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A new calorimetric technique is described that allows high-throughput heat production rate measurements on small biological tissue samples. The technique is based on the widely used thermopile chip technology combined with an innovative method for precise transport and positioning of samples of different biological materials at the thermal power detector inside the calorimeter. The new transport and positioning technique is a combination of fluidic and mechanical transport, where the latter is realized by a magneto-motor drive. The transport facility ensures good diffusive oxygen penetration into the sample, which is essential for highly metabolically active materials. The proper functioning of the device is demonstrated by measuring the heat production of metabolically active brown adipose tissue, biopsied tegu lizard muscle, and live Drosophila larvae at different stages and temperatures. [ABSTRACT FROM AUTHOR]

The first evidence of native cyclodextrins fusion was registered using fast scanning calorimetry (FSC) with heating rates up to 40,000 K s−1. The endothermal effects, detected at low heating rates, correspond to the decomposition processes. Upon the increase of the heating rate the onset of these effects shifts to higher temperatures, reaching a limiting value at high heating rates. The limiting temperatures were identified as the melting points of α-, β- and γ-cyclodextrins, as the decomposition processes are suppressed at high heating rates. For γ-cyclodextrin the fusion enthalpy was measured. The activation energies of thermal decomposition of cyclodextrins were determined by dependence of the observed thermal effects on heating rates from 4 K min−1 in conventional differential scanning calorimetry to 40,000 K s−1 in FSC. The lower thermal stability and activation energy of decomposition of β-cyclodextrin than for the other two cyclodextrins were found, which may be explained by preliminary phase transition and chemical reaction without mass loss. The obtained values of fusion parameters of cyclodextrins are needed in theoretical models widely used for prediction of solubility and solution rates and in preparation of cyclodextrin inclusion compounds involving heating. [ABSTRACT FROM AUTHOR]

Ca2+ signaling in trypanosomatids is an important component of energy metabolism regulation and therefore, cytosolic Ca2+ concentration is finely regulated by Ca2+ transport through the plasma membrane and Ca2+ uptake and release by intracellular organelles. To maintain intracellular Ca2+ homeostasis with different gradients of the ion within the cellular compartments, there is an energy cost and also energy dissipation in the form of heat. Using an innovative segmented fusion technique of a chip-calorimeter and CRISPR/Cas9 knockout (–KO) Trypanosoma cruzi cell lines, we evaluated the heat generation during Ca2+ uptake by digitonin-permeabilized T. cruzi epimastigotes, a system consisting of Ca2+ uptake predominantly by mitochondria and acidocalcisomes. We used three T. cruzi epimastigotes cell lines: control cells denominated scrambled, cells with the absence of the pyruvate dehydrogenase phosphatase (TcPDP-KO) and cells lacking mitochondrial Ca2+ uptake via the mitochondrial calcium uniporter (TcMCU-KO), that presented, in this respective order, decreasing rates and capacities of Ca2+ uptake. TcPDP-KO cells exhibited the lowest heat production following Ca2+ addition, which may be due to its lower mitochondrial oxidative phosphorylation capacity and lower ATP availability for acidocalcisomal Ca2+ uptake. Scrambled and TcMCU-KO cells exhibited similar Ca2+-induced heat effects, which correlates with a higher ATP-dependent acidocalcisomal Ca2+ uptake in these cells. Our results show evidences that mitochondrial Ca2+ transport via the uniporter is minimally heat dissipative, while ATPase pumps in acidocalcisomes possess a predominant contribution to the heat generated during Ca2+ uptake. [ABSTRACT FROM AUTHOR]

The development of the segment-flow technology has considerably extended the application range of miniaturized calorimeters. The transport of samples in aqueous µL segments by a water-immiscible carrier liquid enables the investigation of aggregated, complex biological samples in flow-through. The protection from contaminations of the fluidics of the calorimeter by the carrier liquid is an excellent precondition for the design of efficient automatic experiment protocols. In this paper, a new operation mode of this technique is presented, which allows the measurement of fast transient heat-dissipating processes using a chip calorimeter. Heat dissipation is initiated by the merging of separate µL-sample-segments arriving successively at the measuring chamber. The potential of the segment fusion technique was demonstrated here using two different applications. First, we showed the use of this method for an automatic screening of the strength of receptor–substrate interactions by the measurement of the heat of the adduct formation of carbohydrate octyl ß-d-glucopyranoside and three different receptor molecules. Next, we used the method for the determination of transient heat effects in the seconds range allowing the investigation of metabolic processes in Trypanosoma cruzi cells induced by Ca2+ ions. [ABSTRACT FROM AUTHOR]

We describe a chip calorimetric technique that allows the investigation of biological material under anoxic conditions in a micro-scale and in real time. Due to the fast oxygen exchange through the sample flow channel wall, the oxygen concentration inside the samples could be switched between atmospheric oxygen partial pressure to an oxygen concentration of 0.5% within less than 2 h. Using this technique, anaerobic processes in the energy metabolism of Trypanosoma cruzi could be studied directly. The comparison of the calorimetric and respirometric response of T. cruzi cells to the treatment with the mitochondrial inhibitors oligomycin and antimycin A and the uncoupler FCCP revealed that the respiration-related heat rate is superimposed by strong anaerobic contributions. Calorimetric measurements under anoxic conditions and with glycolytic inhibitors showed that anaerobic metabolic processes contribute from 30 to 40% to the overall heat production rate. Similar basal and antimycin A heat rates with cells under anoxic conditions indicated that the glycolytic rates are independent of the oxygen concentration which confirms the absence of the "Pasteur effect" in Trypanosomes. [ABSTRACT FROM AUTHOR]

A new calorimetric technique is described which allows the measurement of metabolic heat rates in biological materials which are triggered by changes in the oxygen tension. It uses the high permeability for oxygen of a thin-walled Teflon flow channel of a chip calorimeter in order to adjust variable but defined oxygen concentrations in the samples. Using this technique, for the first time, the heat production rate of sickle cell erythrocytes (SS-RBCs) in sickled and non-sickled state could be compared. To measure heat rate changes in real time when sickled SS-RBCs return to the non-sickled state, the heat dissipation was measured during the re-oxygenation of the cell samples which had been treated before under anoxic conditions. We found higher heat production rate of the blood cells in non-sickled state, which is in agreement with the reported increased glucose uptake. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Nanocalorimetry of specimens with different emissivities and thermal conductivities. • Comparison of measured heat capacity with detailed finite element analysis. • Quantification of the heat loss mechanisms during nanocalorimetry. • Strong impact of size effects on thermal radiation. Abstract We investigate the accuracy of a MEMS-based nanocalorimeter for determining specific heat in the temperature range from 300 K to 800 K. By comparing DC differential scanning measurements of materials of known specific heat capacities with detailed finite element studies, the dominant sources for heat losses and inaccuracies have been identified. The main source of error comes from radiative losses at elevated temperatures, but even near room temperature thermal gradients and thermal conductivity in the specimen lead to moderate discrepancies. Furthermore, studies on de-wetted Au films and Bi particles show that specimen emissivities differ strongly from literature values, presumably due to effects associated with the specimen dimensions being smaller than the thermal wavelength. By including the emissivity as a fitting parameter in the simulations, specimen heat capacities can be obtained to an accuracy of better than 7% over the entire temperature range. [ABSTRACT FROM AUTHOR]

A combination of fast scanning chip calorimetry and X-ray ptychography is explored to study the effects of thermal annealing on the active layer of bulk heterojunction organic photovoltaics. The well-known P3HT/PC 61 BM 1:1 system is investigated as a test case. By using a custom chip calorimetry setup, it is possible to give a thermal treatment at 127 °C (400 K) to P3HT/PC 61 BM 1:1 thin layers, using a heating and cooling rate of 30000 K s −1 , after which the resulting morphology is investigated with X-ray ptychography. Applying only heating and cooling, without isothermal annealing, yields a featureless morphology. This corresponds well with thermal data which indicate a mixed amorphous phase only. For increasing isothermal annealing times, a well-defined morphology appears with increasing domain size, corresponding to the formation of an endothermal melting trajectory. This melting trajectory is expected to consist of both eutectic melting and melting of coarsened crystals. In contrast to chip calorimetry results, large domain sizes are obtained for heating and cooling without isothermal annealing at a conventional rate of 20 K min −1 . This initial morphology then develops further with increased isothermal annealing. The combination of chip calorimetry and ptychography allows separating the effects of each single thermal step on morphology development. [ABSTRACT FROM AUTHOR]

Flash differential scanning calorimetry has been used to determine the glass transition response of the rapidly crystallizing energetic material, TNT. After heating at 600 K/s, it was found that for cooling rates from 1000 K/s to 10 K/s the glass transition changes from 247.5 K to 239.3 K. The dynamic fragility index was determined to be m = 62 ± 6 and the activation energy determined from the range of cooling rates in which vitrification occurred was found to be 290 ± 16 kJ/mol. Crystallization was found to occur during cooling at rates below 0.3 K/s, whereas cold crystallization was found on subsequent heating after cooling between 10 K/s and 30 K/s. At cooling rates of 100 K/s and above, and for the same heating rate of 600 K/s investigated, the glass transition event was observed, but cold crystallization during heating did not occur. Hence, the crystallization behavior of the fully amorphous TNT upon heating depends on the cooling rate and vitrification path. [ABSTRACT FROM AUTHOR]

Numerical simulation of DSC traces is used to study the validity and limitations of the Kissinger method for determining the temperature dependence of the crystal-growth rate on continuous heating of glasses from the glass transition to the melting temperature. A particular interest is to use the wide range of heating rates accessible with ultra-fast DSC to study systems such as the chalcogenide Ge 2 Sb 2 Te 5 for which fast crystallization is of practical interest in phase-change memory. Kissinger plots are found to show three regimes: (i) at low heating rates the plot is straight, (ii) at medium heating rates the plot is curved as expected from the liquid fragility, and (iii) at the highest heating rates the crystallization rate is thermodynamically limited, and the plot has curvature of the opposite sign. The relative importance of these regimes is identified for different glass-forming systems, considered in terms of the liquid fragility and the reduced glass-transition temperature. The extraction of quantitative information on fundamental crystallization kinetics from Kissinger plots is discussed. [ABSTRACT FROM AUTHOR]

The adaptation of segmented-flow technology to flow-through calorimetry was demonstrated by different kinds of newly designed chip calorimeters useful for liquids and suspensions as well as for solid samples. In segmented-flow technology, sample material is suspended in aqueous segments of nano- or microliter volume and transported by a water-immiscible carrier liquid. The analysis of the signal dynamics given by segmented samples in flow led to optimal settings of flow rate and sample volume for maximal throughput. For 12 μL sample segments, a cycle time of 4 min could be achieved. The protection of the measuring chamber of the calorimeters against biofouling caused by the water-immiscible carrier liquid was verified for segmented bacterial samples. The unique possibility to measure solid and aggregated samples in flow-through was demonstrated by the investigation of human hair follicles and fibroblast spheroids. [ABSTRACT FROM AUTHOR]

Abstract: We present the first silicon chip-based calorimeter with segmented-flow technology (SFT) for the study of solid and aggregated samples. Solid particles or biological aggregates up to 1.5mm are immersed in segments of aqueous solutions. The segments are transported to the heat flow detector of the calorimeter by a carrier liquid. The interfacial tension between the aqueous segments and the water immiscible carrier liquid ensures plug flow and prevents sample dispersion. At a typical segment volume of 11μL, a volume specific calorimetric resolution of 2mWL−1 is achieved. The proper functioning of the new calorimeter is proved by measuring the metabolic heat production of biofilms cultivated on glass beads and by measurement of the basal microbial activity of soils. Results demonstrated the capability of the device to measure solid samples with coarse texture. With the implementation of the segmented-flow technology, the application range of chip calorimetry is substantially extended. [Copyright &y& Elsevier]

Abstract: With the increasing complexity of model systems for the investigation of antibacterial effects of nanoparticles, the demands on appropriate analysis methods are rising. In case of biofilms grown on small particles, the high inhomogeneity of the samples represents a major challenge for traditional biofilm analysis. For this purpose, we developed a new calorimetric method which allows non-invasive and real-time investigation of the effects of nanoparticles on beads-grown biofilms which meets the requirements for an increased sample throughput. The method employs a newly developed chip calorimeter that is able to detect changes in the metabolic activity of biofilm samples within minutes. Using this novel device, the antibacterial effect of silver nanoparticles on Pseudomonas putida biofilms grown on agarose beads was investigated. The superparamagnetic properties of the embedded particles within the agarose beads allow an automated sample throughput. Growth inhibition and inactivation effects of silver nanoparticles (AgNPs) on biofilm bacteria were quantified by analyzing the metabolic heat production rate. As a result, a concentration dependent manner of growth inhibition and inactivation was found demonstrating the suitability and sensitivity of the methodology. [Copyright &y& Elsevier]

Highlights: [•] Sample deposition by electrospray has been demonstrated for chip-based nanocalorimeter measurements. [•] Greatly simplifies sample deposition for small scale thermal analysis and expands applications for nanocalorimetry. [•] Samples include nanoparticles, nanofibers, chalcogenide Ge2Sb2Te5 (GST), ammonium nitrate and the lipid DPPC. [ABSTRACT FROM AUTHOR]

We present a new chip calorimeter for fast and quantitative measurement of metabolic heat rates of microorganisms attached to magnetic beads. In biomagnetic separation (BMS) experiments, Escherichia coli K12 immobilized on nonspecifically functionalized beads has a specific heat rate of around 1 pW per cell at 37°C. Therefore, at least 2 × 104 bacteria are required to exceed the calorimetric signal resolution of 20 nW. If the samples to be analyzed have the original volume of 4 mL, bacteria at less than 104 cells mL−1 should be detectable. In practice, we achieved the detection of approximately 2 × 104 cells mL−1. The method presented here might also find some applications in the investigation of biofilms and study of biomolecular interactions. [ABSTRACT FROM AUTHOR]

Abstract: In conventional bioreactors, the assessment of metabolic heat via heat balancing is difficult. The reason is the influence of inherent variables such as power input due to stirring, environmental heat loss and evaporation. Thus, the aim of this study is to present a newly designed chip calorimeter which can be linked to any kind of bioreactor. This chip calorimeter with a new integrated real-time sample dilution was developed and tested during batch fermentation of the bacteria Escherichia coli VH33 and the yeast Arxula adeninivorans CBS8244. The presented device is operable up to an upper limit of 4WL−1 for the volumetric metabolic heat production rate of these biological systems. [Copyright &y& Elsevier]

Abstract: A chip calorimeter to measure thermal properties of bio-chemical fluid samples is successfully demonstrated. The chip calorimeter design enables the simultaneous measurement of thermal conductivity and thermal diffusivity of 2.5μl liquid samples with high-sensitivity and high-throughput. The micro-calorimeter consists of two silicon nitride membranes, with integrated heaters and thermopiles that are 300μm apart and enclose the liquid chamber. The sensor shows 5V/W sensitivity and 200K/W thermal resistance for water. The applicability of the micro-calorimeter to bio-chemical fluids thermal characterization is demonstrated by measuring thermal conductivity and thermal diffusivity of methanol–water mixtures and protein aqueous solutions (bovine serum albumin, BSA). Methanol–water mixtures thermal properties reveal good agreement with earlier reported experimental and theoretical data, showing approximately 2% deviation. Thermal properties of BSA solutions with concentrations up to 20% (w/v) were measured and values for thermal conductivity and diffusivity of (pure) BSA were estimated to be 0.20W/Km and 0.64×10−7 m2/s, respectively. The fluidic chip-calorimeter resolves thermal properties for concentrations down to 1% of both methanol and BSA. [Copyright &y& Elsevier]

Rapid detection of antibiotic resistances of clinical bacterial strains would allow an early selective antibiotic therapy and a faster intervention and implementation of infection control measurements. In clinical practice, however, conventional antibiotic susceptibility tests of bacteria often need 24 h until the results are obtained. The metabolic heat production of bacteria is an excellent possibility to record their physiological activities and could therefore be used for a rapid discrimination of bacterial strains which are resistant or non-resistant to antibiotics and also to lytic bacteriophages, respectively. Unfortunately, conventional calorimeters suffer from need of comparably large volumes of bacterial suspensions are characterised by slow operation and high costs which restrict their application in clinical laboratories. The present paper demonstrates that a new type of calorimeters developed on silicon-chip technology enables the detection of antibiotic resistances on a minute-timescale. For this reasons, a prototype chip calorimeter was used which sensitivity is 20 nW related to the heat production of about 10 bacteria. For a clear discrimination of antibiotic resistance about 10 bacteria are required. The antibiotic resistances and susceptibilities of different strains of Staphylococcus aureus to cefoxitin and the sensitivities of S. aureus DSM 18421 and E. coli DSM 498 to a mixture of two bacteriophages were studied. Comparing the heat productions of cultures incubated with antibiotics or bacteriophages to those without these antibacterial preparations enabled a clear discrimination of resistant and non-resistant strains already after totally 2 h. [ABSTRACT FROM AUTHOR]

Abstract: In order to fully exploit the graft copolymer poly(ethyleneglycol-g-vinylalcohol) (EG/VA) in the formulation of solid dispersions, a characterization of its phase behavior before, during and after spray-drying and hot-melt extrusion is performed. Solid state characterization was performed using MDSC and XRPD. The effect of heating/cooling rate on the degree of crystallinity was studied using HPer DSC and ultra-fast chip calorimetry. EG/VA consists of two semi-crystalline fractions, one corresponding to the polyethyleneglycol (PEG) fraction (T g =−57°C, T m =15°C) and one corresponding to the polyvinylalcohol (PVA) fraction (T g =45°C, T m =212°C). XRPD analysis confirmed its semi-crystallinity, and EG/VA showed Bragg reflections comparable to those of PVA. Spray-drying at a temperature lower than 170°C resulted in amorphization of the PVA fraction, while after hot-melt extrusion at different temperatures, the crystallinity of this fraction increases. In both cases, the PEG fraction is not influenced. Plasticization of the amorphous domains of the PEG or PVA fraction of the copolymer was dependent on the type and concentration of plasticizer, suggesting that also other small organic molecules like drugs may not homogeneously mix with both amorphous domains. A controlled cooling rate of 3000°C/s was necessary to make the copolymer completely amorphous. [Copyright &y& Elsevier]

Abstract: Rules for the design of silicon chip based devices for liquid phase calorimetry are discussed. In contrast to the study of fast reactions the investigation of slow processes like the metabolic heat production requires sample volumes of at least a few micro-liters if a signal resolution in the mWl−1 range is necessary. On the other hand, increasing sensitivity gradients inside the reaction chamber and external temperature perturbations restrict its enlargement. Therefore, a careful optimization of the device with respect to the sample volume is necessary if one likes to use the advantages of chip calorimeters. The presented study was performed by use of a new designed flow-through chip calorimeter. [Copyright &y& Elsevier]

Abstract: Based on a new thermopile heat power sensor, which was developed in MEMS technology, a miniaturized flow-through calorimeter was constructed. The heat power sensor consists of a silicon chip with a thin film BiSb/Sb thermopile and a PMMA reaction chamber. To ensure high signal resolution the heat power sensor is mounted inside a high-precision thermostat, which has a temperature stability of less than 100μK. The heat power sensitivity of the calorimeter is 4–7VW−1 depending on the thermal conductivity of the liquid, the height of the chosen reaction chamber and the volume flow rate. A limit of detection of less than 50nW can be obtained for volume flows lower than 5μlmin−1. An important advantage is the low sample consumption of the calorimeter. For special applications the sample need for one measurement pulse does not exceed 20μl. [Copyright &y& Elsevier]