthesis and antioxidant response or respiratory chain. Hence, the main purpose of this work was to evaluate how nanoparticles of titanium dioxide modulate the effects of temperature on pyruvate availability in S. cerevisiae BY4741, a EUROCAST strain. Yeast (106 cells mL-1) at mid-exponential phase were inoculated in YEPD medium with 2% (w/v) glucose and allowed grown in a water bath, with orbital stirring at 25, 28, 30 or 40ºC, during 200 min in absence or presence of 0.1 or 1.0 µg/mL TiO2-NP. Samples from each treatment, suspended in 10 mM phosphate buffer, pH 7.0 were lysed by sonication and centrifuged at 12,000 g during 20 min, at 4ºC. Aliquots of supernatant and pellet were stored at -20ºC for later use. Protein contents in the cell fractions as well as enzyme activities MDH2, G6PD and ME1 were determined in the post-12,000 g supernatant or pellet by spectrophotometry. ROS and MDA contents were estimated in the post-12,000 g supernatant by fluorimetry. Nanoparticles of titanium dioxide (<100 nm) were purchased from Sigma-Aldrich. Statistical analysis (five independent experiments) included ANOVA I and Duncan test. The results showed that the enzymes MDH2, ME1 and G6PD of S. cerevisiae BY4741 exhibited an optimal of activity at 28ºC. Secondly, it was observed a significant increase in the ROS and MDA levels when temperature range from 25 to 30°C, countered by a significant drop at 40 °C. Thus, the increase of temperature in the range from 25 to 30°C may have blocked the renewal of cytoplasmic and mitochondrial pyruvate, slowing down the carbon flux via citric acid cycle and de novo fatty acids biosynthesis, assisted by G6PD. The decrease of MDH2, ME1 and G6PD activities detected at 40°C may be interpreted as cell death, confirmed by the increase in the MDA levels. The exposure to TiO2-NPs triggered an increase in the MDH2 activity in any realized assays, effect that was more pronounced at 28°C. On the other hand, the ME1 activity which decreased in yeast grown at 25°C and 28°C, exposed to TiO2-NPs, underwent an increase in yeasts grown at 30°C or 40°C. Although the ROS levels have increased with the presence of TiO2-NP in any realized assays, it was only detected an increase of cell damages in cell grown at 25, 28 and 40°C. Thus, it can be inferred that exposure of S. cerevisiae BY4741 to TiO2-NP can counteract the adaptation to temperature of their energy metabolism, reversing the cytoplasmic and mitochondrial pyruvate availability, that in the latter case only occurred at 30 and 40ºC

Heat-shock and titanium dioxide nanoparticles decrease SOD and glutathione enzymes activities in Saccharomyces cerevisiae

It is well-known that the majority of living organisms depend on oxygen for survival. However, organisms also had to evolve a multitude of enzyme antioxidant defences as superoxide dismutase (SOD1, SOD2), glucose-6-phosphate dehydrogenase (G6PD), glutathione reductase (GR), glutathione peroxidase (GPx), and catalases (CTT1, CTA1) as well as non-enzyme defences as glutathione, to protect their cells from toxicity of reactive oxygen species (ROS). Exposure of living organisms to xenobiotic can also induce significant generation of ROS. Failure of cell antioxidant defences to prevent ROS accumulation inevitably results in oxidative stress. This potentially causes severe oxidative damages in vital biomolecules, thus compromising cell viability. Yeasts can provide a significant contribution to our understanding of oxidative stress, and its consequences on cell death, because its cellular structure and functional organization share many similarities with plant and animal cells. Although ROS accumulation in yeast generally results from cell respiration, environmental stress stimuli can be also another important source. Despite the intensive use of engineered nanoparticles (NPs) in various consumer and industrial products, data on their potential hazards are still rare and mechanisms of action only partially understood. In addition, NPs as titanium dioxide nanoparticles (TiO2-NP) possessing unique physicochemical characteristics such as high specific surface area, high reactivity, and rapid diffusion, which differ from bulk materials of the same composition (TiO2). On the other hand, yeast response to ROS (H2O2) or the toxicity of NPs depends on environmental conditions as temperature. Consequently, the aim of this work was to evaluate the antioxidant response of Saccharomyces cerevisiae, grown in presence of glycerol or glycerol and glucose, to 5 μg/mL TiO2-NP in heat-shock conditions

How does heat-shock affect the influence of titanium dioxide nanoparticles in growth and antioxidant power of Saccharomyces cerevisiae BY4741?

Nanomaterials include all substances that contain nanoscale structures sized between 1 and 100 nm. At this size, the characteristics of materials change: their strength, conductivity, and reactivity, which differ substantially from macro- or micron- sized materials, shifting the rules of physics and chemistry to the sidelines. Although, the geological origin and the ubiquitous occurrence of nanoparticles in the earth crust can lead to suppose a good phylogenetic adaptation of living beings to such substances, the unique charateristics of nanoparticles (NPs) bring a new dimension to environmental effects testing. The industrial development coupled with vast new applications of nanomaterials, have contributed to raise their environmental levels, reason because, concern over the environmental pressure of the nanoparticles in certain regions of the world as well as its effects on the biosphere has grown in recent years, since its reactivity with biomolecules mainly depends on the surface area/molecular size ratio and physicochemical factors such as pH and temperature. Thus, the main objective of this study was to evaluate how heat-shock affects cell survival and antioxidant response of S. cerevisiae BY4741, a Eurocast strain, exposed to titanium dioxide nanoparticles (TiO2-NPs). Cells in exponential phase were inoculated in liquid YEPD medium 2 % (w/v) glucose at 28 °C are exposed at 0.1 or 1.0 μg/mL NP-TiO2 prepared by sonication, during 200 min at 40 °C. Samples from each treatment were used to obtain the post-12000 g fractions, which were used for protein content, DPPH, glutathione antioxidant capacity and, ALP, catalase and LOX activities determinations. The results show that the presence of TiO2-NPs in the culture medium induced cell death, response evidenced by a decrease of proliferative capacity detected by the alkaline phosphatase (ALP, EC 3.1.3.1) activity, loss of redox buffer capacity mediated by glutathione, evidenced by a decrease of GSH+GSSG contents and GSH/GSSG ratio. On the other hand, cell death also appears depend on the loss of ability to scavenge free radicals, estimated by DPPH method. We also observed an increase of lipoxygenase (LOX, EC 1.13.11.12) activity, a marker of lipid peroxidation, which may be related with a loss of antioxidant power mediated by peroxisomal catalase (CAT A, EC 1.11.1.6), probably due a slowdown of β-oxidation. Finally it was observed an increase of the antioxidant cytoplasmic catalase (CAT T, EC 1.11.1.6) in cells exposed to concentrations of 0.1 mg/mL, but a significantly decrease of this enzyme activity in cells exposed to 1 mg/mL TiO2-NPs. This apparently bimodal response indicates a loss of proliferative capacity by an active process when the level exposure was 0.1 mg/mL. However, for 1 mg/mL TiO2-NPs level, appears to occur a transition for necrosis

Heat shock and titanium dioxide nanoparticles decrease superoxide dismutase and glutathione enzymes activities in Saccharomyces cerevisiae.

The exposure of living organisms to metals can generate reactive oxygen species and failure in their antioxidant defences, triggering oxidative stress and oxidative damage. Despite the intensive use of engineered nanoparticles in numerous consumer and industrial products, data on their potential hazards in eukaryotic cells and their dependence on environmental factors such as temperature are still scarce. The aim of this study was to evaluate the antioxidant response of Saccharomyces cerevisiae, grown in presence of glycerol and glucose, to 5 μg/ml titanium dioxide nanoparticles (size<100 nm) under heat shock conditions. The results showed that biomass, levels of reactive oxygen species and glutathione reductase activity in respiratory/fermentative cells were higher than those detected in respiratory cells. Furthermore, respiratory/fermentative cells exhibited lower levels of glutathione, malondialdehyde, cytoplasmic catalase and glutathione peroxidase than those detected in the respiratory yeast. Saccharomyces cerevisiae grown in the presence of glycerol, glucose and titanium dioxide nanoparticles, under heat shock conditions, caused oxidative stress, due to a decrease in antioxidant defences such as superoxide dismutases or a slowdown of the glutathione cycle, relative to cells grown in presence of glycerol and glucose

Antioxidant response to titanium dioxide nanoparticles by Saccharomyces cerevisiae grown in different carbon sources and heat-shock conditions

The physicochemical properties that make nanomaterials unique, also equip them with potential for affect environment adversely, causing oxidative injuries in the living beings. However, organisms also had to develop antioxidant defences to protect their cells from reactive oxygen species (ROS). Failure in the cell antioxidant defences, due to the contact with xenobiotic, results in stress causing oxidatives damages leading to loss of cell viability. Yeasts can contribute to understand the toxicity of titanium dioxide nanoparticles (TiO2-NP), because its cell structure and functional organization, share similarities with mammalians. Since the response of yeast to NPs can be influenced by temperature and available carbon source, the aim of this study was to evaluate the antioxidant response of Saccharomyces cerevisiae, grown in presence of glycerol with addition of 2% glucose and 5 g/mlTiO2-NP, in heat-shock conditionsTiO2-NP (size <100 nm) stock suspensions were prepared by sonication. Bioassays were performed in YEPG medium (1% yeast extract, 2% peptone, 3% glycerol). Culture flasks were inoculated with wild-type Saccharomyces cerevisiae UE-ME3 and shaken 150 rpm, at 28°C. At exponential phase was added glucose and TiO2-NP stock solution (YEPGD-NP) to obtain a final concentration of 2% and 5 lg/ml. Yeasts grown 200 min at 28 or 40°C (heat-shock, HS). Flasks lacking glucose (YEPG) or NPs served as controls. Biomass was quantified by dry weight. Post-12000 g supernatants were used for determination of GSH, GSSG and ROS contents by fluorescence as well as glutathione reductase (GR), glutathione peroxidase (GPx), glucose-6-phosphate dehydrogenase (G6PD), catalase (CTT1) activity by spectrophotometry. Post-12000 g pellets were used for determination of catalase (CTA1) activity. Statistical analysis by ANOVA I and Duncan test. The results showed that biomass,ROS level and GR activity in the cells grown in YEPGD were higher than those detected in cells grown in YEPG. Furthermore, cells grown in YEPGD exhibited lower levels of GSH and MDA and CTT1activity comparatively with yeasts grown in YEPG. S. cerevisiae grown in YEPGD-NP in HS showed growth inhibition to levels near of cells which used glycerol as carbon source. Additionally, it was also detected a decrease in the GSH contents, GSH/GSSG ratio, GPx, CTT1 and CTA1 activities as well as an increase in ROS content and GR activeity, relatively to the cells growing only in glycerol. It was also observed an increase in ROS level and GR activity in the yeast grown in YEPGD-NP, relatively to S. cerevisiae grown in YEPGD. TiO2-NP in HS caused oxidative stress in yeast grown in presence of glycerol and glucose, decreasing GSH/GSSG ratio,increasing ROS content and GR activity

Early exposure to titanium dioxide nanoparticles caused a decrease in the cytoplasmic catalase activity, inducing lipid peroxidation in the Saccharomyces cerevisae.

The massive production of nanomaterials has created new pollutants whose interaction with living organisms is unclear. Recent studies have revealed that these materials generate reactive oxygen species, causing cell damage, when antioxidant systems fail, fact which justifies its inclusion in toxicological studies. Thus, the aim of this study was to test if early exposure of Saccharomyces cerevisiae to 5 μg/mL of titanium dioxide nanoparticles (TiO2-NP, size < 100 nm), with heat shock, does not disturb its antioxidant response mediated by superoxide dismutase and catalase activity. S. cerevisiae UE-ME3, a wild-type strain belonging to Oenology Laboratory of the University of Évora were grown in YEPG medium (3% glycerol) at 28 °C. At middle-exponential phase 2% glucose (YEPGD) and/or 5 μg/mL TiO2-NP stock solution were added and cells were grown for 200 min at 28 °C or 40 °C (heat-shock, ST). Culture medium lacking glucose or NPs served as control samples. At the end of the experiment, the dry weight was determined and remaining cells were disintegrated in 10 mM phosphate buffer pH 7.0 by ultra-sonication. The post-12,000 × g supernatant was used for determination of MDA content and catalase (CTT1) and superoxide dismutase (SOD1) activity. The pellet was used for determination of activities catalase (CTA1) and superoxide dismutase (SOD2). The results showed that the presence of glucose in the medium caused an increase of biomass, a decrease in the MDA content and CTT1 activity without change CTA1, SOD1 and SOD2 activity. Additionally, it was determined an increase in CTA1, SOD1 and SOD2 activity in the cells grown in YEPGD-ST medium. The NP-TiO2 exposure with ST, decreased CTT1 activity for similar levels to those estimated in the cells grown in YEPGD medium with nanoparticles, did not affect the CTA1 and SOD1 activity, increased the MDA level and kept the SOD2 activity in similar levels to those detected in cells grown in YEPGD-ST medium. The decrease in the CTT1 activity caused by NPs may justify, in part, the increase in MDA level

Thermal fatigue assessment of components made with particulate polymer composites

Many appliance materials are made of PMMA/Si acrylic casting dispersion. In these situations, failure can occur by thermal fatigue induced by severe temperature variations such as alternating flows of cold and hot water. This paper is concerned with the numerical analysis of the thermal stresses in three composites with different volume fractions of filler and particle size. Their trade marks are Asterite, Amatis and Ultra-quartz. Cosmos/M finite element method software was used to study the influence of the cold and hot water temperatures as well as the time of interruption of water flow in the transition between hot and cold water on thermal stresses. Residual stresses were measured and superimposed to thermal stress in fatigue analysis. Typical defects in the corner of holes produced by drilling were predicted using experimental fatigue lives and da/dN curves. Based on predicted defects thermal fatigue assessment of commercially available sinks made with the three materials mentioned earlier was done by taking into account the influence of both cyclic thermal and static residual stresses induced by the manufacturing process.http://www.sciencedirect.com/science/article/B6V55-4DF4C7S-2/1/e913309acfd159679eb06b390853e5e

Nanopartículas de dióxido de titânio ativam vias de desintoxicação celular citoplasmáticas de Saccharomyces cerevisiae UE-ME3

A origem geológica e a ocorrência ubíqua das nanopartículas (NPs) podem levar a supor uma boa adaptação filogenética dos seres vivos a este tipo de substâncias. Contudo, o desenvolvimento industrial, associado a novas e vastas aplicações dos nanomateriais, tem contribuido para elevar os seus níveis ambientais [1]. Por esse motivo, a preocupação com a pressão ambiental das nanopartículas em determinadas regiões do globo, bem como os seus efeitos na biosfera tem crescido nos últimos anos, uma vez que o tipo de interacção destes materiais, com dimensão entre 1 e 100 nm, com as biomoléculas é fortemente condicionado pela sua área superficial/ dimensão molecular [2]. Assim, o principal objetivo deste estudo foi compreender como diferentes níveis de nanopartículas de dióxido de titânio afetam o crescimento e a capacidade de resposta antioxidante de Saccharomyces cerevisiae UE-ME3, uma levedura vínica nativa do Alentejo, com elevada capacidade de resistência a condições de crescimento adversas. S. cerevisiae, em fase exponencial média foram inoculadas em meio sólido YEPD (2%) e deixadas crescer durante 72 h, a 28 ºC, na ausência e na presença de TiO2-NPs, na concentração de 0,5 a 5 μg.mL-1. Os resultados mostraram que a exposição de S. cerevisiae UE-ME3 a nanopartículas de dióxido de titânio, inibiu o crescimento celular, causando uma diminuição do peso seco e do teor lipídico. Por outro lado, o aumento significativo de danos celulares, via peroxidação lipídica e estimada pelo conteúdo intracelular de MDA, leva-nos a crer que esta tenha sido uma das principais causas de morte celular. O facto da exposição a TiO2-NPs causar uma diminuição da razão GSH/GSSG, e aumentar as atividades enzimáticas GR e G6PD sugere que as TiO2-NPs induziram stress oxidativo. O aumento dos níveis de atividade CAT T e GT em leveduras crescidas na presença de TiO2-NPs leva-nos a admitir um papel relevante destes enzimas na eliminação do peróxido de hidrogénio e de mercapturatos. O decréscimo das atividades CAT A e GPx apontam também para um abrandamento da β-oxidação lipídica que terá ocorrido maioritariamente no peroxissoma. Estas respostas provavelmente refletem uma ativação de vias de desintoxicação celular citoplasmáticas que determinaram a depleção de GSH com consequente transição redutor-oxidante do ambiente celular de leveduras crescidas na presença de TiO2-NPs