A continuous supply of oxygen to tissues is vital to life and interruptions in its delivery are poorly tolerated. The treatment of low-blood oxygen tensions requires restoration of functional airways and lungs. Unfortunately, severe oxygen deprivation carries a high mortality rate and can make otherwise-survivable illnesses unsurvivable. Thus, an effective and rapid treatment for hypoxemia would be revolutionary. The i.v. injection of oxygen bubbles has recently emerged as a potential strategy to rapidly raise arterial oxygen tensions. In this report, we describe the fabrication of a polymerbased intravascular oxygen delivery agent. Polymer hollow microparticles (PHMs) are thin-walled, hollow polymer microcapsules with tunable nanoporous shells. We show that PHMs are easily charged with oxygen gas and that they release their oxygen payload only when exposed to desaturated blood. We demonstrate that oxygen release from PHMs is diffusion-controlled, that they deliver approximately five times more oxygen gas than human red blood cells (per gram), and that they are safe and effective when injected in vivo. Finally, we show that PHMs can be stored at room temperature under dry ambient conditions for at least 2 mo without any effect on particle size distribution or gas carrying capacity.hypoxemia | microparticle | oxygen | core-shell | colloids

A new approach has been developed to prepare stable microbubbles (MBs) by interfacial nanoprecipitation of bioabsorbable polymers at air/liquid interfaces. This facile method offers robust control over the morphology and chemophysical properties of MBs by simple chemical modifications. This approach is amenable to large-scale manufacturing, and is useful to develop functional MBs for advanced biomedical applications. To demonstrate this, a MB-based intravenous oxygen carrier was created that undergoes pH-triggered self-elimination. Intravenous injection of previous MBs increased the risk of pulmonary vascular obstruction. However, we show, for the first time, that our current design is superior, as they 1) yielded no evidence of acute risks in rodents, and 2) improved the survival in a disease model of asphyxial cardiac arrest (from 0 to 100 %), a condition that affects more than 100 000 in-hospital patients, and carries a mortality of about 90 %.

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