Coatings & surface treatment
environments. These creatures use mechanisms to actively push away water from surfaces, enabling strong bonds to form. Inspired by these natural strategies, the MIT team designed a dry-crosslinking adhesive to mimic the approach. It removes water from wet tissues at the interface, allowing a secure bond to form even in moist conditions. The MIT hydrogel adhesive rapidly absorbs fluid from body tissues using polyacrylic acid, an absorbent material used in nappies. Once the water is cleared, chemical groups called NHS esters from the acid form strong bonds with proteins at the tissue surface in a matter of seconds.
Double and single-sided tapes made with this bioadhesive were initially intended for surgical incisions and internal injuries. However, Zhao and his colleagues were curious about how it could be applied to implants. “I wondered whether the conformal and robust adhesion could prevent fibrosis on the implant-tissue interfaces,” Zhao explains. The team’s research changed direction – they began to apply the bioadhesive to medical implants to see if it could mitigate fibrous capsule formation. The team’s adhesive employs a dual strategy to stop scarring in its tracks, Zhao reveals.
Double action
For one, the MIT hydrogel prevents scar tissue formation by reducing protein absorption on the
implant’s surface. Additionally, micromotion – tiny movements between the implant and surrounding tissue – can activate inflammation and scarring. The MIT hydrogel forms a tight bond with tissues, stabilising the interface and minimising mechanical forces that could provoke an immune response. “The adhesion reduces and delays protein absorption on the interfaces and prevents any relative micromotion between the implant and the tissue,” Zhao explains. “Overall, this dramatically reduces immune cell infiltration to the interfaces.” Zhao’s team demonstrated the hydrogel’s effectiveness in animal models, as detailed in a study published in Nature in June 2024. Coating polyurethane devices with the adhesive, the scientists implanted them onto the abdominal wall, colon, stomach, lung or heart of rats. Weeks later, the devices were removed with no visible scar tissue. Tests in other animals, including humanised mice and pigs, yielded similar results: no fibrosis for the three-month experiment. To analyse the animals’ immune response, the researchers used bulk RNA sequencing and fluorescent imaging. Results showed that when devices with the MIT adhesive coating were first implanted, immune cells did begin to infiltrate the area. But the immune attack was quickly quelled before any scar tissue formed.
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www.parylene.co.uk +353 91 780 300 Curtiss-Wright, Surface Technologies Division, Parkmore Business Campus, Parkmore West, Galway, Ireland Medical Device Developments /
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