Hemoglobin microparticles as combined drug/oxygen carriers with long circulation - Mechanisms of elimination of hemoglobin microparticles as combined drug/oxygen carriers from the circulation

• Applicant: Professor Dr. Hans Bäumler
• Subject Area: Pharmacology ; Immunology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 512448250

Hemoglobin-based oxygen carriers (HBOCs) as artificial oxygen transporters or oxygen therapeutics for medical applications have been the subject of scientific investigations for decades. Currently no artificial oxygen carrier is approved in the EU and the USA. A promising strategy of HBOC development is the production of hemoglobin microparticles (HbMP) using the coprecipitation-crosslinking-dissolution (CCD) technique. By selecting of a suitable salt solution, HbMP in the size range of 3 μm or 700 nm can be fabricated, in which up to 100% of the Hb molecules in the solution are encapsulated. HbMPs have a high oxygen affinity (p50 < 15mmHg) and can release oxygen in a targeted manner in the undersupplied tissue. It could be shown that neither NO-scavenging nor vasoconstriction can be detected when using such HbMP. HbMP have many functional groups as potential binding sites for various drugs. Many macromolecule-based drugs can also be co-encapsulated during the CCD process. Thus, HbMP have a very high potential as an innovative combined drug / oxygen carrier (Drug-Oxygen-Carriers, DOCs), e.g. in tumor therapy. All HBOCs developed to date have significantly shorter half-lives compared to erythrocytes. Although only a low rate of phagocytosis has been demonstrated in vitro for the new HbMP/DOCs, they are rapidly eliminated in vivo. However, the mechanism(s) leading to the rapid elimination of the particles from the circulation has not yet been elucidated. The main goal of the project is therefore to elucidate the elimination mechanisms of the HbMP-based DOCs. The hypotheses that the DOCs are specifically recognized and eliminated by monocytes/macrophages by binding to haptoglobin, hemopexin or acute phase proteins or non-specifically by binding of receptors/receptor clusters on their surface that have not yet been clearly defined are to be tested. The interactions between DOCs and the mononuclear phagocyte system, especially macrophages, will be investigated in vitro. Monocytes, Kupffer cells as well as co-culture of Kupffer cells and hepatocytes serve as a model system. Based on these findings, the HbMP/DOCs are to be "stealth" modified using suitable block polymers to reduce phagocytosis of HbMP/DOCs by leukocytes and macrophages. The oxygen transport function of the DOCs should not be impaired during the modification. Depending on the results regarding the elucidation of the elimination mechanisms and "stealth" modification of the DOCs, further ex vivo or in vivo studies are to be planned as proof of concept studies outside of the project with our scientific cooperation partners.

• DFG Programme: Research Grants