Nanotechnology could revolutionise medicine and pharmacy in the future. Today, tiny taxis can already transport active substances to specially selected targets in the body instead of flooding the entire body. In the future, nanobots could also take cell samples and help defeat previously incurable diseases.
The watering can principle is generally regarded as a less effective method of resource distribution. But this is exactly how most medicines still work today. If you have a headache, you take painkillers that block the production of an enzyme that is necessary for pain transmission. The spinal cord doesn't notice that the head is throbbing, the patient feels better, the medication works. With the small catch that all enzymes of this group are blocked - everywhere in the body.
And since the enzymes, in this case prostaglandins, also take over other functions in the body - for example, the regulation of gastric acid - the unpleasant side effects that are inherent in most medicines occur: The side effects. If you are unlucky, you may not have a headache after taking a painkiller, but you will have a stomach ache.
The question therefore belongs to one of the major fields of research in the field of pharmacy and medicine: How do we deliver an active ingredient precisely to the one place in the body where it is needed? And thus spare the rest of the tissue from useless to undesirable reactions?
The solution lies in nanotechnology and, as the ancient Greek name "nanos" suggests, takes place in a veritable dwarf world. For researchers such as Cornelia Keck, Professor of Pharmaceutical Technology and Biopharmacy at the University of Marburg, 100 nanometres is quite a commercial order of magnitude.
It is difficult to imagine this world of tininess. After all, a nanometre fits into a metre a billion times. A hundred nanometres fit ten million times into a metre. The principle Keck and her colleagues are working on, however, is simple: "We are building tiny taxis that take active substances super-specifically to where the body needs them.
Sometimes it is necessary to camouflage the active substance for this purpose, as the body wants to get rid of foreign substances immediately and breaks them down again before they reach their destination. "We call this PEGylation, in which added active substances are conjugated with polyethylene glycol and can thus travel unmasked by the body's defence mechanisms to the place where we need them," says Keck. Polyethylene glycol is water-soluble - and completely non-toxic. It is therefore perfectly suited as a taxi for medicines.
The principle can also be used successfully in cancer medicine. Since it is inherent in tumour tissue to grow quickly, its texture is often less dense. Nanotechnology takes advantage of this when, for example, it introduces iron particles into the body, which do not penetrate healthy tissue so easily, but can get stuck in the holes in the tumour tissue. "If we then irradiate the tumour, the iron particles become extremely hot - the malignant cells burn from the inside," says Keck.
Where chemical taxis reach their limits, scientists are already researching microscopically small nanorobots that, when injected into the body, transport active substances directly into the interior of a tumour, for example. This is still a bit of a pipe dream. But in Culver City, California, for example, they are already working on micro-robots that can be used in the body.
Michael Shpigelmacher, co-founder of the start-up Bionaut, describes the micro-robot of the same name developed by his company in an article in the "Süddeutsche Zeitung" as follows: "Actually, it's like a tiny screw that, as if moved by an invisible screwdriver, comes through the veins to the place where the tumour is located." What Shpigelmacher calls an "invisible screwdriver" is nothing more than a magnet that controls the tiny robot from the outside and pulls it along the spine to the brain.
Shpigelmacher and his colleagues hope that nanorobots could revolutionise medicine in the future and cure diseases that are considered incurable today: "Alzheimer's, Huntington's, Parkinson's, all these diseases that are considered invincible today - microrobots could be the bridgehead to access the brain directly and either place drugs there, take cell samples or stimulate certain brain regions."
One hurdle on the road to revolution: Because nanobots are so unimaginably small, they naturally offer no room for steering software inside them. Making them mobile and controllable is therefore one of the great challenges. Because frictional resistance lurks in the body, the nanobot cannot flow effortlessly as if through water. Rather, it finds a tough environment similar to that in a honey pot.
In order to be able to move small robots precisely through the body, research is being carried out at the Max Planck Institute, for example, to programme them so that they act in swarms. The models, which are 500 times smaller than a hair, are 3D printed from a polymer and coated with a thin layer of cobalt that makes them magnetic. This allows them to change direction and even dance in a rotating magnetic field.
But it is not only the magnets that can influence the movement of the mini-robots. The researchers also discovered that particles floating next to each other on a liquid tend to swim towards each other. The scientists from the Max Planck Institute for Intelligent Systems (MPI-IS), Cornell University and Shanghai Jiao Tong University call this the Cheerio effect: if you let two cereals float on milk, they will eventually collide. Conversely, this effect can also cause two things to repel each other.
To be able to act as nanobots in the body, the robots must become even smaller, according to Gaurav Gardi, a doctoral student in the Department of Physical Intelligence at MPI-IS: "Our vision is to develop a system that is even tinier. We want to build the particles as small as one micrometre soon. These collectives could possibly one day penetrate the human body and navigate through complex environments, for example to administer drugs, release blockages or stimulate hard-to-reach areas," explains Gardi.
While some are working on the realisation of scenarios that so far have been more reminiscent of the plot of a science fiction film, Cornelia Keck from the University of Marburg finally draws attention to a benefit of nanotechnology in pharmacy and medicine that is as banal as it is groundbreaking.
In their research on cosmetic products that protect the skin from damaging sunlight and thus also from cancer, Keck and her colleagues came across a natural substance that occurs in pansies. Since the substance is difficult to dissolve, it was difficult to transport it to its target, i.e. into the skin, and it had to be laboriously chemically reconstructed - which turned out to be very resource-intensive. "Using nanotechnology, we succeeded in dissolving the natural substance in water. Now we achieve twice as good an effect with a 500-fold lower dose," says Keck.
From the point of view of effectiveness, this is a revolution. Because: less active ingredient also means less waste water, less pollution in the septic tanks, less impact on fish living in rivers and thus also on humans. Nanotechnology is therefore not only a possibility to cure serious diseases in the future. It also offers the key to a resource-saving, sustainable and environmentally friendly pharmacy. The watering can principle will eventually become obsolete.
Text: Ronald Voigt