A novel surface treatment could reduce the risk of hospital and clinic infections from “superbugs”.
Such infections affect some 1.7m Americans annually, resulting in nearly 100,000 deaths from infection-related complications and roughly $30bn in direct medical costs. But the new treatment, developed by a University of California Los Angeles (UCLA)-led team of scientists ,could reduce the risk of these infections, and ease the economic burden on the healthcare system.
The biggest culprits responsible for the complications, accounting for two-thirds of these infections, are medical devices like catheters, stents, heart valves and pacemakers, whose surfaces often become covered with harmful bacterial films.
The new approach, tested in both laboratory and clinical settings, involves depositing a thin layer of what is known as zwitterionic material on the surface of a device and permanently binding that layer to the underlying substrate using ultraviolet light irradiation. The resulting barrier prevents bacteria and other potentially harmful organic materials from adhering to the surface and causing infection.
The team’s findings are published in the journal Advanced Materials.
In the laboratory, the researchers applied the surface treatment to several commonly used medical device materials, then tested the modified materials’ resistance to various types of bacteria, fungi and proteins. They found that the treatment reduced biofilm growth by more than 80% – and in some cases up 93%, depending on the microbial strain.
“The modified surfaces exhibited robust resistance against micro-organisms and proteins, which is precisely what we sought to achieve,” said Dr Richard Kaner, UCLA, Professor of Materials Innovation and senior author of the research. “The surfaces greatly reduced or even prevented biofilm formation. And our early clinical results have been outstanding.”
The clinical research involved 16 long-term urinary catheter users who switched to silicone catheters with the new zwitterionic surface treatment. This modified catheter is the first product made by a company Kaner founded out of his lab, called SILQ Technologies Corp, and has been cleared for use in patients by the US Food and Drug Administration (FDA).
Ten of the patients described their urinary tract condition using the surface-treated catheter as “much better” or “very much better”, and 13 chose to continue using the new catheter over conventional latex and silicone options after the study period ended.
“One patient came to UCLA a few weeks ago to thank us for changing her life – something that, as a materials scientist, I never thought was possible,” Kaner said.
“Her previous catheters would become blocked after four days or so. She was in pain and needed repeated medical procedures to replace them. With our surface treatment, she now comes in every three weeks, and her catheters work perfectly without encrustation or occlusion, a common occurrence with her previous ones.”
Such catheter-related urinary tract problems are illustrative of the issues plaguing other medical devices, which, once inserted or implanted, can become breeding grounds for bacteria and harmful biofilm growth, said Kaner, a member of the California NanoSystems Institute at UCLA, who is also a distinguished professor of chemistry and biochemistry, and of materials science and engineering. The pathogenic cells pumped out by these highly resilient biofilms then cause recurring infections in the body.
In response, medical staff routinely give strong antibiotics to patients using these devices, a short-term fix that poses a longer-term risk of creating life-threatening, antibiotic-resistant “superbug” infections. The more widely and frequently antibiotics are prescribed, Kaner said, the more likely bacteria are to develop resistance to them.
“The beauty of this technology,” Kaner said, “is that it can prevent or minimise the growth of biofilm without the use of antibiotics. It protects patients using medical devices, and therefore protects all of us against microbial resistance and the proliferation of superbugs.”
The surface treatment’s zwitterion polymers are extremely biocompatible, and absorb water very tightly, forming a thin hydration barrier that prevents bacteria, fungi and other organic materials from adhering to surfaces, Kaner said. The technology is highly effective, non-toxic and relatively low in cost compared with other current surface treatments for medical devices, like antibiotic- or silver- infused coatings.
Study details
A Readily Scalable, Clinically Demonstrated, Antibiofouling Zwitterionic Surface Treatment for Implantable Medical Devices.
Brian McVerry, Alexandra Polasko, Ethan Rao, Reihaneh Haghniaz, Dayong Chen, Na He, Pia Ramos, Joel Hayashi, Paige Curson, Chueh‐Yu Wu, Praveen Bandaru, Mackenzie Anderson, Brandon Bui, Aref Sayegh, Shaily Mahendra, Dino Di Carlo, Evgeniy Kreydin, Ali Khademhosseini, Amir Sheikhi, Richard B. Kaner.
Published in Advanced Materials on 22 March 2022
Abstract
Unlike growth on tissue, microbes can grow freely on implantable devices with minimal immune system intervention and often form resilient biofilms that continuously pump out pathogenic cells. The efficacy of antibiotics used to treat infection is declining due to increased rates of pathogenic resistance. A simple, one-step zwitterionic surface modification is developed to significantly reduce protein and microbial adhesion to synthetic materials and demonstrate the successful modification of several clinically relevant materials, including recalcitrant materials such as elastomeric polydimethylsiloxane. The treated surfaces exhibit robust adhesion resistance against proteins and microorganisms in both static and flow conditions. Furthermore, the surface treatment prevents the adhesion of mammalian fibroblast cells while displaying no cytotoxicity. To demonstrate the clinical efficacy of the novel technology in the real-world, a surface-treated, commercial silicone foley catheter is developed that is cleared for use by the U.S. Food and Drug Administration (K192034). 16 long-term catheterised patients received surface-treated catheters and completed a Patient Global Impression of Improvement (PGI-I) questionnaire. 10 out of 16 patients described their urinary tract condition post implantation as “much better” or “very much better” and 72% (n = 13) of patients desire to continue using the surface-treated catheter over conventional latex or silicone catheters.
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