Polymers for an iron constitution
Polymers to aid healing
In the medical world, and, in particular, in the world of research, plastics have long proven their worth. They have a prominent place in these fields for many years, and are the source of crucial innovations in terms of purely medical developments and developments in the area of improved comfort and better living. Polymers and health are no strangers because PMMA (polymethyl methacrylate) first made its appearance in the 1930s in contact lenses, a revolution at the time, compared to glasses: they were smaller, more discreet, and more comfortable. More recently, PEEK (PolyEtherEtherKetone), a high performance thermoplastic polymer, became the darling of researchers. A solid, radiolucent and biocompatible material with a density close to that of bone. It enables highly durable prostheses and minuscule implants to be created.
The strength of many polymers resides in their biocompatibility. This is the prerequisite for medical use. Some are also biodegradable, which means that they can be absorbed by the body. This is why many active ingredients (the molecules that heal) are enveloped in an ultra-thin layer of this type of plastic. Not only will it hide a sometimes unpleasant taste or smell, it serves first and foremost to control the dispersion of the drug and facilitates its assimilation in the body. The best known resorbable plastics remain PLA (polylactic acid) and PGA (polyglycolic acid) used in surgery in stitches that degrade upon contact with water or various enzymes.
At Southampton and Edinburgh Universities in the United Kingdom, researchers are currently developing new types of biodegradable polymers able to help in bone healing in the event of a fracture or a crack. Barely a few microns in thickness, this durable and rigid polymer is applied to the broken bone and degrades progressively with the growth of the bone. It enables healing times to be decreased or osteoarthritis or osteoporosis to be treated.
Innerspace: plastics play the guest stars
What will medicine look like twenty years from now? Hard to say. One thing seems certain, though. The medicine of the future will be personalised, and polymers of all kinds will increasingly be a part of them. In fact, this is currently one of the main areas of research for many laboratories. The idea is to develop a type of microrobot able to release the active ingredient directly into the diseased cell or tissue. In order to achieve this aim in the coming years, some researchers are using plastics. This is the case with the IBM Research group and the Singapore Institute of Bioengineering and Nanotechnology (IBN) who are working together on biodegradable polymer particles to fight infections such as staphylococcus, which remain difficult to eradicate with simple antibiotics. The minuscule particles of polyethylene terephthalate (PET), once stuck to each other, are attracted like magnets to the infected cells and subsequently destroy them.
Stings don't even hurt!
MIT, working with the Massachusetts General Hospital (MGH), developed a small capsule covered in microneedles for administering medication directly into the wall of the intestine. The aim is to counteract the natural acidity of the digestive systems which tends to make many ingested drugs less efficient. The drugs are attacked and partially destroyed before having been absorbed by the body. Subcutaneous injections are currently the only alternative and, despite what nurses will say, they are not the most comfortable option for the patient. MIT therefore developed a capsule measuring just a few millimetres in size which has a reservoir in its core containing the active ingredient.
After ingesting the small plastic capsule, a set of microneedles made from polymers derived from sugar and synthetic polymers are deployed and inject the drug directly into the wall of the intestine. The researchers have even proposed an alternative whereby the needles are designed to break off from the capsule and sink into the lining of the intestine. They would then be dissolved by the gastric juices. As for the reservoir, which is also made from polymers, so far kept secret, it is coated with an acrylic coating that can withstand the effect of acids. For many diabetics, or people suffering from cancer, this could signal the end of many painful daily injections!
Polymer organ donors
Some illnesses are due to the weakness of certain organs, such as when the pancreas does not produce sufficient amounts of insulin and causes severe diabetes. The illness is such a global scourge that many universities are striving to "find" a miracle cure by developing an artificial pancreas. A team at King's College London has designed nanoporous capsules made from polysaccharides and alginates containing millions of insulin-producing cells. The recent results of transplants on mice are very encouraging. At San Francisco University, work is being done on an artificial kidney made from minuscule silicon membranes that copy the functioning of the kidney. In the end, how long will it be before these wonderful promises are made available to the greater public? It will still be some years as medical research must advance step by step in order to meet the criteria of international directives aimed at reducing the risks for the patients. And it is safe to bet that unexpected discoveries will disrupt these predictions.