Nonlinear temperature dependency of cell mechanics and consequences for potential filter applications.

Label-free filter systems are of great interest for extracting circulating tumor cells from patient blood based on their mechanical properties. However, temperature dependence in this field has so far hardly been considered and previous studies do not cover a wider range of temperatures, allowing only limited insight into the correlation with the mechanical properties. Here, we use atomic force spectroscopy applied to single cells to investigate temperature dependence of mechanic cell properties at eight different temperatures between 15 °C and 39 °C. A strong, partly non-linear temperature dependency of the Young's modulus E, pause deformation dp and maximal adhesion force Fadh of silicon nitride to A375 melanoma cells is shown, which occurs independently of the cell size and on the time scale of a few minutes after temperature variation. Here, E, dp and Fadh change by a factor of about 2.2, 1.4 and 2.7 respectively between 17 °C and 37 °C. To test the applicability of the results in the field of filtration, a microfluidic experiment with channels that contain filter structures with decreasing pore sizes is conducted to quantify cell capture size and temperature dependency. As predicted from the non-linear temperature dependent viscoelastic properties, the cells can penetrate to smaller pore sizes at higher temperatures. STATEMENT OF SIGNIFICANCE: This study systematically measures how melanoma cell mechanics change with temperature, using fine temperature steps across a broad physiological range. We find that stiffness, deformability, and adhesion vary strongly and nonlinearly with temperature, independent of cell size or scan direction. These results were further validated in microfluidic filter experiments, confirming that temperature-controlled changes in mechanical behavior can be exploited for selective cell separation. The comprehensive dataset and experimental approach advance understanding of temperature-dependent cell viscoelasticity and demonstrate its relevance for biomedical filtration technologies. This work introduces a new perspective on using physical cell properties, rather than biochemical labeling, for potential applications in cancer diagnostics and circulating tumor cell isolation.