Roxana Chotard-Ghodsnia

Casein micelles separation from skimmed milk using a VSEP dynamic filtration module

Abstract A vibratory shear-enhanced filtration system (VSEP) was used for the separation of casein micelles from whey proteins of skim milk reconstituted from low heat milk powder, which has a similar protein content as fresh milk. This paper compares the performances of microfiltration (MF) with a 0.1 μm pore Teflon membrane and of an ultrafiltration (UF) polyethersulfone-one with 150 kD cut-off. The critical flux for stable operation was investigated in MF by increasing the permeate flux in steps while monitoring the transmembrane pressure. It was found to be 50 l h −1 m −2 at a volume reduction ratio of 2 and the maximum frequency of 60.75 Hz (τ w = 34 Pa). The UF membrane minimizes casein loss in the permeate (turbidity below 20 NTU) with a little reduction in permeate flux. Whey protein transmission in UF was found to be 65–70% for α-lactalbumin and 25–30% for β-lactoglobulin.

Rheology of Living Materials

In this chapter, the properties of biological materials are described both from a microscopic and a macroscopic point of view. Different techniques for measuring cell and tissue properties are described. Models are presented in the framework of continuum theories of viscoelasticity. Such models are used for characterizing experimental data. Finally, applications of such modeling are discussed in a few situations of interest

Morphological analysis of tumour cell/ endothelial cell interactions under shear flow

In the process of cancer metastasis, tumor cells (TCs) must shed into blood stream, survive in the blood circulation, and finally migrate through the vascular endothelium (diapedesis) and proliferate in the target organs. However, the precise mechanisms by which TCs penetrate the endothelial cell (EC) junctions remain one of the least understood aspects of TC diapedesis. This question has generally been addressed under static conditions (Voura et al. 1998). However, flow induced mechanical stress plays an important role on the circulating cell-endothelium interactions (Cinnamon and Alon 2003). We used a parallel-plate flow chamber (Chotard-Ghodsnia et al. 2002) to investigate TC–EC interactions under flow conditions. An EC monolayer is cultured on the lower plate of the flow chamber to model the endothelial barrier. Circulating TCs can be introduced into the flow channel under a well-defined flow field and TC adhesion to EC monolayer can be followed in situ using phase contrast and fluorescence microscopy.