Local, three-dimensional strain measurements within largely deformed extracellular matrix constructs

The ability to create extracellular matrix (ECM

Thermodynamic mechanism of particulation of sodium alginate and chitosan polyelectrolyte complexes as a function of charge ratio and order of addition

This study focused on mechanistic understanding of the effect of charge ratio, order of addition and resulting thermodynamics of interaction on the formation and properties of polyelectrolyte complexes (PECs) from sodium alginate and chitosan at a constant tightly controlled pH 4 where the zeta potential difference was maximum for the formation of PECs. The morphology, particle size and particle size distribution as well as the stability of PECs were investigated as a function of molar charge ratio, and the order of addition. The association binding constant K a and the stoichiometry of interaction between the two electrolytes, evaluated using Isothermal titration calorimetry, showed that the stoichiometry and enthalpy of reactions were strongly affected by the order of addition and influenced the average particle size and zeta potential of PECs. The addition of alginate (-) into chitosan (+) gave positively charged particles and resulted in stronger interactions characterized by larger enthalpy and entropy of complexation which led to smaller particles. Reversing the order of addition gave negatively charged particles that were larger. Morphologies of complexes studied using scanning electron microscopy (SEM) showed distorted spherical particles for both orders of addition and at most charge ratios. Stability during 8 weeks was found to depend on the order of addition and charge ratio. Alginate in chitosan gave more stable PECs consistent with the thermodynamics of interaction which showed stronger interactions for this order of addition. The particle sizes and size distributions rapidly increased near electrical neutrality during storage at 4 °C where aggregation was facilitated because of electrical neutrality but particles were stable when the net charge was either strongly positive or strongly negative. © 2019 Elsevier Lt

The influence of specific mechanical energy on cornmeal viscosity measured by an on-line system during twin-screw extrusion

The influence of specific mechanical energy (SME) on cornmeal viscosity during the twin-screw extrusion at feed moisture contents of 25 and 30% and screw speeds in the range from 100 to 500 rpm was measured. Cornmeal was extruded in a co-rotating, intermeshing twin-screw coupled to a slit die rheometer. One approach to the on-line rheological measurement is to use a slit die with the extruder. In the present work it was show that shear viscosity decreased as a function of SME. The viscosity of cornmeal at the exit die was influenced by screw speed, rate of total mass flow, mass temperature inside the extruder and SME. An increase in screw speed resulted in an increase in SME and a decrease in viscosity. A reduction in slit die height and an increase in screw speed and mass temperature led to a remarkable macromolecular degradation of the starch, as evidenced by the decrease in viscosity.28529

Blayne A. Roeder

he other hand, both fibril length and diameter were affected by the pH of the polymerization reaction. Mechanically, all matrices exhibited a similar stress-strain curve with identifiable "toe," "linear," and "failure" regions. However, the linear modulus and failure stress increased with collagen concentration and were correlated with an increase in fibril density. Additionally, both the linear modulus and failure stress showed an increase with pH, which was related to an increased fibril length and a decreased fibril diameter. The tensile mechanical properties of the collagen matrices also showed strain rate dependence. Such fundamental information regarding the 3-D microstructuralmechanical properties of the ECM and its component molecules are important to our overall understanding of cell-ECM interactions (e.g., mechanotransduction) and the development of novel strategies for tissue repair and replacement. #DOI: 10.1115/1.1449904# Keywords: Collagen, Extracellular Matrix, Three-