The way I understand it is this : if an implant is nice and smooth and well integrated with it's surrounding tissue then a titanium implant is safe. Safe in the sense that the immune system won't attack it just because it's there, like it would with metal or frankly almost any substance (the 2 exceptions are titanium and gold, just ask someone with earrings what happens if you insert a silver or metal earring near a scratch).
If the implant has sharp edges, or rips into the surrounding tissue, or otherwise causes cells to die or prevents repair of damaged tissue somehow, the immune system will go looking for a culprit[1]. If it decides that the implant is the culprit, bad luck. It will attempt to surround the implant and expel it. Depending on the size this may or may not work (this is what happens to splinters of wood that get into your body, for example). This can even cause the immune system to decide a bone is the culprit, if it does you have rheumatoid arthritis (it's a condition that you are very likely to get if you live long enough)
Furthermore, implants may actually infect, as in a bacterial colony may develop on their surface (because the contact surface with the immune system is much smaller, an infection has a bigger chance to maintain that position. Always keep in mind that the immune system wins against bacteria not because it's better or smarter, but because it has 80kg of cells working logistics for it). The same can happen to bones.
[1] To be exact, cells have an "alarm" signal molecule floating inside them. If the cell is ordered to commit suicide (apoptosis), it will put out an enzyme that neutralizes this alarm molecule before ripping itself to shreds, the same will happen if the immune system orders a cell to eat itself (autophagy). But if the cell dies for some other reason (e.g. getting ripped to shreds, explosion due to infection, ...) the alarm signal will be spread into the surrounding tissue where the immune system can find it. When it finds it, it will come in force to check out the situation. If it keeps seeing this signal without finding a cause, the immune system will go insane/react badly.
Titanium dental implants are rough: the rougher, the better. It helps them to osseointegrate (bond with bone).
Because the majority of titanium implants are two-piece (a screw and an abutment), bacteria can enter through micro-gaps between the components, and thrive within the actual implant. This often leads to peri-implantitis.
Single-piece implants don't have this problem (but usually have many others).
Disclaimer: I'm working with a 'maverick' doctor who invented a (revolutionary) non-surgical dental implant.
The article says he had two microelectrode arrays(MEA) implanted, one jack per array, The MEA was probably a standard Utah MEA, 10x10 multiplexed to 100 electrodes, so, just 20 leads per array per "data port"
The device in the article was implanted over 10 years ago.
I'm sure there are research teams looking into the wireless methods, in 2002 it just wasn't possible yet. Magnetic induction has it's own challenges, especially when being used with a device inside living tissue.
Wireless power for medical devices has only been practical for the past couple years, and even now the technology is in it's infancy.
This would be prohibitively large to implant in the brain.
Betavoltaics could provide a novel power source, I believe they are used in some pacemakers. RF would be a problem because cancer.
People forget that magnetic induction can also be used for data and power transfer simultaneously, I believe they use this approach with some cochlear implants.
electromagnetic radiation(photons) is VERY VERY VERY different from magnetic fields(fucking magnets how do they work?) the driving physics behind magnetic induction.
Yes RF is non-ionizing, but research linking it to cancer is generally inconclusive. So I concede I was too bold saying RF causes cancer, but right now we just don't know.
It would probably be possible to power it with RF power harvesting and multiplex the MEA with a MSP430. Now that would be a fun research project.
In order to transfer power using magnetic induction you need a _variable in time_ magnetic field, which causes a variable in time electric field to appear. That seems to me to be exactly the description of an electromagnetic wave.
> It will attempt to surround the implant and expel it. Depending on the size this may or may not work (this is what happens to splinters of wood that get into your body, for example)
Very cool. I had a splinter sink into my finger once, and abandoned the project of getting it out. Sure enough, it eventually emerged on its own; in my memory it was coated with a thin layer of some clear substance.
> Always keep in mind that the immune system wins against bacteria not because it's better or smarter, but because it has 80kg of cells working logistics for it
I weigh less than 80 kilograms. What's that g stand for?
Are you sure about this? A friend hit me with a pencil 5 years ago, and this caused some graphite to enter inside my skin. The graphite is still there to date and I got no pain, infection, reaction from it.
Keep in mind that the top 2mm of your skin is mostly dead material. Nothing will happen if you put something into it, and there are places where it doesn't get renewed.
If the implant has sharp edges, or rips into the surrounding tissue, or otherwise causes cells to die or prevents repair of damaged tissue somehow, the immune system will go looking for a culprit[1]. If it decides that the implant is the culprit, bad luck. It will attempt to surround the implant and expel it. Depending on the size this may or may not work (this is what happens to splinters of wood that get into your body, for example). This can even cause the immune system to decide a bone is the culprit, if it does you have rheumatoid arthritis (it's a condition that you are very likely to get if you live long enough)
Furthermore, implants may actually infect, as in a bacterial colony may develop on their surface (because the contact surface with the immune system is much smaller, an infection has a bigger chance to maintain that position. Always keep in mind that the immune system wins against bacteria not because it's better or smarter, but because it has 80kg of cells working logistics for it). The same can happen to bones.
[1] To be exact, cells have an "alarm" signal molecule floating inside them. If the cell is ordered to commit suicide (apoptosis), it will put out an enzyme that neutralizes this alarm molecule before ripping itself to shreds, the same will happen if the immune system orders a cell to eat itself (autophagy). But if the cell dies for some other reason (e.g. getting ripped to shreds, explosion due to infection, ...) the alarm signal will be spread into the surrounding tissue where the immune system can find it. When it finds it, it will come in force to check out the situation. If it keeps seeing this signal without finding a cause, the immune system will go insane/react badly.