Reduction in the toxicity of a component of an artificial blood substitute by supercritical fluid fractionation

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Abstract
Artificial blood substitutes (ABS) containing the surfactant Pluronic F68 (F68) are reported to be cytotoxic to cell lines. Because of F68''s reported impairment of granulocyte function, it was hypothesized that F68 was also responsible for the cytotoxicity of ABS, possibly as a result of a separable fraction of the F68, separation of which could be achieved using supercritical fluid fractionation (SFF). SFF employs gases, such as carbon dioxide, under high pressure to dissolve the parent compound, a process that is followed by step-by-step precipitation and recovery of the dissolved material. The toxicity of F68 to human and animal cells was investigated by culturing Hela and B16 cells in the presence or absence of F68. Cells were grown for 4 days, harvested, and counted. Hela and B16 growth were markedly inhibited by F68. Four lots of F68 at 20 mg per ml inhibited Hela growth by 54 .+-. 10 percent (p < 0.05). In four dose-response experiments, three lots of F68 caused 50 percent inhibition of cell growth at 25 .+-. 17 mg per ml. Four lots of F68 were also processed by SFF. Hela cells were grown in the presence of control media, parent (unextracted) F68, the early fractions of SFF extraction (XT), and the residual (partially purified) (RES F68). All parent F68, XT, and RES F68 were at 20 mg per ml. In 11 studies, the XT were 77 .+-. 25 percent more toxic than the parent F68 (p < 0.02), and the RES F68 were 30 .+-. 11 percent less toxic than parent F68 (p < 0.02). SFF of F68 also significantly diminished or eliminated F68-induced inhibition of granulocyte chemotaxis. It is concluded that the cytotoxicity of ABS, as previously reported, is due to F68; that F68 exhibits marked, dose-dependent toxicity to growth of human and animal cells; that SFF separated a highly toxic fraction of parent F68; and that removal of this fraction significantly diminished the cytotoxicity and chemotaxis-inhibiting properties of F68. Thus, it may be possible to generate a nontoxic F68 polymer using SFF or a similar technology.