Development of a Micro-Scale Differential Scanning Calorimeter for Single Cell Measurements Available to Purchase

Cryopreservation is an effective way to store biological materials for an extended period of time. The process of freezing biological materials is rather traumatic, however, due to the water phase change that takes place. Successful cooling procedures have been developed for a limited number of cell types primarily through a large amount of experimentation. Fundamental cryobiological studies of cellular heat and mass transfer are currently under way in an attempt to develop an accurate model that will reduce the need for many costly experiments. The purpose of this paper is to describe the development of a tool that will allow more accurate measurements of the phase change temperature for a single cell (∼100 μm diameter) as it freezes. The resulting data will be used to improve the fundamental cryopreservation model. A proof-of-concept micro-scale DSC (μDSC) is designed and built using 250 μm × 250 μm × 500 μm thermoelectric elements. The elements are connected electrically in series to one another with metal electrodes that double as the sample and reference pans. The advantage of this configuration is that Peltier heating and cooling of the sample each have the same time constant, in contrast with macro-scale DSC machines. Thermocouples with 25 μm beads are attached to the pans providing the local temperature of the sample used for feedback control. The feedback temperature is used as the control signal for the power supply which supplies electric current to the thermoelectric structure described above. Initial experiments on the prototype μDSC indicate that the phase change of a single swine oocyte with a diameter of about 100 μm can be detected.