Here you will find information regarding calorimeters and how you can extract detailed information using the newest chip technology. Furthermore, we will address the coupling of these chips with microfluidics and with the concomitant implementation of syringe pump systems. We will also present the relevance of these exciting technology with a particular focus on drug development and enzyme kinetics.
What is Calorimetry?
Reaction calorimetry is a powerful tool which provides information regarding enthalpy, heat capacity and activation energy of different reaction mixtures (Reschetilowski, 2013). This information is extracted by a calorimeter. A calorimeter is an instrument that measures the heat transfer difference between a reference system and the reaction system. A standard calorimeter is a sensor with a recognition element and a thermometer or transducer. Recently, the implementation of this insightful technology in small volume micro-reactors allows additional features: a high surface area-to-volume ratio, enhance mass and heat transfer, and promoting fast mixing which derives in precise control over the reaction parameters (Gemoets et al., 2016; Gutmann et al., 2015).
Calorimetry and Microfluidics
Due to the need of merging calorimeters with flow operations, microfluidic systems are employed for that very task. The working procedures in this regime will require as small of a volume as one nL; this is achieved by interfacing the calorimeter with syringe pumps. The microfluidic calorimeter provides thermodynamics characterization of chemical and biochemical reactions label-free at a fast rate. Recent works show the capabilities of the technology for kinetic parameter extraction, protein interactions and molecular changes (Lee, 2013; Lerchner et al., 2008; van Schie et al., 2018). The interest in these devices is for fundamental scientific research and technological development.
New calorimeters are made in a chip form (“chip calorimeters”) which provide detailed information relating to microliter and nanoliter levels. The miniaturization of calorimeters solve the inaccuracy problems; it also enables high-throughput measurements. Two types of chip calorimeters are currently developed:
- The open-chamber chip calorimeters which are thermally isolated and work as small drops. However, this a small batch system that does not allow control during the reaction.
- The closed-chamber chip calorimeters, these are the ones who need a microfluidic operation to perform kinetic studies in the stationary state. Samples are carefully and accurately introduce by syringe pumps. Reaction control is achieved by the flux and by feeding different reactants in the chamber. The Fusion 200 and Fusion 4000 allow small flux rate as the one required in the calorimeter reactor; furthermore, they will enable the feeding of at least two substrates at different rates; allowing the study of the reaction mechanism and protein interaction.
Reaction Calorimetry examples
- One straightforward application earlier developed is the study of enzymatic exothermic reactions during the catalysis. A multi-analyte and multi-array with several chips allow this study, even to the point of identifying critical inhibitions for the enzyme. (Zhang and Tadigadapa, 2004) developed a microfluidic device capable of measuring real-time enthalpy changes during enzymatic catalysis. The reaction heat of glucose oxidase activity on glucose, catalase on hydrogen peroxide, and urease on and urea were determined.
- The new chip-based microfluidic colorimeter systems are capable of characterizing the heat of reaction of 3.5-nL samples with 4.2-nW resolution(Lee et al., 2009)
- Recently, (van Schie et al., 2018) developed a new method to calibrate the microfluidic calorimeter during the enzymatic catalysis of small molecules as in the case of the activity of alkaline phosphatase. Through the new calibration proposed by the authors, it is possible to screen for enzyme inhibitors as drug candidates or to identify new mutants with improved operations. The study was successful by the implementation of dual syringe pumps like the Fusion 200 and Fusion 4000.
Concluding Remarks
Calorimetric reactions provide valued information to chemist and biochemist; these devices coupled as microfluidic reactors need straightforward syringe pump for a smooth operation. The dual syringe pumps supplied by Chemyx (the Fusion 200 and Fusion 4000) allow microliter to picoliter flow. The proper coupling of these devices provides high-quality information in many fields as drug development, chemical synthesis, and enzyme kinetics.
Bibliography
Gemoets, H.P.L., Su, Y., Shang, M., Hessel, V., Luque, R., Noël, T., 2016. Liquid phase oxidation chemistry in continuous-flow microreactors. Chem. Soc. Rev. 45, 83–117. https://doi.org/10.1039/c5cs00447k
Gutmann, B., Cantillo, D., Kappe, C.O., 2015. Continuous-flow technology – A tool for the safe manufacturing of active pharmaceutical ingredients. Angew. Chemie – Int. Ed. 54, 6688–6728. https://doi.org/10.1002/anie.201409318
Lee, W., 2013. Microfluidic Chip Calorimeters for Biological Applications 2008, 6.
Lee, W., Fon, W., Axelrod, B.W., Roukes, M.L., 2009. High-sensitivity microfluidic calorimeters for biological and chemical applications. Proc. Natl. Acad. Sci. 106, 15225–15230. https://doi.org/10.1073/pnas.0901447106
Lerchner, J., Wolf, A., Schneider, H.J., Mertens, F., Kessler, E., Baier, V., Funfak, A., Nietzsch, M., Krügel, M., 2008. Nano-calorimetry of small-sized biological samples. Thermochim. Acta 477, 48–53. https://doi.org/10.1016/j.tca.2008.08.007
Reschetilowski, W. (Ed.), 2013. Microreactors in Preparative Chemistry Practical Aspects in Bioprocessing, Nanotechnology, Catalysis and more. WILEY-VCH Verlag, Dresden Germany.
van Schie, M.M.C.H., Ebrahimi, K.H., Hagen, W.R., Hagedoorn, P.L., 2018. Fast and accurate enzyme activity measurements using a chip-based microfluidic calorimeter. Anal. Biochem. 544, 57–63. https://doi.org/10.1016/j.ab.2017.12.028
Zhang, Y., Tadigadapa, S., 2004. Calorimetric biosensors with integrated microfluidic channels. Biosens. Bioelectron. 19, 1733–1743. https://doi.org/10.1016/j.bios.2004.01.009