Tag Archives: stents

‘Superhemophobic’ medical implants

Counterintuitively, repelling blood is the concept behind a new type of medical implant according to a Jan. 18, 2017 news item on ScienceDaily,

Medical implants like stents, catheters and tubing introduce risk for blood clotting and infection — a perpetual problem for many patients.

Colorado State University engineers offer a potential solution: A specially grown, “superhemophobic” titanium surface that’s extremely repellent to blood. The material could form the basis for surgical implants with lower risk of rejection by the body.

Blood, plasma and water droplets beading on a superomniphobic surface. CSU researchers have created a superhemophobic titanium surface, repellent to blood, that has potential applications for biocompatible medical devices. Courtesy: Colorado State University

A Jan. 18, 2017 Colorado State University news release by Anne Ju Manning, which originated the news item, explains more,

t’s an outside-the-box innovation achieved at the intersection of two disciplines: biomedical engineering and materials science. The work, recently published in Advanced Healthcare Materials, is a collaboration between the labs of Arun Kota, assistant professor of mechanical engineering and biomedical engineering; and Ketul Popat, associate professor in the same departments.

Kota, an expert in novel, “superomniphobic” materials that repel virtually any liquid, joined forces with Popat, an innovator in tissue engineering and bio-compatible materials. Starting with sheets of titanium, commonly used for medical devices, their labs grew chemically altered surfaces that act as perfect barriers between the titanium and blood. Their teams conducted experiments showing very low levels of platelet adhesion, a biological process that leads to blood clotting and eventual rejection of a foreign material.

Chemical compatibility

A material “phobic” (repellent) to blood might seem counterintuitive, the researchers say, as often biomedical scientists use materials “philic” (with affinity) to blood to make them biologically compatible. “What we are doing is the exact opposite,” Kota said. “We are taking a material that blood hates to come in contact with, in order to make it compatible with blood.” The key innovation is that the surface is so repellent, that blood is tricked into believing there’s virtually no foreign material there at all.

The undesirable interaction of blood with foreign materials is an ongoing problem in medical research, Popat said. Over time, stents can form clots, obstructions, and lead to heart attacks or embolisms. Often patients need blood-thinning medications for the rest of their lives – and the drugs aren’t foolproof.

“The reason blood clots is because it finds cells in the blood to go to and attach,” Popat said. “Normally, blood flows in vessels. If we can design materials where blood barely contacts the surface, there is virtually no chance of clotting, which is a coordinated set of events. Here, we’re targeting the prevention of the first set of events.”

nanotubes

Fluorinated nanotubes provided the best superhemophobic surface in the researchers’ experiments.

The researchers analyzed variations of titanium surfaces, including different textures and chemistries, and they compared the extent of platelet adhesion and activation. Fluorinated nanotubes offered the best protection against clotting, and they plan to conduct follow-up experiments.

Growing a surface and testing it in the lab is only the beginning, the researchers say. They want to continue examining other clotting factors, and eventually, to test real medical devices.

Here’s a link to and a citation for the paper,

Hemocompatibility of Superhemophobic Titania Surfaces by Sanli Movafaghi, Victoria Leszczak, Wei Wang, Jonathan A. Sorkin, Lakshmi P. Dasi, Ketul C. Popat, and Arun K. Kota. Advanced Healthcare Materials DOI: 10.1002/adhm.201600717 Version of Record online: 21 DEC 2016

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Brains in the US Congress

Tomorrow, May 24, 2012, Jean Paul Allain, associate professor of nuclear engineering at Purdue University (Illinois) will be speaking to members of the US Congress about repairing brain injuries using nanotechnology-enabled bioactive coatings for stents. From the May 21, 2012 news item on Nanowerk,

“Stents coated with a bioactive coating might be inserted at the site of an aneurism to help heal the inside lining of the blood vessel,” said Jean Paul Allain, an associate professor of nuclear engineering. “Aneurisms are saclike bulges in blood vessels caused by weakening of artery walls. We’re talking about using a regenerative approach, attracting cells to reconstruct the arterial wall.”

He will speak before Congress on Thursday (May 24) during the first Brain Mapping Day to discuss the promise of nanotechnology in treating brain injury and disease.

The May 21, 2012 news release (by Emil Venere) for Purdue University offers insight into some of the difficulties of dealing with aneurysms using today’s technologies,

Currently, aneurisms are treated either by performing brain surgery, opening the skull and clipping the sac, or by inserting a catheter through an artery into the brain and implanting a metallic coil into the balloon-like sac.

Both procedures risk major complications, including massive bleeding or the formation of potentially fatal blood clots.

“The survival rate is about 50/50 or worse, and those who do survive could be impaired,” said Allain, who holds a courtesy appointment with materials engineering and is affiliated with the Birck Nanotechnology Center in Purdue’s Discovery Park.

Allain goes on to explain how his team’s research addresses these issues (from the May 21, 2012 Purdue University news release),

Cells needed to repair blood vessels are influenced by both the surface texture – features such as bumps and irregular shapes as tiny as 10 nanometers wide – as well as the surface chemistry of the stent materials.

“We are learning how to regulate cell proliferation and growth by tailoring both the function of surface chemistry and topology,” Allain said. “There is correlation between surface chemistry and how cells send signals back and forth for proliferation. So the surface needs to be tailored to promote regenerative healing.”

The facility being used to irradiate the stents – the Radiation Surface Science and Engineering Laboratory in Purdue’s School of Nuclear Engineering – also is used for work aimed at developing linings for experimental nuclear fusion reactors for power generation.

Irradiating materials with the ion beams causes surface features to “self-organize” and also influences the surface chemistry, Allain said.

The stents are made of nonmagnetic materials, such as stainless steel and an alloy of nickel and titanium. Only a certain part of the stents is rendered magnetic to precisely direct the proliferation of cells to repair a blood vessel where it begins bulging to form the aneurism.

Researchers will study the stents using blood from pigs during the first phase in collaboration with the Walter Reed National Military Medical Center.

The stent coating’s surface is “functionalized” so that it interacts properly with the blood-vessel tissue. Some of the cells are magnetic naturally, and “magnetic nanoparticles” would be injected into the bloodstream to speed tissue regeneration. Researchers also are aiming to engineer the stents so that they show up in medical imaging to reveal how the coatings hold up in the bloodstream.

The research is led by Allain and co-principal investigator Lisa Reece of the Birck Nanotechnology Center. This effort has spawned new collaborations with researchers around the world including those at Universidad de Antioquía, University of Queensland. The research also involves doctoral students Ravi Kempaiah and Emily Walker.

The work is funded with a three-year, $1.5 million grant from the U.S. Army. Cells needed to repair blood vessels are influenced by both the surface texture – features such as bumps and irregular shapes as tiny as 10 nanometers wide – as well as the surface chemistry of the stent materials.

As I find the international flavour to the pursuit of science quite engaging, I want to highlight this bit in the May 21, 2012 news item on Nanowerk which mentions a few other collaborators on this project,

Purdue researchers are working with Col. Rocco Armonda, Dr. Teodoro Tigno and other neurosurgeons at Walter Reed National Military Medical Center in Bethesda, Md. Collaborations also are planned with research scientists from the University of Queensland in Australia, Universidad de Antioquía and Universidad de Los Andes, both in Colombia.

The US Congress is not the only place to hear about this work, Allain will also be speaking in Toronto at the 9th Annual World Congress of Society for Brain Mapping & Therapeutics (SBMT) being held June 2 – 4, 2012.