Novel Hydrogel Helps Relieve Rheumatoid Arthritis

A new hydrogel that is responsive to nitric oxide (NO) could help treat rheumatoid arthritis by absorbing synovial liquid, according to a new study.

Developed by researchers at Pohang University of Science and Technology (POSTECH; Republic of Korea), the hydrogel rapidly swells in response to NO, and is subsequently converted to an enzyme-responsive gel by cascade reactions. The hydrogel consists of polyacrylamide and a cross-linking agent (NOCCL), which forms net-like connections between the acrylamide molecules. When the hydrogel and NO meet, the gaps in the polyacrylamide open and water flows in, increasing the mass by more than three times.


The same effect can be used to enable the hydrogel to release drug molecules while absorbing liquids. As synovial fluid enters the gel, it can push the drugs out to maximize the therapeutic effect. According to the researchers, the NO-responsive hydrogel could be used not only as the basis for a drug-delivery system for inflammation modulators, but as a potential tissue scaffold as well. The study was published on October 11, 2017, in Advanced Materials.

“Nitric oxide is like a double-edge sword; it regulates inflammation and protects our body by killing external pathogens,” said senior author Professor Won Jong Kim, PhD, of the POSTECH center for self-assembly and complexity. “However, when in excess, it is toxic and may cause rheumatoid arthritis, as well as other autoimmune diseases, cardiovascular diseases, and cancer.”

NO is a ubiquitous signaling molecule produced through the metabolism of L-arginine by nitric oxide synthases. Its formation is crucial for the control of blood pressure, blood flow, and other vital bodily functions; amongst these, it is an important antioxidant, and a regulator of intermediary metabolism and cellular energy production by mitochondria. But in rheumatoid arthritis, the immune system mistakenly attacks healthy joint tissue via macrophages, which release NO into the inflamed joints.

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