Hemoglobin in Non Phospholipid Liposomes

The introduction emphasizes the clinical need for an artificial system which can transporthemoglobin which has been oxygenated in the lung to tissues in the body. Thus, the quest for amodality which could transport, store, and release oxygen to the tissues when required. The transportform must also lack immunogenic properties. Early data on the use of free hemoglobin have beendiscussed and the relative lack of success with free hemoglobin solutions and hemoglobin in phospholipidliposomes has been emphasized. Dr. Wallach has preliminary data which demonstrate that non-phospho-lipid liposomes consisting of biodegradable high capacity amphiphiles would be suitable as an erythrocytesubstitute. The dioxyethylenecetylether/cholesterol will be studied with regard to surface charge,proportion of cholesterol upon encapsulation of alpha-alpha cross-linked human hemoglobin, and stateof oxidation of the hemoglobinas well as the stability of the NPL which is carrying hemoglobin. Also, tobe tested are the effects of chain length and hydrophilic head group on the ability of the NPL to carryoxygen. When the physical properties of the NPL are established, they will be administered to rats forexamination of effects on blood pressure, heart rate, and other important parameters. Dr. Wallach wasactually the first investigator to create a liposome when he injected organic solutions of purifiedphosphatidylethanolamine into aqueous media. These liposome vesicles could shorten the coagulationtime of platelet-poor plasma. This was a landmark paper in blood coagulation studies. For studies inthis proposal, Dr. Wallach has created a stable, sterilizable paucilamellar NPL which is inexpensive,non-toxic and biodegradable. They can also carry a large volume of hemoglobin. The NPL contain 2-4bilayer membranes. A group of investigators has prepared hemoglobin-laden non-phospholipid"niosomes" containing diglycerolcetylether, cholesterol, and dicetylphosphate. Dr. Wallach and his grouphave extended different formulations of NPL which can efficiently encapsulate hemoglobin. Forpreparation and characterization of hemoglobin, alpha-alpha crosslinked hemoglobin will be used. Humanstroma-free hemoglobin will be prepared, deoxygenated, and appropriately stored. The hemoglobin willbe encapsulated by their well-established technique, the results being monitored by phase contrast andother microscopy techniques. Viscosity and leakage problems will be appropriately monitored.Hemodynamic testing will be done in Sprague-Dawley rats. Exchanged transfusions will be done andvarious parameters measured.