Thermoprotective Properties Research Articles

Development and preclinical evaluation of multifunctional hydrogel for precise thermal protection during thermal ablation

Image-guided thermal ablation (TA), which is less invasive, has been widely applied for treating various kinds of tumors. However, TA still poses the potential risk of thermal damage to sensitive tissue nearby. Therefore, an adjunctive thermoprotective hydrodissection technique with constant injection of 5% glucose (5% Glu) has currently been adopted for clinical application, but this may be hazardous to humans. In this study, a multifunctional hyaluronic acid-based hydrogel (HA-Dc) was developed for hydrodissection. Compared with 5% Glu (the most clinically used solution) and the previously reported F127 hydrogel, the HA-Dc hydrogel was studied in vitro in a porcine liver model and in vivo in a rabbit model and showed good injectability and better tissue retention, stability, and thermoprotective properties throughout the TA procedure. Furthermore, in the preclinical evaluation in a Macaca fascicularis (M. fascicularis) model, HA-Dc showed excellent performance in terms of stricter neuroprotection compared with 5% Glu. In addition, the HA-Dc hydrogel with good biocompatibility and controllable degradation behavior in vivo could be a promising platform for thermal protection during clinical TA procedures.

Effect of Phosphorus and Chlorine Containing Plasticizers on the Physicochemical and Mechanical Properties of Epoxy Composites

The possibility of using tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate and tris(4-methylphenyl) phosphate as effective plasticizers for epoxy polymers has been studied. As a result of the research the optimum content of plasticizers (40 parts by mass) has been determined, which has the best effect on the strength and fire safety properties of epoxy composites. Modification of the epoxy polymer with presented plasticizers influences carbonization process increasing char yield and reducing the amount of volatile thermolysis products released into the gas phase, thus improving fire safety parameters of epoxy composites, reducing mass loss on ignition in air from 78 to 2–9% and increasing limiting oxygen index (LOI) values from 19 to 25–31% by volume, giving good fire protective properties to epoxy composites (UL-94 rating—V-0/V-1). The thermo-protective properties and the structure of the char formed by polymer combustion have been studied and the correlation between the thermo-protective properties of the char and the combustibility of the composite has been determined. Furthermore, the behaviour of the modified composite during high rate pyrolysis has been analyzed.

Loss of heat shock factor initiates intracellular lipid surveillance by actin destabilization.

Cells sense stress and initiate response pathways to maintain lipid and protein homeostasis. However, the interplay between these adaptive mechanisms is unclear. Herein, we demonstrate how imbalances in cytosolic protein homeostasis affect intracellular lipid surveillance. Independent of its ancient thermo-protective properties, the heat shock factor, HSF-1, modulates lipid metabolism and age regulation through the metazoan-specific nuclear hormone receptor, NHR-49. Reduced hsf-1 expression destabilizes the Caenorhabditis elegans enteric actin network, subsequently disrupting Rab GTPase-mediated trafficking and cell-surface residency of nutrient transporters. The ensuing malabsorption limits lipid availability, thereby activating the intracellular lipid surveillance response through vesicular release and nuclear translocation of NHR-49 to both increase nutrient absorption and restore lipid homeostasis. Overall, cooperation between these regulators of cytosolic protein homeostasis and lipid surveillance ensures metabolic health and age progression through actin integrity, endocytic recycling, and lipid sensing.

The effect of the application of a powder additive of a phase change material on the ablative properties of a hybrid composite

The necessity to ensure thermal protection for sensitive elements of the aviation technology, being exposed to a high temperature of a thermal stream, enforces the emergence of new materials with high thermo-protective properties. The investigations focused on laminates consisting of six layers of carbon and aramid fabrics, which were laid down in an epoxy resin matrix base L285 MGS and H500 MGS hardener. The ablative thermo-protective properties were modified with powder additives (in the rear part of the composite such as PCM, MMT, SiC, Al2O3). The samples were exposed to a mixture of hot gases at a temperature of over 1000 °C for a period of approximately 180 s. The most important parameter determined on the basis of experimental research was the temperature of the rear surface of the sample. The average loss of mass and the mass ablation rate of the tested material were also analysed. Based on the analysis of the temperature rise on the back of the sample surface, it is possible to observe a clear downward tendency for a hybrid composite modified with powder by >60 °C, as opposed to samples without the addition of powder.

Thermoprotective properties of Opuntia ficus-indica f. inermis cladodes and mesocarps on sheep lymphocytes

This study aims to investigate the thermoprotective properties of Opuntia ficus-indica f. inermis. Extracts were prepared from cladodes (CE) and mesocarps (ME), then subjected to a spectrophotometric and LC-MS analyses. Lymphocytes were isolated from peripheral blood of non-stressed sheep, supplemented with CE, ME, betanin or α-tocopherol, and subjected to two thermal treatments: 40 and 41 °C, for 6 h. Viable lymphocytes and H2O2 production were evaluated.The antioxidant activity of ME was 3.43 folds higher than CE. The LC-MS analysis of CE and ME allowed identifying 11 phenolic acids, 2 flavanones, 6 flavones, 3 flavonols and 1 betanin type betacyanin.Lymphocytes mortality increased linearly as function of the severity and the duration of heat stress. This mortality was correlated with H2O2 production. At 41 °C, only ME allowed maintaining lymphocytes viability. Moreover, ME was more efficient than CE in reducing H2O2 production. This thermoprotection was ensured by betaxanthin and betacyanin pigments. Interestingly, betanin was more efficient than α-tocopherol in preventing hyperthermia-induced lymphocytes’ mortality.We report here for the first time the thermoprotective properties of cladodes and mesocarps of Opuntia ficus-indica f. inermis. Betanin was able to maintain lymphocyte viability through reducing H2O2 production, and therefore the oxidative-induced heat stress.

Thermo-protective properties of polymer composites with nano-titanium dioxide

The present work investigates the ablative and thermal properties of an epoxy resin which was modified with titanium dioxide nanoparticles having different size. Prepared samples were submitted to temperatures above 1900 °C and tested for their thermo-protective and ablative properties. The effect of epoxy composite components on thermo-protective and ablative properties: the maximum back side temperature, and the average weight loss under intensive heat flow conditions as well as temperature distribution on the ablation surface of the sample using a thermographic camera and a pyrometer have been established. A statistical analysis of the test results was made. It was confirmed that epoxy resin crosslinked with polyaminoamide hardener and modified with TiO2(21 nm) i TiO2(100 nm+1% Mn) showed improved thermo-protective properties in comparison with unmodified epoxy matrix.

The Effect of the Addition of Nanotubes Upon the Thermo-Protective Properties of the Aramid-Reinforced Composite

The Effect of the Addition of Nanotubes Upon the Thermo-Protective Properties of the Aramid-Reinforced Composite

Effect of composition on ablative properties of epoxy composites modified with expanded perlite

The present work investigates ablative and thermoprotective properties of epoxy resins modified with expanded perlite (vermiculite – 3% or 10% of weight share). The properties of two epoxy resins (Epidian 52 and Epidian 601 cured with triethylenetetraamine – hardener Z-1 or cured with hardener TFF – triethylenetetraamine with phenol) were studied. Statistical methods for planning experiments were used and the effect of components on thermoprotective properties of epoxy composites was established. The maximal temperature of the rear surface of an ablative sample and an average relative ablative (erosive) mass loss after 120s of the heat flux exposition were analysed. It was shown that the best of both thermoprotective properties, i.e. low temperature of the rear surface area and low ablative mass loss (the highest thermal stability), were achieved by the composite based on Epidian 601 cured with hardener Z-1 and containing 10% mass of vermiculite. More stabilized ablative layer with limited erosion was obtained with a higher vermiculite participation (especially with Epidian 52+TFF). Moreover, the type Z-1 of epoxy hardener showed the most significant effect on the maximum temperature of the rear surface area. Triethylenetetraamine hardener Z-1 decreases this temperature.

Thermoprotective Properties of the Venom of the Transcaucasian Vipera (Macrovipera Lebetina Obtusa Dyigubsky, 1832)

The paper presents data on the study of the thermoprotective properties of the venom of the Transcaucasian Vipeta (Macrovipera lebetina obtuse) on 120 white mongrel mice subjected to thermal exposure (30 - 50°C) for 30 minutes with the injection of zootoxin in doses (2 mg / kg and 4 mg / kg). It was found that the lifespan of mice was increased with respect to a series of experiments in which the injection of venoms under the conditions of normothermia was used for 28 - 30 minutes and 15 - 20 minutes to 120.0 ± 8.5 and 160.0 ± 19.7 minutes, respectively. It was found that in the posthyperthermic period after a 30-minute thermal exposure (30 - 50°C) in the control group of animal experiments, a 100% mortality was observed during 24 hours, and with the preliminary injection of a venom in the range of doses 2 - 4 mg / kg Survival in 30% - 50% of experimental animals was noted. Thus, the thermoprotective property of the venom of the Transcaucasian vipera has been proved.

Involvement of free cholesterol and high-density lipoprotein in development and resistance of the preimplantation bovine embryo to heat shock1

Development of the mammalian preimplantation embryo is susceptible to disruption by elevated temperature. The molecular and biochemical bases for developmental, genetic, and other differences in embryonic resistance to heat shock are largely not known. Here we tested the hypothesis that increasing free cholesterol content could improve embryonic resistance to heat shock. Culture of bovine embryos at 41.0°C for 15 h beginning at 30 h after insemination (1- to 2-cell stage) reduced development to the blastocyst stage. Reduction in embryonic cholesterol content by culture with methyl-β-cyclodextrin (MBCD) reduced development. This effect of MBCD could be abrogated in 1 of 2 experiments if the molecule was loaded with cholesterol before addition to culture medium. Even though culture with cholesterol-loaded MBCD increased free cholesterol content, it did not increase resistance of embryos to heat shock. Treatment of embryos with cholesterol-loaded high density lipoprotein (HDL) increased embryonic resistance to heat shock even though it slightly reduced embryo cholesterol content. It is likely that other actions of HDL (e.g., protection from free radicals) were responsible for the thermoprotective properties of this molecule. A final experiment was performed to determine whether the increased resistance of embryos at d 5 of development to heat shock as compared with the 2-cell embryo was due to changes in free cholesterol content. However, there was no significant difference in cholesterol content between 2-cell embryos and d 5 embryos that were > 16 cells in development. In conclusion, raising cholesterol content does not improve embryonic survival in response to heat shock. Depletion of cholesterol, in contrast, reduces competence of embryos to develop to the blastocyst stage. High density lipoprotein is thermoprotective to embryos and probably acts through a mechanism independent of its actions on embryonic content of free cholesterol.

Radiative-conductive heat transfer in a semitransparent composite with microspherical particles

A mathematical model for calculating the temperature field in a semitransparent composite material that in- cludes a polymethyl methacrylate matrix and quartz microspheres is suggested. In calculating the optical properties of the composite material, use was made of the optical properties of the matrix and of the inter- acting quartz microspheres at different filling factors which characterize the volume concentration of particles in the matrix. Allowance for the interaction between the composite components is made following the Max- well-Garnett approximation. Data on the complex refractive index of the composite were used for calculating the coefficients of absorption, scattering, and attenuation of packed particles by the Mie theory. The tempera- ture fields in a layer of the material are found from solving the boundary-value problem for the energy equa- tion and a system of radiation transfer equations with the use of these coefficients. perature. Introduction. Semitransparent composites are found in number of promising modern materials. Such materials assume a particular significance in articles in which an important role is played by energy transfer by heat conduction and radiation. Therefore investigations of the parameters of the composite components that influence thermal processes are very pressing. One of the means of increasing the thermoprotective properties is the use of materials involving fine particles that scatter thermal radiation. The composite material considered in the present work consists of hollow and solid quartz microspheres with a characteristic dimension of 3-50 μm introduced into a semitransparent binding matrix; the material is the means of heat shielding under the conditions of radiative-conductive transfer of thermal energy only at a high volume concentration of microspheres. To calculate the thermal fields in such a material, it is necessary to have data on the absorption and scattering coefficients with account for the interaction between particles. The problem of the influence of the proximity of particles on these coefficients remains as yet unsolved. Heat losses from the composite material surface include conductive and radiative components. Account for the indicated losses is possible at the known temperature distribution in a layer of this material. Solution of the problem is performed in the approximation of a continuous medium with effective thermophysical and optical properties. Dur- ing the passage of a radiative energy flux, the interaction between particles appears in the case of a high concentration of particles in the composite. It is known that if the distance between particles greatly exceeds that of their size and of the radiation wavelength, then the interaction between them is absent, and the absorption and scattering coefficients can be calculated by the classical Mie theory with the use of complex refractive indices of the particles and matrix (1). For the majority of optical problems, such an approach turns out to be justifiable. Since the composite material considered in the present work is an effective heat shield only at a high volume concentration of microspheres, the condition of the absence of interaction of particles that scatter and absorb radiation does not hold. Therefore the use of the classical Mie theory can lead in this case to considerable errors in calculating the radiative characteristics of a composite material and, as a consequence, of the temperature fields in it. To determine the attenuating and scattering

Extraction of ecdysteron-80 from Serratula coronata L. and assessment of its pharmacological action. Part I. Adaptogenic, gastroprotective, thermoprotective, and antihypoxic activity

A method for extracting ecdysteroids from Serratula coronata L. for the new phytopreparation Edcysterone-80 is proposed. Experiments on white rats established that this preparation has pronounced adaptogenic, antihypoxic, gastroprotective, and thermoprotective properties. Results of this study can be applied both in basic research and in the development of production technology for the new pharmaceutical preparation based on ecdysteroids of Serratula coronata.

Thermoprotective properties of small heat shock proteins from rice, tomato and Synechocystis sp. PCC6803 overexpressed in, and isolated from, Escherichia coli

The present study forms part of a program investigating the role of small heat shock proteins (sHSPs) in the acquired and transgenic thermotolerance of the cyanobacterium Synechococcus PCC7942. The genes for three minimally related sHSPs, OsHSP from Oryza sativacytoplasm, tom111 from Lycopersicon esculentumchloroplasts, and 6803 HSP from Synechocystis sp. PCC6803, were cloned into the Escherichia coli vector pTrcHisA, so as to produce an N-terminal polyhistidine tag. The genes were transformed into E. coli and overexpressed. The tagged HSPs were purified (not completely in the case of tom111) by immobilised metal affinity chromatography. The native proteins exhibited a high degree of oligomerisation when analysed by size-exclusion chromatography. All three proteins were able to protect malate dehydrogenase (MDH) from in vitro thermal aggregation. They could also protect several soluble proteins in E. coli extracts from thermal aggregation in vitro, as well as protecting phycocyanin in extracts from Synechococcus sp. PCC7942. None of the proteins were able to protect photosystem II (measured as ΦPSII, the effective quantum fluorescence yield of PSII) of thylakoids isolated from Synechococcus sp. PCC7942 from heat damage in vitro, although in vivo, after acclimation, photosystem II did exhibit acquired thermotolerance.

Thermo-Protecting Properties of Intumescent Compositions

Intumescent fire retardants have wide applications due to thermo-protective properties, which decrease heat flow on the polymer surface. In this work we present the experimental investigation of thermal-protection properties of a number of polymer mixtures (polycarbonate + ABS plastic, epoxy resin, etc.) with different fire retardant additions.

Sorbitol accumulation in whiteflies: evidence for a role in protecting proteins during heat stress

1. The relationship between sorbitol accumulation and thermotolerance was examined in whiteflies and was related to the thermoprotective properties of sorbitol in vitro. 2. Whiteflies that were conditioned at 40°C on diets that supported sorbitol accumulation had lower mortality rates at 44 and 46°C than unconditioned whiteflies and whiteflies that were conditioned at 40°C on diets that did not support sorbitol accumulation. 3. Physiological concentrations of sorbitol protected soluble whitefly proteins from heat-induced aggregation and inactivation. 4. Sorbitol accumulation in heat-stressed whiteflies was analogous to trehalose accumulation in yeast, and in the same way probably increases the thermotolerance of whiteflies.