CROSS-LINKING ENCAPSULATED HEMOGLOBIN WITH SOLID-PHASE SUPPORTS - LIPID ENVELOPED HEMOGLOBIN ADSORBED TO SURFACE-MODIFIED CERAMIC PARTICLESEXHIBIT PHYSIOLOGICAL OXYGEN LABILITY

To reduce hemoglobin toxicity, a cross linking agent is generally used . To preserve hemoglobin function, an allosteric modifier is generally used. Historically, the use of one has precluded the use of the other . A potential solution to this problem was investigated. Hemoglobin A( 0) was adsorbed irreversibly to carbohydrate coated nano-sized diamond particles and then encapsulated in a standard mixture of phospholipid s. Endotoxin free preparations with concentrations of bound hemoglobin near 10 g/dl were achieved with as Little as 0.1 g/dl of free hemoglo bin and remained stable over a 48 hour period. By transmission electro n microscopy these particles appeared roughly spherical and measured a pproximately 75 nanometers well below that of alveolar capillary vesse ls. In shallow pH gradients, liquid electrophoresis demonstrated that such constructs exhibit Bohr effect behavior by the induction of a dra matic surface charge inversion at around pH 6.8. To evaluate oxygen la bility, oxygen saturation trials were conducted in isosmolar physiolog ical salts. Normal sigmoidal binding behavior of O-2 over a typical pO 2 gradient could be modulated by systemic levels of pyridoxyl-5-phosph ate. Constructs with a P-50 as low as 12 mm Hg could be increased to 3 7 mm Hg with the allosteric effector. Viscosity and bio distribution s tudies are to follow. The use of solid phase nanocrystalline supports to cross link hemoglobin may reduce the toxicity of free hemoglobin wh ile still enabling the use of allosteric modifiers.