At first glance, the Nam Jeong Cho’s lab at Nanyang Technology University in Singapore looks like a typical research facility. However, the orange-yellow stains in the lab suggest that the coat stains that were hanging on the hooks suggest a lesser subject under study.
The powdery stain is pollen. Microscopic granules containing male germ cells, where trees, weeds and grasses are released seasonally. However, Cho has not studied the troublesome effects of hay, such as the fever, or the meaning of pollen for the plants that make it. Instead, materials scientists spent a decade of pioneering and sophisticated techniques remodeling the hard outer shell of pollen. Because it is made of polymer, it is sometimes called “the diamond of the plant world.”
Cho believes that this microgel can become a versatile building block for many environmentally friendly materials, such as paper, film, and sponge.
Many people think about pollen. If you’re not fertilizing your plants or feeding insects, you think they’re useless dust, but if you know how to handle them, there are valuable applications, says Cho. He is not the only scientist who thinks that. Noemi Csaba, a nanotechnology and drug industry researcher at Santiago de Compostela University in Spain, wants to develop a concave pollen shell into a protective vehicle to deliver drugs to the gaze, lungs and stomach.
Csaba said researchers studying the utility of pollen for people are a rare variety. “It’s a bit surprising,” she says. “Pollen is a very interesting biomaterial.”
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Softens the shell
To begin working with pollen, scientists can remove the sticky coating around the grain in a process called scratching. Depriving these lipids and allergic proteins is the first step in creating empty capsules for drug delivery that CSABA seeks. But beyond that, the seemingly inexplicable shell of pollen (comprised of the biopolymer sporopollenin) has long baffled researchers and limited their use.
When the breakthrough occurred in 2020, Cho and his team reported that incubating pollen with an alkaline solution of potassium hydroxide at 80 degrees Celsius (176 degrees Fahrenheit) significantly altered the surface chemistry of pollen grains, allowing them to easily absorb and maintain water.
The resulting pollen is just as flexible as Play-Doh, says Shahrudin Ibrahim, a researcher at Cho’s Lab who helped develop The The. Before treatment, pollen grains are like marble. It is hard, inert and hardly reacts. The particles are then very soft and easily applied, forming a more complex structure. This opens up many applications and proudly lifts a vial of yellow brown slashes into the lab, Ibrahim says.
When thrown into a flat mold and dried, the microgels gather on paper or film depending on the final thickness, making them strong and flexible. It is also sensitive to external stimuli such as changes in pH and humidity. Exposure to alkaline solutions causes the constituent polymers of pollen to become more hydrophilic or water-friendly, so depending on the conditions, the absorption or draining of water causes the gel to expand or contract, Ibrahim explains.
Researchers in Singapore believe this property’s victory combination makes pollen-based films the prospects of many future applications. A smart actuator that allows devices to detect and respond to changes around the environment, and wearable health trackers monitor cardiac signals. Additionally, pollen is naturally protected by UV rays, which could replace certain optoelectronic substrates in perovskite solar cells and other optoelectronic devices.
Cho’s Lab has also demonstrated that it can print paper made from pollen. According to Cho, who has patented Microgel’s production process, it could be a sustainable alternative to traditional paper for writing, printing and packaging. Traditional paper manufacturing destroys wood, is resource intensive, and requires up to 13 liters of water for every page created. Pollen is naturally released in large quantities from seed-producing plants, and deriving paper from it only requires a few simple steps. Ink can be removed with a simple alkaline solution wash. This is a process that allows you to reuse paper.
Additionally, freeze-dried pollen microgels form porous sponges. These can be used to form scaffolds for tissue engineering, or to prevent bleeding or to absorb oil spills.
Cho’s team usually works with Sunflowers and Camellia pollen, which buy cheaply as honeybee pollen mixtures, mainly from China. However, they say their alkaline hydrolysis methods work well over a wide range of plant species. Pollen is abundant, Cho adds – for example, a single flower of a common sunflower produces between 25,000 and 67,000 grains each summer. Plus, it’s easy to collect from bees in a commercial hive.
Pollen-based products have some way to do this before they reach the market, Ibrahim adds. The key to the present is to predict challenges and devise sustainable solutions. Along with other biomaterials, researchers are working on chitosan and cellulose. You need to destroy the crustaceans or trees. In comparison, pollen is rather resource intensive. “We’re not destroying plants,” he says. “We’re not destroying the flowers.”
This article originally appeared in Knowable Magazine, a non-commercial publication dedicated to making scientific knowledge accessible to everyone. Sign up for our Knowable Magazine newsletter.
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