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SWALLOWABLE DISSOLVABLE MICRO DEVICES

12/3/14     A few Hollywood blockbusters over the years (and quite a few more that could be termed “non-Blockbusters”) have been fascinated by the idea of miniaturizing the lead actors so that they operate in a super-sized world. I guess we all remember Dennis Quaid, captain of the mini-submarine injected into an unsuspecting host in the 1980s film Innerspace, and the adventures that ensued!

OK, so the laws of physics (if not common sense) relegate such notions to fiction. But go back to 1966 when the film Fantastic Voyage (upon which Innerspace was based) was released, and some of the advances in medical science that we have seen over the ensuing 50 years would seem just as fanciful as reducing a submarine to the size of a grain of sand.

Today, we talk about the possibility of swallowing medical devices that are able to target specific areas of the body, perform their therapeutic miracles, and then dissolve and disappear, as if they are everyday elements of our lives. The impossible of yesterday is overcome day by day in this modern technologically advanced world.

While I will not now map out how long it will be before Dennis Quaid will be able to navigate his Ohio-Class sub through your body, I would like to look at what is possible today in the medical sector due to massive recent advances in micro manufacturing and material developments.

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Here at MES, we are privileged to work with an array of companies that are pioneering new medical treatments and diagnostic equipment. For the medical sector, miniaturization is key, and the drive is always to move towards minimally invasive treatments and diagnostics. The knock on effect in terms of quicker patient recovery and reduced strain on national health budgets make this an objective that will never go away. Medical device OEMs also know the bottom line advantages that exist if they are able to market miniature, efficient, and innovative products in a timely fashion, hence the number of them that work with MES to tap into our micro medical expertise.

The key to unlocking the potential for dissolving medical devices is recent advances in a new class of biocompatible bio-resorbable polymers.  Bio-resorbable polymers, also referred to as degradable polymers, are polymer materials that can be safely absorbed by the body so that the materials from which a construction is made disappear over time.

The most common bio-resorbable polymer is polylactic acid (PLA), also known as polylactide, which is made from a lactide monomer. Generally speaking, PLA is the main building block for bio-resorbable polymer materials. Common derivatives of PLA are poly-L-lactide (PLLA), poly-D-lactide (PDLA) and poly-DL-lactide (PDLLA). When in the body, PLA degrades into lactic acid, a non-toxic chemical which occurs naturally in the body.

Polyglycolic acid (PGA), or polyglycolide (PG), is another type of bio-resorbable polymer usually used for bio-resorbable sutures. The material can be copolymerized with lactic acid to form poly(lactic-co-glycolic acid) or PLGA, with e-caprolactone to form poly(glycolide-co-caprolactone) or PGCL, and with trimethylene carbonate to form poly(glycolide-co-trimethylene carbonate) or PGA-co-TMC. PGA degrades to form glycolic acid.

There are extremely important steps required when handling, testing, processing, and validating bio-resorbable molded components.  Material characterization throughout the molding process is critical to understand what happens to the Intrinsic Viscosity of bio-resorbable polymers such that when they are in the body, they will not prematurely resorb, or alternatively, stay too long for the implant to properly function.

As is usually the case in micro molding, this type of processing requires specialized equipment, design, and validation expertise, so working with the likes of MES which is experienced in bio-resorbable processing and micro feature generation can create a faster and more cost-effective path to success.

Use of bio-resorbable materials allow for the manufacture of some truly innovative products that can be implanted in the body. We have recently, for example, seen the arrival of dissolvable stents that disappear after two years in situ, a huge step forward in the treatment of heart disease globally.

Countless other implantable bio-resorbable devices exist today, and more appear all the time. But what happens when you are able to include power in your implantable devices. Now the possibilities become endless and the very real possibility of complex functioning dissolvable devices begins to loom.

Welcome to the weird and wonderful world of bio-degradable batteries and dissolvable electronics, the foundation stones of fully functioning powered medical devices that can be swallowed  and which dissolve over time. In one recently announced development, engineers have made a wireless microchip made of silicon, magnesium, and reconstituted silk. Once its work is done, it dissolves, triggered initially by the silk and how it is woven into the other elements, and is flushed out of the body.

As a facilitating technology, this dissolvable microchip could power a tiny device that would fight infections after surgery and then dissolve when its mission is accomplished. How about a small imaging device that takes pictures in the body, sends the images remotely to a computer, and then dissolves.  Such advances would be hugely beneficial, eliminating the need to resort to surgical intervention to remove devices.

In another application, ingestible smart pills containing tiny batteries, sensors, and transmitters to monitor a range of health data and wirelessly share this information with a medical practitioner are being swallowed today. This pill can track medication-taking behaviors, monitor how a patient’s body is responding to medicine, and detect a patient’s movements and rest patterns.

Some battery development is looking at the use of pigments found in cuttlefish ink. Conventional battery materials are not safe in-vivo unless they are encased in bulky protective cases that must eventually be surgically removed. The prototype sodium-ion battery uses melanin from cuttlefish ink for the anode and manganese oxide as the cathode. All the materials in the battery break down into non-toxic components in the body.

MES remains extremely well-informed of developments in this area, and is eager to discuss projects from OEMs that look to exploit “conventional” bio-resorbable materials, or the more ground-breaking advances in edible electronics.

Next week we can perhaps move onto making a miniature submarine!!

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