An illuminating possibility for the treatment of stroke: nano-photosynthesis


Blocked blood vessels in the brains of stroke patients prevent oxygen-rich blood from reaching cells, causing serious damage. Plants and some microbes produce oxygen through photosynthesis. What if there was a way to get photosynthesis to happen in patients’ brains? Now researchers report in ACS ‘ Nano Letters did just that in cells and in mice, using blue-green algae and special nanoparticles, in a proof-of-concept demonstration.

Stroke kills 5 million people around the world each year, according to the World Health Organization. Millions more survive, but they often suffer from disabilities, such as difficulty speaking, swallowing or remembering. The most common cause is blockage of blood vessels in the brain, and the best way to prevent permanent brain damage from this type of stroke is to dissolve or surgically remove the blockage as soon as possible. However, these options only work in a narrow window of time after the stroke and can be risky. Blue-green algae, such as Synechococcus elongatus, have been studied previously to treat oxygen deficiency in heart tissue and tumors by photosynthesis. But the visible light needed to trigger microbes cannot penetrate the skull, and although near infrared light can pass through, it is insufficient to directly fuel photosynthesis. “Upconverting” nanoparticles, often used for imaging, can absorb near infrared photons and emit visible light. So Lin Wang, Zheng Wang, Guobin Wang and their colleagues at Huazhong University of Science and Technology wanted to see if they could develop a new approach that could one day be used for stroke patients by combining these elements – S. elongatus, nanoparticles and near infrared light – in a new “nano-photosynthetic” system.

The researchers paired S. elongatus with up-converting neodymium nanoparticles that transform near infrared light penetrating tissue into a visible wavelength that microbes can use for photosynthesis. In a study of cells, they found that the nano-photosynthesis approach reduced the number of neurons that died after oxygen and glucose deprivation. They then injected the microbes and nanoparticles into mice with blocked brain arteries and exposed the mice to near infrared light. The therapy reduced the number of dying neurons, improved the animals’ motor function, and even helped new blood vessels to grow. Although this treatment is still in the animal testing stage, it promises to one day advance towards clinical trials in humans, according to the researchers.

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The authors acknowledge funding from China’s National Basic Research Program, the National Natural Science Foundation of China, the science and technology program of the Chinese Ministry of Education, the major science and technology innovation projects in Hubei province and the common fund of the Ministry of Education for preliminary research on equipment.

The article summary will be available on May 19 at 8 a.m. EST here: http: // pubs.acs.org /do I/abs /ten.1021 /acs.nanolett.1c00719.

The American Chemical Society (ACS) is a nonprofit organization accredited by the United States Congress. ACS’s mission is to advance the broader chemistry business and its practitioners for the benefit of the Earth and all of its inhabitants. The Company is a world leader in promoting excellence in science education and access to chemistry-related information and research through its multiple research solutions, peer-reviewed journals reading, scientific lectures, electronic books and weekly periodical. Chemistry and Engineering News. ACS journals are among the most cited, trusted, and widely read in the scientific literature; however, ACS itself does not conduct chemical research. As a leader in scientific information solutions, its CAS division partners with global innovators to accelerate breakthroughs by conserving, connecting and analyzing global scientific knowledge. The main offices of ACS are in Washington, DC, and Columbus, Ohio.

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