RU2473368C1 - Method for preparing biocompatible nanostructure conducting composite - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention refers to a method for preparing a biocompatible nanostructured conducting composite. The method involves preparing an ultra-disperse suspension of carboxymethyl cellulose and carbon nanotubes with the mechanical system of carbon nanotube structuring wherein nanostructuring is enabled by exposing the suspension to laser light in a continuous mode at generation wave lengths 0.81÷0.97 mcm and light intensity 0.5÷5 Wt/cm².

EFFECT: invention provides preparing the high-conductivity bio-composite.

1 tbl, 1 ex

Description

The claimed invention relates to the field of biomedical engineering, in particular to methods for creating conductive biocompatible materials used in the diagnosis, treatment, transmission of electrical signals, information and energy. In medical practice, they can be used in cardiac surgery, biosensors, in the fight against epilepsy, in the management of muscle tissue, with electrical stimulation of biological tissue growth and restoration of nerve functionalization, for the transmission of electrical signals in the process of stimulating the work of organs and in other cases.

A known method of producing a biocompatible nanostructured composite electrically conductive material based on polymers, in the matrix of which various nanoparticles can be added, including carbon nanotubes (CNTs), metal oxide nanotubes, etc. [1]. Polymeric materials from various groups are used as a matrix, including: acrylates, acrylic acids, polyacrylic esters, polyacrylamides, polyacrylonitriles, chlorinated polymers, fluorine-containing polymers, styrene polymers, synthetic rubber polymers, vinyl chloride-acrylate polymers, copolymers, etc. To achieve the biocompatibility of the material in its matrix is introduced substances with biological molecules from one or more groups, for example: biological electrolytes, nucleic acids, polyamino acids, albumin, . Itozan, carrageenan, carboxymethylcellulose, etc. The filler (additive) selected from different groups, for example: biomolecule one or more species, electrically conductive materials, CNT, metal oxide nanotubes, nanotubes such as titanium dioxide, etc.

The disadvantage of this method of obtaining a nanostructured electrically conductive material is its complexity of preparation and low specific conductivity of the final product.

A known method of preparing a biocompatible fiber nanostructured composite electrically conductive material, the matrix of which uses materials from one or more groups, for example: biological electrolytes, nucleic acids, polyamino acids, proteins, enzymes, polysaccharides, lipids, etc. [2]. Biological electrolytes can consist of one or several groups, including chitosan, spermidine, albumin, carrageenan, carboxymethyl cellulose, etc. Various materials are chosen as a filler, including CNTs and metal oxide nanotubes. Moreover, CNTs can be either single-walled (SWCNTs) or multi-walled CNTs (MWCNTs), and their concentration in the total mass of the composite material exceeds 20%. The biocompatible nanostructured electrically conductive material in the solid state can be obtained by adding special coagulants to the suspension and drawing and twisting the fibers from it. With this method of preparing an electrically conductive biocompatible material in the form of CNT fibers, they were mainly oriented along its length, and, thereby, a high electrical conductivity of the fibers was achieved.

The disadvantage of this method of obtaining a nanostructured electrically conductive material is the complexity and one-dimensional shape (fiber) of the final electrically conductive product.

The closest technical solution is a method for producing a bulk biocompatible nanomaterial containing carbon nanotubes, characterized in that they conduct laser irradiation of its aqueous solution up to the evaporation of the liquid component of the solution [3]. The disadvantage of this method is not a strict control of the irradiation mode, since the evaporation of the liquid component of the solution is mainly required to obtain the final nanomaterial. However, to obtain a nanomaterial with a maximum electrical conductivity, it is necessary to select the optimal laser irradiation regime.

The objective of the invention is to develop a method for producing a composite biocompatible nanomaterial with high electrical conductivity due to the nanostructuring of carbon nanotubes in suspension by exposing the suspension to laser radiation.

The specified technical result is achieved in that in the known method for producing a biocompatible nanostructured composite electrically conductive nanomaterial, comprising preparing an ultradispersed suspension from a biocompatible material and carbon nanotubes, in which the nanostructure of carbon nanotubes in the suspension is carried out by continuously applying laser radiation to the suspension at 0 wavelengths 81 ÷ 0.97 μm and an irradiation intensity of 0.5 ÷ 5 W / cm ² . In the method for producing a biocompatible nanostructured composite electrically conductive material, carboxymethyl cellulose is used as the biocompatible material.

At wavelengths of 0.81 μm and 0.97 μm, a high absorbing ability of laser radiation with a composite material is observed, and in the intensity range I≈0.5 ÷ 5 W / cm ² , the optimal structuring of carbon nanotubes is observed. It should be noted that at I> 5 W / cm ^{2 the} material overheats and burns, since at I <0.5 W / cm ^{2 the} electric field created by the laser beam in the material is weak, and, accordingly, the nanostructure of carbon nanotubes in the material is insufficient.

In the claimed invention, suspensions were prepared with the main components in the following quantitative proportions (in% by weight):

Carboxymethyl cellulose (CMC) 3-5 MWCNT 0.1-0.5 Water the rest of it.

The proposed preparation method allows to obtain a nanostructured composite electrically conductive material with any topological shape (3-D, 2-D, 1-D) and consistency.

Traditional metal wires have disadvantages: low biocompatibility, insufficient mechanical and electrically conductive properties. For example, tensile strength and electrical conductivity, reduced to the density of the material, are several orders of magnitude lower for a copper nanowire than for carbon nanotubes (CNTs). CNTs withstand a high current density (≥10 ⁸ A / cm ² ), which is 4-5 orders of magnitude greater than that of a copper nanowire [4]. Thus, nanotubes based on CNTs will be in demand both in biomedical applications and in micro- and nanoelectromechanical systems.

The high electrical conductivity of a composite biocompatible nanomaterial with MWCNT additives is associated with many factors, including with high efficiency of coagulation of a suspension of CMC + MWCNTs under the influence of laser radiation; with the structuring of carbon nanotubes mainly in one direction - in the direction of the electric field of the laser beam. The strong electric field of laser radiation in the suspension orientes the carbon nanotubes in the form of parallel filaments and, thereby, increases the conductivity of the nanomaterial.

An example implementation of the proposed method for producing a nanostructured composite electrically conductive material. At room temperature, CMC powder is dissolved in distilled water. The suspension is stirred using a mechanical stirrer for 0.7-0.9 hours. Then, the resulting suspension is dispersed in an ultrasonic bath for 0.8-1.0 hours. In the next step, MWCNT powder is added and the resulting suspension of CMC + MWCNTs is mixed and dispersed similarly to CMC. The resulting ultradispersed suspension is poured into the desired shape and laser irradiation is carried out through its open surface. The source of laser radiation can be a laser with a wavelength λ of a generation wave in the region of (0.81-0.97) μm, in particular a diode infrared laser - λ = 0.97 μm with a fiber-optic radiation output. The radiation intensity feeding on the surface of the suspension is adjustable in the range of 0.5-5 W / cm ² .

Under the influence of laser radiation, coagulation (coagulation, thickening) of the suspension occurs, carbon nanotubes are structured in the direction of the electric field of the laser beam, and at the same time, the suspension loses moisture by evaporation. In the dried state, the mass of the nanomaterial is approximately 10 times less than its mass in the state of suspension.

In the process of preparing a nanostructured composite biocompatible nanomaterial, the following parameters are controlled: irradiation mode (continuous, pulsed), irradiation time, irradiation intensity, suspension heating temperature, and also the percentage by weight of its constituent components. Such control allows you to get the desired material with conductivity in a wide range - 100-5000 S / m

Table 1 shows typical values of σ for composite biocompatible nanomaterials having different compositions, where 4 wt.% CMC (suspension) - 4 wt.% Carboxymethyl cellulose (aqueous suspension); 4 wt.% CMC (dried) - carboxymethyl cellulose in dried form; 4 wt.% CMC + 0.5 wt.% Carbon black K-354 - a mixture of carboxymethyl cellulose and carbon black K-354 in dried form; 4 wt.% CMC + 0.5 wt.% MWCNTs (suspension) - carboxymethyl cellulose and MWCNTs (aqueous suspension); 4 wt.% CMC + 5 wt.% MWCNTs (dried) - carboxymethyl cellulose and MWCNTs in dried form. In the latter case, the concentration of MWCNTs was estimated taking into account the moisture loss of the suspension of 4 wt.% CMC + 0.5 wt.% MWCNTs (suspension) during its coagulation and drying. It should be noted that the final product of 4 wt.% CMC + 5 wt.% Soot K-354 (dried) was prepared for comparison with the main product 4 wt.% CMC + 5 wt.% MWCNT (dried). One can see a huge advantage in electrical conductivity (more than 4 orders of magnitude) of a nanostructured composite nanomaterial based on MWNTs relative to a composite material based on K-354 carbon black. Moreover, the preparation method and the percentage ratios of the compositions for both cases are identical.

Table 1 Electrical conductivity of composite biocompatible materials of various compositions. Material / beats the wire. 4 wt.% CMC (suspension) 4 wt.% CMC (dried) 4 wt.% CMC + 5 wt.% Carbon black K-354 (dried) 4 wt.% CMC + 0.5 wt.% MWCNTs (suspension) 4 wt.% CMC + 5 wt.% MWCNTs (dried) a, cm / m one 0.1 0.1 10 5000

Thus, in the proposed invention, when selecting the optimal nanostructuring regime by laser irradiation, a biocompatible electrically conductive nanomaterial was obtained and a higher electrical conductivity was achieved at low concentrations of multi-walled carbon (~ 5%) nanotubes relative to the electrical conductivity of known biocompatible nanomaterials [1, 2, 5, 6].

Information sources

1. US patent 2010/0068461.

2. US patent 2010/0023101.

3. Ageeva SA, Bobrinetsky I.I., Nevolin V.K., Podgaetsky V.M., Ponomareva O.V., Savransky V.V., Simunin M.M., Selishchev S.V. / Method for nanostructuring bulk biocompatible materials // Patent RU 2347740. (prototype).

4. Ngo Q., Cassell A.M., Austin A.J., and et al. / Characteristics of aligned carbon nanofibers for Interconnect Via applications. // IEEE. Elec. Dev. Lett., 2006, v. 27 (4), pp. 211-224.

5. Ostiguy C., Lapointe G., Trottier M., Menard L., Cloutier Y., Boutin M., Antoun M., Normand Ch. / Health effects ofnanoparticles. Studies and research projects. IRSST 2006.p. 52.

6. Allsopp. M., Walters A., Santmo D. / Nanotechnologies and nanomaterials in electrical and electronic goods: A review of uses and health concerns // 2007. Greenpeace research laboratories. December. 22 p.

Claims (1)

A method of producing a biocompatible nanostructured composite electrically conductive material, including the preparation of an ultradispersed suspension of carboxymethyl cellulose and carbon nanotubes, with a mechanical system for structuring carbon nanotubes, characterized in that the nanostructured carbon nanotubes in the suspension are subjected to continuous wavelength exposure to the laser nanotubes1 at a wavelength of 0.8 at a length of 0.8 -0.97 μm and an irradiation intensity of 0.5-5 W / cm ² .