Thermoelectrical micro-calorimetry and microanalysis on free-standing membranes

What does calorimetry and thermodynamics of living cells tell us?

This article presents and compares several thermodynamic methods for the quantitative interpretation of data from calorimetric measurements. Heat generation and absorption are universal features of microbial growth and product formation as well as of cell cultures from animals, plants and insects. The heat production rate reflects metabolic changes in real time and is measurable on-line. The detection limit of commercially available calorimetric instruments can be low enough to measure the heat of 100,000 aerobically growing bacteria or of 100 myocardial cells. Heat can be monitored in reaction vessels ranging from a few nanoliters up to many cubic meters. Most important the heat flux measurement does not interfere with the biological process under investigation. The practical advantages of calorimetry include the waiver of labeling and reactants. It is further possible to assemble the thermal transducer in a protected way that reduces aging and thereby signal drifts. Calorimetry works with optically opaque solutions. All of these advantages make calorimetry an interesting method for many applications in medicine, environmental sciences, ecology, biochemistry and biotechnology, just to mention a few. However, in many cases the heat signal is merely used to monitor biological processes but only rarely to quantitatively interpret the data. Therefore, a significant proportion of the information potential of calorimetry remains unutilized. To fill this information gap and to motivate the reader using the full information potential of calorimetry, various methods for quantitative data interpretations are presented, evaluated and compared with each other. Possible errors of interpretation and limitations of quantitative data analysis are also discussed.

Chip devices for miniaturized biotechnology

Chip devices were introduced in chemistry and molecular biology to improve the read-out of information from molecular systems by efficient analytical procedures and to organize automated experiments. Biochips and chip reactor systems are of interest for cellular processes, too, and can be regarded as components in interfaces for the information exchange between living nature and digital electronic systems. In this minireview, different types of chip reactors for biotechnological applications like nanotiterplates, chip thermocyclers and devices for segmented flow operations are discussed. Finally, an outlook is given on the application of chip reactor systems, which are promising tools for automated experiments with highly parallelized screening procedures, for artificial microcompartmentation, cell analogue systems, micro-ecological studies, investigations on modulated morphogenesis, and for a bioanalogue molecular nanotechnology.