Pyridoxylated-Polyhemoglobin Solution: A Low Viscosity Oxygen-Delivering Blood Replacement Fluid with Normal Oncotic Pressure and Long-Term Storage Feasibility

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Abstract
Stroma-free hemoglobin (P50 = 14 torr, T1/2 = 3 hr, COP = 60 torr @ 15 g%) was pyridoxylated (PP-SFHb P50 = 28 torr) and then cross-linked with glutaraldehyde to yield pyridoxylated-polyhemoglobin (PP-PolyHb). Sephadex G-200 gel chromatography showed 33% to be in the 470-750,000 dalton range, 60% 470,000 MW, and 10% remaining unmodified. PP-PolyHb (14 g%), was iso-oncotic (COP = 25 torr) with plasma, and had a viscosity at 37 degrees C = 3.8 cP. Despite glutaraldehyde crosslinking PP-PolyHb retained some cooperative oxygen binding (Hill coefficient n = 1.88), with a P50 of 20 torr. MetHb levels ranged from 3.1-4.8% in fresh PP-PolyHb solutions. Storage in liquid form was possible at 4 degrees C for up to 12 months, with MetHb forming at 0.6%/month. At 25 degrees C storage was possible for 6 months if lyophilized with 3.0% glucose, after which MetHb levels rose at 9.4%/year. At -20 degrees C, the lyophilized PP-PolyHb could be stored for up to 3 years, with MetHb levels remaining below 6.0%.