Role of Cell-Mediated Enzymatic Degradation and Cytoskeletal Tension on Dynamic Changes in the Rheology of the Pericellular Region Prior to Human Mesenchymal Stem Cell Motility.

Human mesenchymal stem cells (hMSCs) are encapsulated in synthetic matrix metalloproteinase (MMP) degradable poly(ethylene glycol)-peptide hydrogels to characterize cell-mediated degradation of the pericellular region using multiple particle tracking microrheology. The hydrogel scaffold is degraded by cell-secreted enzymes and cytoskeletal tension. We determine that cell-secreted enzymatic degradation is the main contributor to changes in the pericellular region, with cytoskeletal tension playing a minimal role. Measured degradation profiles for untreated and myosin II inhibited hMSCs have the highest cross-link density around the cell. We hypothesize that cells are also secreting tissue inhibitor of metalloproteinases (TIMPs) to inhibit MMPs, which allow cell spreading and attachment prior to motility. We develop a Michaelis-Menten competitive enzymatic inhibition model which accurately describes the degradation profile due to MMP-TIMP unbinding.

Extraction of Oil from an Aqueous Emulsion by Coupling Thermal Swing with a Capillary Pump.

Separation of oil from water is an area of increasing interest because of the ever-increasing emphasis on reducing discharge of oily wastewater streams and for managing accidental oil spills. While several methods to separate oil from water are available, the current methods often require elaborate processing steps and/or have low extraction rates. Here, we report two simple and potentially inexpensive methods of separating oil from aqueous emulsions. The first method employs hydrophobized glass wool in a pressure-driven capillary pump, while the second method employs novel zeolite pellets the exterior surface of which is hydrophobic. These pellets selectively absorb oil from an aqueous emulsion, which can subsequently be recovered using thermal swing with hot fluid at a temperature far below the boiling point of the oil. Separation of oil with a very high yield (ca. 97%) appears possible using a combination of the two methods.

Monitoring solid oxide CO2 capture sorbents in action.

The separation, capture, and storage of CO2 , the major greenhouse gas, from industrial gas streams has received considerable attention in recent years because of concerns about environmental effects of increasing CO2 concentration in the atmosphere. An emerging area of research utilizes reversible CO2 sorbents to increase conversion and rate of forward reactions for equilibrium-controlled reactions (sorption-enhanced reactions). Little fundamental information, however, is known about the nature of the sorbent surface sites, sorbent surface-CO2 complexes, and the CO2 adsorption/desorption mechanisms. The present study directly spectroscopically monitors Na2 O/Al2 O3 sorbent-CO2 surface complexes during adsorption/desorption with simultaneous analysis of desorbed CO2 gas, allowing establishment of molecular level structure-sorption relationships between individual surface carbonate complexes and the CO2 working capacity of sorbents at different temperatures.