Blood substitute composition and method of use

A method for providing oxygen to an organ ex vivo, the method comprising perfusing an organ with an effective amount of an oxygen-carrying nanoparticle, wherein the nanoparticle has a substantially bi-concaved disc shape and comprises an aqueous core, a bi-layered shell comprising an amphiphilic polymer, and a payload;

• and wherein
• the bi-layered shell has a hydrophilic outer layer, a hydrophilic inner layer, and a hydrophobic region between the hydrophilic outer layer and the hydrophilic inner layer;
• the amphiphilic polymer comprises a branched, amine-containing polymer linked to a lipid;
• and
• the payload comprises an oxygen-carrying agent, an allosteric effector, and a reducing agent.