Next‐generation polymerized human hemoglobins in hepatic bioreactor simulations

Abstract

Hepatic hollow fiber (HF) bioreactors can be used to provide temporary support to patients experiencing liver failure. Before being connected to the patient's circulation, cells in the bioreactor must be exposed to a range of physiological O 2 concentrations as observed in the liver sinusoid to ensure proper performance. This zonation in cellular oxygenation promotes differences in hepatocyte phenotype and may better approximate the performance of a real liver within the bioreactor. Polymerized human hemoglobin (PolyhHb) locked in the tense quaternary state (T-state) has the potential to both supply and regulate O 2 transport to cultured hepatocytes in the bioreactor due to its low O 2 affinity. In this study, T-state PolyhHb production and purification processes were optimized to minimize the concentration of low-molecularweight PolyhHb species in solution. Deconvolution of size-exclusion chromatography spectra was performed to calculate the distribution of polymeric Hb species in the final product. Fluid flow and mass transport within a single fiber of a hepatic HF bioreactor was computationally modeled with finite element methods to simulate the effects of employing T-state PolyhHb to facilitate O 2 transport in a hepatic bioreactor system. Optimal bioreactor performance was defined as having a combined hypoxic and hyperoxic volume fraction in the extracapillary space of less than 0.05 where multiple zones were observed. The Damköhler number and Sherwood number had strong inverse relationships at each cell density and fiber thickness combination. These results suggest that targeting a specific Damköhler number may be beneficial for optimal hepatic HF bioreactor operation. K E Y W O R D S fluid flow modeling, hemoglobin-based oxygen carrier, hollow fiber bioreactor, polymerized human hemoglobin, red blood cell substitute

Biophysical properties of tense quaternary state polymerized human hemoglobins bracketed between 500 kDa and 0.2 μm in size

“…The final product was stored at 10 g dl À1 and À80 C until use. 6 Storage in this manner has been shown to maintain T-state PolyhHb as a stable colloidal suspension for at least 2 years with proper thawing before in vivo use. 38…”

Polymerized human hemoglobin facilitated modulation of tumor oxygenation is dependent on tumor oxygenation status and oxygen affinity of the hemoglobin-based oxygen carrier

“…The hHb/ PolyhHb kinetics of O 2 offloading ( k off ,O 2 ) were measured with an Applied Photophysics SF-17 microvolume stopped-flow spectrophotometer (Applied Photophysics Ltd., Surrey, United Kingdom) using protocols previously described by Rameez and Palmer [51][52][53] . The MW distribution was estimated using an Acclaim SEC-1000 column (Thermo Scientific, Waltham, MA) on a Thermo Scientific Dionex Ultimate UHPLC system using previously described methods 17,54 . Dorsal chamber window model.…”

Apohemoglobin-haptoglobin complexes attenuate the hypertensive response to low-molecular-weight polymerized hemoglobin

“…[27][28][29] The MW distribution was estimated by using an Acclaim SEC-1000 column (Thermo Scientific, Waltham, MA) connected to a Thermo Scientific Dionex Ultimate UHPLC system using previously described methods. 14,30 All measurements were taken from the same sample used in the animal study.…”

“…The resulting changes in size distribution after Hp binding was estimated with SEC-HPLC by using previously described methods. 14,30 All measurements were taken from the same sample used in the animal study.…”