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Biopolymer structures with a single-walled carbon nanotubes framework for the restoration of heart tissue

Alexander Yu. Gerasimenko1,2, Uliana E. Kurilova1, Olga E. Glukhova3,2
1 National Research University of Electronic Technology MIET, Shokin Square 1, 124498 Zelenograd, Moscow, Russia
2 I.M. Sechenov First Moscow State Medical University, Bolshaya Pirogovskaya street 2-4, 119991 Moscow, Russia
3 Saratov State University, Astrakhanskaya street 83, 410012 Saratov, Russia

Abstract

Myocardial infarction is one of the most harmful diseases of the cardiovascular system. Effective treatment is aimed at creating 3D scaffolds that filled with living cells and implanted in the desired area. One of the most effective ways to create such scaffolds is 3D laser printing. In this regard, the aim of our work is to create a method for the formation of biopolymer electrically conductive structures for cell and tissue engineering. Carbon nanotubes have dimensions close to those of the main components of the natural extracellular matrix, their mechanical properties are similar to the properties of protein structures. Therefore, using a given configuration of nanotubes, it is possible to ensure the structure of composites, which is similar to the structure of biotissues. Biopolymers were used as matrices for composites: proteins — albumin and collagen, and amino sugar — chitosan. Albumin performs the function of transferring biologically active substances. When added to the composition of implants, it performs binding functions. Collagen is the main protein of connective tissue. Collagen fibers have high strength due to the close arrangement of the polypeptide chains, this allows tissue elasticity. Aminosugar chitosan is a powerful sorbent of natural origin. The absorbing base of chitosan is crustacean chitin (linear polymer). Single-walled carbon nanotubes (SWCNT) were used as a reinforcing filler of a matrix of biopolymers. The average diameter of SWCNT was 1.4-1.6 nm, length ~ 0.3–0.8 μm. We produced homogeneous aqueous dispersions from biopolymers and SWCNT. The concentration of nanotubes was 0.1-0.001 wt.%. Albumin with a concentration of 25 wt.% and collagen, 1 wt.%, as well as the chitosan, 2 wt.%, were added to the aqueous dispersion of SWCNT.
Further, these dispersions were deposited layer by layer on a substrate and irradiated with laser radiation. We developed a laser setup that generated pulsed laser radiation. Laser radiation was moved along the dispersion layer using mirrors of a galvanometric scanner. The trajectory of the focused radiation was set by a computer model. As a result of irradiation, a phase transition from liquid to solid (rubbery) form occurred and a series of layers of albumin, collagen and chitosan with SWCNT were formed. We controlled the temperature with a thermal imager. We did not allow the dispersion to increase above 80 Celsius degrees.
We found out a mechanism for the functionalization of SWCNT by biopolymer molecules inside a structures. We determined that SWCNTs covalently bind to oxygen atoms of surface amino acid residues of biopolymers. The internal and surface SWCNT nanostructures were studied using SEM and AFM. We observed a branched tree structure of a carbon nano framework. The formation of C–C bonds occurred in the regions of defects of neighboring SWCNTs in the framework upon laser heating. It was found that the diameter of SWCNT increased by several nm due to their functionalization with biopolymers. The composites had a bimodal pore distribution: 1-5 and 100-200 microns. Such porosity of composites is necessary, on the one hand, for innervation and vascularization, and, on the other hand, for the penetration of cells into them. The presence of a carbon nano framework inside the nanocomposite provided an electrical conductivity of about 1 S/m. We demonstrated better cell viability (fibroblasts, mesenchymal stem) on composites than on control coverslips. It was achieved due to a significant degree of cell adhesion to composites with a special structure. We also demonstrated electrical stimulation of cell growth using the developed device. Cells grew much faster on the surface of composites when we passed electrical signals through them. This study was supported by the Russian Science Foundation, Project No. 20-49-04404.

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Alexander Gerasimenko
National Research University of Electronic Technology MIET / I.M. Sechenov First Moscow State Medical University
Russia

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