Biorobots

Fiction or reality?

Evgenia Shabalina, "Biomolecule"

The key feature of a person is the thirst to create. For centuries, the best minds have been creating something new, changing life for the better – when smoothly, when dramatically. Inventions that once shook the world seemed an impossible reality. Electricity, the worldwide information network Internet – now it's our routine, familiar and boring. The way of the twenty-first century is similar to magic, fiction for previous generations. Perhaps we will also contemplate innovative technologies with the same amazement, which our grandchildren will not cause a drop of surprise. Centuries are running, the world is constantly changing, transforming. Only the desire of scientists to comprehend and create something new does not weaken. Thanks to their efforts, what appears in films about the future will soon become a reality. Teleportation, flights into space are akin to bus rides – the list can go on endlessly until the imagination runs out. However, this time we will talk about something else. About biorobots.

"There is nothing more inventive than nature"

It is difficult to create a biological system more perfect than the one that already exists in nature. There is nothing superfluous in it, evolution has done everything for a person – and scientists just need to make their own adjustments to the time-adjusted mechanism. The iBionicS laboratory of the University of North Carolina in 2012 presented a radio-controlled cockroach (Fig. 1). The principle of its operation is to influence the nervous system through sensors-antennae.

Figure 1. Comparison of the size of the modified insect with a US coin with a face value of 25 cents (diameter – 2.4 cm). Drawing from the website slate.com .

A chip was fixed on the insect's back, which sends signals to the cockroach's antennae and thus corrects the trajectory of its movement (video 1). Scientists faced a difficult dilemma: for the successful operation of the chip, batteries were required, which significantly weighed down the cockroach. An elegant solution was found, which can be called a demonstration of the coordinated work of scientific branches: with the help of physics, it was possible to find a new application for natural biological processes in the cockroach's body. When digesting food, the cockroach secretes sugar trehalose. On one of the electrodes, trehalose is decomposed into two glucose molecules. With the help of the hexokinase enzyme, a glucose phosphorylation reaction occurs and glucose phosphate is formed. This reaction is accompanied by the release of electrons, which move to the second electrode, that is, create an electric current. Scientists have managed to ensure that the cockroach itself ensures the successful operation of the chip by its vital activity. The implemented technologies successfully fit into the mechanisms debugged by evolution.

Video 1. The movement of a radio-controlled cockroach

In March 2016, another study was published, also related to insect management, but based on a different principle. A group of scientists from Nanyang University worked with beetles Mecynorhina torquata [1]. The impact was made on the muscle groups of beetles responsible for the movement of the legs (Fig. 2). That is, they stimulated the musculoskeletal system, and not the nervous system.

Figure 2. Anatomy of the beetle's front leg. a – Muscles of the upper side of the beetle's body. b – Muscles on the lower side. Crosses mark muscle groups stimulated by electrical impulses. Figure from [1].

The sequence of the impact and its strength were changed – thus the speed of movement of the beetle was regulated (Fig. 3).

Figure 3. Tracking the width of the step and the speed of movement of the beetle. The red crosses indicate the coordinates of the beetle's front leg and horn, which were used to calculate the step width, calibrated according to the usual ruler. Figure from [1].

His movements were tracked using motion capture technology. Three special cameras tracked the beetle's movements and presented them as movements of a simplified three-dimensional insect model. Biology, physics and computer science have made an invaluable contribution to the final result – Figure 4.

Figure 4. Insect motion capture setup and computer model. a is a computer motion capture system. b – Reflective markers were attached to the front legs and back of the beetle to track movements. b – The collected 3D motion data was transformed and displayed as three independent graphical segments. Figure from [1].

Modified insects have long excited the human imagination. They have excellent cross-country ability, which can be useful in espionage activities. Such an application has been covered in the cinema and has undeniable advantages (video 2).

Video 2. Excerpt from the film "The Fifth Element" (directed by L. Besson)

However, cyborg insects will also be useful for more peaceful purposes. For example, in the search for victims under the rubble.

Creating a new

But at the same time, scientists set themselves more ambitious goals. How about creating something new? In 2012, employees of Harvard University and the California Institute of Technology demonstrated an artificial jellyfish created by them (Fig. 5) [2]. Medusoid is the world's first artificial muscle consisting of a mixture of special polymers and rat muscle fibers.

Figure 5. A construction made of silicone and rat heart cells, repeating a real jellyfish. Drawing from the website mk.ru .

Muscle fibers taken from mouse heart tissue cells are grown on a polymer matrix. Polydimethylsiloxane, which is similar in properties to the connective tissue of jellyfish – mesoglea, was used as a material for it. The required shape was achieved by drawing a pattern from a protein solution.

Focusing on the structure of the long-eared aurelia jellyfish (Aurelia aurita), scientists have achieved the same principle of movement for the biobot. It moves by pushing out fluid, which requires muscle contraction. To ensure this, the "medusoid" was placed in an electrically conductive saline solution. Under the influence of electrical impulses, muscle cells contract, and the biorobot performs movement. It is not yet possible to achieve full control of the trajectory of its movement, but this direction is very promising. The work is being actively carried out and inspires scientists to new achievements.

This study gave an impetus to the following. In 2016, a group of scientists from Harvard presented the development of the "golden" stingray to the world community (Fig. 6) [3, 4].

You can read more about the artificial stingray on the biomolecule: "Do bathoids dream of electric rats?" [5]. – Ed

Figure 6. Eye and stingray. Now we are watching the stingray, and then it will help us to observe other organisms. Figure from [4].

This system, according to the principle of structure, in many ways resembles a natural stingray (Fig. 7).

Figure 7. Features of the structure of an artificial ramp. a is a Live stingray. b – The structure of the fin of a live stingray. b – Four layers of the artificial stingray body: layer 1 – a polydimethylsiloxane body (silicone used in medicine, cosmetology and even the food industry); layer 2 – a golden skeleton; layer 3 – again a thin layer of polydimethylsiloxane, on which muscle cells are located (layer 4). g – Concept. d – Avoiding obstacles depending on the intensity of the signal being sent. Figure from [3].

Chemistry and optogenetics played an important role in the study. Due to the chemical properties of gold, namely non-reactivity under normal conditions, it was chosen as a material for the skeleton. Optogenetics made it possible to develop a technology for controlling the movement of the ramp. Previously, the genome was changed in muscle cells: scientists introduced a gene responsible for the production of the light-sensitive protein KR2 in the cell. Under the influence of light pulses, it becomes a carrier of sodium ions, creates an electrical potential, as a result of which the cells contract and the slide moves (video 3).

Very accessible about how cleverly optogenetics works is described in the article "Bright Head" [6]. And how optogenetics can make you see even in the case of total damage to the photoreceptor cells of the retina, described in the article "Optogenetics + holography = epiphany?" [7]. – Ed.

Video 3. How, with the help of living muscle cells and pulses of light, it is possible to successfully control a biobot created in the laboratory

The above studies prove that science has reached a sufficiently high level to create quasi-organisms artificially, focusing on natural similarities. So far, only the first steps have been taken, which open the way for more advanced research. Perhaps in the near future, scientists will be able to create biorobots that are more complex in structure and less limited in terms of environment and living conditions.

Flight of fancy

As a result of evolution, the organisms now living on Earth have reached perfection. All processes for their successful life are debugged and complement each other. It seemed that nothing more was needed. However, there are no limits to human imagination. If there is a proper scientific apparatus, why not create something new that has no analogue in nature? A group of scientists from the University of Illinois has taken the first steps in this direction. In 2012, a biobot powered by mouse heart tissue cells was shown [8, 9]. It was a 3D-printed hydrogel frame with cardiomyocytes sown on its surface (Fig. 8). Cells contract and relax independently under certain external conditions, and the biobot, no larger than 1 cm, moves.

Some time ago, biomolecule wrote about a semi-soft robot jumper, also created by 3D printing: "A 3D printer produced a semi-soft robot jumper" [10]. – Ed.

Figure 8. Biobot movements on heart muscle cells. Drawing from the website news.nationalgeographic.com . However, controlling the contraction of heart cells is not an easy task, and in 2014 the same group of scientists presented an upgraded version of the biorobot: already using skeletal muscle cells of mice (Fig. 9).

Under the influence of electrical impulses supplied from an external electronic device, they are reduced, as a result of which the biobot moves.

Figure 9. Structure of the biobot: hydrogel framework and skeletal muscle tissue. Drawing from the website dailymail.co.uk .

The speed of movement is regulated by the frequency of the supplied field – this was established experimentally (video 4).

Video 4. 3D-printed biobots driven by muscle cells and controlled by electrical impulses

The developed technology allows the use of hydrogel frameworks of various shapes and gives enough freedom for further research. The already achieved control over the movement of the biorobot is planned to be improved. Scientists are going to introduce neural networks into muscle tissues. This will complicate the motion algorithms, but will allow you to connect other control methods, for example, light or the chemical composition of the medium.

High hopes

The twenty–first century is a time when the achievements of science make it possible to realize long-standing dreams. The described types of biorobots can be used in many areas of human life. Cyborg insects will be useful in espionage and operations of the Ministry of Emergency Situations, optogenetics will allow you to create drones that stay in the air by reducing muscle rings. The military industry will face drastic changes. Biorobots, analogues of natural creatures, are still limited by the environment, but in the future these limits will be overcome. It will be possible to create biorobots of a more complex structure that will surpass the living originals. A new direction in biology will appear – how could previous generations even dream of such a thing?

Fiction becomes reality. Scientists of the twenty-first century had a lucky chance not only to observe, but also to take part in this fascinating process.

Literature

1. Cao F., Zhang C., Choo H.Y., Sato H. (2016). Insect–computer hybrid legged robot with user-adjustable speed, step length and walking gait. J. R. Soc. Interface. 13. pii: 20160060;
2. Nawroth J.C., Lee H., Feinberg A.W., Ripplinger C.M., McCain M.L., Grosberg A. et al. (2012). A tissue-engineered jellyfish with biomimetic propulsion. Nat. Biotechnol. 30, 792–797;
3. Park S.J., Gazzola M., Park K.S., Park S., Di Santo V., Blevins E.L. et al. (2016). Phototactic guidance of a tissue-engineered soft-robotic ray. Science. 353, 158–162;
4. Pennisi E. (2016). Robotic stingray powered by light-activated muscle cells. Science News.
5. biomolecule: "Do bathoids dream of electric rats?";
6. biomolecule: "Bright head";
7. Biomolecule: "Optogenetics + holography = epiphany?";
8. Raman R., Cvetkovic C., Uzel S.G., Platt R.J., Sengupta P., Kamm R.D., Bashir R. (2016). Optogenetic skeletal muscle-powered adaptive biological machines. Proc. Natl. Acad. Sci. USA. 113, 3497–3502;
9. Cvetkovic C., Raman R., Chan V., Williams B.J., Tolish M., Bajaj P. et al. (2014). Three-dimensionally printed biological machines powered by skeletal muscle. Proc. Natl. Acad. Sci. USA. 111, 10125–10130;
10. biomolecule: "A 3D printer has produced a semi-soft jumping robot."

Portal "Eternal youth" http://vechnayamolodost.ru  20.09.2016