Technique could make better membranes for next-generation filtration

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Photo of researchers in lab.

UCLA doctoral student Mackenzie Anderson, postdoctoral scholar Brian McVerry and professor Richard Kaner. Photo Credit: Marc Roseboro/UCLA

Deriving drinkable water from seawater, treating wastewater and conducting kidney dialysis are just a few important processes that use a technology called membrane filtration.

The key to the process is the membrane filter — a thin, semi-porous film that allows certain substances such as water to pass through while separating out other, unwanted substances. But in the past 30 years, there have been no significant improvements in the materials that make up the key layers of commercially produced membrane filters.

Now, UCLA researchers have developed a new technique called thin-film liftoff, or T-FLO, for creating membrane filters. The approach could offer a way for manufacturers to produce more effective and energy-efficient membranes using high-performance plastics, metal-organic frameworks and carbon materials. To date, limitations in how filters are fabricated have prevented those materials from being viable in industrial production.

A study describing the work is published in the journal Nano Letters.

“There are a lot of materials out there that in the lab can do nice separations, but they’re not scalable,” said Richard Kaner, UCLA’s Dr. Myung Ki Hong Professor of Materials Innovation and the study’s senior author. “With this technique, we can take these materials, make thin films that are scalable, and make them useful.”

In addition to their potential for improving types of filtration that are performed using current technology, membranes produced using T-FLO could make possible an array of new forms of filtration, said Kaner, who also is a distinguished professor of chemistry and biochemistry, and of materials science and engineering, and a member of the California NanoSystems Institute at UCLA. For example, the technique might one day make it feasible to pull carbon dioxide out of industrial emissions — which would enable the carbon to be converted to fuel or other applications while also reducing pollution.

Filters like the ones used for desalination are called asymmetric membranes because of their two layers: a thin but dense “active” layer that rejects particles larger than a specific size, and a porous “support” layer that gives the membrane structure and allows it to resist the high pressures used in reverse osmosis and other filtering processes. The first asymmetric membrane for desalination was devised by UCLA engineers in the 1960s.

Today’s asymmetric membranes are made by casting the active layer onto the support layer, or casting both concurrently. But to manufacture an active layer using more advanced materials, engineers have to use solvents or high heat — both of which damage the support layer or prevent the active layer from adhering.

In the T-FLO technique, the active layer is cast as a liquid on a sheet of glass or metal and cured to make the active layer solid. Next, a support layer made of epoxy reinforced with fabric is added and the membrane is heated to solidify the epoxy.

The use of epoxy in the support layer is the innovation that distinguishes the T-FLO technique — it enables the active layer to be created first so that it can be treated with chemicals or high heat without damaging the support layer.

The membrane then is submerged in water to wash out the chemicals that induce pores in the epoxy and to loosen the membrane from the glass or metal sheet.

Finally, the membrane is peeled off of the plate with a blade — the “liftoff” that gives the method its name.

“Researchers around the world have demonstrated many new exciting materials that can separate salts, gases and organic materials more effectively than is done industrially,” said Brian McVerry, a UCLA postdoctoral scholar who invented the T-FLO process and is the study’s co-first author. “However, these materials are often made in relatively thick films that perform the separations too slowly or in small samples that are difficult to scale industrially.

“We have demonstrated a platform that we believe will enable researchers to use their new materials in a large, thin, asymmetric membrane configuration, testable in real-world applications.”

The researchers tested a membrane produced using T-FLO for removing salt from water, and it showed promise for solving one of the common problems in desalination, which is that microbes and other organic material can clog the membranes. Although adding chlorine to the water can kill the microbes, the chemical also causes most membranes to break down. In the study, the T-FLO membrane both rejected the salt and resisted the chlorine.

In other experiments, the new membrane was also able to remove organic materials from solvent waste and to separate greenhouse gases.

Mackenzie Anderson, a UCLA doctoral student, is co-first author of the study.

The research was supported by the U.S./China Clean Energy Research Center for Water-Energy Technologies and the National Science Foundation. The project is aligned with UCLA’s Sustainable LA Grand Challenge.

Among the many other devices developed by Kaner’s laboratory is a commercial membrane that separates oil from water and cleans up the debris left by fracking. Fracking is a technique that uses high-pressure mixes of water, sand or gravel and chemicals to extract gas and oil from shale rock.

Kaner is among the world’s most highly cited scientific researchers, and he was one of the 2019 recipients of the American Institute of Chemists’ Chemical Pioneer Award, which honors chemists and chemical engineers for contributions that advance the science of chemistry or the chemical profession.

This article originally appeared in the UCLA Newsroom.

Biochemists discover new insights into what may go awry in brains of people with Alzheimer’s

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Photo of two researchers in lab.

Research by UCLA professor Steven Clarke and former graduate student Rebeccah Warmack, as well as UCLA colleagues, reveals new information about the brain’s biochemistry.

More than three decades of research on Alzheimer’s disease have not produced any major treatment advances for those with the disorder, according to a UCLA expert who has studied the biochemistry of the brain and Alzheimer’s for nearly 30 years. “Nothing has worked,” said Steven Clarke, a distinguished professor of chemistry and biochemistry. “We’re ready for new ideas.” Now, Clarke and UCLA colleagues have reported new insights that may lead to progress in fighting the devastating disease.

Scientists have known for years that amyloid fibrils — harmful, elongated, water-tight rope-like structures — form in the brains of people with Alzheimer’s, and likely hold important clues to the disease. UCLA Professor David Eisenberg and an international team of chemists and molecular biologists reported in the journal Nature in 2005 that amyloid fibrils contain proteins that interlock like the teeth of a zipper. The researchers also reported their hypothesis that this dry molecular zipper is in the fibrils that form in Alzheimer’s disease, as well as in Parkinson’s disease and two dozen other degenerative diseases. Their hypothesis has been supported by recent studies.

Alzheimer’s disease, the most common cause of dementia among older adults, is an irreversible, progressive brain disorder that kills brain cells, gradually destroys memory and eventually affects thinking, behavior and the ability to carry out the daily tasks of life. More than 5.5 million Americans, most of whom are over 65, are thought to have dementia caused by Alzheimer’s.

The UCLA team reports in the journal Nature Communications that the small protein beta amyloid, also known as a peptide, that plays an important role in Alzheimer’s has a normal version that may be less harmful than previously thought and an age-damaged version that is more harmful.

Rebeccah Warmack, who was a UCLA graduate student at the time of the study and is its lead author, discovered that a specific version of age-modified beta amyloid contains a second molecular zipper not previously known to exist. Proteins live in water, but all the water gets pushed out as the fibril is sealed and zipped up. Warmack worked closely with UCLA graduate students David Boyer, Chih-Te Zee and Logan Richards; as well as senior research scientists Michael Sawaya and Duilio Cascio.

What goes wrong with beta amyloid, whose most common forms have 40 or 42 amino acids that are connected like a string of beads on a necklace?

The researchers report that with age, the 23rd amino acid can spontaneously form a kink, similar to one in a garden hose. This kinked form is known as isoAsp23. The normal version does not create the stronger second molecular zipper, but the kinked form does.

“Now we know a second water-free zipper can form, and is extremely difficult to pry apart,” Warmack said. “We don’t know how to break the zipper.”

The normal form of beta amyloid has six water molecules that prevent the formation of a tight zipper, but the kink ejects these water molecules, allowing the zipper to form.

When one of its amino acids forms a kink, beta amyloid creates a harmful molecular zipper, shown here in green. Photo credit: Rebeccah Warmack/UCLA

When one of its amino acids forms a kink, beta amyloid creates a harmful molecular zipper, shown here in green.
“Rebeccah has shown this kink leads to faster growth of the fibrils that have been linked to Alzheimer’s disease,” said Clarke, who has conducted research on biochemistry of the brain and Alzheimer’s disease since 1990. “This second molecular zipper is double trouble. Once it’s zipped, it’s zipped, and once the formation of fibrils starts, it looks like you can’t stop it. The kinked form initiates a dangerous cascade of events that we believe can result in Alzheimer’s disease.”

Why does beta amyloid’s 23rd amino acid sometimes form this dangerous kink?

Clarke thinks the kinks in this amino acid form throughout our lives, but we have a protein repair enzyme that fixes them.

“As we get older, maybe the repair enzyme misses the repair once or twice,” he said. “The repair enzyme might be 99.9% effective, but over 60 years or more, the kinks eventually build up. If not repaired or if degraded in time, the kink can spread to virtually every neuron and can do tremendous damage.”

“The good news is that knowing what the problem is, we can think about ways to solve it,” he added. “This kinked amino acid is where we want to look.”

The research offers clues to pharmaceutical companies, which could develop ways to prevent formation of the kink or get the repair enzyme to work better; or by designing a cap that would prevent fibrils from growing.

Clarke said beta amyloid and a much larger protein tau — with more than 750 amino acids — make a devastating one-two punch that forms fibrils and spreads them to many neurons throughout the brain. All humans have both beta amyloid and tau. Researchers say it appears that beta amyloid produces fibrils that can lead to tau aggregates, which can spread the toxicity to other brain cells. However, exactly how beta amyloid and tau work together to kill neurons is not yet known.

In this study, Warmack produced crystals, both the normal and kinked types, in 15 of beta amyloid’s amino acids. She used a modified type of cryo-electron microscopy to analyze the crystals. Cryo-electron microscopy, whose development won its creators the 2017 Nobel Prize in chemistry, enables scientists to see large biomolecules in extraordinary detail. Professor Tamir Gonen pioneered the modified microscopy, called microcrystal electron diffraction, which enables scientists to study biomolecules of any size.

Eisenberg is UCLA’s Paul D. Boyer Professor of Molecular Biology and a Howard Hughes Medical Institute investigator. Other researchers are co-author Gonen, a professor of biological chemistry and physiology at the UCLA David Geffen School of Medicine and a Howard Hughes Medical Institute investigator; and Jose Rodriguez, assistant professor of chemistry and biochemistry who holds the Howard Reiss Career Development Chair.

The research was funded by the National Science Foundation, National Institutes of Health, Howard Hughes Medical Institute, and the UCLA Longevity Center’s Elizabeth and Thomas Plott Chair in Gerontology, which Clarke held for five years.

This article originally appeared in the UCLA Newsroom.