Nanorobots in medicine

How nanorobots are used in medicine

Pir Fischer, Post-science

Ordinary people by the word "nano" mean something very small. So, "nanosurgery" can only mean that a surgeon uses a microscope to work with an object several millimeters in size. One nanometer is one billionth of a meter (1 nm= 10-9 m). How will nanorobots help in the diagnosis of diseases? Why are nanorobots difficult to assemble? This is told by Professor of physical Chemistry Pir Fischer.

– What are nanorobots?

– The goal of nanorobotics is to implement in systems that are much smaller than a cell or a microprocessor, perception, information processing and, possibly, communication, that is, the capabilities inherent in full–scale robots. This is an incredibly difficult task, and it should be emphasized that it is not yet possible to implement all these functions in nanorobots, only some of them can be implemented in part of synthetic nanorobotic systems. Another option is to use an external control device. Then some of the necessary functions will be performed at the macro level using external devices, which can be quite large. At the nanoscale, particles most often act. To be different from passive nanoparticles, they must be active: move independently or under the influence of an external force.

– What are nanorobots?

– Imagine a nanorobotic system that consists of nanoparticles and an external controller. The particles in it must have such properties to react to the field controlling them – magnetic, acoustic or light. For example, a nanorobotic system may consist of submicron particles with a magnetic moment and a macroscopic laboratory setup with magnetic fields that are used for controlled particle guidance. Also, the system may have a visualization function that allows you to track their location. In one of the recent works, the possibility of conducting a swarm of magnetic nanopropellers twisted into a spiral through biological tissues was demonstrated. Such a system consists of nanopropeller particles and an auxiliary device that allows them to be set in motion.

Another approach is not to use external fields and devices, but to introduce an "engine" into the particle itself – then all processes will occur at the nanoscale. To do this, chemical reactions are used, with which the system becomes more autonomous. Imagine a simple submicron or microparticle: usually it is a spherical particle containing the right materials and equipped with enzymes or a catalyst in the place where the reaction should take place. The reaction changes the chemical environment around the particle, so it begins to move in a solution containing a suitable chemical fuel. The purpose of this line of research is to design these chemically active particles so that they can move to an area with the desired chemical properties.

In all these examples, there is no hardware that is in full-scale robots: no batteries, chips or motors. All these components can only be found on devices ranging in size from hundreds of microns to millimeters.

– What functions do nanorobots perform and how are nanorobots used in medicine?

– One of our tasks is to design nanorobots for use in various medical procedures: diagnostics, treatment and surgery. So, during a surgical operation, a particle heated with a laser or an alternating magnetic field can destroy tissues. In addition, the nanoparticle is able to deliver a contrast agent to the desired area to help physicians with diagnostic imaging. The particles can be supplied with a drug and sent to the area of interest to us.

All three areas are now being actively developed. In part, these tasks can be solved with the help of passive nanoparticles, but nanorobots have an advantage: they are able to cross barriers that passive nanoparticles overcome with difficulty, for example, the blood–brain barrier or mucous membranes. Also, nanorobots penetrate into those areas where passive particles do not pass at all. The use of nanorobots will allow you to inject powerful drugs directly into the desired area, which cannot be injected into the systemic bloodstream.

It should be emphasized that currently no system has reached the stage of clinical trials or application in medical practice, but passive particles have already been tested, and active particles are considered as a continuation of this work. However, at the moment we are focused on laboratory research, testing ideas and demonstrating general principles of work.

– What are the difficulties in developing nanorobots?

– In order to move nanorobots and for them to perform any tasks, you need to influence them and control them at the same time, and all this in an environment where it is quite difficult to move in general, that is, in tissues or, for example, in vessels with a powerful blood flow. It can be difficult to construct them, especially at submicron scales, but now most of the research is focused on how to set them in motion, and the first in vivo experiments are taking place.

Finding ways to interact with such a particle is not easy. Light cannot penetrate deep into tissues, and acoustic fields can, but their effect is too weak. Magnetic fields are already used in medicine, but to interact with such small particles, magnetic field gradients or time-varying magnetic fields are needed: both are difficult to implement at relatively long distances. In theory, this is possible, but it is still a technical difficulty. So one of the promising areas of research is to find a good way to minimize the impact needed to work with nanorobots.

To control the particles, you need to know where they are, but it's not easy to see them because of their size. We also need to find a suitable visualization method. Photoacoustics can be used for this, but in tissues it works only at a depth of up to one centimeter and most often with larger particles. Infrared light and fluorescence together give the necessary resolution, but are poorly suited for working inside tissues. Magnetic imaging can be used in larger structures, but it is sometimes poorly compatible with some forms of magnetic locomotion methods. Thus, there is no single solution to this problem, and different research groups are developing different directions. There are many difficulties, but the result is worth it: any breakthrough in research will immediately bring many opportunities for its practical application.

– What benefits can research in the field of nanorobotics bring?

– It is clear that most of the expectations are focused on the medical use of nanorobots: the ability to deliver drugs to the right areas in a controlled, purposeful manner opens up completely new horizons in medicine. But important technological breakthroughs can also be expected from research in the field of nanorobotics. In order to realize perception, information processing, movement and communication on scales much smaller than those that modern microelectronics allows, new technologies are needed. No battery works on such a scale, and besides, new production methods need to be invented.

To ensure the autonomy of the system on such a scale, it is necessary to introduce physico-chemical processes inspired by nature itself. Complex biological systems, such as bacteria, can be considered as biological micro robots, and they serve as a source of inspiration in many studies of synthetic nanorobotic systems. No synthetic system has yet been able to approach the level of biological microorganisms in terms of autonomy and complexity, but synthetic nanorobots should not work like natural systems and can take different forms. I believe that research in the field of nanorobotics will lead us to new medical and technological opportunities and give impetus to the most interesting areas of research.

About the author:
Peer Fischer – Professor of Physical Chemistry at the Institute of Physical Chemistry, University of Stuttgart; Max Planck Institute for Intelligent Systems Research Group Leader.

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