Soft and hard micromachining techniques used to develop microfluidic devices can yield microchannels of many different cross-sectional profiles. For semi-circular microchannels, these techniques often produce only par...Soft and hard micromachining techniques used to develop microfluidic devices can yield microchannels of many different cross-sectional profiles. For semi-circular microchannels, these techniques often produce only partialsemicircular (PSC) cross-sections. This study investigated fully developed laminar flow in PSC microchannels as a function of a circularity index, κ, defined as the ratio of the radiuses along the curved and flat surfaces of the PSC profile. A correction factor, K, to the Hagen-Poiseuille relation was determined and was well-fitted by the power-law relationship K=5.299/κ2.56. Actual correction factors were compared to estimates based on several hydraulic models for flow in microchannels of arbitrary cross-section, as well as the half-ellipsoid cross-section. The level of wall shear stress, when normalized by the pressure drop per unit length, increased approximately linearly with increase in the circularity index, κ.展开更多
Cytokines are of chief importance in the pathophysiology of sepsis and other systemic inflammatory response syndromes. We are designing and testing an extracorporeal cytokine adsorption device (CAD) that can remove cy...Cytokines are of chief importance in the pathophysiology of sepsis and other systemic inflammatory response syndromes. We are designing and testing an extracorporeal cytokine adsorption device (CAD) that can remove cytokines via adsorption on biocompatible, microporous beads. The goal of this study was to determine whether a previously reported TNF binding DNA aptamer, 5’-GCGGCCGATA AGGTCTTTCC AAGCGAACGA ATTGAACCGC-3’, could be immobilized our hemoadsorption polymer surface to increase the removal rate of TNF. A reservoir consisting of horse serum spiked with a known concentration of TNF was perfused through our CAD packed with aptamer modified or unmodified (control) polymer beads. The binding affinity of the TNF aptamer was characterized using an enzyme-linked oligonucleotide assay (ELONA). As a positive control a well-established DNA aptamer that binds PDGF BB was also subjected to the same ELONA to validate the assay. TNF capture using the CAD showed no TNF removal over four hours for both the aptamer modified and unmodified control beads. Additionally, the results of the ELONA showed no binding of TNF to the reported aptamer;however the PDGF BB aptamer did bind PDGF BB. Based on these results we are able to conclude that the reported TNF specific aptamer does not bind TNF. These results will be of importance to other studies exploring aptamers for specific binding of TNF.展开更多
文摘Soft and hard micromachining techniques used to develop microfluidic devices can yield microchannels of many different cross-sectional profiles. For semi-circular microchannels, these techniques often produce only partialsemicircular (PSC) cross-sections. This study investigated fully developed laminar flow in PSC microchannels as a function of a circularity index, κ, defined as the ratio of the radiuses along the curved and flat surfaces of the PSC profile. A correction factor, K, to the Hagen-Poiseuille relation was determined and was well-fitted by the power-law relationship K=5.299/κ2.56. Actual correction factors were compared to estimates based on several hydraulic models for flow in microchannels of arbitrary cross-section, as well as the half-ellipsoid cross-section. The level of wall shear stress, when normalized by the pressure drop per unit length, increased approximately linearly with increase in the circularity index, κ.
文摘Cytokines are of chief importance in the pathophysiology of sepsis and other systemic inflammatory response syndromes. We are designing and testing an extracorporeal cytokine adsorption device (CAD) that can remove cytokines via adsorption on biocompatible, microporous beads. The goal of this study was to determine whether a previously reported TNF binding DNA aptamer, 5’-GCGGCCGATA AGGTCTTTCC AAGCGAACGA ATTGAACCGC-3’, could be immobilized our hemoadsorption polymer surface to increase the removal rate of TNF. A reservoir consisting of horse serum spiked with a known concentration of TNF was perfused through our CAD packed with aptamer modified or unmodified (control) polymer beads. The binding affinity of the TNF aptamer was characterized using an enzyme-linked oligonucleotide assay (ELONA). As a positive control a well-established DNA aptamer that binds PDGF BB was also subjected to the same ELONA to validate the assay. TNF capture using the CAD showed no TNF removal over four hours for both the aptamer modified and unmodified control beads. Additionally, the results of the ELONA showed no binding of TNF to the reported aptamer;however the PDGF BB aptamer did bind PDGF BB. Based on these results we are able to conclude that the reported TNF specific aptamer does not bind TNF. These results will be of importance to other studies exploring aptamers for specific binding of TNF.
