Characterization of the Microscopic Behavior in the Structures of Oxygen Carriers Based On Perfluorocarbon Emulsions

Blood is a highly perishable fluid with an estimated lifespan of 6 days after that, hemolysis occurs leaving the blood useless. The imbalance between demand and supply of blood often leads to shortages, in addition to this, problems such as the blood transfusion-transmitted diseases (hepatitis C, HIV, etc.) are some of the factors that have led to the development of blood substitutes called hemosubstitutes. The main hemosubstitutes includes perfluorocarbon-based emulsions (PFC) and different types of hemoglobin solutions, such as hemoglobin oxygen carriers (HBOCS) An adequate substitute for blood, currently under development, must meet the following requirements: universal compatibility, unrestricted use of the patient's blood type receiver, carrying of the oxygen with a quickly releasing, room temperature stability, and long lifespan. In addition, the substitute should not have toxic effects, should have pH and viscosity similar to blood, should not cause vasodilation or vasoconstriction. Moreover, it should not have reactivity with oxygen and absence of active metabolisms, and it also should be easy to use in emergency situations such as hemorrhagic shock and severe anemia. Among the above, there are two main properties of a good hemosubstitute: one is the good transportation of oxygen because its absence may jeopardize the physical integrity of the patient and the other one is the particle size related to the stability of the emulsion that could cause toxicity problems in the patient's body. While ensuring the property of the oxygen transportation and the carbon dioxide dilution using PFC emulsions, the next problem to consider is the particle size. In the formulation of the PFC-based emulsion are present the continuous phase (water and alginate), the dispersed phase (perfluoro octyl bromide 99%,PFOB, Exfluor Research Corp, USA), the surfactant (lecithin, Epikuron 170®, DEGUSSA, Germany) and a pH adjuster solution. The particle size is affected by lecithin in excess forming liposomes with water, and the perfluorocarbon droplets that can suffer the effects of the unstability (coalescence / flocculation). A quantification of the particle size is a complex task because of the variety of the structures found in the emulsion, then, it is necessary to find tools that allow the characterization of each specific particle in order to propose strategies for reducing liposomes formations. For the characterization of the particles, it is presently used techniques such as the particle analyzer based on dynamic light scattering. This technique allows the determination of the average particle size of the PFC droplets and liposomes. However, this technique cannot distinguish a PFC drop or a liposome. In order to characterize the present structures in the emulsion (PFC drops and liposomes), it has been used the near-infrared (NIR) spectroscopy technique. This method identifies changes in the absorbance within some wavelength ranges associated with mechanisms of instability of the emulsion. The result of this research has shown that it is possible to differentiate specific zones of the NIR spectrum that varies only with changes associated to the PFC droplets as well as zones that vary only with changes associated to the liposomes.