How are you influencing implantable
devices?
Gabriel O. Adusei, MSc, PhD
Independent MedTech Consultant, Founder, International Association of MedTech Consultants
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Over the years, a significant number of implantable devices since their
introduction into the market have seen changes from being inert to being
bioactive to iterative developments to enhance their efficacy. One area with
significant growth and success is the use of hydroxyapatite (HA) and amorphous
calcium phosphate nanoparticles in implantology. Many modern implants (e.g.,
hip replacements and dental implants) are coated with hydroxyapatite. It has
been suggested that this may promote osseointegration. The application of
nanostructured titanium with nanocrystalline bioactive hydroxyapatite coatings
has offered many biocompatibility benefits. For example, nanotubular structured
titanium (Ti) substrates coated with nanoparticulate hydroxyapatite (nano-HA)
offers a surface that promotes osteoblast cell adhesion and is particularly
suitable for orthopedic and dental implants where deposition of osteoblasts and
other proteins is important in bone formation. This enhances device-tissue
integration. HA nanoparticles can be produced by a process such as sol-gel and
plasma spray techniques, chemical and vapour deposition including discrete
crystalline deposition (DCD) among a number other methods; however, factors
such as the crystallinity, nano-particle size and shape(s) influence the
surface area as well as resultant strength if they are to be as stress-bearing
composites or as part of drug-release system.
Joe
Pustka
Medical Device Leak Testing Technical Support Manager, Uson
Uson has helped manufacturers to leak test nearly every type of implantable
medical device used today. Initially, it was quite common for our team to tell
design engineers to go back to the drawing board. The problem had been, and
still sometimes is, that in totally sealed components, there is no air gap when
there needs to be. Adding a free volume of air into such a sealed part will
allow a gross leak to be detected. Sometimes, and
especially if the overall size of the part is very small and the acceptable
leak rate is comparably small, an alternate approach is to re-design processes
to perform leak testing of subassemblies.
Uson’s message to any developer of an
implantable device is short and to the point. It is never too early to get your
supplier of test equipment involved in helping to design your process and the
device itself. If you are dealing with a test equipment supplier that gives you
such “advice” at premium cost—sometimes to the tune of six figures—that is
money down the drain. Any reputable supplier of test equipment builds up-front
consultation on application details into their pricing system.
Andrew Kelly
Member of Technical Staff, Cactus Semiconductor Inc.
Cactus Semiconductor enables the miniaturization of implantable medical devices
(IMDs) by designing customized ICs specifically for the latest battery, MEMs, wireless,
and packaging technologies. This miniaturization allows for placement of IMDs
near the point of therapy, instead of in the chest or abdomen, thus enabling better
performance and less-invasive implant surgery.
Recent advances in battery technology have
led to the availability of chip-scale batteries, which can drastically reduce
the volume of IMDs. Cactus develops circuits to optimize the charging and
monitoring of these unique batteries. In addition, Cactus designs ultra-low power
circuits that minimize power consumption to enable use of these lower capacity
batteries. One example is our fully-integrated timekeeping solution that
consumes less than 200 nW.
MEMs devices are rapidly replacing traditional
sensors and actuators in IMDs to enable miniaturization. These MEMs devices are
often customized to specific applications so they require customized
electronics to optimize power and performance.
Cactus also has wireless solutions that support
simultaneous wireless communication and battery charging with a single coil. Our
communication solutions employ passive back-telemetry, to minimize battery
power, thus enabling the use of smaller batteries.
Finally, Cactus designs custom ICs for multi-chip
die-stacks that integrate ASICs with microcontrollers and EEPROMs in a single package.
The size of the entire IMD is thus optimized in ways only achievable by customization.
Tanner Hargens, MS
Senior Biomedical Engineer, Medical Murray Inc.
Medical Murray develops and manufactures medical devices with a focus on
complex catheter systems and their components. Our implantable components often
intend to repair or regenerate native tissue with absorbable polymers that
begin to degrade after accomplishing their initial task. Medical Murray is influencing the
bioabsorbable industry through knowledgeable material selection and injection
molding of the smallest and most detailed profiles on the market.
Bioabsorbable innovation at Medical Murray
has been driven largely by vascular, orthopedic, and surgical applications. The
absorbable polymers are initially designed by polymer scientists and engineers
to meet the specific mechanical properties and degradation kinetics for each
application. Each material will then have its own restrictions when processing
to the desired shape. When injection molding absorbables, each material will
have limits on the cavity size it is capable of properly filling and must often
be processed at the lowest temperatures possible to prevent alteration of the
degradation kinetics.
The Sesame nano-molder, invented by Medical
Murray, is capable of producing the smallest and most detailed bioabsorbable
polymer components by allowing the material to melt to sufficient flow at a
lower processing temperature so the material can normalize quicker with a
shorter cooling time than is otherwise available. This has also allowed minimal
loss of very expensive materials through use of smaller sprues, runners, and
reduced melted material in the injection unit. As an example to the
understanding the materials and processing, Medical Murray has been able to
design and mold the first absorbable living hinges, which allow expansion of a
device into the tissue from a small delivery catheter.