The stiffness of elastomeric surfaces influences the mechanical properties of endothelial cells

Optimal characterization of the mechanical properties of both cells and their surrounding is an issue of major interest. Indeed, cell function and development are strongly influenced by external stimuli. Furthermore, a change in cell mechanics might, in some cases, associate with diseases or malfunctioning. In this work, atomic force microscopy (AFM) was applied to examine the mechanical properties of the silicone elastomer polydimethylsiloxane (PDMS) a common substrate in cell culture. Force spectroscopy analysis was done over different specimens of this elastomeric material containing varying ratios of resin to cross-linker in its structure (5:1, 10:1, 20:1, 30:1 and 50:1), which impacts the final material properties (e.g., stiffness, elasticity). To quantify the mechanical properties of the PDMS, factors as the modulus of Young, the maximum adhesive forces as well as both relaxation amplitudes and times upon constant height contact of the tip (dwell time different of zero) were calculated from the different segments forming the force curves. It is demonstrated that the material stiffness is increased by prior oxygen plasma treatment of the sample, required for hydrophilic switching, contrarily to what observed for its adhesiveness. Subsequent incubation of endothelial HUVEC cells on top of these plasma treated PDMS systems yields minor variation in cell mechanics in comparison to those obtained on a glass reference, on which cells show much higher spreading tendency and, by extension, a remarkable membrane hardening. Thus, surface wettability turns a factor of higher relevance than substrate stiffness inducing variations in the cell mechanics.Comment: manuscript (12 pages, 4 figures, 2 tables), supplementary information (2 pages and 3 figures), the main results of the manuscript are based on a master thesi

Time- and Zinc-Related Changes in Biomechanical Properties of Human Colorectal Cancer Cells Examined by Atomic Force Microscopy

Monitoring biomechanics of cells or tissue biopsies employing atomic force microscopy (AFM) offers great potential to identify diagnostic biomarkers for diseases, such as colorectal cancer (CRC). Data on the mechanical properties of CRC cells, however, are still scarce. There is strong evidence that the individual zinc status is related to CRC risk. Thus, this study investigates the impact of differing zinc supply on the mechanical response of the in vitro CRC cell lines HT-29 and HT-29-MTX during their early proliferation (24–96 h) by measuring elastic modulus, relaxation behavior, and adhesion factors using AFM. The differing zinc supply severely altered the proliferation of these cells and markedly affected their mechanical properties. Accordingly, zinc deficiency led to softer cells, quantitatively described by 20–30% lower Young’s modulus, which was also reflected by relevant changes in adhesion and rupture event distribution compared to those measured for the respective zinc-adequate cultured cells. These results demonstrate that the nutritional zinc supply severely affects the nanomechanical response of CRC cell lines and highlights the relevance of monitoring the zinc content of cancerous cells or biopsies when studying their biomechanics with AFM in the future.DFG, 316442145, FOR 2558: Interaktionen von essenziellen Spurenelementen in gesunden und erkrankten älteren Menschen(TraceAge