ABSORBABLE TOPICAL HEMOSTAT

Abstract: A hemostatic material which is a cotton like material comprising the fibers of an atherocollagen prepared by regenerating a solubilized collagen, wherein the diameters of the collagen fibers range from 10 to 70 mm, the lengths of the fibers range from 3 to 70 mm, and at least part of the collagen molecules that constitute the fibers have been thermally cross-linked. Because this material comprises an assembly of the fibers having suitable lengths and diameters and at least part of the collagen molecules have been thermally cross-linked, it is improved in the effect of stopping bleeding as the first stage of hemostasis and has a sufficient hemostatic activity without detriment to the hemostatic effect inherent in collagen. In addtion, it has such an appropriate specific volum that it can readily be fabricated in accordance with the shape of the bleeding site, can rapidly be applied in effecting hemostasis, and can be brought into tight contact with the bleeding surface, thus having a high hemostatic effect.

Description: This invention relates to an absorbable topical hemostat comprising a cotton-like product of collagen fibers to be used in the field of surgery, particularly to an absorbable topical hemostat which can be applied rapidly and effectively to hemorrhage from parenchymatous internal organs and capillary hemorrhage. As a hemostatic method during a surgical operation, there may be mentioned a compression method, a ligation method, an electrocoagulation method, application of a physiologically active substance such as thrombin, fibrin paste, etc. and others. To arterial hemorrhage with clear hemorrhagic sites, a ligation method or an electrocoagulation method has generally been applied. In the case of venous hemorrhage, hemostasis is easily and sufficiently obtained by compression. However, these hemostatic methods are sometimes ineffectual to hemorrhage from parenchymatous internal organs and capillary hemorrhage, and when there is a tendency of hemorrhage in hepatic insufficiency or in the field of cardiovascular surgery, hemostasis is particularly difficult. In such a case, an absorbable topical hemostat which accelerates a blood coagulation reaction only by contacting it with a bleeding surface, whereby thrombus is formed rapidly to inhibit hemorrhage, is effective since not only an operation time is shortened, but also post-operative rehemorrhage is prevented to contribute to safe postoperative control. For this purpose, various topical hemostats using oxidized cellulose as a material have been developed and applied clinically. They have advantages that they are inexpensive and have excellent handling property, but they have disadvantages that since they do not use a material derived from an animal body, absorption into a living body is slow, and a strong hemolysis reaction and a reaction rejecting a foreign body are caused. In recent years, topical hemostats using collagen which is protein derived from an animal body have frequently been applied clinically since the collagen has low antigenicity and is absorbed into a living body safely to minimize an allergic reaction and a reaction rejecting a foreign body and further the collagen itself also has physiological functions (coagulation of platelets by adhesion, acceleration of a blood coagulation system by the platelet factor III released from coagulated platelets and formation of thrombus) (thus, its hemostatic effect is high). Topical hemostats made of collagen which have been put to practical use at present include those in which microfibrils of collagen are made flaky and those in which collagen sponge is made plate-shaped. As to the former, telopeptide which is a determinant of antigenicity of collagen remains to exhibit antigenicity in a living body, so that they are required to be removed after use, they are flaky, so that they are flowed by blood to be scattered, whereby a large hemostatic effect cannot be expected, and they are easily charged with static electricity, so that there is a drawback in handling that they are easily attached to hands and tweezers during use. On the other hand, as to the latter, some of them comprise atelocollagen in which telopeptide has been removed, but they are plate-shaped, so that adhesiveness to a wound surface with a complicated shape is not sufficient and also astriction cannot be carried out, whereby a large hemostatic effect cannot be expected similarly as in the former. As a material which can solve the above drawbacks, cotton-like topical hemostats comprising atelocollagen have been published. There may be mentioned, for example, a material obtained by spinning atelocollagen derived from porcine skin, drying it and forming it into a cotton-like product (Shimizu et al., Artificial Internal Organs 19 (3), 1235 (1990)), a material obtained by treating spun collagen with a crosslinking agent, washing it and lyophilizing it to be formed into a cotton-like product with a surface on which fine crack-like fissures are made (Japanese Provisional Patent Publication No. 61862/1992; EP-A-0 463 887), etc. Since the former uses soluble atelocollagen as such, when it is used for hemostasis, it absorbs blood to significantly lower fiber strength, whereby it is difficult to inhibit blood stream and therefore a sufficient hemostatic effect cannot be expected. On the other hand, in the latter, there are problems that since crosslinking treatment with a crosslinking agent is carried out prior to lyophilization, a hemostatic effect possessed by collagen is impaired, and from the point of safety, a washing operation for completely removing an unreacted crosslinking agent is required. EP-A-0 463 887 discloses fiber thicknesses of 10 to 40 µm and fibers cut to a length of 5 cm. EP-A-0 466 383 discloses an adhesive composition for surgical applications which is an aqueous solution of natural collagen whose crosslinking density has been increased by thermal means. (DISCLOSURE OF INVENTION) An object of the present invention is to provide a hemostat in which the tasks of the conventional hemostats made of collagen as described above can be solved, i.e., to provide a topical hemostat made of collagen, which has sufficient hemostatic ability, is degraded in and absorbed into a living body safely and rapidly after use, and also has good handling property. As a result of investigation for such an object, the present invention has been made. That is, the present invention is a cotton-like product comprising fibers of atelocollagen obtained by reconstituting solubilized collagen, wherein each of said fibers has a diameter of 10 to 70 µm and a fiber length of 3 to 70 mm, and at least a part of collagen molecules constituting said fibers are crosslinked by heat. In the present invention, the solubilized collagen refers to collagen subjected to solubilization by carrying out solubilization treatment with protease or solubilization treatment with alkali and also subjected to an operation of removing telopeptide which is a determinant of antigenicity of collagen. Derivation of the collagen to be used as a material of the present invention is not particularly limited, but collagen obtained from skin, bone, cartilage, tendon, internal organs, etc. of a mammal (e.g. a human, a cattle, a swine, a rabbit, a sheep, a mouse, etc.) is generally used. Also, collagen-like protein obtained from birds, fish or the like can be used. In general, collagen subjected to solubilization treatment with protease has higher activity to platelets as compared with one subjected to solubilization treatment with alkali, so that it is preferred to use collagen subjected to solubilization treatment with protease. Hemostasis by the collagen hemostat is carried out by physically suppressing sprung blood in the first place and then exhibiting a hemostatic effect of collagen itself. Therefore, in order to make a sufficient hemostatic effect exhibited, the strength of fibers constituting the hemostat is an important factor. The strength of the fibers is larger as the diameter of the constituting fibers is larger. However, when the diameter thereof is too large, the fibers become rigid, so that shape processing is difficult. Thus, it may be 10 to 70 µm, preferably 15 to 45 µm. The length of the fibers can be any desired length since said fibers are obtained by reconstituting solubilized collagen. However, when the length thereof is too long, it is difficult to disperse the fibers sufficiently when said fibers are formed into a cotton-like product, and when the length thereof is too short, the fibers are hardly entangled with each other, so that said fibers are scattered in application of the hemostat and strength resisting blood pressure cannot be obtained. Thus, it may be 3 to 70 mm, preferably 5 to 50 mm. The absorbable topical hemostat of the present invention is swollen by absorbing blood to increase a whole volume thereof. As a result, an astriction effect on peripheral tissues of applied sites is exhibited. The astriction effect is exhibited only when the hemostat has a certain degree of strength. In the fibers obtained from the solubilized collagen, a swelling degree thereof is significant, and the strength is lowered accompanied with swelling. Therefore, in the present invention, by crosslinking at least a part of collagen molecules constituting said fibers by heat, suitable swellability (said fibers have a dense surface structure, but they absorb blood rapidly to cause volume expansion, whereby an astriction effect on bleeding sites is brought about) and strength (an action of inhibiting blood stream completely to achieve hemostasis in an early stage) as a hemostat are imparted while maintaining a hemostatic action inherently possessed by collagen. In the prior art, when collagen is crosslinked, there has been used a method of using a crosslinking agent such as aldehydes, diepoxides, etc. However, in collagen treated by the crosslinking agent, activity to platelets of collagen is lost so that improvement of hemostatic ability cannot be expected (reactivity to platelets of collagen is hardly deactivated by heat treatment). Further, the method of using the crosslinking agent has many problems that the reaction cannot be stopped at the time when crosslinking proceeds to a degree that a swelling degree suitable as a hemostat remains, and the crosslinking agent to be used has toxicity in many cases so that a washing operation for removing an unreacted crosslinking agent is required. The crosslinking treatment by heat is preferably carried out at a range of 50 to 200 °C. If it is lower than 50 °C, crosslinking becomes insufficient or crosslinking cannot be carried out, while if it exceeds 200 °C, denaturation of collagen is remarkable, whereby swellability and physiological activity are lost. When both factors of production and quality are considered, it is more preferably 60 to 180 °C, particularly preferably 95 to 150 °C. As other physical property to be possessed by the absorbable topical hemostat, a specific volume of the cotton-like product of collagen fibers is also important in the points of handling property of the hemostat and adhesiveness to wound sites. The specific volume of the fibers is preferably higher from easiness of shape processing in application (the hemostatic effect can be exhibited maximally by changing the shape of the hemostat in accordance with wound sites having various shapes and uniformly adhering it thereto). However, there is a limitation thereof in order to suitably entangle the fibers with each other, and if it is too high, the fibers are scattered or gaps are formed in application, whereby complete hemostasis is difficult. Thus, it may be 20 to 80 cm 3 /g, preferably about 40 to 70 cm 3 /g. Here, the specific volume is determined as described below (hereinafter, description is made with the cotton-like product of collagen fibers being a standard, but the flake-like product is also measured in the same manner). 1 ○ Under standard conditions (20 °C, 65 % RH), about 1 g of the cotton-like product of collagen fibers obtained is taken and weighed correctly (measured weight: Wg). 2 ○ Under the standard conditions, a transparent plastic tube having an inner diameter of 35 mm is uniformly filled with the product. 3 ○ Next, a flat disc having a diameter of 30 mm and a weight of 5.0 g is placed on the cotton-like product prepared in 2 ○, and 50 g of a weight is further placed thereon for 30 seconds. Thereafter, said weight is removed, and the remainder is left to stand for 30 seconds. This operation is repeated three times, and then the height of the filled cotton-like product is measured at three positions in the peripheral direction (the average value is defined as H mm). 4 ○ The specific volumes of three samples are determined according to the following equation, and an average value thereof is used. Specific volume (cm 3 /g) = ((35/20) 2 x π x H/10)/W BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a microphotograph (magnification: 1,000) showing a shape of a surface of atelocollagen fiber constituting the absorbable topical hemostat of the present invention. Fig. 2 is a microphotograph (magnification: 7,000) in which said surface is further enlarged. Example 1 By treating insoluble collagen obtained from fresh cattle skin with protease (pepsin, hereinafter the same), telopeptide was digested and a solution of solubilized atelocollagen was obtained. Next, this solution was dissolved in an aqueous hydrochloric acid adjusted to pH 2 (collagen concentration: 6 %), and atelocollagen fibers were obtained by a wet spinning method using 20 % aqueous ammonium sulfate as a coagulating agent. The atelocollagen fibers obtained were desalted and dehydrated with methanol, dried and then cut to have a length of 50 mm. The fibers were dispersed by air blow (at a wind speed of 30 m/s for 10 minutes) and then subjected to heat treatment at 105 °C (for 3 hours) to obtain a cotton-like product of the collagen fibers. The physical property values of the cotton-like product obtained were a fiber length: 5 to 50 mm, a fiber diameter: 15 to 45 µm and a specific volume: 60 cm 3 /g. The shape of the fiber surface of the cotton-like product obtained is shown in Fig. 1 and Fig. 2 (which are the results of observation by a scanning type electron microscope manufactured by Nihon Denshi Co.: Model JSM-804). Example 2 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for carrying out the heat treatment at 60 °C (for 24 hours). The physical property values of the cotton-like product obtained were the same as those of Example 1. Example 3 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for carrying out the heat treatment at 180 °C (for 10 minutes). The physical property values of the cotton-like product obtained were the same as those of Example 1. Example 4 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for not carrying out the dispersion treatment of the fibers by air blow. The physical property values of the cotton-like product obtained were a fiber length: 30 to 50 mm, a fiber diameter: 15 to 45 µm and a specific volume: 28 cm 3 /g. Example 5 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for changing the conditions of the dispersion treatment of the fibers by air blow to a wind speed of 40 m/s for 60 minutes. The physical property values of the cotton-like product obtained were a fiber length: 5 to 50 mm, a fiber diameter: 15 to 45 µm and a specific volume: 78 cm 3 /g. Example 6 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for carrying out alkali solubilization treatment (using a mixed solution of sodium sulfate, sodium hydroxide and monomethylamine) in place of the enzyme treatment of insoluble collagen. The physical property values of the cotton-like product obtained were the same as those of Example 1. (Example 7) A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for using fresh porcine skin in place of fresh cattle skin. The physical property values of the cotton-like product obtained were the same as those of Example 1. Comparative example 1 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for not carrying out the heat treatment. The physical property values of the cotton-like product obtained were the same as those of Example 1. Comparative example 2 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for carrying out alkali solubilization treatment (using a mixed solution of sodium sulfate, sodium hydroxide and monomethylamine) in place of the enzyme treatment of insoluble collagen and not carrying out the heat treatment. The physical property values of the cotton-like product obtained were the same as those of Example 1. Comparative example 3 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for carrying out treatment with glutaraldehyde in place of the heat treatment. The physical property values of the cotton-like product obtained were the same as those of Example 1. Comparative example 4 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for changing the spinning conditions. The physical properties of the cotton-like product obtained were a fiber length: 5 to 50 mm, a fiber diameter: 7 to 9 µm and a specific volume: 65 cm 3 /g. Comparative example 5 A cotton-like product of collagen fibers was obtained in the same manner as in Example 1 except for changing the spinning conditions. The physical properties of the cotton-like product obtained were a fiber length: 5 to 50 mm, a fiber diameter: 80 to 100 µm and a specific volume: 35 cm 3 /g. Comparative example 6 A flake-like product of collagen fibers was obtained in the same manner as in Example 1 except for changing the cut length after drying to 3 mm. The physical property values of the flake-like product obtained were a fiber length: 0.5 to 1 mm, a fiber diameter: 15 to 45 µm and a specific volume: 18 cm 3 /g. Comparative example 7 By treating insoluble collagen obtained from fresh cattle skin with protease, telopeptide was digested and a solution of solubilized atelocollagen was obtained. Next, this solution was dissolved in an aqueous hydrochloric acid adjusted to pH 2 (collagen concentration: 3 %), and collagen fibers were obtained by a wet spinning method using a saturated solution of sodium sulfate as a coagulating agent. Next, these fibers were treated with a glutaraldehyde solution and then washed with water to remove inorganic salts and unreacted glutaraldehyde. Next, the fibers were cut to have a length of 50 mm and lyophilized to obtain a cotton-like product of the collagen fibers. The physical properties of the cotton-like product obtained were a fiber length: 40 to 50 mm, a fiber diameter: 10 to 30 µm and a specific volume: 17 cm 3 /g. Experiment Mongrel adult dogs to which 100 u/kg of heparin had been systemically administered before initiation of the experiment were subjected to laparotomy under general anesthesia, and only spleen integument with an exact size of 1 cm x 1 cm was peeled off by a surgical knife. Next, each 0.1 g of the collagen cotton-like products and flake-like products obtained in the respective Examples and Comparative examples described above were put on the above peeled surfaces and compressed for 30 seconds, and bleeding amounts were measured at intervals of 1 minute (Dried gauze was put on a bleeding surface for 1 minute, and the bleeding amount was determined by a radius of a circle made by blood absorbed by the gauze. This index is hereinafter referred to as Bleeding Degree: BD. An initial value of BD is defined as BD t=0 , BD with each lapse of time is defined as BD t=t , and a value determined according to the following equation is defined as a hemostatic rate: HR. At the time when no blood permeated into the gauze, hemostasis was regarded to be completed.). HR (%) = (1-(BD t=t /BD t=0 )) x 100 Data obtained when the respective 10 samples were examined are shown in Table 1. In said table, also shown are results of measuring a time required for processing 0.1 g of the collagen cotton-like products and the flake-like products obtained in the respective Examples and Comparative examples described above in accordance with the shape of the peeled surfaces and applying them to the peeled surfaces (referred to as a reprocessing time). From the results, it is apparent that the hemostatic collagen cotton-like products of the present invention have excellent hemostatic ability and excellent handling property (In experiment examples of this experiment, in which hemostasis was not completed in an early stage of hemostasis (in 2 minutes), exuded blood was sprung out by partially pushing through the hemostat (because the fibers constituting the hemostat could not maintain strength enough to resist blood pressure), whereby hemostasis was difficult. That is, it is extremely important that hemostasis is completed in 2 minutes.). HR (%) After 1 min After 2 min After 3 min After 4 min After 5 min Reprocessing time (sec) Example 1 100 ← ← ← ← 2 Example 2 51 100 ← ← ← 2 Example 3 53 100 ← ← ← 2 Example 4 75 100 ← ← ← 5 Example 5 69 100 ← ← ← 3 Example 6 88 100 ← ← ← 2 Example 7 100 ← ← ← ← 2 Comparative example 1 35 63 95 100 ← 2 Comparative example 2 18 24 ← ← ← 2 Comparative example 3 59 67 ← ← ← 3 Comparative example 4 31 40 59 ← ← 3 Comparative example 5 36 54 ← ← ← 6 Comparative example 6 56 86 ← ← ← impossible Comparative example 7 38 46 62 ← ← 6 NOTE: '←' means that the value is the same as in the column to the left. INDUSTRIAL APPLICABILITY The cotton-like product of collagen fibers according to the present invention is a gathering of fibers which are obtained by reconstituting solubilized collagen and have suitable length, diameter and specific volume. Since at least a part of collagen molecules constituting said fibers are crosslinked by heat, a suppression effect on hemorrhage which is the first stage of hemostasis is improved, and sufficient hemostatic ability is exhibited without impairing a hemostatic activity inherently possessed by collagen. Also, since it has a suitable specific volume, it can be easily processed in accordance with a shape of a hemorrhagic site, it can be used for hemostasis rapidly, and also adhesiveness to a bleeding surface is good, whereby a hemostatic effect is high.

Claims: An absorbable topical hemostat which comprises a cotton-like product comprising fibers of atelocollagen obtained by reconstituting solubilized collagen, wherein each of said collagen fibers has a diameter of 10 to 70 µm and a fiber length of 3 to 70 mm, and at least a part of collagen molecules constituting said fibers are crosslinked by heat. The absorbable topical hemostat according to Claim 1, wherein crosslinking by heat is carried out at 50 to 200 °C. The absorbable topical hemostat according to Claim 1 or 2, wherein the cotton-like product has a specific volume of 20 to 80 cm 3 /g.

Inventors: AKASAKA MASANORI, MAKIHARA TOSHIKAZU, NATSUME TORU, SAKAKIBARA HIROKI, SHIMIZU YASUHIKO, AKASAKA, MASANORI, MAKIHARA, TOSHIKAZU, NATSUME, TORU, SAKAKIBARA, HIROKI, SHIMIZU, YASUHIKO, AKASAKA, Masanori, Prod. Developm. Lab. Mitsubishi, MAKIHARA, Toshikazu, Research and Development Ctr., NATSUME, Toru, Research and Development Center, SAKAKIBARA, Hiroki, Mitsubishi Rayon Co., Ltd.
Applicants: NIPPON MEAT PACKERS, SHIMIZU YASUHIKO, NIPPON MEAT PACKERS, INC., SHIMIZU, YASUHIKO
Application year: 1993
Main classification: A61L15
IPC codes: A61L15