How SSG Solved a Dangerous MedTech Coating Issue

At Surface Solutions Group, we came up with an answer for a medical device coatings issue that had puzzled the industry.

Pure polytetrafluoroethylene (PTFE) coatings for decades were the “gold standard” for coating guidewires and related products, with unmatched low friction coefficient.

But then the EPA required that manufacturers eliminate perfluorooctanoic acid (PFOA) from their PTFE formulations by 2015. The move, meant to answer cancer concerns, also appears to be related to a series of recalls involving flaking coatings.

The FDA over the past six months has announced Class I designations involving coated guidewire recalls at Medtronic (245 lot numbers) and Medline (3 lot numbers).

On April 1, Covidien issued a voluntary recall of 650 of its Pipeline embolization devices and Alligator retrieval devices after internal testing revealed coating delamination. In a communication to customers, Covidien noted that, “Delamination of the PTFE coating could potentially lead to embolic occlusion in the cerebral vasculature with the risk of stroke and/or death.”

The FDA itself now says: “There is a potential for PTFE (polytetrafluoroethylene) coating to delaminate and detach from guidewires. … Uses of this recalled product may result in serious adverse health consequences.”

The delamination problem is taking place around the same time as the reduction and eventual elimination of PFOA, which as a surfactant was thought to enhance adhesion in water-based PTFE formulations.

It is also worth noting that medical device manufacturers have starting to require saline soak testing performed at coating facilities, after reports of “green flakes” in an operating room when PTFE coated guidewires were immersed in a saline soak tank prior to an intravascular procedure. The PTFE coating process, in the past, may have been less sensitive to saline, but not anymore.

The reflex reaction for some device engineers has been to turn to resin-bonded PTFE coatings that have better adhesion to most surfaces. Many coating manufacturers also make these coatings that contain PTFE, but that is where the similarity ends.

The resin-bonded coatings are tough, tenacious, and abrasion resistant, but they have neither the extremely low friction nor flexibility pure PTFE coatings. Plus, they have limited elongation.

However, Surface Solutions Group (SSG) of Chicago has discovered that by using new stringent surface preparation techniques and adjusting how the coating is applied makes the problem go away. The new coatings adhere as well as the old ones did.

Applying low-friction films to biomedical products-from stainless steel, titanium, nitinol, and even plastic or glass-has been our exclusive focus. For the guidewire problem, we were able to bond pure PTFE-containing no PFOA-so tenaciously that delamination is eliminated, even after saline exposure, tape test, mandrel wrap test, and cross hatch/ boil and fingernail tests.

This is how the process works:

The wire surface is hypercleaned, and then the coating is applied in a controlled environment, using a robotic system to keep precise control of all the physical parameters (pressure, feed rate, and electrostatic level) in the spray system so that only an exact amount of coating is deposited to the wire. Finally, every individual part can be saline and tape tested, per the OEM’s requirements, if necessary.

Both patient and physician benefit from the SSG breakthrough. The patient benefits from the improved safety of guidewires that won’t delaminate. The physician benefits from guidewires that, once again, deliver the smooth tactile “feel” that he counted on from wires that were coated with the original gold standard coating.