Spin labelled hemoglobin-based oxygen carriers (HBOC): preparation and evaluation of in vivo / in vitro stability

Site-directed spin labeling and EPR characterization (continuous wave as well as DEER) of two blood substitute candidates is described for the first time: glutaraldehyde-polymerized bovine hemoglobin and the related hemoglobin-albumin copolymer. In vitro, with two different types of cell cultures, these spin-labeled candidates are relatively stable; however, they appear to be rapidly reduced in vivo, most likely via removal or reduction of the spin label (as opposed to removal of the blood substitute candidate from the circulatory system altogether). Keywords: hemoglobin, albumin, blood substitute, HBOC, EPR, spin label, MTSSL, in vivo, cell culture, free radical