High-performance microcalorimeters: Design, applications and future development

Exploring the Frontiers of Cell Temperature Measurement and Thermogenesis

The precise measurement of cell temperature and an in-depth understanding of thermogenic processes are critical in unraveling the complexities of cellular metabolism and its implications for health and disease. This review focuses on the mechanisms of local temperature generation within cells and the array of methods developed for accurate temperature assessment. The contact and noncontact techniques are introduced, including infrared thermography, fluorescence thermometry, and other innovative approaches to localized temperature measurement. The role of thermogenesis in cellular metabolism, highlighting the integral function of temperature regulation in cellular processes, environmental adaptation, and the implications of thermogenic dysregulation in diseases such as metabolic disorders and cancer are further discussed. The challenges and limitations in this field are critically analyzed while technological advancements and future directions are proposed to overcome these barriers. This review aims to provide a consolidated resource for current methodologies, stimulate discussion on the limitations and challenges, and inspire future innovations in the study of cellular thermodynamics.

The development of ultrasensitive microcalorimeters for bioanalysis and energy balance monitoring

Heat generation or consumption is required for all biological processes. Microcalorimetry is an ultrasensitive method to measure heat change for various applications. In this paper, we aimed to review the ultrasensitive microcalorimeter systems and their extensive applications in bioanalysis and energy balance monitoring. We first discussed the basic structure of microcalorimeters, including the closed system and open system, temperature sensing methods, isolation materials, and temperature stabilization. Then, we focused on their applications, such as cell metabolism research, biomolecule interaction measurement, biothermal analysis, and calorimetric detection. Finally, we compared the advantages and disadvantages of commercially available microcalorimeters and their contributions to bioresearch. The development of ultrasensitive microcalorimeters provides the tools for bioanalysis at the single-cell, or even subcellular, level, as well as for precise calorimetric detection.

Thermoelectric Nanofluidics Probing Thermal Heterogeneity inside Single Cells

Accurate temperature measurement in one living cell is of great significance for understanding biological functions and regulation. Here, a nanopipet electric thermometer (NET) is established for real-time intracellular temperature measurement. Based on the temperature-controlled ion migration, the temperature change in solution results in altered ion mobilities and ion distributions, which can be converted to the thermoelectric responses of NET in a galvanostatic configuration. The exponential relationship between the voltage and the temperature promises highly sensitive thermoelectric responses up to 11.1 mV K-1, which is over an order of magnitude higher than previous thermoelectric thermometry. Moreover, the NET exhibits superior thermal resolution of 25 mK and spatiotemporal resolution of 100 nm and 0.9 ms as well as excellent stability and reproducibility. Benefiting from these unique features, both thermal fluctuations in steady-state cells and heat generation and dissipation upon drug administration can be successfully monitored, which are hardly achieved by current methods. By using NET, thermal heterogeneities of single cancer cells during immunotherapy were reported first in this work, in which the increased intracellular temperature was demonstrated to be associated with the survival benefit and resistance of cancer cells in immunotherapy. This work not only provides a reliable method for microscopic temperature monitoring but also gains new insights to elucidate the mechanism of immune evasion and therapeutic resistance.