Designing a way to make oxygen injectable

Designing a way to make oxygen injectable

Designing a way to make oxygen injectable

Designing a way to make oxygen injectable

Jarad Mason and his team have permanently created “porous” water, allowing gases to be stored in the liquid in high concentrations. Credit: Kris Snibbe/Harvard Staff Photographer

What if emergency medical personnel could treat a desperately ill patient in need of oxygen with a simple injection instead of relying on mechanical ventilation or rushing to get them on a heart-lung bypass machine?

A new approach to transporting gases using a class of materials called porous liquids represents a major step towards artificial oxygen carriers and demonstrates the immense biomedical potential of these unusual liquids.

In a study published last month in Nature, a team of scientists from Harvard’s Department of Chemistry and Chemical Biology describes a new approach to transporting gases in aqueous environments using porous liquids. The authors have identified and tailored multiple porous frameworks that can store much higher concentrations of gases, including oxygen (O2) and carbon dioxide (CO2), than normal aqueous solutions. This breakthrough may hold the key to creating injectable oxygen sources as bridging therapy for cardiac arrest, creating artificial blood substitutes and overcoming long-standing challenges in preserving organs for transplants.

“We realized there would be many benefits to using liquids with permanent microporosity to address gas transport challenges in water and other aqueous environments,” said Jarad Mason, senior author of the paper and assistant professor of chemistry. and chemical biology. “We have designed fluids that can transport O2 at densities exceeding those of blood, opening up exciting new possibilities for transporting gases for a variety of biomedical and energy applications.”

Liquids with permanent microporosity are a new class of materials composed of microscopic porous particles dispersed in a liquid medium. Imagine small, recyclable, spongy bits that can suck up and release gases in their holes. Until now, all porous liquids have consisted of microporous nanocrystals or organic cage molecules dispersed in organic solvents or ionic liquids too large to diffuse through the pore entrances. The researchers developed a new strategy to create aqueous porous liquids – called “microporous water” – with high gas capacities based on thermodynamics.

The work was led by members of Mason’s lab, including doctoral students Daniel P. Erdosy, Malia Wenny, Joy Cho, Miranda V. Walter, postdoctoral researcher Christopher DelRe, and undergraduate Ricardo Sanchez. Computational simulations and biological experiments were also conducted in collaboration with scientists from Boston Children’s Hospital and Northwestern University, including Felipe Jiminez-Angeles, Baofu Oiao and Monica Olvera de la Cruz.

Water is a polar molecule, making it a great solvent for other polar molecules like ethanol and sugar, but it’s much worse at dissolving non-polar molecules like O2 gas. As such, pure water can carry 30 times less oxygen than red blood cells. The extremely low solubility of gases in water has placed a hard limit on many biomedical and energy-related technologies that require the transport of gas molecules through aqueous liquids. This novel gas transport mechanism overcomes the low solubility of gases in water and enables rapid gas transport.

Inspired by pores in certain proteins that are accessible to water molecules but generally remain dry in aqueous solutions, the team proposed that microporous nanocrystals with hydrophobic internal surfaces and hydrophilic external surfaces could be designed to leave the microporous framework permanently dry in water and available to absorb gas molecules.

“We had to reconcile two seemingly contradictory traits,” Erdosy said. “We designed the inner surface to be hydrophobic and water-repellent, and the outer surface to be hydrophilic and water-loving, otherwise the liquid would separate like oil and water.”

The team synthesized the materials in their lab and tested their ability to absorb and release gases. They found that microporous water can reversibly transport extremely high densities of gases through water-based environments. Using this strategy, the team developed a porous liquid that has a higher density of O. can wear2 than is even present in the pure gas. These aqueous porous liquids exhibit a remarkable shelf life, allowing them to be stored for months at room temperature before use.

“With a little more development, you could envision storing oxygen in a microporous liquid on an ambulance to have it ready to inject into a person when needed,” Wenny said.

The lab plans to conduct more experiments on microporous water to test the biomedical applications, while continuing to explore other potential uses for the materials.

“We want to develop more materials and animal models to make and test an oxygen carrier in vivo,” Erdosy said. “We are also planning a more energy-oriented project on using microporous water to address the gas transport challenges in electrocatalysis.”

Water clusters in hydrophobic crystalline porous covalent organic structures

More information:
Daniel P. Erdosy et al, Microporous water with high gas solubilities, Nature (2022). DOI: 10.1038/s41586-022-05029-w

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