Preparation and characterisation of poly(lactic acid) hemoglobin microspheres.

For many years, a lot of research effort has been carried out with a view to preparing blood substitutes. Our group has developed a process of encapsulation of hemoglobin in polylactid microspheres. An aqueous solution of hemoglobin was emulsified into a solution of polymer in methylene chloride to form a W/O emulsion. This primary emulsion was then added to a external aqueous phase under stirring until the evaporation of methylene chloride. The microspheres were separated by filtration and washed with distilled water. Microspheres were spherical and their sizes vary between 10 and 500 microns. More than 80% of the hemoglobin was encapsulated. From the absorption spectra of hemoglobin from microspheres, we did not notice any alteration of the oxygen carrier. The dissociation curve of the hemoglobin demonstrated the permeability of the polymeric wall of these microspheres to oxygen. This curve was relatively sigmoidal and presented a P50 similar to that of free hemoglobin in the same experimental conditions. A cellulose's acetate gel electrophoresis of hemoglobin extracted from the microspheres showed one band that correlates with intact hemoglobin. These results suggest that hemoglobin does not interact chemically with the polymer matrix and that the process of microencapsulation does not alter the hemoglobin molecule.