Osmotic Loading of Spherical Gels: A Biomimetic Study of Hindered Transport in the Cell Protoplasm

Abstract

Osmotic loading of cells has been used to investigate their physicochemical properties as well as their biosynthetic activities. The classical Kedem-Katchalsky framework for analyzing cell response to osmotic loading, which models the cell as a fluid-filled membrane, does not generally account for the possibility of partial volume recovery in response to loading with a permeating osmolyte, as observed in some experiments. The cell may be more accurately represented as a hydrated gel surrounded by a semi-permeable membrane, with the gel and membrane potentially exhibiting different properties. To help assess whether this more elaborate model of the cell is justified, this study investigates the response of spherical gels to osmotic loading, both from experiments and theory. The spherical gel is described using the framework of mixture theory. In the experimental component of the study alginate is used as the model gel, and is osmotically loaded with dextran solutions of various concentrations and molecular weight, to verify the predictions from the theoretical analysis. Results show that the mixture framework can accurately predict the transient and equilibrium response of alginate gels to osmotic loading with dextran solutions. It is found that the partition coefficient of dextran in alginate regulates the equilibrium volume response and can explain partial volume recovery based on passive transport mechanisms. The validation of this theoretical framework facilitates future investigations of the role of the protoplasm in the response of cells to osmotic loading.

Micro- and nano-mechanics of osteoarthritic cartilage: The effects of tonicity and disease severity

“…One explanation might be that there are two transport time-scales that are involved, one is the movement of the water into the tissue, and the other one is the diffusion of the macromolecular osmolytes such as PGs degradation products or intact molecules freed from the swollen collagen matrix out of the tissue (Houard et al, 2013;Vynios, 2014). Transient response to osmotic loading has been also reported in computational studies of swelling and volumetric changes of multi-phasic materials under osmotic loading (Albro et al, 2007).…”

Novel Nanofiber-Based Scaffold for Rotator Cuff Repair and Augmentation

“…In addition, scaffold porosity and pore diameter (n ¼ 5=group) were evaluated using mercury porosimetry (Micromeritics Autopore III, Norcross, GA) following published protocols, 36 in which porosity was determined by measuring the volume of mercury infused into the sample. Scaffold permeability (n ¼ 5=group) was determined by measuring the pressure difference across the scaffold with a custom device 37,38 and then calculating permeability according to Darcy's Law.…”

“…tissues. 37,[53][54][55][56] Moreover, the observed differences in cell response to aligned or unaligned scaffolds and the resultant matrix properties can be readily exploited for functional repair of rotator cuff injuries and the formation of complex tissues. A distinct advantage of the nanofiber scaffold is that matrix anisotropy can be incorporated into scaffold design by varying nanofiber organization and alignment.…”

Nonlinear Osmotic Properties of the Cell Nucleus

“…In the case of the cell nucleus, the surrounding bath is the cytoplasm and it contains many solute species, each of which has a different partition coefficient between the cytoplasm and the nucleoplasm so it is necessary to define an equivalent partition coefficient. Note that: (2) for a cell that behaves as a perfect osmometer where c cyt is cytoplasmic concentration and c * is the extracellular concentration.…”