RU2425700C1 - Laser-beam bio-tissue welding technique - Google Patents

Abstract

FIELD: medicine. ^ SUBSTANCE: laser-beam welding is conducted with using a biological solder which represents a dispersion of binding agent in the form of an aqueous composite of proteins and/or biocompatible polymers additionally containing carbon nanotubes and surface-active substances. ^ EFFECT: technique provides reliable connection of injured bio-tissues, including due to creating in a composite an internal volume nanoskeleton determining high mechanical strength of laser joint weld, and ease of laser-beam welding without applying expensive materials. ^ 3 dwg, 2 tbl, 1 ex

Description

The invention relates to the field of laser medicine, in particular to methods for joining damaged biological tissues by laser welding.

The most important tasks of modern surgery are the development and implementation in clinical practice of new methods of connecting organs and tissues, simple in execution for the surgeon and sparing for the patient. Their implementation requires a number of necessary conditions to ensure the reliability of the connection of organs or tissues, guaranteeing their functioning in the early postoperative period and the speedy restoration of the functions of the operated organ. Existing traditional methods of restoring the integrity of the fabric using suture materials, metal brackets, staplers, adhesive compositions and other means are imperfect.

One of the most important areas of laser medicine - laser surgery - distinguishes from most traditional areas of surgery the possibility of dissection, melting (ablation) and evaporation of biological tissues with minimal concomitant injuries, along with a reduced chance of wound infection and minimal blood loss during surgery. Laser surgical engineering continues to develop in the direction of joining (seamless welding) dissected biological tissues, which can be used with both open and closed surgical fields (through a small laparoscopic incision).

Thanks to laser welding, the tightness of the wound is ensured, there is no compression of the seams of tissues and their marginal necrosis, wound healing is not accompanied by the formation of a rough scar. In vascular and heart surgery, laser sutures can be used to fix the patch in the area of a defect in the vessel wall, with the goal of hemostasis and sealing the suture line of the vascular anastomosis; in pulmonary surgery - to close large wound surfaces that arose after resection of the lung or isolation of the lung from adhesions, to close small bronchial fistulas, to seal and strengthen the suture line of the anastomosis or bronchus stump; in abdominal surgery - for additional sealing of anastomoses, in particular, during resection of the rectum; in urology, as an addition to catgut sutures, for closing sections of the renal pelvis, ureter and bladder, during kidney transplantation [1].

Of particular importance is the laser welding of the smallest surgical objects, such as nerve fibers, blood capillaries, vas deferens, etc., where the suture connection of biological tissues is difficult and not very reliable [2].

In the case of the practical implementation of laser welding for strong and reliable welding, bio-solders are used, which include binders, which allows you to replace the usual stitching of the surgical wound with a surgical needle and thread. Laser heating of the bio-solder leads to thermal deformation of cells in the welding area with the release of the cell matrix, a biological tissue binding in the form of a laser suture [3].

Nevertheless, the conventional laser welding technique does not always provide the same strength of joints as a conventional surgical suture [4]. For this reason, it is interesting to search for new methods of laser welding using bio-solders based on carbon nanotubes. In this case, one can expect structuring of the suture material and increase its strength due to the creation of a fastening nanotube framework, as is the case in bulk nanocomposite materials based on carbon nanotubes created by laser radiation [5, 6].

The use of carbon nanotubes for connecting bone elements and adjacent bones in orthopedic implants is known [7].

The specified device does not provide for the use of the action of laser radiation and bio-solders, which makes it inapplicable for laser welding of biological tissues.

A known method of laser welding of biological tissues using bioholders, which introduce binders - proteins, polysaccharides, nucleic acids, vitamins, metals or synthetic organic molecules [8].

The disadvantage of this method of laser welding of biological tissues is the lack of strength of laser seams, which can be overcome using bio-solders containing nanoparticles, in particular carbon nanotubes.

It is known to use bulk nanostructures based on carbon nanotubes obtained by the action of laser radiation for laser welding of human cartilage, which makes it possible to increase the strength of a laser weld compared to using solder based on albumin [9].

The disadvantage of this method of laser welding of biological tissues is the absence of surface-active substances in the bio-solders, which leads to an erratic connection of nanotubes under the action of van der Waals forces, which significantly reduces the efficiency of their use in bio-solders, without providing a sufficiently reliable connection of damaged biological tissues.

The closest technical solution of the proposed method for laser welding of biological tissues is a method of connecting biological tissues into which nanoparticles are introduced inside protein and biopolymer shells that are heated using optical radiation [10]. However, such shell nanoparticles, in particular nanogold, nanosilver and fullerenes, are an expensive material and cannot be used in general practice. In addition, the placement of nanoparticles in shells and the absence of surface-active substances in the bio-solders do not allow for a sufficiently reliable connection of damaged biological tissues.

For the above reasons, it is necessary to search for new, more efficient laser welding methods.

The invention is aimed at providing a reliable connection of damaged biological tissues. The specified technical result is achieved in that the method of laser welding of biological tissues involves the use of bio-solder, which is a dispersion of binders in the form of a composite in water based on proteins and / or biocompatible polymers, when laser irradiated, it differs in that carbon nanotubes are introduced into the bio-solder and surfactants in the following quantitative ratio of components (in% by weight):

Binder 10-50 Carbon nanotubes 0.1-0.5 Surface-active substance 1-3 Water Rest

A binder of 10-50 wt.% Can be introduced into the composition of the bio-solder; carbon nanotubes 0.1-0.5 wt.%; surfactant 1-3 wt.%; water is the rest.

Proteins (albumin), the natural biocompatible polymer chitosan, polysaccharides (amylose) and ethoxylated starch, collagens can be introduced into the composition of the binder of bio-solder.

The bio-solder may contain ionic surfactant (sodium) - dodecylbenzenesulfonate sodium, nonionic surfactant Neonol AF 9-12, zwitterionic surfactant - phosphatidylcholine, which is a biocompatible surfactant that performs certain functions in the human body.

The proposed method for laser welding of biological tissues using the specified composition of the solder and irradiating the connected biological tissues with an IR laser, characterized by the above set of essential features, guarantees high quality of the welded samples of biological tissues, ease of implementation and does not require the use of expensive reagents.

The results of laser welding of biological tissues in vitro, obtained using the proposed method for laser welding of biological tissues (bio solder compositions and laser irradiation conditions) are shown in Table 1.

Table 1 The compositions of the proposed bio-solders and the known composition taken as a prototype, the conditions of laser irradiation and the tensile strength of the laser seam for samples of bovine cartilage The compositions of the proposed bio solders The content of the components of the proposed bio-solders, wt.% Prototype (nanogold solution), wt.% Binder: - - - - - Albumen 25 - - - - 25 Amylose - thirty - - - - Chitosan - - 10 - - - Collagen - - - 40 - - Oxyethylated Starch - - - - fifty - Carbon nanotubes of the Taunit type 0.1 0.25 0.5 0.2 0.3 - Surface-active substance:
Sodium dodecylbenzenesulfonate
Neonol AF 9-12
Phosphatidylcholine - - - - - - one - - 1,5 - - 2 - - - - - - 2.5 - - - Water Rest Rest Rest Rest Rest 75 Irradiation power, W 13.0 9.2 13.0 11,4 9.2 11,4 Irradiation time, min 2.2 3.9 2,8 2.1 3.4 2.1 Laser seam tensile strength, MPa 1.4 1,1 1,2 0.85 0.95 0.65 The relative strength of T,% 23 eighteen twenty fourteen 16 eleven

Implementation example

First, prepare the laser solder as follows.

In distilled water at room temperature, a binder, a surfactant, carbon nanotubes are dissolved. The mixture is placed in an ultrasonic bath and dispersed for 2-5 hours at a temperature of 40-50 ° C until a homogeneous colloidal solder solution is obtained.

Welding was carried out on specimens of pig skin and cartilage of bovine trachea.

The cartilages of the bovine trachea were washed in water, then muscle tissue was separated from them using scissors and a surgical scalpel. After this, the trachea was divided into smaller parts and the surgical scalpel was cleaned of the fat layer and films, after which the perichondrium was separated in order to isolate pure cartilage.

The cleaned plates were immersed in soapy water for 5-10 minutes to finally remove the layer of adipose tissue from cartilage samples. After 10 minutes, the cartilage plates were washed in cold water and left in a container with physiological saline (5% aqueous sodium chloride solution).

Preparation for welding pig skin samples was carried out in a similar way.

Prior to the laser irradiation and welding of biological tissue samples, the container with the samples was stored in the refrigerator for no more than one day. Immediately before the start of the experiment, the plates were removed from the container with the solution and dried for 10 min in order to evaporate excess moisture from them.

Before welding, a cross section was applied to the cartilage, dividing it into 2 parts (Fig. 1). Laser solder was applied along the incision line of the samples with an insulin syringe (Fig. 2) and the cartilage was pressed tightly against each other for 20 s.

As a source of laser irradiation, a diode infrared laser with a fiber-optic radiation output with a generation wavelength λ _gene = 0.97 μm was used. Laser welding of the samples was carried out using the aforementioned device - the systematic advancement along the entire length of the incision from the outer side of the cartilage until a certain level of heating and adhesion of the samples was achieved (to prevent overheating and burning of tissue / solder), after which the reverse side of the plates was welded. The distance from the tip of the laser optical fiber to the surface to be welded was ~ 5 mm (Fig. 3).

The operations for pig skin samples were similar.

Measurement of tensile strength of cooked samples of pig skin and bovine cartilage

Tensile strength was measured as follows.

First, in the studied area of the welded sample, a narrowing was made with the center at the proposed location of the rupture so that the sample took the form of a dumbbell. The ends of the sample were fixed using clamps, one of which was attached a dynamometer, with which the value of the applied force was measured.

The tensile strength was determined by the formula

,

,

where F is the applied force at which the biological tissue ruptures, and S is the cross-sectional area of the sample in the narrowing region.

The cross-sectional area of samples S was approximately 1.2 to 10 mm ² . The load force F is from 3 to 7 N.

To calculate the relative tensile strength of welded samples, the tensile strength of intact biological tissue was measured, and the relative tensile strength was calculated by the formula:

,

,

where T is the relative tensile strength,

σ _bt is the tensile strength of intact biological tissue,

σ _sv is the tensile strength of welded samples.

The results of measurements of the tensile strength of cooked samples of pig skin and bovine cartilage are given in table 2.

For statistical accuracy, strength measurements of samples welded with different composition of solder were carried out using several samples in each test group. To calculate the relative tensile strength, the average values for each group were used.

The results of measurements of the tensile strength of cooked samples of pig skin and bovine cartilage are given in Table 2 for the composition of bio-solder based on a 25% aqueous solution of bovine serum albumin with sodium dodecylbenzenesulfonate (1.5 wt.%) And various types of single-layer and multilayer carbon nanotubes.

The data in Table 2 indicate that the use of single-walled carbon nanotubes as a part of bio-solder increases the strength of welded laser welds compared to albumin-based bio-solder without nanotubes [2, 10] ~ 2 times, while the use of multilayer carbon nanotubes gives an increase in weld strength 2-3 times.

table 2 The results of measurements of the tensile strength of samples of pig skin and cartilage of bovine trachea Compositions of laser bio-solders Tensile strength Pig skin (σ _bt = (15 ± 5) MPa Bovine cartilage σ _bt = (6 ± 2) MPa σ _sv , MPa T% σ _sv , MPa T% 1. BSA 0.4 ± 0.1 2.7 0.9 ± 0.3 fifteen 2. BSA + MWNT1 1.4 ± 0.3 9.3 1.9 ± 0.5 32 3. BSA + MWNTP 1.2 ± 0.3 8.0 1.4 ± 0.4 23 4. BSA + SWCNT 0.8 ± 0.3 5.3 1.7 ± 0.5 28 [four] 0.09 0.6 - - Note. BSA - bovine serum albumin, MRAU - finely divided activated carbon, MWNT I - multilayer carbon nanotubes manufactured by MIET; MWNT II - multilayer carbon nanotubes manufactured by the Tambov plant Komsomolets (type “Taunit”); SWCNTs are single-walled carbon nanotubes manufactured by CarbonLight LLC.

Compared with the measurement data for the tensile strength of pigskin laser seams obtained with albumin-based solder using CO ₂ laser radiation (wavelength 10.6 μm) [4], an increase in strength by 10–15 times was obtained using respectively single-layer and multilayer carbon nanotubes as part of solder.

To verify the biocompatibility of the proposed compositions, samples of bio-solder based on an aqueous solution of bovine serum albumin were introduced under the perichondrium of the ear cartilage of a rabbit in vivo. Negative dynamics of animals was not observed.

Thus, due to the application of the proposed method for laser welding of biological tissues with bioholder containing a dispersion of carbon nanotubes and surfactants and binders in the form of a composite based on proteins and biocompatible polymers using a laser radiation source, reliable connection of damaged biological tissues is ensured at the convenience in the implementation of laser welding and without the use of expensive reagents.

Information sources

1. Lasers in surgery, ed. O.K.Skobelkina // M .: Medicine, 1989.

2. Nevorotin A.I. Introduction to Laser Surgery // St. Petersburg: Spetslit, 2000.

3. C. B. Bleustein, D. Felsen, D.P. Poppas. Welding Characteristics of Different Albumin Species with and without Fatty Acids. - Lasers in Surgery and Medicine, 2000, v. 27, No. 2, p. 82-86.

4. Simhon D., Halpern M., Brosh T., Vasilyev T., Ravid A., Tennenbaum T., Nevo Z., Katzir A. Immediate Tight Sealing of Skin Incisions Using an Innovative Temperature-controlled Laser Soldering Device. - Annals of surgery, 2007, v. 245, No.2, p. 206-213.

5. V.M. Podgaetsky, V.V. Savransky, M.M.Simunin, M.A. Kononov. Obtaining bulk nanocompositions based on an aqueous albumin solution under the action of laser radiation. - Quantum Electronics, 2007, v. 37, No. 9, 801-803.

6. RF patent No. 2347740.

7. Application for US patent No. 20070198090.

8. Eurasian patent No. WO / 1996/038093.

9. S.A. Ageeva, V. A. Medvedeva, V. M. Podgaetsky, S. V. Selishchev, A. Yu. Tolbin, L. G. Tomilova. The use of organic dyes in laser welding of biological tissues. - Sat scientific works "Lasers in science, technology, medicine", ed. V.A. Petrova // M .: MNTORES named after A.S. Popov, 2007, v. 18, pp. 96-100.

10. US patent No. 6685730 B2.

Claims (4)

1. A laser welding method using bio-solder, which is a dispersion of binders in the form of a composite in water based on proteins and / or biocompatible polymers, by laser irradiation, characterized in that carbon nanotubes and surface-active substances are introduced into the bio-solder. 2. The laser welding method using bio-solder according to claim 1, characterized in that the bio-solder is introduced in the following quantitative ratio (in% by weight):
Binder 10-50 Carbon nanotubes 0.1-0.5 Surface-active substance 1-3 Water Rest 3. The laser welding method with the bio-solder composition according to claim 1, characterized in that proteins (albumin), a natural biocompatible polymer chitosan, polysaccharides (amylose), ethoxylated starch, collagen are introduced into the composition of the bio-solder binder. 4. The laser welding method with the composition of bio-solders according to claim 1, characterized in that the ionic surface-active substance (SAS) sodium dodecylbenzenesulfonate, nonionic surfactant Neonol AF 9-12, zwitterionic surfactant Phosphatidylcholine are introduced into the bio-solder.

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