We have developed an injectable foam suspension containing self-assembling, lipid-based microparticles encapsulating a core of pure oxygen gas for intravenous injection. Prototype suspensions were manufactured to contain between 50 and 90 ml of oxygen gas per deciliter of suspension. Particle size was polydisperse, with a mean particle diameter between 2 and 4 μm. When mixed with human blood ex vivo, oxygen transfer from 70 volume % microparticles was complete within 4 s. When the microparticles were infused by intravenous injection into hypoxemic rabbits, arterial saturations increased within seconds to near-normal levels; this was followed by a decrease in oxygen tensions after stopping the infusions. The particles were also infused into rabbits undergoing 15 min of complete tracheal occlusion. Oxygen microparticles significantly decreased the degree of hypoxemia in these rabbits, and the incidence of cardiac arrest and organ injury was reduced compared to controls. The ability to administer oxygen and other gases directly to the bloodstream may represent a technique for short-term rescue of profoundly hypoxemic patients, to selectively augment oxygen delivery to at-risk organs, or for novel diagnostic techniques. Furthermore, the ability to titrate gas infusions rapidly may minimize oxygen-related toxicity.

A detailed study is presented on the synthesis and characterization of purely oxygen-filled microbubbles (OMBs) stabilized by phospholipids. Microbubbles with a diameter of less than 10 μm were generated and concentrated to >50 vol % in saline. The lipid acyl chain length had little effect on the size distribution but profoundly affected the foam stability. For example, OMBs stabilized by dipalmitoyl phosphatidylcholine (DPPC) degraded over 3 weeks, but OMBs stabilized with distearoyl phosphatidylcholine (DSPC) retained over half of their initially encapsulated gas. Interestingly, the polydisperse size distribution remained nearly constant as the foam slowly broke down. Injection into an undersaturated solution led to the immediate release of the oxygen gas core. Injectable gas delivery by OMBs may find use in a variety of medical and industrial fields.

Magnesite is the most desirable phase within the magnesium carbonate family for carbon storage for a number of reasons: magnesium efficiency, omission of additional crystal waters and thermodynamic stability. For large-scale carbonation to be a viable industrial process, magnesite precipitation must be made to occur rapidly and reliably. Unfortunately, the formation of metastable hydrated magnesium carbonate phases (e.g. MgCO3·3H2O and Mg5(CO3)4(OH)2·4H2O) interferes with the production of anhydrous magnesite under a variety of reaction conditions because magnesite crystals are slower to both nucleate and grow compared to the hydrated carbonate phases. Furthermore, the reaction conditions required for the formation of each magnesium carbonate phases have not been well understood with conflicting literature data. In this study, the effects of both magnesite (MgCO3) and inert (Al2O3) seed particles on the precipitation of magnesium carbonates from a Mg(OH)2 slurry were explored. It was interesting that MgCO3 seeding was shown to accelerate anhydrous magnesite growth at temperatures (80-150 °C), where it would normally not form in short time scale. Since the specific surface areas of MgCO3 and Al2O3 seeding particles were similar, this phenomenon was due to the difference in the surface chemistry of two seeding particles. By providing a template with similar chemistry for the growth of magnesite, the precipitation of anhydrous magnesite was demonstrated. The effect of temperature on seeded carbonation was also investigated. A comparison with published MgCO3 precipitation rate laws indicated that the precipitation of magnesite was limited by either CO2 adsorption from the gas phase or the dissolution rate of Mg(OH)2.

Silicate minerals such as olivine (Mg2SiO4) and serpentine [Mg3(OH)4(Si3O5)] can react with CO2 to form mineral carbonates to permanently store CO2. Despite significant advancements in carbon mineralization, major discrepancies in the reported kinetics exist because of inconsistencies among various experimental methodologies, the heterogeneity and aging of the minerals, and inadequate fast kinetics and morphological data to probe the reaction mechanisms. In this work, it was found that aged and freshly ground olivine produce very different carbonation yields. A new mineral cleaning protocol to remove fines (<5 μm) was developed. Fast and slow serpentine dissolution regimes were distinguished using a custom-built differential-bed reactor. Mineral carbonate formation using a bubble-column reactor was described. Different carbon analyses were evaluated for accurate estimation of the extent of carbon mineralization. Therefore, this study focused on the development of an experimental framework and a data analysis method for the systematic investigation of mineral dissolution and carbonation behaviors.

Injectable oxygen delivery is an emerging technology that presents an opportunity for improved patient care in a number of medical disciplines. Here, we report on the fabrication and characterization of novel protein-encapsulated oxygen microbubbles (OMBs) designed for intravenous injection. The nanothick albumin encapsulation provided OMBs small enough for transcapillary passage: 99% of the microbubbles were less than 3-m diameter and less than 1% of the oxygen was encapsulated in microbubbles greater than 8-m diameter. The protein OMBs were remarkably stable, losing less than 40% of the encapsulated gas over 12 days. Upon injection into an oxygen-depleted saline solution, the protein OMBs rapidly equilibrated by releasing their oxygen core. These results indicate that protein microbubbles may serve as a suitable platform for direct injection of bioactive and therapeutic gases.