You are here: MEDICA Portal. Part IV: Substances. Polymers.
Material Rush Hits Medicine (Part 1)
„Imagine a pot full of spaghetti“, Ulrich Suter says. The topic is polymers – very large molecules that are made up of the same units, so called monomers. „When one spaghetto stands for a monomer, the whole pot is the polymer“, the professor for macromolecular chemistry explains. Polymers were responsible for changing medicine - it put an end to the century-long sole use of wood and metal instruments, they became one of the most important materials of the 20th century par excellence. This is due to a big advantage they exhibit: These materials can be designed in any possible way - it all just depends on the contents of the pot: Polymers have different properties depending on the kind of monomers used and the length of the chain – that way it is possible to create linear, branched or cross-linked polymers.
Long, longer, the longest:
Polymer chains; © Y. Roiter
and S. Minko
These materials occur everywhere in our life with the most famous example being the plastic bag that is actually made up of the gas ethene bound to each other so many times until it is called polyethylene - the main ingredient of the modern shopping bag. Styrofoam, teflon or nylon are synthetically produced polymers, cellulose, paper, starch or hair are naturally occurring ones.
„There are hardly more versatile substances around than polymers“, Suter, who has been studying the large moelcules his whole life and works at ETH Zurich, raves. They are virtually a neurotic's dream because they can be totally controlled - it is feasible to influence them in order to create any desired property. „They are adjustable – a little harder, a little softer, a bit of another colour, that all is no problem at all“, Suter says. The reason why polymers are so important in medicine and are in use in diagnostics as well as for surgery and in the laboratory.
Implants that disappear into nowhere
Other polymers have the property that they are degradable by the human body over time without leaving toxic substances behind. For example, suture material and bone nails disappear after having fulfilled function. „In future such resorbable materials will be used predominantly during controlled drug release“, Suter explains. In addition also in tissue engineering where they could serve as scaffolds for muscle, fat and connective tissue cells. Rigid scaffolds made of ceramics render good services in order to culture and grow bone graft substitutes, however soft tissue needs soft scaffolds - polymers could solve this problem.
As has been done with cardiac valves. „At the moment heart valves are made of pig tissue or hard artificial material that causes a loud click with every heartbeat“, Suter says. Since the patient almost always feels uncomfortable walking around with a foreign object inside physicians try to use polymers to change this. “We need a degradable substance that is present as long as it takes to build the house“, Suter talks about a polymer similar to a sponge. Heart cells can settle well on such a structure and grow there. The more abundant the tissue becomes the more of the spongy polymer dissolves - until the heart valve out of own body cells is ready.
On top of these properties polymers have the ability the exhibit intelligent behaviour - when the scientist manipulates them accordingly. That results in plastics with shape memory that are able to change when heated up or being illuminated. The idea behind it is to create polymers in such a form that they can turn themselves into any imaginable shape and at the same time memorising their original state. That would enable scientists to program sutures that contracts with feeling and not with forcing maximum pressure upon the tissue as well as suture material that makes a knot under the influence of warm temperatures similar to those created by the body.
- Part 1: Material Rush Hits Medicine
- Part 2. Biosilicates from the Abyss
- Part 3: Transistor at Nanolevel