Hepatocyte function within a stacked double sandwich culture plate cylindrical bioreactor for bioartificial liver system.

Bioartificial liver (BAL) system is promising as an alternative treatment for liver failure. We have developed a bioreactor with stacked sandwich culture plates for the application of BAL. This bioreactor design addresses some of the persistent problems in flat-bed bioreactors through increasing cell packing capacity, eliminating dead flow, regulating shear stress, and facilitating the scalability of the bioreactor unit. The bioreactor contained a stack of twelve double-sandwich-culture plates, allowing 100 million hepatocytes to be housed in a single cylindrical bioreactor unit (7 cm of height and 5.5 cm of inner diameter). The serial flow perfusion through the bioreactor increased cell-fluid contact area for effective mass exchange. With the optimal perfusion flow rate, shear stress was minimized to achieve high and uniform cell viabilities across different plates in the bioreactor. Our results demonstrated that hepatocytes cultured in the bioreactor could re-establish cell polarity and maintain liver-specific functions (e.g. albumin and urea synthesis, phase I&II metabolism functions) for seven days. The single bioreactor unit can be readily scaled up to house adequate number of functional hepatocytes for BAL development.

Changes of airflow pattern in inferior turbinate hypertrophy: a computational fluid dynamics model.

BACKGROUND: Nasal obstruction (NO) is a very common symptom, but its effect on nasal physiology has not been fully understood. We performed this study to determine the effect of severity of NO due to inferior turbinate hypertrophy on airflow pattern using the computational fluid dynamics simulations. METHODS: A three-dimensional nasal cavity model was constructed from the MRI scans of a healthy human subject. Nasal cavities corresponding to healthy, moderate, and severe NO was simulated by enlarging the inferior turbinate geometrically, which can be documented by approximately one-third reduction of the minimum cross-sectional area (1.453 cm(2) in the healthy nose) for the moderate (0.873 cm(2)) and two-thirds (0.527 cm(2)) for the severe obstruction. RESULTS: Total negative pressure through the nasal cavity increased during the inspiratory phase by almost twofold (-19 Pa) and threefold (-33 Pa) for moderate and severe blockage, respectively, compared with the increase of total negative pressure of -10 Pa in a healthy nose. In cases of moderate and severe blockage, a higher velocity and shear stress was observed at the nasopharynx and dorsal region of the nasal cavity. Moreover, nasal valve function will not exist in severe NO because of the changes of airflow pattern at the original nasal valve location. CONCLUSION: Impairment of nasal airflow and physiology is evidenced in NO caused by inferior turbinate hypertrophy. Data of this study may help in predicting the aerodynamic effects of surgical correction of the inferior turbinate hypertrophy.