Narrow Results

The following sections are included:

• The Continuous Promotion of Blood Bank
• The Continuous Promotion of New Technologies and Methods for Blood for Clinical Use
• Challenges of Chinese Transfusion Medicine in the Future
• Development of Blood Substitutes Research in China
• References

Hemoglobin-based oxygen carriers (HBOCs) are human, animal or recombinant hemoglobins modified chemically and/or genetically to carry oxygen in the bloodstream and deliver it to peripheral tissues. They have been proposed as blood substitutes in case blood transfusions are not immediately available or for other selected applications. As hemoglobin has evolutionarily optimized to exert this role inside red blood cells (RBCs), acellular HBOCs exhibit oxygen binding properties markedly different from those of blood. Moreover, outside of the protective environment of RBCs, hemoglobin exhibits a vasoactive and pro-oxidant activity. The modulation of the oxygen-binding properties of HBOCs has been tackled by exploiting different modification strategies with the aim of producing a fine-tuned oxygen affinity.

We report a novel method to simultaneously extract superoxide dismutase (SOD), catalase (CAT) and carbonic anhydrase (CA) from the same sample of red blood cells (RBCs). This avoids the need to use expensive commercial enzymes, thus allowing this to be cost effective for large-scale production of a nanobiotechnological polyHb-SOD-CAT-CA with enhancements to all three RBC functions. The best concentration of phosphate buffer for ethanol-chloroform treatment results in good recovery of CAT, SOD and CA after extraction. Different concentrations of the enzymes can be used to enhance the activity of polyHb-SOD-CAT-CA to 2, 4 or 6 times that of RBCs.

Polyhemoglobin-superoxide dismutase-catalase-carbonic anhydrase (poly-[Hb-SOD-CAT-CA]) contains all three major functions of red blood cells (RBCs) at an enhanced level. It transports oxygen, removes oxygen radicals and transports carbon dioxide. Our previous studies in a 90-minute 30 mm Hg MAP-sustained hemorrhagic shock rat model showed that it was more effective than blood in the lowering of elevated intracellular PCO₂, recovery of ST-elevation and histology of the heart and intestine. This paper analyzes the storage and temperature stability. The allowable storage time for RBCs is about 1 day at room temperature and 42 days at 4°C. Also, RBCs cannot be pasteurized to remove infective agents like HIV and Ebola. PolyHb can be heat sterilized and can be stored for a year even at room temperature. However, poly-[Hb-SOD-CAT-CA] contains both Hb and enzymes, and enzymes are particularly sensitive to storage and heat. We thus carried out studies to analyze its storage stability at different temperatures and heat pasteurization stability. The results of the storage stability show that lyophillization extends the storage time to a year at 4°C and 40 days at room temperature (compared to 42 days and 1 day, respectively, for RBCs). After the freeze-dry process, the enzyme activities of poly-[SFHb-SOD-CAT-CA] was 100 ± 2% for CA, 100 ± 2% for SOD, and 93 ± 3.5% for CAT. After heat pasteurization at 70°C for 2 hours, lyophilized poly-[Hb-SOD-CAT-CA] retained good enzyme activities of CA (97 ± 4%), SOD (100 ± 2.5%) and CAT (63.8 ± 4%). More CAT can be added during the crosslinking process to maintain the same enzyme ratio after heat pasteurization. Heat pasteurization is possible only for the lyophilized form of poly-[Hb-SOD-CAT-CA] and not for the solution. It can be easily reconstituted by dissolving it in suitable solutions that continue to have good storage stability (though less than that for the lyophilized form). According to the P50 value, poly-[SFHb-SOD-CAT-CA] retains its oxygen-carrying ability before and after long-term storage.

Perfluorocarbons are a class of substances ideally suited for the transport of respiratory gases in order to support tissue oxygenation when red blood cells are diminished or not available. As these totally synthetic molecules intrinsically avoid any infection risks and even stay functional in the presence of flue gases, they display (theoretical) advantages to hemoglobin-based artificial oxygen carriers. Unfortunately perfluorocarbons were abandoned by most of the researchers in favor of hemoglobin-based products as unresolved, harmful side effects, the halt of advanced clinical trials and financial reasons have been reported. At least some countries have recognized the potential of perfluorocarbons and clinically approved perfluorocarbon-based products.

However, we believe in these exceptional substances and thus want to increase the access to perfluorocarbon-based products by developing albumin-derived perfluorocarbon-based artificial oxygen carriers. This formulation is based on an idea dating back to the 1970s, which we have now transformed successfully. The aim of this study was to prove whether albumin-derived perfluorocarbon-based artificial oxygen carriers (capsules) can supply an isolated perfused rat heart (Langendorff model) with oxygen even under massive ischemic conditions induced by a reduction of the flow rate to only 20%. Capsules did not change the rheological properties of the Krebs–Henseleit buffer (KH-buffer) and could repeatedly reload with oxygen. Hearts perfused with capsules showed increased left ventricular pressure (LVDP) and rate pressure product (RPP, markers of heart vitality) compared to hearts perfused with a pure KH-buffer. The capsules prevented the myocardium from malfunctioning when in their absence a noxious ischemia was observed. Thus an albumin-derived perfluorocarbon-based artificial oxygen carrier preserved the function of the rats’ hearts due to the transport of oxygen in a satisfactory manner.