Solubility and transport phenomena in perfluorochemicals relevant to blood substitution and other biomedical applications

Abstract

Perfluorochemical–based artificial blood substitutes are on the verge of entering medical practice. About 500 patients, mainly in Japan, have already received an emulsion of perfluorochemicals (PFCs) instead of blood, for a variety of reasons : non–availability or delayed delivery of compatible blood; blood transfusion refused on religious grounds (Jehovah's Witnesses); bloodless surgery; improvement of cerebral hypoxia, etc. They open new prospects in therapeutics, including the treatment of heart infarct, cerebral circulatory troubles, severe burns, CO poisoning, activation of the body's defenses, or the use of PFC emulsions in angiography, organ and limb preservation, extracorporeal circulation, etc., that exploit not only the properties these emulsions have in common with blood (transport of the respiratory gases, maintenance of blood volume, osmotic and oncotic pressures, pH, etc.), but also those in which they differ from it (absence of chemical bonding of 02, lower viscosity, smaller particle size, extraneousness to the organism, absence of sensitivity to osmolarity, mechanical resistance, etc.). The requirements to be met by the PFCs for this use : high O2/CO2 dissolving capacity, chemical and biological inertness, high state of purity and definition, industrial feasibility, aptitude of giving stable emulsions, fast excretion rates, are briefly commented on. The PFCs that are present prominent candidates for serving as oxygen carriers for second generation blood substitutes, including new homologous series of tailor–made ones, are critically presented. The data available on the solubility of gases in PFCs, methods of predicting them, and investigations on the mechanism of dissolution, are discussed in greater detail. The various factors that act upon the vn ViVO transport of O2 by PFCs as compared with blood : linear VS sigmoid 02–dissolution curves with lower O2 uptake at atmospheric pO2 (making it necessary to have the patient breathe an 02–enriched atmosphere); absence of chemical bonding of O2, which permits the attainment of higher arterial p02, and better extraction of O2 by the tissues (making it possible to deliver an oxygen boost to anoxic tissues); lower viscosity, which allows increased cardiac output and faster circulation, are evaluated. The factors that influence the excretion rate of the PFCs are examined. Preliminary data on the capacity of PFCs to dissolve other biologically relevant substances, as well as some of their other biomedical applications, including the culture of microorganisms and their use as radiopaque agents and as vectors for conveying drugs, are briefly presented. © 2013, Walter de Gruyter. All rights reserved.