The human body is designed to rid itself of foreign materials. That makes medical implants, which often need to have a useful life in the body that's measured in decades, a pernicious challenge for industry. The business is littered with examples of implant or treatment device surfaces or coatings that have later proven to cause problems for patients.
Coatings and surfaces that take advantage of nanoscale technology have been proven useful in myriad ways, include working to deliberately manipulate the immune system as well as to promote better and more specialized kinds of bone and tissue growth.
Major companies, such as Medtronic plc and Smith & Nephew plc each sell at least one device that incorporates nanotechnology. The former markets a nonstick nanocoating on its Ligasure laparoscopic surgical sealer, while the latter sells the Acticoat antimicrobial dressing that incorporates bactericidal concentrations of silver with nanocrystalline technology. Neither company deigned to comment on their own interests regarding the future of nanotech.
FDA also has been approving novel efforts on this front. But even as academic researchers remain enamored of nanotech-friendly materials such as graphene, much of the science has yet to be adopted by industry.
The technical definition of nanotech relates specifically to alterations at smaller than 100 nanometers. Just to put that in context, DNA is about two nanometers wide and a sheet of paper is around 100,000 nanometers thick. The size of one nanometer to a meter is akin to a comparison of the size of a marble as compared to Earth.
More biology in implants
Basic bioscience observations behind the fact that smooth implants are typically harder on the body have been around for a long time. Many kinds of companies, ranging from dental to breast implants, have started non-specifically roughening or even nanotexturing their implants, but they may not be particularly scientific or systematic in how they are doing it.
That could be, at least in part, because of the lack of sophisticated biological knowledge in product development teams, who are routinely dominated by engineers. Orthopedics implant startups, however, seem to be leading the way when it comes to scientific exploration of the implications of nanoscale surfaces.
"Companies that have a predominantly engineering focused development pathway, certainly aren't in the position to take advantage of blending the engineering and the biologic sciences," Nanovis CEO Matt Hedrick told BioWorld MedTech. "The potential for a large company that actually implements a careful and capable strategy on the nanosurface side is very high."
He noted the recent moves by Medtronics into robotics and image guidance, for example through its spine partnership with Israeli startup Mazor Robotics, as well as Medtronic's existing commitment to biological sales, particularly with its Infuse bone graft product. Hedrick sees these as signs that sophistication about biology isn't foreign to the company – and that it may eventually be open to nanotexturing its implants.
"Whichever of the major companies that puts together the right surface strategy that's rooted in good science – it is a long-term strategy for growth. By layering up multiple surfaces they stand a good chance of differentiating in the market for a five- or 10-year period or creating another way to compete with this type of a science driven strategy," added Hedrick.
An early go-ahead
Nanovis gained FDA clearance in March for its Forticore transforaminal lumbar interbody fusion (TLIF) and posterior lumbar interbody fusion (PLIF) interbodies that have a nanosurface-enhanced, deeply porous titanium scaffold intermolded with a polyether ether ketone (PEEK) core. The Carmel, Ind.-based startup prides itself on layering its implants surfaces based on the latest science.
"The nanosurface in and of itself should be integrated as part of an overall surface or fixation strategy. Our objective is to reduce fixation-related complications. So, we've developed our interbodies and other implants with layered, optimized surface strategies at each layer," said Hedrick.
"So, our interbodies have that deeply porous, interconnected standpoint, so it's a great design for bone in-growth. It's made of titanium, which is a great material. So, you pick a good material, you make a micro or macro porosity to encourage bone or soft tissue growth, it depends on what you're trying to accomplish," he continued. "Then you put a very specific nanosurface on it to try to encourage that endpoint. People can put a nanosurface on other things and improve it, but we think that the best strategy will be to layer up very carefully tailored surfaces at each size/scale to optimize the kind of clinical benefit that they are trying to design into the implant."
The newly cleared implants incorporate a specifically designed nanotech surface, as well as precise surfaces on a larger scale, to reduce fixation-related complications such as loosening. Nanovis is also developing a next-generation iteration that aims to incorporate that benefit, as well as to offer an antibacterial component to kill microbes that could cause infection via nanotech surfacing.
Hedrick noted that surgeons are intrigued by the idea of using implants that incorporate a scientific approach to surfaces, which they see as cutting edge. "They're certainly interested in being at the forefront of new technology. Nanotechnology has been kind of working its way here for a while. They're excited to be on the cutting edge of a next-generation surface, not just a simple kind of random roughness that most of the other things out there have been," he said.
But a lack of momentum has plagued the incorporation of scientifically driven nanotech surfaces into orthopedic implants, caused not only by the lack of involvement of biology-oriented scientists with the engineering staff, as well as concerns about pushing claims so far that a PMA approval pathway would be required rather than the 510(k) process that is common for orthopedic implants, he argued.
Another startup, Vallum Corp., recently garnered an FDA clearance for a PEEK spinal interbody fusion device with a nanotextured surface. Its nanosurface is specifically designed to encourage bone growth. (See BioWorld MedTech, July 19, 2018.)
PEEK can repel cells, but the nanotextured PEEK plus surface from the Nashua, N.H.-based startup is designed to attract osteoblasts that become bone, thereby potentially strengthening results for patients having the spinal fusion procedure.
"Nanotechnology is a relatively new science, as sciences go. But there's been a tremendous amount of work done in terms of what happens with the nanoscale in terms of osteoblasts and that work has been ongoing for the last 12 to 13 years," Vallum President and CEO Stephen Blinn told BioWorld MedTech. "So, there's a tremendous amount of peer-reviewed literature – not just on PEEK, but on titanium surfaces, on other kinds of polished surfaces, on other types of metals. And the end result is always the same if you affect the surface of the nanoscale."