Solving all the technical challenges may take 20 years or more, but the first steps towards remote control medicine have already been taken
The distant future that the researchers involved in nano-medicine envision will include tiny medical messengers that will navigate the body intelligently and independently to reach a defined goal anywhere in the body, and only there. When these machines reach their target on their own, they will be able to act in several ways, from releasing drugs to providing live updates on the progress of their fight against the disease. Then, upon completion of their mission, they will undergo safe biological decomposition and will leave almost no traces. These nano-robots will be made of materials suitable for the biological environment - magnetic metals or even thin DNA threads. All materials will be carefully selected according to the usefulness of their properties on an atomic scale and their ability to slip through the body's defense systems without interfering and without causing any cellular damage.
Although the realization of this vision will take about ten or twenty years, researchers in the field of medicine have already begun to consider some of the technical problems it raises. One of the biggest challenges is making sure that the devices reach their goal in the body.
by the force of the wave
Most of the drugs on the market today are easily absorbed into the body's bloodstream, whether injected directly or absorbed through the digestive tract, via pills, for example. But they end their journey not only where they are needed, but also where they may cause unwanted complications. Sophisticated nano-medicines, on the other hand, will be designed so that it is possible to direct them to a cancerous tumor or to another problematic site and discharge the stimulant there, thus reducing the risk of side effects.
Magnetic fields and supersonic waves (ultrasound) are the leading candidates for nanomedicine guidance in the near term, says Joseph Wong, holder of the chair in nanoengineering and senior professor at the University of California, San Diego. Researchers applying the magnetic approach incorporate nanoparticles of iron oxide or nickel, for example, into the drug. Then they activate an array of magnets located outside the body of a mouse or other experimental animal and push the metallic drug or pull it inside the body towards the chosen site through the operation of different magnetic fields. Researchers applying the ultrasound approach direct the sound waves to drugs containing nanobubbles. The sound waves cause the bubbles to explode with great force and launch the cargo they carry deep into the target tissue or tumor.
In 2014, researchers at the University of Keele and the University of Nottingham, both in England, made a slight and useful change to the magnetic approach in work aimed at healing broken bones. They attached nanoparticles of iron oxide to stem cells and injected the preparation into two different experimental environments: the femurs of chicken embryos and a synthetic bone scaffold made from a gel (water-based) of engineered collagen tissue. When the stem cells reached the fracture site, the researchers applied an oscillating external magnetic field to quickly divert the mechanical stress of the nanoparticles. This placed biomechanical stress on the stem cells, which helped the stem cells differentiate more efficiently into bone. New bone growth occurred in both environments, but overall healing was not uniform. The researchers hope that eventually adding different growth factors to these iron oxide-bound stem cells will streamline the repair process, says James Henstock, a postdoctoral fellow at Keele University's Institute of Medical Science and Technology.
Self-controlled nano-medicine
The main disadvantages of the magnetic approach and the acoustic approach are the need for the bulky external guidance and the fact that magnetic fields and ultrasound waves can only penetrate a certain distance in the body. Developing independent microscopic motors to deliver the drugs may overcome these problems.
Such microscopic motors would be driven by chemical reactions, so toxicity could pose a problem. For example, it is possible to oxidize glucose, a sugar molecule found in the blood, to produce hydrogen peroxide (hydrogen peroxide) which can be used as fuel. But researchers already know that this particular method will not work in the long term. Hydrogen peroxide is a substance that eats living tissue, and the reaction with blood glucose will not produce enough hydrogen peroxide to power the engines. Efforts to use substances found naturally in the body, for example stomach acids (for applications in the stomach) or water (abundant in blood and tissues), as power sources seem more promising.
However, accurate navigation of self-propelled devices may be an even higher hurdle. The ability of nanoparticles to move anywhere is not enough to ensure that they progress exactly to the place the researchers are interested in. Independent navigation is still not an option, but the problem can be circumvented by creating a situation that will ensure that the nanomedicines will only become active when they find themselves in the right environment.
To perform this trick, researchers began to create nano-machines from synthetic structures of DNA. By arranging the subunits of the molecule so that their electrical charges force them to fold into a particular structure, scientists can pre-design the structures to perform certain tasks. For example, some segments of DNA can fold themselves into containers that will open and release their contents only when the package comes close to a protein essential in the process of a disease, or encounters the acidic conditions typical of a tumor, says Professor Yamuna Krishnan, a chemist at the University of Chicago.
Krishnan and her colleagues envision another advance: modular entities made of DNA that can be programmed for various tasks, such as simulating other nanorobots or even assembling them. However, synthetic DNA is an expensive material. Its price is 100 times higher than the price of traditional materials that are used to launch medicines. Therefore, currently, the price relaxes the hands of the pharmaceutical companies, and they avoid investing in this way for treatments.
All of this is as far east as west from the construction of the fleet of tiny and smart submarines in the 1966 science fiction film "The Amazing Voyage", which were supposed to extract a blood clot from a scientist's brain. And yet the nanorobots are finally moving in the same direction.
About the author
Larry Greenmeyer is an associate editor at Scientific American.
The article was published with the permission of Scientific American Israel
in brief
- A day will come when a fleet of medicines and nano-devices will set out on its own on a journey to any place in the body where it is needed with the help of biological engines and the appropriate fuel to get there.
- Before that day comes, researchers must learn how to design such compounds that can move without causing harm or interfering with biological activity.
- In the near future, scientists will use magnetic fields and ultrasound waves to propel nanoparticles to their target areas. But this way it is impossible to penetrate deep into the body.
- Nanorobots made of DNA are another possibility. Some of these compounds were designed to act as boxes that would open and release the coolant only under certain conditions.
More on the subject
Motion Control at the Nanoscale. Joseph Wang and Kalayil Manian Manesh in Small, Vol. 6, no. 3, pages 338-345; February 5, 2010.
Designer Nucleic Acids to Probe and Program the Cell. Yamuna Krishnan and Mark Bathe in Trends in Cell Biology, Vol. 22, no. 12, pages 624–633; December 2012.
Remotely Activated Mechanotransduction via Magnetic Nanoparticles Promotes Mineralization Synergistically with Bone Morphogenetic Protein 2: Applications for Injectable Cell Therapy. James R. Henstock et al. in Stem Cells Translational Medicine, Vol. 3, no. 11, pages 1363–1374; November 2014.
More of the topic in Hayadan:
- Nano robots will appear at the beginning of the next decade - what will they know how to do? (An article by the futurist Dr. Aharon Hauptman from 2003 referring to the current decade)
- Ray Kurzweil at the iNNOVEX 2015 conference: Life extension is expected to come in three stages: stopping aging diseases, DNA programming and nanotechnology inside the body
- The robot that will fix me: nanotechnology in the human body - from Dr.Roey Tsezana's book "The Guide to the Future"
The article was published with the permission of Scientific American Israel
