RU2350075C1 - Method of preservation and sterilisation of biological prostheses for cardiovascular surgery - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention concerns medicine area, namely to cardiovascular surgery, and can be used at preservation and biomaterial sterilisation, in particular at manufacturing of heart valve prostheses, vessels. The way of preservation and sterilisation of biological prostheses is performed in the diglycidyl ether solution at temperature of 5-25°C within 2-21 days, prepared on 0.05-0.1 M of the phosphate-tetraborate buffer (pH 7.4) with addition of 1-15% ethyl alcohol. The osmolarity of the 0.05-0.1 M phosphate-tetraborate buffer is close to parametres of blood and keeps stable pH of the solution. Addition of 1-15% ethyl alcohol allows to lower rate of diglycidyl ether decomposing at storage.

EFFECT: invention allows raising durability and elasticity of a biotissue, to strengthen sterilising effect of a preserving solution, to enlarge the period from the moment of a native tissue acquisition before bracing of a biological prosthesis.

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Description

The invention relates to medicine, namely to pre-implantation processing of biological prostheses for cardiovascular surgery, and can be used in the preservation and sterilization of biological material.

A known method of sterilization of medical devices, including biological prostheses for cardiovascular surgery (PCT patent No. 92/09309, class A61L 2/00, A01N 43/20, published 11.06.92). Its essence lies in the fact that for the sterilization of biological prostheses use a 2-4% solution of polyepoxide compounds prepared on 0.1 M carbonate buffer pH 9.5-10.0. To enhance the sterilizing effect, it is proposed to add up to 20 parts of ethanol to the solution of polyepoxide compounds. The greatest sterilizing effect was obtained at a solution temperature of 37 to 45 ° C and the addition of 20% ethanol. The main disadvantages of this method include:

- the use of high temperatures of the solution;

- to prepare a preservative, a buffer solution with an alkaline pH value in excess of physiological is used;

- the addition of 20% ethanol has a tanning effect on biological tissue, giving it rigid properties.

All this can adversely affect the structural stability of the biomaterial and lead to prosthesis dysfunction after implantation.

Currently, in the manufacture of bioprostheses for cardiovascular surgery, a preservative solution of ethylene glycol diglycidyl ether (DEE) based on 0.05 M phosphate buffer (RF patent No. 2008767, class A01N 1/00, published in 1994, bull. No. 5). This method allows to achieve a high density cross-linking and sufficient sterilizing effect. However, the buffer used is not optimal, because the concentration of DEE on phosphate buffer decreases by 21 days from 5 to 0.7%. In this case, the pH of the DEE solution by the 9th day reaches 11.5-12 (compared with the initial 7.4-7.5), which may have an adverse effect on the structure of collagen. The osmotic pressure of the solution prepared in accordance with this method is 140-145 mOsm / l, which is 2 times lower than the osmolarity of blood plasma. Low osmotic pressure and alkaline environment (pH 11.5-12) of the preserving and sterilizing solution in phosphate buffer cause swelling of the valvular and muscle parts of the aortic complex. This method of conservation cannot be used for the procurement and storage of biomaterial, because limits the duration of the first technological stage - the time from the collection of native tissue to the modeling of the bioprosthesis is limited to 6 hours.

The use of DEE on borate buffer with the addition of 20% isopropyl alcohol for preserving biomaterial is known (Belarus Patent No. 8118, published June 30, 2006). The use of borate buffer makes it possible to slow down the decomposition of DEE - after 21 days, the concentration decreases to 2.17%. The disadvantage of this method is that the pH of the sterilizing solution is 9.0-10.0 (pH of borate buffer) and can have a negative effect on the biomaterial.

The technical result of the invention is the prevention of edema of the biological tissue of the prosthesis due to the stable pH of the solution, the osmotic pressure of the phosphate-tetraborate buffer close to the osmotic pressure of the blood plasma, and dehydration of the biomaterial with small concentrations of ethyl alcohol, as well as increasing the strength and elasticity of the biological tissue.

A method of preservation and sterilization of biological prostheses is proposed, including preservation and sterilization with a solution of ethylene glycol diglycidyl ether at a temperature of 5-25 ° C for 2-21 days.

The difference of the proposed method is that 0.05-0.1 M phosphate-tetraborate buffer pH 7.4 with the addition of 1-15% ethyl alcohol is used for the base of the preservation solution.

The proposed method of preservation and sterilization of bioprostheses allows you to increase the period from the moment of collection of native tissue to the manufacture of a biological prosthesis up to 7 days, which is extremely important for remotely located raw material bases. The use of 1-15% ethanol allows moderate dehydration of the biomaterial, thereby giving it additional strength.

The following is an example implementation of the proposed method.

The native tissue prepared by existing selection procedures is washed with 0.9% sodium chloride solution, then placed in a 5% DEE solution prepared in 0.05-0.1 M phosphate-tetraborate buffer with 1-15% ethyl alcohol added.

When preserving biological prostheses, it is extremely important to use solutions with a physiological pH value - acidic and alkaline environments can have a damaging effect on biological tissue. During prolonged storage, the pH of the DEE solution in phosphate-tetraborate buffer remains stable. In addition, the use of phosphate-tetraborate buffer allows one to reduce the decomposition of the epoxy compound - by 21 days, 1.74% DEE remains in the solution (intermediate version).

Adding ethyl alcohol to a buffer solution of DEE in a concentration of 1-15% also allowed to reduce the rate of decomposition of the preservative (according to the proposed method). When using 1-15% ethanol on the 21st day, 2.36% DEE remained, while the pH of the solution, both with and without ethanol, rises to a value of 8.1 over 21 days of storage. The dynamics of the decomposition of DEE and the change in pH of the solutions are shown in table 1.

The use of phosphate-tetraborate buffer at a concentration of 0.05-0.1 M allows you to get the osmolarity of the preservation solution close to blood parameters.

The addition of ethyl alcohol of more than 15% has a tanning effect on biological tissue.

Table 1 The dynamics of the pH of the solution and the decomposition of DEE in various buffer solutions Duration of storage (day) Phosphate buffer (prototype) Phosphate buffer with 1-15% ethanol Phosphate-tetraborate buffer (intermediate) Phosphate-tetraborate buffer with the addition of 1-15% ethanol (according to the proposed method) pH DEE,% pH DEE,% pH DEE,% pH DEE,% 0 7.4 5.13 7.4 5.13 7.4 5.33 7.4 5.19 2 8.0 4.67 7.9 4.67 7.4 4.63 7.5 4.9 7 9.0 3.67 8.8 3.67 7.7 3.27 7.9 3.95 eleven 11.9 2.68 11.6 2.68 8.0 2.80 8.1 3,55 16 11.9 1.31 11.8 1.31 8.1 2.18 8.1 2.93 21 12.1 0.7 12.0 0.7 8.1 1.74 8.1 2,36 The residual content of DEE,% of the original fourteen fourteen 33 45

As the studies show, the addition of 1-15% ethanol to the composition of 0.05 M phosphate buffer (according to the prototype) did not lead to positive results - for 21 days 0.7% DEE remained in the solution, as well as when using phosphate buffer without ethanol additions.

To study the effect of the proposed method of preservation and sterilization on the structure of the biomaterial, a histological study of the valves of the aortic valve of the pig and cattle pericardium, preserved in experimental solutions, was carried out. Storage of the biomaterial processed by the proposed method does not adversely affect the biomaterial — the collagen fibers are crimped and compact.

The proposed method has a good sterilizing effect - after a day of storage of biomaterial contaminated with St.aureus, E. coli Ent.faecalis and fungal flora in a solution prepared by the proposed method, the growth of all microorganisms is completely suppressed.

The proposed method allows to improve the strength and elasticity of the biomaterial (see table 2).

table 2 Assessment of the strength and elasticity of biomaterial Preservative Used Strength, kg / cm ² Elasticity,% Cattle pericardium DEE on 0.05 M phosphate buffer (prototype) 68.1 + 5.1 39.5 + 1.1 GA on 0.05 M phosphate buffer (analogue) 88.1 + 10.9 38.6 + 2.4 DEE on 0.05-0.1 M phosphate-tetraborate buffer with the addition of 1-15% ethanol (the proposed method) 109.1 + 7.0 47.3 + 2.5 Aortic leaflet DEE on 0.05 M phosphate buffer (prototype) 36.2 + 5.1 34.2 + 2.8 GA on 0.05 M phosphate buffer (analogue) 45.4 ± 5.3 35.2 ± 3.7 DEE on 0.05-0.1 M phosphate-tetraborate buffer with the addition of 1-15% ethanol (the proposed method) 72.3 + 8.2 43.3 + 3.5

Assessment of the strength and elasticity of the biomaterial showed that the use of biomaterial canned in a DEE solution on 0.05-0.1 M phosphate-tetraborate buffer with 1-15% ethanol added increases the strength by 50-100% and the elasticity by 25-30% biomaterial.

Claims (1)

The method of preservation and sterilization of biological prostheses for cardiovascular surgery, including preservation and sterilization with a solution of ethylene glycol diglycidyl ether at a temperature of 5-25 ° C, for 2-21 days, characterized in that 0.05-0 is taken for the basis of the preservation solution 1 M phosphate-tetraborate buffer pH 7.4 with the addition of 1-15% ethyl alcohol.