Thermal conductivity of a Jurkat cell measured by a transient laser point heating method

Abstract

To understand and quantify the thermal energy transfer in a biological cell, the measurement of thermal properties at a cellular level is emerging as great importance. We report herein a unique technique that utilizes a laser point heat source for temporal temperature rise in a micro-pipette thermal sensor; this technique characterizes heat conduction of a measured sample, the Jurkat cell, thus measuring the sample's thermal conductivity (TC). To this end, we incorporated the computational model in COMSOL to solve for the transient temperature and used the multi-parameter fitting of the experimental data using MATLAB. To address the influence of a Jurkat cell's chemical composition on TC, we compared three structural models for prediction of effective thermal conductivity in heterogeneous materials thereby determining the weight percentage of the Jurkat cell. When considering water and protein as the major constituents, we found that a combination of Maxwell-Euken and Effective Medium Theory modeling provides the closest approximation to published weight percent data and, therefore, is recommended for prediction of the cell composition. We validate the accuracy of the measurement technique, itself, by measuring polyethylene microspheres and observed 1% deviation from published data. The unique technique was determined to be mechanically non-invasive, capable of maintaining viable cells, and capable of measuring the thermal conductivity of a Jurkat cell, which was demonstrated to be 0.538 W/(m⋅K) ± 1%.