Biocompatible and electrically conductive
MIET found a way to repair heart defects
A new electrically conductive design proposed by scientists Institute of Biomedical Systems NIU MIET, can be used both to create independent tissue-engineered implants for the restoration of heart defects, and coatings for cardiovascular devices, for example, circulatory support devices, stents, etc. This is evidenced by the results of studies of the atomic-molecular structure, electrical conductivity and hardness, as well as bio- and hemocompatibility of layers.
When used as a coating, composite layers can be a link between a cardiovascular device and flowing blood, preventing damage to blood cells and thereby reducing adverse effects for the patient and reducing the overall burden on the healthcare system.
The social significance of the new technology
More than 17 million deaths from cardiovascular diseases occur annually in the world, and this number continues to grow. A significant part of deaths is associated with heart failure, the treatment of which in the terminal stage is the transplantation of a donor heart or the installation of auxiliary blood circulation devices. At the same time, there is an acute shortage of donor hearts, and in the case of auxiliary blood circulation devices, side effects associated with poor compatibility of the device material with flowing blood are not uncommon. Scientists are actively looking for ways to regenerate patients' tissues without using donor tissues, and one of the options is to use tissue engineering methods – growing healthy tissue from the patient's own cells on special scaffolds. Skeletons with cells are then implanted into the site of the defect, ensuring the healing of damaged tissue.
What is in the composition
The design proposed by MIET scientists consists of composite layers, which include carbon nanotubes and biopolymers. Blood protein albumin, connective tissue protein collagen and natural absorbent polysaccharide chitosan were used as biopolymers. Composite layers were formed using a developed 3D laser printer, and a liquid dispersed medium of biopolymers and nanotubes acted as ink for it. "The layers of structures were created by forming an extensive three–dimensional network of nanotubes with conduction nodes in biopolymer matrices," explains Alexander Gerasimenko, head of the research group, Ph.D., Associate Professor at the Institute of BMS MIET, head of the Laboratory of Biomedical Nanotechnology. "Laser radiation has made it possible to ensure the electrical conductivity of the network and, accordingly, of structures exceeding the electrical conductivity of similar samples obtained by conventional heating, for example, in a thermostat."
Researches
The obtained experimental effect was preceded by theoretical studies of the binding of nanotubes to each other to form an electrically conductive structure. The values of the electrical conductivity of the developed structures correspond to the electrical conductivity of the myocardium (heart muscle). This is important for the creation of cardiac implants, which must be electrically conductive, since the heart generates an electric current that spreads through the heart tissue and ensures its contraction. An extensive network of carbon nanotubes formed with the help of laser radiation contributed to an increase in mechanical strength throughout the entire volume of structures.
In addition, as a result of experiments, it was revealed that the technology allows you to control the porosity of structures. Scientists have discovered a physical mechanism for the formation of a vapor shell around nanotubes that affects the formation of pores when exposed to laser pulses with a certain energy. For this purpose, knowledge in the field of nonlinear optical studies of materials with nanotubes was used.
Microscopic images of the porous 3D structure of composite layers of structures made of biopolymers based on albumin, collagen, chitosan and carbon nanotubes obtained by exposure to laser pulses with different energy densities.
The porosity of the structures was adjusted in such a way that they contained pores with small and large sizes. Small pores will ensure the germination of blood capillaries and nerve fibers, and large ones will be filled with heart cells.
As a result of the experiment, it was possible to demonstrate the vital activity of heart cells in the porous 3D structure of each of the composite layers of structures. After two days, the cells in the structure of the composite layers began to form fragments of the elementary layer of the endothelium, and the composite layers at the same time provided a favorable effect on the blood. Since cardiovascular implants should prevent the destruction of the membranes of red blood cells (erythrocytes), which contain hemoglobin, which carries oxygen through the body, upon contact, the scientists conducted studies of the level of blood hemolysis in contact with the developed structures in accordance with the protocol of the ethics committee of Sechenov University. Tests with blood also ended positively.
For more information about the development of laser technology for fabricating structures from composite layers based on biopolymers and single-walled carbon nanotubes, developed as part of the project 20-49-04404 of the Russian Science Foundation, you can read in the scientific journal Composite Structures (Gerasimenko et al., Laser fabrication of composite layers from biopolymers with branched 3D networks of single-walled carbon nanotubes for cardiovascular implants).
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