RU2509091C1 - Biocompatible, biodegradable composite fibre and method for production thereof - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method of producing fibre involves mixing hydrosilicate filler, which is pre-dispersed in an aqueous medium with pH 5-7 in an ultrasonic field with frequency v=20-100 kHz for 5-60 minutes, with chitosan in an amount which corresponds to concentration thereof in the solution of 1-4 wt %. The amount of the filler is 0.05-2% of the mass of the chitosan. The obtained mixture is intensely stirred at temperature of 20-50°C for 20-60 minutes. Concentrated acetic acid is then added in an amount which enables to obtain aqueous acetic acid solution with concentration of 1-8 wt % in the mixture. The mixture is intensely stirred at temperature of 20-50°C for 20-250 minutes. The mixture is filtered and deaerated. The fibre is formed through a draw plate into an alcohol or alcohol-alkaline precipitation agent, wherein the shear velocity of the solution in the plane of the cross-section of the capillary when the solution passes through the draw plate is selected in the range of 1.0-10^-3 s^-1. The fibre is stretched by 10-120%, washed with water and dried at temperature of 20-50°C. The fibre contains chitosan and hydrosilicate filler - halloysite, chrysotile, montmorillonite - in form of nanoparticles in amount of 0.05-2% of the mass of chitosan. The fibre has a single-phase homogeneous structure which corresponds to the basic form of chitosan.

EFFECT: obtaining a biocompatible, biodegradable composite elastic and strong fibre based on chitosan for use in medicine and biotechnology, particularly in suture filaments and in cellular engineering.

2 cl, 3 dwg, 8 ex

Description

Technical field

The invention relates to the chemistry of macromolecular compounds, more specifically to biocompatible biodegradable composite fibers based on chitosan and a hydrosilicate filler in the form of nanoparticles, and the technology for their preparation.

Biocompatible biodegradable composite fibers can be used to make surgical suture threads.

The invention may find application in medicine and veterinary medicine.

State of the art

In modern biotechnology and medicine, biocompatible biodegradable materials are extremely relevant. Chitosan is of particular interest as the basis for these materials. Chitosan is obtained from the natural polymer of chitin, which is part of the shell of crustaceans. Chitosan has biocompatibility, biodegradability, bactericidal activity, high sorption characteristics, as well as environmental friendliness of processing [G. Vikhoreva, L. S. Golbreich. Films and fibers based on chitin and its derivatives / In collection: Chitin and chitosan. Obtaining, properties and application. - M .: Nauka, 2002. - S.254-278]. Chitosan is widely used in pharmacology, cosmetology, food industry and a number of other areas. Recently, chitosan is increasingly used in cell technology to produce one-, two- and three-dimensional matrices for cell proliferation. Such matrices have good adhesion to stem and somatic cells, cell proliferation is effective on them, and cytotoxicity is absent [Composite matrices based on chitosan and montmorillonite for cell transplantology. Popryadukhin P.V., Dobrovolskaya I.P., Yudin V.E. et al. // Cytology. 2011. No. 12. S.952-958].

Chitosan fibers are promising for the creation of surgical suture threads.

A known method for producing biocompatible biodegradable fibers from chitosan is described in US patent No. 5896821 (publ. 04/27/1999). According to a known method, a molding solution is prepared by dissolving chitosan with a degree of deacetylation of 70% in an aqueous solution of sodium thiocyanate at 100 ° C for two hours; fiber forming is carried out in a precipitation bath of acetone at 4 ° C; the spun fiber is washed with water at 80 ° C.

Known fibers and a method for their preparation have several disadvantages. The obtained fibers are elastic, but have a strength of 0.46-0.52 g / denier (41.4-67.5 MPa), at least 1.36 g / denier required for the fibers from which the surgical sutures are made (182 MPa ), preferably 250 MPa. Providing a certain temperature regime at each stage of the process leads to high energy costs. In addition, the use of acetone is explosive and fire hazard.

A known method of producing chitosan acetate and biocompatible biodegradable fibers from it (US patent No. 4861527, publ. 08.29.1989). After treatment of the crab shell with acetone, hydrochloric acid, neutralization with alkali at 100 ° C, the chitosan released is washed with water, treated with concentrated formic acid in a nitrogen atmosphere at 0 ° C. The precipitation of chitosan acetate is carried out with methanol and acetone. To prepare the molding solution, the obtained chitosan acetate is dissolved in glacial acetic acid with the addition of acetic anhydride. The fiber is formed in a wet manner; methanol is the precipitant. Chitosan acetate fibers are treated with a 30% NaOH solution at a temperature of 116 ° C. under nitrogen. The average fiber strength is 6.6 g / denier (890 MPa). The multi-stage process of obtaining fibers from chitosan acetate, the use of concentrated acids and alkalis, high temperatures complicates the industrial implementation of the known method. The method is not environmentally friendly. The use of a large number of chemical treatments increases the toxicity of the fiber, especially cytotoxicity, reduces the biocompatibility of the obtained fibers. In addition, chitosan acetate has a low water resistance and, as a result, a high swelling of the polymer in aqueous media, which sharply reduces the mechanical characteristics of the fibers and makes them difficult to use in aqueous media.

The process of obtaining woven, non-woven products and sponges with biocompatibility, biodegradability, antimicrobial properties, from the fibers of regenerated chitin-chitosan is described in US patent No. 5756111 (publ. 05.26.1998). A molding solution is prepared by dissolving the alkaline chitin-chitosan obtained from the crab shells in carbon disulfide, while the process of xanthogenization of chitosan occurs. The fibers are formed into an acid bath. The specified method for the production of fibers carries a large environmental burden, since carbon disulfide is used, which has high toxicity, fire and explosion hazard.

Fibers, films and sponges of biodegradable polymers based on a composition consisting of two immiscible phases, one of which is a polymer, and the second is a therapeutic substance, described in US patent No. 6596296 (publ. 22.07.2003). To obtain fibers from chitosan and chitosan sulfate, the polymer is dissolved in hydrochloric acid; a 5% NaOH solution was chosen as the precipitant. Known compositions can be used mainly as a matrix for cell technology.

In [Preparation of chitosan filament applying new coagulation system. Tomura H., Tsuruta Yu, Itoyama K. et al. // Carbohydrate Polymers. 2007. V. 56. P.205-211; Effect of Hydroxyethylation on Structure and Properties of Chitosan Fibers. Liu Y., Liu Z., Yu J. et al. // J. of Macromol. Science, B: Physics, 2008. V. 47. P.392-400] describes the structure and properties of biocompatible biodegradable fibers formed from a solution of chitosan in acetic acid. It was shown that the optimal solvent for chitosan is a 2% aqueous solution of acetic acid; the precipitant may be alkali, mixtures of alcohol and water, a water-alcohol solution of NaOH. The obtained fibers are elastic, but have insufficient strength for the manufacture of surgical sutures.

Analysis of the above analogues of the claimed invention shows that chitosan can be obtained elastic biocompatible biodegradable non-cytotoxic fibers for surgical sutures, but there is a problem of their hardening.

The traditional way of hardening polymeric materials is to use crosslinkers. Thus, biocompatible biodegradable sponge materials based on chitosan and a method for their preparation are described in US patent application 20070254016. To increase the stability of the wet size of the sponge, chitosan was subjected to intermolecular crosslinking. To do this, the sponge in the wet state is treated with vapors of a solution of a cross-linking agent Na-triphosphate, dried at a temperature of 80 ° C for 1-2 hours. However, the introduction of cross-links affects the elasticity of the material.

Hematized filament from chitosan is not known. This is due to the fact that the use of crosslinking agents dramatically increases the fragility of the fibers.

The authors of the claimed invention made an attempt to obtain composite chitosan fibers, including natural hydrosilicate fillers, because It is known that composite materials may have better strength than pure polymers.

Closest to the claimed invention are biocompatible biodegradable composite fibers based on chitosan and a hydrosilicate filler - hallotite and chrysotile nanotubes described in the article of the authors of the claimed invention [Structure and properties of chitosan-based fibers containing chrysotile and halloysite. Dobrovolskaya I.P., Popryadukhin P.V., Dresvyanina E.H. and others. // High mol. conn. 2011. T.A53, No. 5. S.726-732] (analogue prototype).

In known fibers, chitosan has a deacetylation degree of 80%, a molecular weight of 255 kDa. Nanoparticles — nanotubes of halloysite and synthetic chrysotile (natural chritosyl cytotoxic) —are selected as fillers. These excipients are non-cytotoxic. A known method for producing fibers includes preparing a molding solution: obtaining a 4% solution of chitosan in a 2% aqueous solution of acetic acid, introducing filler particles into the solution in an amount of 3-5 wt.%, Forming the fiber into an alcohol-alkaline precipitation bath, it 100-120% extraction, washing and drying of the fiber. When this is controlled, the shear rate of the polymer solution in the longitudinal direction $$\dot{\gamma }$$

, $$\dot{\gamma }=\left(\frac{D^2}{d^2}-\mathrm{one}\right)V_{\mathrm{one}}^2/l$$

,

where D is the diameter of the syringe, d is the diameter of the hole of the die,

V ₁ - polymer feed rate, l - die thickness.

Known fibers are characterized by a two-phase structure corresponding to the salt and basic forms of chitosan [Structure and transport properties of chitosan films modified by heat treatment. Ageev E.P., Vikhoreva G.A., Zotkin M.A. and others. // High mol. conn. 2004. T.A46, No. 12. S.2035].

The strength characteristics of the known fibers are: strength, σ = 14.6 Sn / tex (219 MPa), elastic modulus, E = 6.5 GPa. They have a heterogeneous, heterogeneous structure: a loose core, a dense shell. Known fibers have a strength insufficient for surgical sutures. Upon contact with water, their strength and elastic modulus are significantly reduced.

Analysis of the above analogues of the claimed invention indicates that the resource of improving the strength of the fiber and preventing its cytotoxicity due to chemical modification of chitosan is practically exhausted. At the same time, the search for new approaches in creating biocompatible biodegradable fibers from chitosan is still relevant, because it is one of the few natural polymers available that are promising from the point of view of use in medicine.

One of such new approaches used by the authors of the claimed invention is the creation of composite fibers with original valuable practical properties from chitosan with nanofillers. The development of the technology for producing composites is currently a relatively young and promising field of material science, which allows, based on a combination of already known and produced polymers, to give them fundamentally new properties more efficiently and quickly compared to the time-consuming and lengthy way of creating new synthetic materials. The use of hydrosilicate nanoparticles not causing cytotoxicity as a regulatory mechanism can significantly expand the possibilities for varying the physicochemical properties of such biomaterials and, accordingly, their clinical application.

Disclosure of invention

The objective of the invention is the creation of a biocompatible biodegradable composite elastic and durable fiber based on chitosan for use in medicine and biotechnology, for example, in surgical suture threads and in cell technologies. The resulting fiber should not contain traces of chemicals that are potentially cytotoxic.

This problem is solved by the claimed group of two inventions - biocompatible biodegradable composite fiber and the method for its preparation.

The inventive biocompatible biodegradable composite fiber is characterized by the following set of essential features:

в плоскости поперечного сечения капилляра при прохождении раствора через фильеру в интервале 1-18 с^-1, вычисленной по формуле $$\dot{\gamma }=\frac{2Q}{\pi R^3}$$

.1. A biocompatible biodegradable composite fiber, including chitosan with a degree of deacetylation of 60-95%, a molecular weight of 20 - 450 kDa and a hydrosilicate filler - halloysite, chrysotile, montmorillonite - in the form of nanoparticles in the amount of 0.05-2% by weight of chitosan, with single-phase a homogeneous structure corresponding to the main form of chitosan formed when the fiber is formed through a spinneret with a radius R at a feed rate of the molding solution Q, at a given value of the shear rate of the solution $$\dot{\gamma }$$

in the plane of the cross section of the capillary when the solution passes through the die in the range of 1-18 s ^-1 , calculated by the formula $$\dot{\gamma }=\frac{2Q}{\pi R^3}$$

.

The set of essential features of the claimed fiber provides a technical result - increase the strength characteristics of the fiber to 290 MPa and higher while maintaining elasticity, as well as the absence of cytotoxicity. Fibers retain mechanical properties in aqueous media.

The inventive fiber differs from the known prototype fiber in the qualitative and quantitative composition of the hydrosilicate filler and is characterized by a different morphology - a single-phase structure corresponding to the main form of chitosan, formed due to a different molding method (in the case of the prototype analog, the fiber is characterized by a two-phase structure corresponding to the salt and main forms of chitosan )

The analysis of the prior art did not allow to find a solution that completely coincides in the totality of essential features with the claimed, which may indicate the novelty of a biocompatible biodegradable composite fiber.

Only the set of essential features of the claimed biocompatible biodegradable composite fiber allows to achieve the specified technical result. It was completely unexpected that, in comparison with the prototype analogue, in which the authors of the claimed invention had previously made an attempt to introduce hydrosilicate filler nanoparticles into chitosan and obtained a two-phase structure fiber, changing the parameters of the filler composition and the conditions for forming the fiber would result in the claimed fiber being different, single-phase, a structure that remains elastic and surpasses the known strength characteristics by 30%, and will also retain mechanical properties in water. The first result was obtained by chance when preparing a composite fiber in the conditions of the prototype for study. This allows us to confirm the compliance of the claimed material with the eligibility condition "inventive step" ("non-obviousness").

The inventive method for producing a biocompatible biodegradable composite fiber has the following set of essential features:

в плоскости поперечного сечения капилляра при прохождении раствора через фильеру выбирают из интервала 1-18 с^-1, при этом скорость сдвига $$\dot{\gamma }$$

вычисляют по формуле $$\dot{\gamma }=\frac{2Q}{\pi R^3}$$

, формование волокна проводят в спиртовый или спиртово-щелочной осадитель, волокно вытягивают на 10-120%, промывают водой, сушат при температуре 20-50°C.1 (2). A method of producing a biocompatible biodegradable composite fiber, which consists in mixing a hydrosilicate filler — halloysite, chrysotile, montmorillonite — in the form of nanoparticles with a degree of chitosan, which is previously dispersed in water in an ultrasonic field with a frequency of ν = 20-100 kHz deacetylation of 60-95%, a molecular weight of 20 to 450 kDa, with a chitosan content of 1-4 wt.%, the amount of filler being 0.05-2% by weight of chitosan, the resulting mixture is intensively mixed at a temperature of 20-50 ° C for 20-60 minutes, add concentrated acetic acid in an amount corresponding to the preparation of an aqueous solution of acetic acid with a concentration of 1-8 wt.%, Mix the mixture intensively at a temperature of 20-50 ° C for 20-250 minutes, filter, dehydrate, form the fiber from the mixture through a die of radius R at the feed rate of the polymer solution Q; solution shear rate $$\dot{\gamma }$$

in the plane of the cross section of the capillary during the passage of the solution through the die, choose from the interval 1-18 s ^-1 , while the shear rate $$\dot{\gamma }$$

calculated by the formula $$\dot{\gamma }=\frac{2Q}{\pi R^3}$$

, fiber forming is carried out in an alcohol or alcohol-alkaline precipitant, the fiber is pulled out by 10-120%, washed with water, dried at a temperature of 20-50 ° C.

The set of essential features of the proposed method allows to achieve a technical result: simplification and cheapening of the method for producing fibers for surgical sutures, providing control over the operations and morphology of the final product, obtaining material with better strength characteristics than analogues. The proposed method is environmentally friendly, because the fiber is obtained directly from chitosan in a solution of acetic acid, traces of which are not observed in the final product. For the same reason, the fiber is non-cytotoxic.

The proposed method for producing a biocompatible biodegradable composite fiber differs from the known prototype method in that it includes a shift in the transverse direction of the jet of a mixture of a solution of chitosan and filler nanoparticles when passing through a die, the speed of which is set from the interval 1-18 s ^-1 , which allows a shear field oriented system of macromolecules and thereby change the morphology of the fiber and its properties. Moreover, in the claimed invention, the shear rate (speed gradient) in loskosti cross-section of the capillary (the die), in the analogue - longitudinally. The method also differs in that less filler is added.

The analysis of the prior art did not allow to find a solution that completely coincides in the totality of essential features with the claimed, which may indicate the novelty of the method.

Only the set of essential features of the proposed method for producing a biocompatible biodegradable composite fiber allows to achieve the specified technical result. The very possibility of obtaining an elastic durable biocompatible biodegradable non-toxic fiber directly from chitosan, completely bypassing the stage, for example, chemical crosslinking, was completely unobvious. As the analysis of analogues shows, the use of filler in itself does not guarantee the production of elastic and at the same time strong fiber. Only the original set of conditions of the method led to the target result - an increase in fiber strength by a significant amount, by 30%, without compromising elasticity. This allows us to confirm the compliance of the proposed method with the eligibility condition "inventive step" ("non-obviousness").

Thus, the group of claimed inventions as a whole has novelty and non-obviousness.

The proposed group of inventions allows to solve the problem of obtaining a biocompatible biodegradable composite fiber for surgical filaments with a stable strong structure and not having cytotoxicity.

Graphic materials:

Figure 1 shows micrographs of the surface (a) and cross section (b) of a fiber made of pure chitosan and a composite fiber containing 0.5 wt.% Chrysotile (c and d, respectively). It is seen that the filler nanoparticles are uniformly distributed throughout the volume, well oriented along the fiber axis, the composite fiber is uniform in cross section.

Figure 2 shows x-ray diffraction patterns of fibers of pure chitosan (a) and a composite fiber containing 0.5 wt.% Chrysotile (b). In the case of a composite fiber, the salt form of chitosan is absent, the main form of chitosan and the single-phase homogeneous fiber structure are observed. On the roentgenogram of the composite fiber there are no reflections of the salt form of chitosan in the angle range 2θ = 8.1 °; 16.2 °; 25.3 °; 27.5 ° and 35.3 °.

Figure 3 shows micrographs of adipose tissue mesenchymal stem cells (ASCs) on the surface of a composite fiber containing 2 wt.% Chrysotile (a) and a film of chitosan containing 2 wt.% Montmorillonite (b). Good adhesion and flattening of stem cells is visible, which indicates the absence of cytotoxicity of composite fibers.

To confirm the compliance of the claimed group of inventions with the requirement of "industrial applicability" we give examples of specific implementations.

Starting materials and reagents:

Chitosan manufactured by BioChemika (Japan) from crab shells, the degree of deacetylation of 60-95%, molecular weight of 20-450 kDa, the content of insoluble substances less than 1%.

Hydrosilicate filler:

Nanoparticles - halloysite nanotubes (Al ₄ [Si ₄ O ₁₀ ] (OH) ₈ × 4H ₂ O), the average diameter of which is 100 nm, a length of 0.5 - 1.2 microns; Chrysotile (Mg ₃ Si ₂ O ₅ (OH) ₄ ) nanotubes with a diameter of 15–20 nm and a length of 100–200 nm obtained by the method of hydrothermal synthesis at the Institute of Silicate Chemistry of the Russian Academy of Sciences (St. Petersburg). Montmorillonite (Na-MMT) manufactured by Southern Clay Products, Inc. (USA), cation-exchange capacity of 92.6 meq / 100 g. Nanoparticles in the form of basic dies of montmorillonite (the exfoliated state of montmorillonite) are obtained by sonication during the dispersion of the filler when implementing the inventive method. Characterized using a Supra 55VP scanning electron microscope (C. Zeiss).

Glacial acetic acid, glacial NaOH, chemically pure ammonia, alcohols - products of CJSC Vecton (Russia).

Ultrasonic treatment of the filler in an aqueous medium was carried out on an IL 100-6 installation.

Methods and instruments for characterizing a biocompatible biodegradable composite fiber:

The fiber structure was studied using a Supra 55VP scanning electron microscope (C. Zeiss), before measurements according to the standard method, a thin layer of gold was sprayed onto the surface of the samples, as well as X-ray diffraction on a ULTIMA IV multifunctional diffractometer (Rigaku, Japan), Cu Kα - radiation.

The elastic modulus E and strength σ were determined using a universal fiber testing facility (UMIV, Ivanovo), the test base was 15 mm, and the loading speed was 1 mm / min. Before the tests, the fibers were kept in a desiccator at a relative humidity of 66% for 3 days, the time required to reach the equilibrium moisture content of the fibers, the value of which was 20 ± 2%.

The absence of cytotoxicity is determined by the adhesion of adipose tissue mesenchymal stem cells (ASCs) on the surface of composite fibers and chitosan films containing filler nanoparticles.

Examples of obtaining composite fiber.

Example 1

A biocompatible biodegradable composite fiber comprising chitosan and chrysotile in an amount of 0.5% by weight of chitosan.

Getting fiber.

, Disperse 0.2 g of chrysotile in 1000 ml of water in an ultrasonic field with a frequency of ν = 20 kHz for 10 min, mix with chitosan with a degree of deacetylation of 60%, and a molecular weight of 20 kDa. in an amount of 40 g, corresponding to its concentration in the mixture of 4 wt.%, while the amount of filler is 0.5% by weight of chitosan, the resulting mixture is stirred vigorously at a temperature of 20 ° C for 20 min, concentrated acetic acid in an amount of 20 ml is added corresponding to obtaining in a mixture of an aqueous solution of acetic acid with a concentration of 2 wt.%, intensively mix the mixture at a temperature of 20 ° C for 20 minutes, filter, dehumidify, the fiber is formed through a die with a radius of R = 0.3 mm, at a shear rate of the solution in the plane and the cross-section by passing it through a die $$\dot{\gamma }=\frac{2Q}{\pi R^3}=\mathrm{eighteen}{c}^{-\mathrm{one}}$$

,

wherein the feed rate of the polymer solution is Q = 0.023 ml / min; fiber forming is carried out in an alcohol-alkaline mixture, the fiber is pulled by 40%, washed with water, dried at a temperature of 20 - 50 ° C.

Mechanical characteristics: E = 7.2 GPa, σ = 290 MPa.

An electron microscopic image of the cross section of the fiber showed that the filler nanoparticles are uniformly distributed throughout the volume, well oriented along the fiber axis. Composite fiber is uniform in cross section (figure 1).

The fiber structure is homogeneous single-phase. The X-ray diffraction pattern indicates the presence of the main and the absence of the salt phase of chitosan, as evidenced by the absence of x-ray reflections in the range of angles 2θ = 8.1 ° and 16.2 ° (figure 2). The fiber does not swell in water and retains mechanical properties.

Example 2

A biocompatible biodegradable composite fiber comprising chitosan and chrysotile in an amount of 2% by weight of chitosan. Getting fiber.

в плоскости поперечного сечения капилляра при прохождении раствора через фильеру вычисляют по формуле $$\dot{\gamma }=\frac{2Q}{\pi R^3}=18c^{-1}$$

, Disperse 0.8 g of chrysotile in 1000 ml of water in an ultrasonic field with a frequency of ν = 100 kHz for 5 min, mix with chitosan with a degree of deacetylation of 95%, a molecular weight of 450 kDa, in an amount of 40 g, corresponding to its concentration in a mixture of 4 wt. %, while the amount of filler is 2% by weight of chitosan, the resulting mixture is intensively stirred at a temperature of 50 ° C for 60 minutes, concentrated acetic acid is added in an amount of 80 ml, which corresponds to the preparation of an aqueous solution of acetic acid with a concentration of 8 wt.% , int vigorously mix the mixture at a temperature of 50 ° C for 250 min, filter, dehydrate, form the fiber through a die with a radius of R = 0.3 mm at a polymer solution feed rate of Q = 0.001 ml / min, the shear rate of the solution $$\dot{\gamma }$$

in the plane of the cross section of the capillary during the passage of the solution through the die is calculated by the formula $$\dot{\gamma }=\frac{2Q}{\pi R^3}=\mathrm{eighteen}{c}^{-\mathrm{one}}$$

,

fiber forming is carried out in ethanol, the fiber is pulled by 120%, washed with water, dried at a temperature of 20-50 ° C.

The fiber structure is homogeneous single-phase. The X-ray diffraction pattern indicates the presence of the main and absence of the salt phase of chitosan.

Mechanical characteristics: E = 8.2 GPa, σ = 310 MPa.

An electron microscopic image of the cross section of the fiber showed that the filler nanoparticles are uniformly distributed throughout the volume, well oriented along the fiber axis. Composite fiber is uniform in cross section.

The fiber does not swell in water and retains mechanical properties.

Example 3

A biocompatible biodegradable composite fiber comprising chitosan and chrysotile in an amount of 0.05% by weight of chitosan.

Obtaining fiber carried out according to example 1.

The fiber structure is homogeneous single-phase. The X-ray diffraction pattern indicates the presence of the main and absence of the salt phase of chitosan.

Mechanical characteristics: E = 5.2 GPa, σ = 260 MPa. It takes 7.0.

An electron microscopic image of the cross section of the fiber showed that the filler nanoparticles are uniformly distributed throughout the volume, well oriented along the fiber axis. Composite fiber is uniform in cross section.

The fiber does not swell in water and retains mechanical properties.

Example 4

A biocompatible biodegradable composite fiber comprising chitosan and halloysite in an amount of 2% by weight of chitosan.

Getting fiber carried out according to example 2.

The fiber structure is homogeneous single-phase. The X-ray diffraction pattern indicates the presence of the main and absence of the salt phase of chitosan.

Mechanical characteristics: E = 7.2 GPa, σ = 250 MPa.

An electron microscopic image of the cross section of the fiber showed that the filler nanoparticles are uniformly distributed throughout the volume, well oriented along the fiber axis. Composite fiber is uniform in cross section.

The fiber does not swell in water and retains mechanical properties.

Example 5

A biocompatible biodegradable composite fiber comprising chitosan and halloysite in an amount of 2% by weight of chitosan.

Getting fiber.

в плоскости поперечного сечения капилляра при прохождении раствора через фильеру вычисляют по формуле $$\dot{\gamma }=\frac{2Q}{\pi R^3}=10c^{-1}$$

, Disperse 0.2 g of halloysite in 1000 ml of water in an ultrasonic field with a frequency of ν = 20 kHz for 10 min, mix with chitosan with a degree of deacetylation of 80%, a molecular weight of 250 kDa, in an amount of 10 g, corresponding to its concentration in a mixture of 1 wt. %, while the amount of filler is 2% by weight of chitosan, the resulting mixture is stirred vigorously at a temperature of 20 ° C for 60 minutes, concentrated acetic acid is added in an amount of 10 ml, corresponding to the preparation of an aqueous solution of acetic acid in a mixture of 1 wt.% , in vigorously mix the mixture at a temperature of 20 ° C for 20 min, filter, dehydrate, form the fiber through a die with a radius of R = 0.3 mm at a polymer solution feed rate of Q = 0.013 ml / min, the shear rate of the solution $$\dot{\gamma }$$

in the plane of the cross section of the capillary during the passage of the solution through the die is calculated by the formula $$\dot{\gamma }=\frac{2Q}{\pi R^3}=10c^{-\mathrm{one}}$$

,

fiber forming is carried out in ethanol, the fiber is pulled by 10%, washed with water, dried at a temperature of 20-50 ° C.

The fiber structure is homogeneous single-phase. X-ray diffraction pattern indicates the presence of the main and absence of the salt phase of chitosan

Strength characteristics: E = 6.5 GPa, σ = 270 MPa.

An electron microscopic image of the cross section of the fiber showed that the filler nanoparticles are uniformly distributed throughout the volume, well oriented along the fiber axis. Composite fiber is uniform in cross section. The fiber does not swell in water and retains mechanical properties.

Example 6

A biocompatible biodegradable composite fiber comprising chitosan and halloysite in an amount of 0.5% by weight of chitosan.

Obtaining fiber carried out according to example 1.

The fiber structure is homogeneous single-phase. X-ray diffraction pattern indicates the presence of the main and absence of the salt phase of chitosan

Strength characteristics: E = 6.5 GPa, σ 250 MPa.

An electron microscopic image of the cross section of the fiber showed that the filler nanoparticles are uniformly distributed throughout the volume, well oriented along the fiber axis. Composite fiber is uniform in cross section.

The fiber does not swell in water and retains mechanical properties.

Example 7

A biocompatible biodegradable composite fiber comprising chitosan and montmorillonite in an amount of 0.05% by weight of chitosan.

Getting fiber.

0.005 g of montmorillonite is dispersed in 1000 ml of water, pH 7, in an ultrasonic field with a frequency of ν = 20 kHz for 10 min to obtain a dispersion of montmorillonite in an exfoliated state (dispersed to base layers) in the form of nanoparticles.

в плоскости поперечного сечения капилляра при прохождении раствора через фильеру вычисляют по формуле $$\dot{\gamma }=\frac{2Q}{\pi R^3}=18c^{-1}$$

, Montmorillonite and chitosan dispersed in an aqueous medium are mixed with a degree of deacetylation of 95%, a molecular weight of 50 kDa in an amount of 10 g, corresponding to a solution concentration of 1 wt.%, While the amount of montmorillonite is 0.05% by weight of chitosan. The resulting mixture was stirred vigorously at a temperature of 20 ° C for 20 min, concentrated acetic acid was added in an amount of 10 ml, corresponding to the preparation of an aqueous solution of acetic acid in a mixture of 1 wt.%. Intensively mix the mixture at a temperature of 20 ° C for 20 minutes, filter, dehydrate. The fiber is formed through a die with a radius of R = 0.3 mm at a polymer solution feed rate of Q = 0.023 ml / min; solution shear rate $$\dot{\gamma }$$

in the plane of the cross section of the capillary during the passage of the solution through the die is calculated by the formula $$\dot{\gamma }=\frac{2Q}{\pi R^3}=\mathrm{eighteen}{c}^{-\mathrm{one}}$$

,

fiber forming is carried out in ethanol, the fiber is pulled by 40%, washed with water, dried at a temperature of 20-50 ° C.

The fiber structure is homogeneous single-phase. The X-ray diffraction pattern indicates the presence of the main and absence of the salt phase of chitosan.

Mechanical characteristics: E = 7.2 GPa, σ = 260 MPa.

An electron microscopic image of the cross section of the fiber showed that the filler nanoparticles are uniformly distributed throughout the volume. Composite fiber is uniform in cross section.

The fiber does not swell in water and retains mechanical properties.

Example 8

A biocompatible biodegradable composite fiber comprising chitosan and montmorillonite in an amount of 2% by weight of chitosan.

Getting fiber.

в плоскости поперечного сечения капилляра при прохождении раствора через фильеру вычисляют по формуле $$\dot{\gamma }=\frac{2Q}{\pi R^3}=18c^{-1}$$

, 0.8 g of montmorillonite is dispersed in 1000 ml of water in an ultrasonic field with a frequency of ν = 20 kHz for 60 minutes, mixed with chitosan with a degree of deacetylation of 60%, a molecular weight of 20 kDa, in an amount of 40 g, corresponding to its concentration in a mixture of 4 wt. %, while the amount of filler is 2% by weight of chitosan, the resulting mixture is stirred vigorously at a temperature of 20 ° C for 20 minutes, concentrated acetic acid is added in an amount of 20 ml, corresponding to the preparation of an aqueous solution of acetic acid with a concentration of 2 ma in a mixture .%, The mixture was stirred vigorously at 20 ° C for 20 minutes, filtered, obezvozdushivayut, fiber was spun through a spinneret radius R = 0,3 mm at a feed speed of the polymer solution Q = 0,023 ml / min, the shear rate value of the solution $$\dot{\gamma }$$

in the plane of the cross section of the capillary during the passage of the solution through the die is calculated by the formula $$\dot{\gamma }=\frac{2Q}{\pi R^3}=\mathrm{eighteen}{c}^{-\mathrm{one}}$$

,

the fiber is formed into ethanol, the fiber is pulled 100%, washed with water, dried at a temperature of 20-50 ° C.

The fiber structure is homogeneous single-phase. The X-ray diffraction pattern indicates the presence of the main and absence of the salt phase of chitosan.

Mechanical characteristics: E = 7.5 GPa, σ = 265 MPa. Filler nanoparticles are uniformly distributed throughout the volume. Composite fiber is uniform in cross section.

The fiber does not swell in water and retains mechanical properties.

Application:

The inventive fibers are promising for obtaining surgical filaments, matrices for cell technology.

Such materials should have the necessary strength, elasticity, preservation of these properties in contact with aqueous media, the absence of cytotoxicity, and biodegradability.

As shown above, the inventive fibers have the strength and elasticity required for surgical sutures (E = 6.5-8.2 GPa, σ = 250-290 MPa).

The absence of cytotoxicity of fibers from chitosan and composite fibers containing hydrosilicate nanoparticles follows, firstly, from the fact that chitosan and the nanoparticles used are nontoxic in themselves, and, secondly, from the observed good adhesion and high proliferation of stem cells on the surface obtained fibers (figure 3).

Information on the kinetics of resorption of chitosan fibers and composite fibers in vivo is necessary to predict the properties of suture materials in a living organism.

The environment in which the resorption process occurs consists of a complex of proteolytic enzymes of animal and bacterial origin characteristic of this tissue, as well as amino acids, macrophages, etc. Due to the complexity of the biological and enzymatic composition of the environment surrounding the matrix or suture, it is extremely difficult to model it in vitro complicated. Data on the kinetics of resorption of fibers from chitosan in a living organism are not available in the literature.

In order to obtain the most complete and reliable information about the behavior of suture materials and one-dimensional matrices in an active biological environment, which is most consistent with the environment of muscle tissue, an in vivo study of resorption in rat tissue was performed.

To study the resorption of chitosan and composite chitosan fibers, a 25 mm long bundle containing 10 monofilaments with a diameter of 90-100 μm, after sterilization in ethanol, was placed between the fibers of the rat spinal muscle. For comparison, in one of the animals a bundle of threads was placed in the subcutaneous tissue. Rats had one line, the weight of experimental animals was 180-200 g. After application of the external suture, the rats were kept in individual cages. With an interval of 5-7 days, the fiber was removed from one of the animals. The resorption process can be represented by the following scheme. Up to 12 days, the fiber practically does not change its diameter, destruction is not observed. In some places, focal surface destruction can be observed. After exposure for 17 days, fiber fragmentation to segments of 3-5 mm length and partial resorption of fiber fragments are observed. Intensive destruction occurs on the 21st day of exposure; a significant part of the fibers is resorbed, the remaining fibers are fragmented. On day 30, fibers from both chitosan and composite are completely resorbed.

It should be noted that in no case was inflammation of the wound surfaces surrounding the tissues observed, animals were active.

Thus, an in vivo study of the resorption of chitosan fibers and composite fibers showed that after exposure of the fibers in the rat spinal muscle for 15 days, fiber fragmentation to segments of 3-5 mm length and their partial resorption is observed. On the 30th day of exposure, complete fiber resorption is observed.

The implementation of the claimed invention is not limited to the above examples.

Going beyond the lower boundaries of the claimed intervals leads to a decrease in the strength of the claimed fiber.

Going beyond the upper boundaries of the claimed intervals dramatically increases the viscosity of the mixture of filler and a solution of chitosan in acetic acid, which significantly complicates the process of uniform distribution of the filler and the formation of the fiber.

The range of concentrations of the filler is due to the fact that, firstly, the minimum filler provides better resorption. Secondly, the introduction of filler in an amount similar to the prototype affects the properties of the fiber - it loses its strength. This indicates that the claimed technical result is due to a combination of essential features - the composition, orientation of the fiber, and in the method - the concentrations and conditions of preparation of the molding solution and the formation of the fiber.

The data given in examples 1-8 indicate that, as a result of the implementation of the claimed group of inventions, elastic durable biocompatible biodegradable composite fibers are obtained that are not cytotoxic and suitable for the manufacture of surgical sutures in terms of properties. The method of producing fibers is well reproducible and environmentally friendly.

Claims (2)

1. A method of producing a biocompatible biodegradable composite fiber, which consists in mixing a hydrosilicate filler — halloysite, chrysotile, montmorillonite — in the form of nanoparticles with chitosan, which is previously dispersed in water in an ultrasonic field with a frequency of ν = 20-100 kHz with a degree of deacetylation of 60-95%, a molecular weight of 20-450 kDa, with a chitosan content of 1-4 wt.%, while the amount of filler is 0.05-2% by weight of chitosan, the resulting mixture is intensively mixed at a temperature of 20- fifty C for 20-60 minutes, add concentrated acetic acid in an amount corresponding to the preparation of an aqueous solution of acetic acid with a concentration of 1-8 wt.% In the mixture, mix the mixture intensively at a temperature of 20-50 ° C for 20-250 minutes, filter , dehydrate, fiber is formed from the obtained molding solution through a die of radius R at the feed rate of the polymer solution Q, the shear rate of the solution

in the plane of the cross section of the capillary during the passage of the solution through the die, choose from the interval 1-18 s ^-1 , while the shear rate

calculated by the formula

, the fiber is formed in an alcohol or alcohol-alkaline precipitant, the fiber is pulled out by 10-120%, washed with water, dried at a temperature of 20-50 ° C. 2. A biocompatible biodegradable composite fiber obtained by the method according to claim 1, comprising chitosan with a degree of deacetylation of 60-95%, a molecular weight of 20-450 kDa and a hydrosilicate filler - halloysite, chrysotile, montmorillonite - in the form of nanoparticles in the amount of 0.05-2 % of the mass of chitosan, with a single-phase homogeneous structure corresponding to the main form of chitosan formed when the fiber is formed through a die with radius R at the feed rate of the molding polymer solution Q, at a given value of the shear rate of the solution

in the plane of the cross section of the capillary during the passage of the solution through the die in the interval
1-18 s ^-1 calculated by the formula

.

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