Polymerized human hemoglobin (PolyhHb) is being studied as a possible red blood cell (RBC) substitute for use in scenarios where blood is not available. While the O 2 carrying capacity of PolyhHb makes it appealing as an O 2 therapeutic, the commercial PolyhHb PolyHeme® (Northfield Laboratories Inc., Evanston, IL) was never approved for clinical use due to the presence of large quantities of low molecular weight polymeric (LMW) Hb species (<500 kDa), which have been shown to elicit vasoconstriction, systemic hypertension, and oxidative tissue injury in vivo. Previous bench-top scale studies in our lab demonstrated the ability to synthesize and purify PolyhHb using a two-stage tangential flow filtration (TFF) purification process to remove almost all undesirable Hb species (>0.2 µm and <500 kDa) in the material to create a product that should be safer for transfusion. Therefore, in order to enable future large animal studies and eventual human clinical trials, PolyhHb synthesis and purification processes need to be scaled up to the pilot scale. Hence in this study, we describe pilot scale synthesis and purification of PolyhHb. Characterization of pilot scale PolyhHb showed that PolyhHb could be successfully produced to yield biophysical properties conducive for its use as an RBC substitute.

The presence of iron in circulating monocytes is well known as they play an essential role in iron recycling. It has been demonstrated that the iron content of blood cells can be measured through their magnetic behavior; however, the magnetic properties of different monocyte subtypes remain unknown. In this study, we report for the first time, the magnetic behavior of classical, intermediate and non-classical monocytes, which is related to their iron storage capacity. The magnetic properties of monocytes were compared to other blood cells, such as lymphocytes and red blood cells in the oxyhemoglobin and methemoglobin states, and a cancer cell type. For this analysis, we used an instrument referred to as Cell Tracking Velocimetry (CTV), which quantitatively characterizes the magnetic behavior of biological entities. Our results demonstrate that significant fractions of the intermediate and non-classical monocytes have high magnetophoretic mobilities, equivalent to methemoglobin red blood cells and higher than the classical subset, suggesting their higher iron storage capacities. Moreover, our findings have implications for the immunomagnetic separation industry; we demonstrate that negative magnetic isolation techniques for recovering monocytes from blood should be used with caution, as it is possible to lose magnetic monocytes when using this technique.

A new method for hemoglobin (Hb) deoxygenation and re-oxygenation, in suspension or within red blood cells, RBCs, is described using the commercial enzyme product, EC-Oxyrase®. This method using EC-Oxyrase has several advantages over established deoxygenation methodologies, such as avoiding side reactions that produce methemoglobin, eliminating the need of a sparging deoxygenation gas and airtight vessels, as well as easy re-oxygenation by washing and adding to a normal buffer with dissolved oxygen (DO). Spectra of deoxyHb and metHb from RBCs using three preparation methods: sodium dithionite, sodium nitrite and Oxyrase, show high purity of the deoxyHb using Oxyrase (with little to no methemoglobin or hemichrome production from side reactions). The deoxygenation action of Oxyrase follows first order reaction kinetics. Paramagnetic characteristics of intracellular hemoglobin in RBCs are compared using cell tracking velocimetry for healthy and sickle cell disease (SCD) donors and oxygen dissociation curves show that the function of healthy RBCs is unchanged after Oxyrase treatment. The results confirm that this enzymatic approach to deoxygenation produces pure deoxyhemoglobin, can be re-oxygenated easily, prepared aerobically and has similar paramagnetic mobility to the existing methods.

Previously, our lab developed high molecular weight (MW) tense (T) state glutaraldehyde polymerized bovine hemoglobins (PolybHbs) that exhibited reduced vasoactivity in several small animal models. In this work, we prepared PolybHb in the T- and relaxed (R) quaternary state with ultrahigh MW (> 500 kDa) with varying cross-link densities and investigated the effect of MW on key biophysical properties (i.e., O2 affinity, cooperativity coefficient, hydrodynamic diameter, polydispersity, polymer composition, viscosity, gaseous ligand-binding kinetics, autoxidation, and haptoglobin-binding kinetics). To further optimize current PolybHb synthesis and purification protocols, we performed a comprehensive meta-data analysis to evaluate correlations between procedural parameters (i.e. cross-linker:bovine Hb (bHb) molar ratio, gas/liquid exchange time, temperature during dithionite addition, and number of diafiltration cycles) and the biophysical properties of both T-state and R-state PolybHbs. Our results showed that, the duration of the fast-step autoxidation phase of R-state PolybHb increased with decreasing glutaraldehyde:bHb molar ratio. Additionally, T-state PolybHb exhibited significantly higher biomolecular rate constants for binding to haptoglobin and unimoleular O2 offloading rate constants compared to R-state PolybHb. The methemoglobin (metHb) level in the final product was insensitive to the molar ratio of glutaraldehyde to bHb for all PolybHb. During tangential flow filtration processing of the final product, 14 diafiltration cycles was found to yield the lowest metHb level.