Haemoglobin-based oxygen carrier (HBOC) is highly susceptible to autoxidation that renders a series of tissue and cellular toxicities. HBOC is prepared by chemical modification of haemoglobin (Hb), which typically increases the autoxidation rate of Hb. Thus, it is necessary to decrease the autoxidation of HBOC. In the present study, two dextran-bHb conjugates (dex20-bHb and dex40-bHb) were prepared by conjugation with 20 kDa or 40 kDa dextrans, where the thiol group of Cys-93(β) was reversibly protected. The autoxidation rate of bHb was decreased by conjugation with 20 kDa dextran and maintained by conjugation with 40 kDa dextran. In order to understand the low autoxidation rate of dex20-bHb, the effects of aldehyde modification and dextran on the autoxidation rate of dex20-bHb were investigated. The high oxygen affinity, high tetramer stability and dextran itself were found to decrease the autoxidation rate of dex20-bHb. The conjugated dextran had a predominant effect on decreasing the autoxidation rate of bHb, which was particularly promising for the potential development of safe HBOCs. Conjugation with dextran is of general significance to decrease the oxidation process of the heme-containing proteins, such as Hb and myoglobin.
Keywords: HBOC; autoxidation; dextran; haemoglobin; tetramer stability.