Hydrophobically derivatized hyperbranched polyglycerol as a human serum albumin substitute

There is a huge clinical demand for Human Serum Albumin (HSA), with a world market of $1.5B/year. Concern over prion and viral transmission in the blood supply has led to a need for safer substitutes and offers the opportunity for development of materials with enhanced properties over the presently available plasma expanders. We report here the synthesis and testing of a new synthetic plasma expander that can replace not only the osmotic and volume expansion properties of HSA but, uniquely, its binding and transport properties. We have synthesized several hyperbranched polyglycerols derivatized with hydrophobic groups and short poly(ethylene glycol) (PEG) chains. The hydrophobic groups provide regions for binding fatty acids and other hydrophobic materials while PEG imparts the necessary protection from host defense systems and enhances circulation longevity. These polymers, being hyperbranched, have only a small effect on plasma viscosity. We have shown in vitro that our materials bind 2–3 moles palmitic acid per mole, do not activate the platelet, coagulation or complement systems and do not cause red cell aggregation. In mice these materials are non-toxic with circulation half-lives as high as 34 h, controllable by manipulating the molecular weight and the degree of PEG derivatization.