A well-plate format isothermal multi-channel microcalorimeter for monitoring the activity of living cells and tissues

•An isothermal calorimeter (CalScreener) with a well-plate format is described.•Detection limit is ca. 0.1 μW as baseline stability is 0.2 μW over 24 h.•Metabolic heat production of microorganisms is accurately determined.•Metabolic heat production of mammalian cells is accurately measured.

Design and properties are reported for a novel type of multi-channel isothermal microcalorimeter. It is equipped with 48 calorimetric units (channels) and is primarily intended for use as a monitor of the activity of living cells, tissues and small animals. Calorimetric vessels are positioned in a holder with the format of a 48-well microtiter plate. At most, 47 samples can be measured simultaneously; one vessel is then used as reference. The standard configuration is 32 sample positions using 16 channels as references in a twin calorimeter setup. The detection limit is then 0.1 μW. Sample volumes are usually 100 μl-300 μl. The 24 h baseline stability is typically 0.2 μW (room temperature variation ≤1 °C). The instrument was designed considering feasible uses in applied biology, especially in pharmaceutical and clinical laboratories and in environmental work. However, it can be employed as a general monitor of slow processes in different fields of biology and for non-biological systems, including accurate determination of their thermal powers (heat production rates). In the present report, properties of the instrument are characterized by chemical calibration experiments and in measurements of growth of bacteria and mammalian cells.