Coatings & surface treatment
NO stored in micro-pores
On contact with moisture, NO is released from surface
The mechanism of action of nitric oxide device coatings and its interaction with the human body.
Vasodilated artery
NO: ■
Porous material (MOF) is incorporated into the devices to allow safe storage/release of NO
Device containing NO loaded MOF/ polymer matrix
The challenge to these types of coatings, however, is that bacteria are increasingly becoming resistant to antibiotics. Not to mention that not all coatings are suitable for every device, and in the case of silver coatings, they can also run the risk of elements leaking into the body. Melissa Reynolds, Boettcher investigator and chemistry professor at Colorado State University (CSU), knows the complications of implant infections all too well; having been diagnosed with hydrocephalus as a child, she has had to have her shunt replaced multiple times due to bacteria and infections. She puts this as an undoubted influence behind her interest in the subject and her work on creating materials that interact better with the body for longer-lasting medical devices. “To address infection, current medical devices, either release some type of antibiotic or they can release some other type of silver or other type of species that will interrupt or kill bacteria on the surface,” she explains. Reynolds also points to recent work on hydrophilic coatings that cause bacteria to almost “bounce” off the surface.
Fighting infection With this in mind, researchers have been investigating different coatings that could prevent and fight infection. In a joint effort between researchers at CSU and the University of St Andrews in Scotland, they combined their metal-organic frameworks to develop a flexible antimicrobial material that slowly releases nitric oxide into the body. “We were interested in how we could mimic what the body does to produce nitric oxide in the right amounts so that we could use it for beneficial things,” explains Russell E Morris, Bishop Wardlaw professor, School of Chemistry, University of St Andrews.
Medical Device Developments /
www.nsmedicaldevices.com
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relaxes smooth muscle lining of the arteries
prevents thrombosis kills bacteria
Nitric oxide offers several benefits to the body, including controlling blood pressure by relaxing blood vessels, preventing blood clots inside blood vessels and is the first line of defence against bacteria. “If you cut yourself, one of the first things the body does is produce some nitric oxide to kill the bacteria,” Morris continues. “So, we’ve been looking at various different ways of either storing and delivering or producing nitric oxide from actual materials for medical devices, whether it be dressing on wounds or catheters that go into the bloodstream.” While some of these are short-term, longer-lasting medical devices such as indwelling catheters or surfaces that might attract bacteria could benefit from this material.
At CSU, Reynolds and her students discovered that they could prevent bacteria from sticking to surfaces over a prolonged period of time through a metal- organic framework technology that could be an additive for medical devices. “Unlike drug-eluding coatings where eventually the drug runs out because it has to be eluted to have it in effect, ours just keeps on going,” she adds. By combining the research from both universities, both teams have combined their two frameworks to create a single thin-filmed membrane that can release nitric oxide slowly over an extended period and have long-term NO generation from the catalytic MOF. This collaboration was published in ACS Applied Materials & Interfaces, ‘Mixed Metal-Organic Framework Mixed-Matrix Membranes: Insights into Simultaneous Moisture-Triggered and Catalytic Delivery of Nitric Oxide using Cryo-scanning Electron Microscopy’, with both Reynolds and Morris authors on the paper.
MOFs (metal-organic frameworks), as detailed in the paper, are porous polymers that Morris
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USTAN Technology
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