On the measurement of human osteosarcoma cell elastic modulus using shear assay experiments

Actin cytoskeletal structure and the statistical variations of the mechanical properties of non-tumorigenic breast and triple-negative breast cancer cells

This paper presents the results of a study of the actin cytoskeletal structures and the statistical variations in the actin fluorescence intensities and viscoelastic properties of non-tumorigenic breast cells and triple-negative breast cancer cells at different stages of tumor progression. The variation in the actin content of the cell cytoskeletal structures is shown to be consistent with the viscoelastic properties of the cell as it progresses from non-tumorigenic to more metastatic states. The corresponding viscoelastic properties of the nuclei and the cytoplasm (Young's moduli, viscosities, and relaxation times) of the cells are also measured using Digital Image Correlation (DIC) and shear assay techniques. These properties are shown to exhibit statistical variations that are well characterized by normal distributions. The changes in the mean properties of individual cancer cells are tested using Fisher pairwise comparisons and the analysis of variance (ANOVA). The implications of the results are then discussed for the development of shear assay techniques and mechanical biomarkers for the detection of triple-negative breast cancer at different stages of tumor progression.

Influence of neighboring adherent cells on laminar flow induced shear stress in vitro-A systematic study

Cells experience forces if subjected to laminar flow. These forces, mostly of shear force character, are strongly dependent not only on the applied flow field itself but also on hydrodynamic effects originating from neighboring cells. This particularly becomes important for the interpretation of data from in vitro experiments in flow chambers without confluent cell layers. By employing numerical Finite Element Method simulations of such assemblies of deformable objects under shear flow, we investigate the occurring stress within elastic adherent cells and the influence of neighboring cells on these quantities. For this, we simulate single and multiple adherent cells of different shapes fixed on a solid substrate under laminar flow parallel to the substrate for different velocities. We determine the local stress within the cells close to the cell-substrate-interface and the overall stress of the cells by surface integration over the cell surface. Comparing each measurand in the case of a multiple cell situation with the corresponding one of single cells under identical conditions, we introduce a dimensionless influence factor. The systematic variation of the distance and angle between cells, where the latter is with respect to the flow direction, flow velocity, Young's modulus, cell shape, and cell number, enables us to describe the actual influence on a cell. Overall, we here demonstrate that the cell density is a crucial parameter for all studies on flow induced experiments on adherent cells in vitro.

Natural-Synthetic Polymer Blend Composite Scaffold for Bone Tissue Engineering: Study of In Vitro Degradation and Protein Adsorption

In the current study, poly (hydroxy butyrate-co-hydroxy-valerate) (PHBV) was blended with a synthetic polymer poly (L-lactic acid) (PLLA), to control the degradation rate and process of composite scaffolds, as PLLA has a much higher degradation rate than PHBV. PHBV/PLLA blends were used as polymer matrices for composite scaffolds. Emulsion freezing / freeze-drying technique was used to fabricate composite scaffolds based on these blends and containing nanosized hydroxyapatite (nHA).In vitrodegradation tests of composite scaffolds were conducted by immersing samples in phosphate buffered saline (PBS) for various periods of time. It was found that the composition of polymer blends affected water uptake of scaffolds. Composite scaffolds exhibited enhanced adsorption of bovine serum albumin (BSA), a model protein.