Calorimetry as an analytical tool in biochemistry and biology

A Review on the Role of Nanosensors in Detecting Cellular miRNA Expression in Colorectal Cancer

BACKGROUND

Colorectal cancer (CRC) is one of the leading causes of death across the globe. Early diagnosis with high sensitivity can prevent CRC progression, thereby reducing the condition of metastasis.

OBJECTIVE

The purpose of this review is (i) to discuss miRNA based biomarkers responsible for CRC, (ii) to brief on the different methods used for the detection of miRNA in CRC, (iii) to discuss different nanobiosensors so far found for the accurate detection of miRNAs in CRC using spectrophotometric detection, piezoelectric detection.

METHODS

The keywords for the review like micro RNA detection in inflammation, colorectal cancer, nanotechnology, were searched in PubMed and the relevant papers on the topics of miRNA related to CRC, nanotechnology-based biosensors for miRNA detection were then sorted and used appropriately for writing the review.

RESULTS

The review comprises a general introduction explaining the current scenario of CRC, the biomarkers used for the detection of different cancers, especially CRC and the importance of nanotechnology and a general scheme of a biosensor. The further subsections discuss the mechanism of CRC progression, the role of miRNA in CRC progression and different nanotechnology-based biosensors so far investigated for miRNA detection in other diseases, cancer and CRC. A scheme depicting miRNA detection using gold nanoparticles (AuNPs) is also illustrated.

CONCLUSION

This review may give insight into the different nanostructures, like AuNPs, quantum dots, silver nanoparticles, MoS2derived nanoparticles, etc., based approaches for miRNA detection using biosensors.

Temperature stability of proteins: Analysis of irreversible denaturation using isothermal calorimetry

The structural stability of proteins has been traditionally studied under conditions in which the folding/unfolding reaction is reversible, since thermodynamic parameters can only be determined under these conditions. Achieving reversibility conditions in temperature stability experiments has often required performing the experiments at acidic pH or other nonphysiological solvent conditions. With the rapid development of protein drugs, the fastest growing segment in the pharmaceutical industry, the need to evaluate protein stability under formulation conditions has acquired renewed urgency. Under formulation conditions and the required high protein concentration (∼100 mg/mL), protein denaturation is irreversible and frequently coupled to aggregation and precipitation. In this article, we examine the thermal denaturation of hen egg white lysozyme (HEWL) under irreversible conditions and concentrations up to 100 mg/mL using several techniques, especially isothermal calorimetry which has been used to measure the enthalpy and kinetics of the unfolding and aggregation/precipitation at 12°C below the transition temperature measured by DSC. At those temperatures the rate of irreversible protein denaturation and aggregation of HEWL is measured to be on the order of 1 day^-1 . Isothermal calorimetry appears a suitable technique to identify buffer formulation conditions that maximize the long term stability of protein drugs.

DFT-based prediction of reactivity of short-chain alcohol dehydrogenase

The reaction mechanism of ketone reduction by short chain dehydrogenase/reductase, (S)-1-phenylethanol dehydrogenase from Aromatoleum aromaticum, was studied with DFT methods using cluster model approach. The characteristics of the hydride transfer process were investigated based on reaction of acetophenone and its eight structural analogues. The results confirmed previously suggested concomitant transfer of hydride from NADH to carbonyl C atom of the substrate with proton transfer from Tyr to carbonyl O atom. However, additional coupled motion of the next proton in the proton-relay system, between O2′ ribose hydroxyl and Tyr154 was observed. The protonation of Lys158 seems not to affect the pKa of Tyr154, as the stable tyrosyl anion was observed only for a neutral Lys158 in the high pH model. The calculated reaction energies and reaction barriers were calibrated by calorimetric and kinetic methods. This allowed an excellent prediction of the reaction enthalpies (R² = 0.93) and a good prediction of the reaction kinetics (R² = 0.89). The observed relations were validated in prediction of log K_eq obtained for real whole-cell reactor systems that modelled industrial synthesis of S-alcohols.

Performance of microcalorimetry for early detection of methicillin resistance in clinical isolates of Staphylococcus aureus

We describe a calorimetric assay for the detection of methicillin-resistant Staphylococcus aureus (MRSA) within 5 h. Microbial heat was calculated in culture with and without cefoxitin. Among 30 genetically distinct clinical isolates, 19/20 MRSA (95%) and 10/10 methicillin-susceptible Staphylococcus aureus (100%) were correctly identified. Microcalorimetry may be useful for rapid MRSA screening.

The human protease inhibitor cystatin C is an activating cofactor for the streptococcal cysteine protease IdeS

Human cystatin C is considered the physiologically most important inhibitor of endogenous papain-like cysteine proteases. We present here an unexpected function of cystatin C. Instead of acting as an inhibitor, cystatin C acts as a facultative, endogenous cofactor for the papain-like IgG-cleaving enzyme IdeS of the human pathogen Streptococcus pyogenes. IdeS activity is not dependent on cystatin C, but is significantly enhanced in the presence of cystatin C. We report a protease inhibitor that accelerates the activity of its putative target protease and a unique example of how a host protease inhibitor is "hijacked" by a bacterial protease to increase its activity. This finding has important implications for the view on protease-inhibitor interactions, and is relevant to consider in the therapeutic use of protease inhibitors.

Enzyme kinetics determined using calorimetry: a general assay for enzyme activity?

Two techniques for determining enzyme kinetic constants using isothermal titration microcalorimetry are presented. The methods are based on the proportionality between the rate of a reaction and the thermal power (heat/time) generated. (i) An enzyme can be titrated with increasing amounts of substrate, while pseudo-first-order conditions are maintained. (ii) Following a single injection, the change in thermal power as substrate is depleted can be continuously monitored. Both methods allow highly precise kinetic characterization in a single experiment and can be used to measure enzyme inhibition. Applicability is demonstrated using a representative enzyme from each EC classification, including (i) oxidation-reduction activity of DHFR (EC 1.5.1.3); (ii) transferase activity of creatine phosphokinase (EC 2.7.3.2) and hexokinase (EC 2.7.1.1); (iii) hydrolytic activity of Helicobacter pylori urease (EC 3.5.1.5), trypsin (EC 3.4.21.4), and the HIV-1 protease (EC 3.4.21.16); (iv) lyase activity of heparinase (EC 4.1.1.7); and (v) ligase activity of pyruvate carboxylate (EC 6.4.1.1). This nondestructive method is completely general, enabling precise analysis of reactions in spectroscopically opaque solutions, using physiological substrates. Such a universal assay may have wide applicability in functional genomics.

Principles and applications of thermal biosensors

A review of thermistor-based calorimetric measurement is presented. The principles of thermometric measurements are highlighted in the introduction followed by the instrumentation, materials and methods. Various applications relating to enzyme activity measurements, clinical monitoring, process monitoring, multianalyte determination, hybrid sensing, environmental monitoring, non-aqueous measurements and other miscellaneous applications are described. A brief note on future developments and a detailed reference list is also included.

Investigation of catalytic properties of immobilized enzymes and cells by flow microcalorimetry

The investigation of catalytic properties of immobilized biocatalysts (IMB) is a time-consuming and not-always-simple procedure, requiring a simple and accurate method of enzyme-activity measurement. In comparison with generally-used techniques, flow microcalorimetry (FMC) has proven to be a very practical and versatile technique for direct monitoring of the course of enzyme reactions. The principal advantage of FMC is integration of the enzyme reaction and its monitoring in one step. This review summarizes the information needed for the complete kinetic or catalytic characterization of the IMB by FMC, without the requirement of any independent analytical method. The optimal experimental procedure is proposed. Examples of experimental studies on immobilized biocatalysts using the FMC are provided. The method is applicable to purified enzymes as well as to enzymes fixed in cells.

Principles of enzyme thermistor systems: applications to biomedical and other measurements

This chapter presents an overview of thermistor-based calorimetric measurements. Bioanalytical applications are emphasized from both the chemical and biomedical points of view. The introductory section elucidates the principles involved in the thermometric measurements. The following section describes in detail the evolution of the various versions of enzyme-thermistor devices. Special emphasis is laid on the description of modern "mini" and "miniaturized" versions of enzyme thermistors. Hybrid devices are also introduced in this section. In the sections on applications, the clinical/biomedical areas are dealt with separately, followed by other applications. Mention is also made of miscellaneous applications. A special section is devoted to future developments, wherein novel concepts of telemedicine and home diagnostics are highlighted. The role of communication and information technology in telemedicine is also mentioned. In the concluding sections, an attempt is made to incorporate the most recent references on specific topics based on enzyme-thermistor systems.

Pharmaceutical applications of microcalorimetry

General principles and applications of microcalorimetry are reviewed. Microcalorimetry is useful in the study of physical, chemical, and biological drug interactions. The sensitivity of the present instrumentation is approximately 0.1 microW. With this high sensitivity, additional applications have been developed, including the interactions of drugs with food, lymphoma cells, microorganisms, blood, excipients, and cyclodextrin. A recent application of microcalorimetry is the measurement of degradation rates of drugs.

In vitro measurements of heat production rate of rat kidney. A microcalorimetric study

In the present study heat production rate (P) of rat kidney tissue in vitro has been measured with a microcalorimetric technique. Cortex slices (0.3-0.7 mm) were incubated in a balanced electrolyte solution or in medium E-199. The metabolic activities in these different media were found to be 0.87 microW/mg and 0.98 microW/mg, respectively, determined by using 5-mg slices after 1 h of incubation (P1h). Medulla slices with a thickness of 0.4 mm demonstrated a lower P, i.e., 0.65 microW/mg. The heat output was not influenced by the thickness of those slices, ranging from 0.3 to 0.7 mm. However, an increase in the wet weight of the tissue sample was accompanied by a reduced P, expressed as power per milligram wet weight. The magnitude of this crowding phenomenon decreased as the time of incubation increased. Storage of tissue for 3.5 h prior to measurement caused a 6-7% reduction of P. This study indicates that the microcalorimetric technique is a sensitive method for measuring metabolism in small kidney biopsies.

Microcalorimetric studies on metabolism of hepatic tissue. I. A methodological study of normal tissue

In the present study, the heat production of liver biopsies (5-8 mg) was measured by a microcalorimetric technique. Tissue incubated in Leibowitz L-15 medium (L-15) showed a higher metabolic rate compared to tissue incubated in a medium without substrate 2.8 microW/mg and 1.75 microW/mg, respectively. Heat production was found to be related to weight density. No difference in the metabolic rate was found after organ perfusion in comparison to nonperfused liver. Storage in medium L-15 at 4 degrees C caused a lower rate of heat production, but if the tissue was stored in an electrolyte balance solution without substrate, no difference was seen compared to fresh tissue. Recording heat production with the present calorimetric technique is relatively simple and rapid and allows measurement of small samples.

A stopped-flow mixer device for a batch microcalorimeter application to NAD-NADase reaction

A new molded polypropylene, diamond-like carbon (DLC)-coated mixing cell has been developed for use in the batch microcalorimeter. Reagent volume can be varied from 25 microliters to 100 microliters. A 10 microcalorie reaction heat can be measured to 5%. Repeat reactions can be done as often as every 10 min for a fast reaction. Reactions can be started within 1 h or less after loading. A pre-equilibrator and a temperature-controlled syringe drive unit permit solutions to be stored at 4 degrees C while being run at any temperature from -20 degrees C to 40 degrees C. The kinetics and enthalpy of reaction of NAD-NADase have been measured. delta H is about 21 kcal/mol endothermic.

Effects of calcium entry blockers on human platelet metabolism measured by microcalorimetry

1. The direct overall metabolic effects of calcium entry blockers on human platelets were evaluated using a sensitive microcalorimetric method. 2. The effect on platelet metabolism of four calcium entry blockers with different profiles of action was examined and compared with the relaxant response on human cerebral vessels in vitro. 3. Diltiazem (10(-8), 10(-4) M) and nifedipine (10(-10), 10(-6) M) were without effect on overall platelet metabolism. On the other hand flunarizine (10(-4) M) and verapamil (10(-4) M) significantly reduced metabolism, while lower concentrations of these agents did not change heat production. 4. The thermogenic response occurred at concentrations of the calcium entry blockers that were much higher than those observed during therapy and the concentrations which relax human cerebral arteries in vitro.

Effect of gentamicin on human blood cells metabolism as measured by microcalorimetry

The effect of gentamicin on overall metabolism in human blood cells was studied by microcalorimetry. At concentrations above therapeutic levels, the drug induced an increase in heat production rate in red cells, whereas no effect was found at lower concentrations. The Na/K-pump was unaffected at any gentamicin concentration. A slight increase in heat production rate was noted in granulocytes when incubated with gentamicin at concentrations above therapeutic levels, otherwise no effect was recorded at lower concentrations. Lymphocytes were unaffected by gentamicin at any concentration. Microcalorimetry seems to be a suitable method for studying the effect of drugs on overall cell metabolism, and for evaluating the Na/K-pump activity.

Microcalorimetric studies on the effect of adenosine receptor agonists and xanthine derivatives on overall metabolism in human platelets

The direct overall metabolic effects of drugs acting on adenosine receptors in human platelets were evaluated using a sensitive microcalorimetric method. Adenosine induced a concentration-dependent increase in the heat production rate at concentrations above 100 microM. The adenosine uptake inhibitor, dipyridamole (3 microM) did not modify the effect of adenosine. Two putative adenosine receptor agonists were tested: NECA (5-N-ethyl carboxamide adenosine) and PIA (L-N6-phenylisopropyl-adenosine). NECA induced, at significantly lower concentrations than adenosine, an enhanced heat production rate. Concentrations above 1 mM had no effect. PIA, on the other hand, invariably induced a reduction in the heat production rate already at a concentration of 100 microM. The two xanthine derivatives enprofylline (25 microM) and theophylline (100 microM) were tested at concentrations found during antiasthmatic therapy. Neither had any thermogenic effect by themselves nor showed any significant modification of the heat production rate induced by adenosine (300 microM). These results indicate that adenosine and NECA increase human platelet metabolism, whereas PIA has an opposite effect. The proposed adenosine receptor antagonists enprofylline and theophylline were without effects. This microcalorimetric study gives new insights into the complex nature of adenosine mechanisms in a human test system and indicates that the thermogenic effect of adenosine is unrelated to adenosine receptors.

Heat production as a cell cycle monitoring parameter

A microcalorimetric method was applied to define the cell cycle by measuring heat production of mouse breast cancer cell line, FM3A. FM3A cells, were synchronised at the Go phase and produced 13.0 mu Watts (W) per 1 X 10(6) cells. Although the number of cells in fresh medium remained unchanged during the following 24 hour, a dramatic increase of heat production was observed and maximum heat (46.2 mu W) was produced by the cells at 24 hours when the cell cycle was presumably at the G2 phase. At 26 hours, although cell number increased, heat production decreased. Since the cells were not treated in any manner, this microcalorimetric method of measuring the cell cycle by monitoring heat production can be a very useful tool.

L-carnitine and haemodialysis: double blind study on muscle function and metabolism and peripheral nerve function

Twenty-eight haemodialysis patients were randomized to L-carnitine, 2 g i.v. three times a week, and saline over a 6-week period. No obvious deficiency of carnitine was found in vastus lateralis with a median value of 12.9 mmol/kg dry weight; range 6.2-21.4. Female patients had lower total plasma carnitine compared to female controls, p less than 0.002, whereas no decrease was found in males. No relationship was found between muscle and total plasma carnitine. After carnitine administration the muscle carnitine level increased about 60%, p less than 0.01, and the total plasma carnitine level more than tenfold, whereas the initially high degree of acylation decreased, p less than 0.02. Maximum dynamic muscular strength was reduced with a mean value of 44% compared with healthy controls. Total metabolic activity of isolated skeletal muscle fibres, measured as heat production with a new technique using a perfusion microcalorimeter, showed a median value of 0.40 mW/g, 25% lower than normal, p less than 0.02. Carnitine administration had no effect on several different tests of muscular function. Neurophysiologically, discrete improvements in the temperature responses were recorded, but no changes in sensory and motor nerve conduction velocities or in vibration thresholds were noted. No symptomatic improvement was observed even in patients with the lowest carnitine levels prior to treatment. Our data do not support the hypothesis that carnitine deficiency contributes to muscle and nerve dysfunction in patients on chronic haemodialysis.

Heat production rate in polymorphonuclear granulocytes from patients with acute myelogenous leukaemia and healthy individuals

Heat production rate in polymorphonuclear granulocytes (PMN) from 18 AML patients and 21 healthy individuals was measured using microcalorimetry. An increased PMN heat production rate was found in most AML patients at diagnosis and during the first 6 months of remission. In 7/7 patients showing values above the normal mean level the heat production rate decreased during sequential analysis. The increased PMN heat production rate is serum dependent and leukaemic sera induced increased calorimetric values also in PMN from healthy donors. This effect was not due to heat labile complement factors.

A twin titration microcalorimeter for the study of biochemical reactions

A small-volume (200 microliter) titration calorimeter of high sensitivity (1 mu cal ) has been developed for the purpose of studying biochemical reactions where the amounts of material are limited to a few nanomoles. High sensitivity is achieved by calorimetric twining , use of glass cells, elimination of vapor space, effective low-energy stirring, and reduction of measurement time. The calorimeter operates using the heat conduction principal with computer-controlled electrical compensation, which reduces the measurement time of each point from 10 to 3 min. This reduction in time is accompanied by a corresponding increase in the precision of measurement. The use of the calorimeter is demonstrated by a measurement of the heat of oxygenation of hemocyanin.

Heat production by adipocytes from obese subjects before and after weight reduction

Microcalorimetry has been employed to measure the heat production by adipocytes obtained by percutaneous biopsy from lean subjects and from obese subjects before and after weight reduction. Cellular heat production was significantly lower in obese than in lean subjects. After weight reduction cellular heat production increased in fat cells from the obese subjects but was still significantly lower than in cells from control subjects. A number of variables reflecting uptake and mobilization of depot fat have measured and correlated to the heat production values in the obese subjects. The findings are consistent with the view that a decreased total metabolic activity might contribute to the development or perpetuation of obesity.

A test and calibration process for microcalorimeters used as thermal power meters

A test and calibration process for microcalorimeters is described. The method has been developed with particular reference to instruments used for measurements of thermal power produced by suspensions of living cells. The process investigated is the hydrolysis of triacetin in imidazole/acetic acid buffer. The power levels are regulated by changing the buffer composition. The power will decrease slowly and very nearly linearly with time. Five test solutions, power levels 7-90 microW X ml-1, have been characterized at 37 degrees C and one of them at 25 degrees C (13 microW X ml-1). The power values for these reaction mixtures can be accurately calculated (+/- 0.5%) as a function of time during extended reaction periods, about 20 h or more.

Application of differential scanning microcalorimetry to the study of cellular processes: heat production and glucose oxidation of murine macrophages

Differential scanning microcalorimetry provides a noninvasive method for studying heat evolution in living cells. We used this technique to measure the heat evolved by thioglycollate broth-elicited mouse macrophages, and the effects of NaF, KCN, cycloheximide, and cytochalasins B and D on this parameter. The total heat evolved in the interval 10--37 degrees C scanned at 1 degree C min-1 ranged from 300 to 2500 X 10(-12) cal (1 Cal = 4.184 J) per cell, depending on cell density, glucose concentration, and the presence or absence of various drugs.

Microcalorimetric measurement of production heat in isolated human adipocytes

A method for the quantitative measurement of heat production in isolated human adipocytes is described. Fat cells are isolated by collagenase treatment of biopsy specimens of adipose tissue, and heat production measured by microcalorimetry. The heat effect was constant for at least 4 h. Heat values increased with increasing pH (about 6% per 0.1 pH unit) and temperature (about 9% per degrees C at 37 degrees C). The apparent activation energy was calculated as 44 kJ/mol. Heat production was about 50% higher in cell suspensions containing glucose and insulin. Imprecision was about 6.5% (coefficient of variation) and sensitivity allowed measurements in samples containing 20-30 mg adipocyte lipid. Heat production in normal volunteers under standardized conditions (i.e. in Krebs-Ringer-bicarbonate buffer pH 7.4, at 37 degrees C and in the presence of 11 mmol/l glucose and 0.1 U/ml insulin) was 133 +/- 48 (mean +/- SD) microW/g adipocyte lipid weight, corresponding to 49 +/- 15 pW/cell. The technique seems of importance for the characterization of energy balance in the fat cell under normal and pathophysiological conditions.

Microcalorimetric measurements of heat production in human erythrocytes. IV. Comparison between different calorimetric techniques, suspension media, and preparation methods

Heat production in human erythrocytes from healthy subjects has been measured under different experimental conditions. Simultaneous measurements were made on the same samples using different types of microcalorimeters: a static ampoule calorimeter, an air perfusion calorimeter, and a flow calorimeter. Obtained heat effect values for specified standard conditions, P degrees, were within uncertainty limits the same for the different calorimeters. Cells were suspended either in autologous plasma or in a phosphate buffer. P degrees values for buffer suspensions were significantly higher than those for plasma suspensions. Erythrocyte samples prepared by the column adsorption technique gave higher P degrees values than those obtained by a conventional centrifugation procedure.

Microcalorimetric measurements of heat production in human erythrocytes. III. Influence of pH, temperature, glucose concentration, and storage conditions

Heat production in human erythrocytes has been measured under different conditions of pH, glucose concentration, and temperature. Storage conditions have also been varied. The erythrocytes, which were from healthy subjects, were suspended either in autologous plasma or in phosphate buffer. The heat effect, P, was shown to increase linearly in the physiological pH range: 1.2% per 0.01 pH unit. Variation of the glucose concentration within a wide range, 3-32 mmol/1, did not affect the P value. The temperature coefficient for P was determined to be Q10 = 2.8 for the temperature range 32-42 degrees C. A constant energy of activation was found, 82.6 kJ/mol, for the temperature range 25-42 degrees C. When the erythrocytes were stored at 4 degrees C, P values (measured at 37 degrees C) increased initially by 6%/h. After 24 h of storage P was about 50% higher than the initial value. Determinations of glucose consumption were made in parallel with most of the calorimetric experiments.

Kinetics of the actions of tetracyclines on Escherichia coli as studied by microcalorimetry

Microcalorimetry was used to study the kinetics of the actions of various tetracyclines on a strain of Escherichia coli. Differences in the capacity to suppress the metabolism of this bacterium were observed. When the antibiotic was present from the start of the experiment, a heat production of 2.0 muW/ml was registered after 12.5 h using minocycline; the corresponding figures for doxycycline, oxytetracycline, and tetracycline were 7.3, 6.6, and 4.5 h, respectively. In these experiments, equal concentrations, i.e., half the minimum inhibitory concentration (MIC), of each drug were used. The MIC for all the tetracyclines tested, determined by the broth dilution technique, was 0.8 mug/ml. In other experiments, the antibiotic (concentration, 1.6 mug/ml = 2x MIC) was introduced into the growth vessel during the logarithmic growth phase of the organism. The extent and duration of the inhibitory effect on the metabolism, as judged from the decrease in heat production, varied with the different tetracyclines. Immediately after introduction, minocycline, doxycycline, oxytetracycline, and tetracycline decreased the heat production in decreasing order of potency. With tetracycline, the heat production rose after about 1 h, and with minocycline it rose after about 9 h. The heat production remained at a low level for at least 19 h when using doxycycline and oxytetracycline. The results indicate that microcalorimetry offers a means for studies of the kinetics of the antibacterial actions of antibiotics and provides information that cannot be obtained by conventional bacteriological techniques. This information may be of use, in conjunction with pharmacokinetic data, in establishing optimum doses and dose intervals in antibiotic therapy.