CA2367024C - A thrombin blood fraction for use in a medical procedure - Google Patents

Abstract

The subject invention relates to the use of thrombin in a medical procedure in an animal.
More specifically, the subject invention relates to such use of thrombin wherein the thrombin is a thrombin blood fraction, as defined hereinbelow.

Description

v A THROMBIN BLOOD FRACTION FOR USE IN A MEDICAL PROCEDURE.
1, FTEDD OF THE INVEN',~ON
The subject invention relates to the uses of thrombin in a medical procedure in an animal. Mores s~~.acif ically, the subject invention relates to such uae of thrombin wherein the thrombin is a thrombin blood fraction, a defined hereinbelow.

2. B_,ACKG~OUND OF THE INVENTION
One mechar. ~m for hemostasis, i.e., prevention of blood loss, of an animal is the formation of a blood clot. Clot formation, i.e., blood coagulation, occurs by means of a complex cascade of reactions With the final steps being the conversion of fibrinogen by thrombin, calcium ions and activated factor XZII to form the fibrin clot. For a review of the mechanisms of blood coagulation and the 2o structure of fibrinogen, see C.M. Jackson, Ann. Rev.
Biochem., 49:765-811 (1980) and 8. Furie and B.C.
Furie, Cell, 53:505-518 (1988).
Thrombin, which is a prateolytic enzyme, is derived Prom prothrombin. Prothrombin is converted to 25 t~'ombin by calcium and prothrombinase.
Prothrombinase is formed through a cascade of reactions that begins with the proteins factor XI and factor XII.
A fibrin sealant is a biological adhesive 30 whose effect imitates the final stages of coagulation, thereby resulting in a fibrin clot. Conventional fibrin sealants generally consist of concentrated human fibrinogen, bovine aprotinin and factor XIII, as the first component and bovine thrombin and calcium 3s chloride as the second component. Application is generally carried out with a double-barrelled syringe, z which permits simultaneous application of both components to the site where one wants to form the ffibrin clot. Aprotinin is a fibrinolytic inhibitor added to promote stability of fibrin sealants.
The fibrinogen component of the fibrin sealant is prepared from pooled human plasma. The (fibrinogen can be concentrated from the human plasma ~by cryoprecipitation and precipitation using various reagents, e.g., polyethylene glycol, ether, athanol, 1o ammonium sulfate ar glycine. For an excellent review.
of fibrin sealants, sae M. Brennan, Blood Reviews, 5:240-244 (1991); J.W. Gibble and P.N. Ness, Transfusion, 30:741-747 (1990); H. Matras, J. Oral Maxillofac Surg., 43:605-611 (1985) and R. Lerner and N. Binur, J. of Surgical Research, 48:165-181 (1990).
Recently, there has also been an interest in the preparation of fibrin sealants that utilize autolagous fibrin. An autologous fibrin sealant is a fibrin sealant wherein the fibrinogen component of the 2o fibrin sealant is extracted from the patients own blood. The use of an autologous fibrin sealant is pref erred because it eliminates the risk of transmission of blood-transmitted infections, e.g., hepatitis B, non A, non B hepatitis and acquired 2S immune deficiency syndrome (AIDS), that could otherwise be present in the fibrinogen component extracted from pooled human plasma. See L.E.
Silberstein et al., Transfusion, 28:319-321 (1988); K.
Laitakari and J. Luotonen, Laryngoscope, 99:974-976 30 (1989) and A. Dresdale et al., The Annals of Thoracic Surgery, 40:385-387 (1985).
An infection can be trans~citted by a fibrin sealant not only by means of the fibrinogen but also by means of the bovine aproti.nin and the bovine 35 thrombin component. Bovine thrombin has been known to r __ -- ~ .wu... fir. vVyi VV-~

carry the infectious agent bovine spongiform encephalitis (BSF) and other viruses pathogenic to mammals.
Furthermore, bovine thrombin is a potential antigen, which can cause immunological reactions in humans. Thus, the use of bovine thrombin could result in the recipient of the bovine thrombin being adversely affected. See D_M. Taylor, J. of Hospital Infection, 18(Supplement A) :141-146 (1993,) , S.B. Prusiner et al . , Cornell 'let, 81 No. 2: 85-96 (1991) and D. Matthews, J. Roy. Soc. Health, CItIC.I)~
3-5 (February 1991).
Accordingly, there is the need for a sealant that utilizes thrombin that can be delivered to a patient without the risk of viral contamination or other adverse affects .
3. SIJMr2ARY OF THE INVENTION
The subject invention relates to a composition for use in a medical procedure in an animal, which composition is a thrombin containing blood fraction which comprises:
(a) a thrombin concentration of from about 1 NIH unit/ml to about 2,000 NIH units/ml, and (b) a specific activity of thrombin of from '''~ 25 about 1 NIH unit/mg of blood protein to about 200 NIH units/mg of blood protein, wherein said thrombin blood fraction is substantially free of active antithrombin III.
The subject invention also relates to a method for preparing a prothrombin blood fraction from whole blood comprising:

_ ,y _ (a) diluting whole blood to an ionic strength of less than about 100 millimolar;
(b) separating plasma from said whole blood;
(c) lowering the pH of said plasma to precipitate a prothrombin blood fraction; and (d) separating said prothrombin blood fraction from said plasma.
The prothrambin blood fraction is then redissolved and converted to thrombin, i.e., the thrombin blood fraction is farmed, which can then be utilized in a medical procedure in an animal, e.g., as a component of a fibrin sealant.

4. DETAILED DES IPTION OF THE INVENTION
The subject invention relates to the use of a thrombin blood fraction, as defined hereinbelow, in Z8 a medical procedure, e.g., as a component of a fibrin sealant, in an animal, preferably a mammal. Suitable mammals include a human, a caw, a pig, a dog and a rabbit, or other mammals that have an adequate blood volume to prepare the thrombin blood fraction. The 25 thrombin blood fraction can be prepared from whole blood and is impure in that it contains blood proteins .- other than thrombin. However, the thrombin blood fraction can be prepared very simply and rapidly, e.g., in less than about one or two hours, and is 30 believed to be as efficacious as a highly pure thrombin preparation.
The thrombin blood Fraction can be prepared from whole blood. It is preferred that the whole hloo3 be obtained from a single individual animal.
35 Also, it is preferred that the thrombin blood fraction _ g be administered to the same individual animal from which the whole blood was taken. thus, one aspect of the invention is the use of an autologous thrombin blood fraction in a medical procedure. In this embodiment, there is also no risk of transmission of blood~transmitted infections because the thrombin blood fraction is to be administered to the same individual animal that donated the whole blood. Also, for the same reason, the blood proteins other than 1o thrombin that are present in the thrombin blood fraction would not be antigenic.
Furthermore, since the thrombin blood fraction is preferred to be prepared from a single individual animal and used in the same, generally i5 small volumes of whole blood are required, especially since it is also preferred to prepare a thrombin blood fraction for a single use. Also, it is preferred to prepare the fraction within several hours of the time of use. It is preferred that from about 10 ml to 2o about 80 ml, more preferably from about 10 ml to about 30 ml and most preferably from about 10 ml to about 20 ml of whole blood be utilized to prepare the thrombin blood fraction of the subject invention.
The thrombin blood fraction of the subject 25 invention has a thrombin concentration of from about 1 NIH unit to about 2,000 NIH units, preferably from .. about 100 NIH units to about 800 NIH units and most preferably from about 100 NIH units to about 500 NIH
units per ml of the thrombin blood fraction.
30 It is believed that at such concentrations the thrombin blood fraction possesses a sufficient thrombin concentration for the desired medical use.
Of course, the preferred thrombin concentration depends an the medical use of the thrombin blood 35 fraction.

The thrombin concentration of the thrombin blood fraction can be determined by measuring the coagulation time of a standard fibrinogen solution after addition of the thrombin blood fraction in a ' suitable diluted form. As a reference, standard thrombin solutions, containing from 2 to 25 NIH
units/ml, can be utilised.
The thrambin blood fraction of the subject invention has a specific activity of thrombin of from to about 1 HIH unit to about 200 NIH units, preferably from about 5 NIH units to about 100 NIH units and most preferably from about 5 NIH units to about 50 NIH
units per mg. of total blood protein. Such lower specific activities of the thrombin blood fraction are believed to be as effective in a medical procedure as the more pure thrombin blood fractions. However, such lower specific activity of the thrombin blood fractions can be prepared more readily.
The specific activity of the thrombin blood 2o fraction is, in essence, a measurement of the amount of thrombin per a~aount of blood protein in the thrombin blood fraction. Thus, the specific activity of the thrombin blood fraction of the subject ~.
invention is quite low relative to thro~abin preparations that have been prepared heretofore. For example, United States Patent No. 5,143,838 discloses a thrombin preparation with a specific activity of at least 800 NIH units per mg. of total protein. Also', United States Patent No. 5,151,355 discloses a thrombin preparation with a specific activity of greater than 1,000 NIH units/mg. of total protein.
Although the specific activity of the thrombin blood fraction of the subject is low, never the less it is believed that the blood fraction is efficacious for use in medical procedures.

r WO 94/00566 PCf/G893/01323 The specific activity of the thrombin blood fraction of the subject invention can be calculated by measuring the thrombin concentration (NIH units/ml) and by dividing that number by the protein concentration (mg/ml) measured by any standard protein assay, e.g., W absorbance.
The thrombin blood fraction is also substantially free of active antithrombin III. For the purpose of the subject invention, ~~substantially 1o free of active antithrambin III" means that the thrombin blood fraction par unit volume contains an amount of active antithrombin III that is less than about SO% by activity of antithrombin IZI in normal plasma per unit volume. It is preferred that such percentage be less than about 30%, more preferably less than about 10% and most preferably less than about 5%. 1t is essential that the antithrombin III
either be removed frarn or in-czivated in the thrombin blood fraction. Otherwise, antithrombin III will prevent the conversion of the prothrombin in the blood fraction to thrombin and/or inactivate the thrombin that is farmed.
It is preferred that the thrombin blood fraction also be substantially free of fibrinogen and fibrin. For the purpose of the subject invention, substantially free of fibrinogen and fibrin means that the thrombin blood fraction per unit volume contains an amount of fibrinogen plus fibrin that is less than about 1% by weight of fibrinogen in normal plasma per unit volume. It is preferred that fibrinogen not be present in the thrombin blood fraction because the thrombin will convert --.he fibrinogen to fibrin, which will polymerize to fog a clot, thereby rendering the thrombin blood fraction impracticable. The fibrinogen itself pan be removed from the thrombin blood fraction c WO 94/0066 PCf/G893/01323 .._ g _ or the fibrinogen can be removed as the fibrin clot, thereby, of course, also removing the fibrin.
However, the fibrinogen need not be removed if, for example, the thrombin is inactivated as described in PCT publication No. W091/09641.
The thrombin blood praction can be utilized immediately after it is prepared. If the Fraction is not utilized immediately after its preparation, the fraction can be stored. Storage of the fraction to requires that the fraction be preserved by, for exaxapie, freezing ' or lyophilizing the fraction or holding the composition at 4°C. The fraction in frozen or lyophilized fona will be stable f or a period of months. When the fraction is held at 4°C, it is ~5 stable for at least a period of days.
If the fraction is frozen, the fraction must be tha~red at the time of use. If the fraction is lyophilized, at time of use, it is preferred that the fraction be reconstituted by addition of distilled 20 water.
The thrombin blood fraction can be in virtually any foria, for example, n solution, suspension, emulsion or solid, with a solution being preferred. Thus, Por example, such fraction can be a 25 liquid, gel, paste or salve. Also, of course, the fraction can be in the form of a granule.
If the thrombin blood fraction is in a solid form, then the concentration of the thronbir. blood fraction can be determined by dissolving it in a 3o solution and then measuring the thrombin concentration. If the resulting thrombi~
concentration is from about Z NIH unitj:~l to about 2,000 NIH units/ml, then the thrombin blood fraction is within the scope of the subject invention.

WO 94!00566 PCT/GB93/01323 -. 9 4.1. METHOD FOR PREPARATION OF TFiE
T,~TROM9 N BLOOD FRACTION
The thrombin blood fraction of the subject invention can be prepared by any method known or to be developed. Also, the thrombin blood fraction can be prepared in a device as described in the PCT publication No. W091/17778.
Zo 4,1.1. METHOD FOR PREPARATION OF THE TIiROMHIN
BLOOD FRACTION BY FORMATION OF THE
EUGLOBULIN FRACTION FROM PLASMA
Whole blood can be withdrawn from an individual animal, e.g., a human, and preferably in the presence of an anticoagulant. Any anticoagulant 1.5 can be utilized so long as it does not act by directly inactivating thrombin. Suitable anticoagulants are heparin, EDTA, citrate or any other agent that can, directly or indirectly, prevent the formation~of thrombin, with citrate being preferred.
2o The plasma, which contains the prothrombin, is then separated from the whole blood. Any separation tecrinigue can be utilized, for example, sedimentation, centrifugation or filtration.
Centrifugation can be carried out at about ?,500 to 25 about 3,000 g. Eor about 10 ninutes. The supernatant, which contains the plas~aa, can be re~aoved by standard technigues. If it is desired to obtain a thrombin blood fraction that contains growth factors, then such centrifugation should be at about ;25 g. Eor about 20 30 minutes or 1,000 g. for about 2 to 3 ainutes. The thrombin blood fraction of the subject invention will then contain growth factors, which are released from the platelets during the conversion o~ prothrombin to throtabin .

r WO 9a/OOS66 PCT/CB93/01323 Tha plasma in then treated, for example, by dilution with distilled water, followed by the addition of acid, e.g., citric acid, to lower the ionic strength to less than about 100 millimolar, preferably less than about 50 millimolar and most preferably from about 20 to about 40 millimolar and lower the pH to about 4.5 to about 6 and preferably to from about 5 to about 5.5. Lactic acid or acetic acid are also suitable acids. Generally. a weight ratio of 1o the plasma: distilled mater or acid of from about 1:5 to about 1:50, with 1:10 being pref erred.
This treatment, i.e., the lowering of the ionic strength and pH of the plasma, results in the formation of a precipitate that is generally referred i5 to as the "euglabulin fraction." The euglobulin fraction captains the prothrombin, fibrinogen and many other blood proteins, hut is substantially free of antithrambin III.
Rather than diluting the plasma to lower the 2o ionic stxength, and before acidifying the plasma, the ~ianic strength can ba lowered by dialyzing the plasma by placing the plasma in a dialysis bag, which is then placed in distilled water. The dialysis permits the ions to diffuse out of the plasma, thereby lowering 25 the ionic strength. A suitable dialysis bag is composed of cellulose nitrate. Also, the ionic strength can be lowered by diafiltration ar occlusion chromatography.
The euglobulin fraction can be prepared as 3o described in A. Quick, Production of Thrombin From Precipitate Obtained by Acidification of piluted Plasma, Am. J. Physiol., ,~,:11~-118 (1955) and R.
Biggs and R.G. Macfarlane, Human 8load Coagulation, pages 375-376, Blackwells Scientif is Publications, WO 94/00566 PCT/GB93/Ot323 Oxford, 3rd Edition (1962).
The excess fluid can then be separated from the euglobulin fraction by, for example, centrifugation, filtration or sedimentation.
Centrifugation can be carried at about 1,500 g, for about 2 to about 5 minutes.
The prothrombin of the euglobulin fraction is then redissolved and converted to thro~abiz~, thereby forming a thrombin blood fraction of the subject invention. This can be carried out by solubilizing the euglobulin fraction in a physiologically acceptable solution, e.g., saline, in an amount equal to or preferably less than (about 10%) the original amount of plasma. An alkaline buffer can be added in an amount to raise the pH of the solution to about 6 to about 8 and preferably to about 6.5 to about 7.5..
Honlimiting examples of suitable alkaline buffers include sodium hydroxide, potassium hydroxide, calcium 2o hydroxide, bicarbonate buffers such as sodium bicarbonate and potassium bicarbonate, salts of acetic acid and salts of sulfuric acid. Preferred alkaline buffers include: Sodium carbvnate/bicarbanate pH
Sodium bicarbonate/NaOH pH 7.0, 1.5M Glycine/NaOH pH
6.5-7.5, Bis hydroxyethyiaminoethane sulphanic acid (BES) pH 7.5, Hydroxyethylpiperazine propane sulphanic acid (EPPS) pH 7.5, Tra:cine pH '7.5, Morphalino propane sulphonic acid (MAPS) pH ?.0, Trishydroxy~nethy?
aminaethane sulphonic acid (TES) pH 7.0 and Cyclohexylamincethane sulphanic acid (CHES) ~H 7.o;
with sodiu.~ carbanate/bicarbonate pH 6.5 - ':.5 Bis hydroxethylaminoethane sulphonic acid (8E5) pH 7.5, Hydroxyethylpiperazine propane sulphonic acid (EPPS) pH 7.5 and Trishydroxymeth~fl aminoethane sulphonic acid (TES) pH ?.5 being most preferred.

WO 94/00566 PCT/GB93l01323 ~ 12 -Calcium is added to the neutral solution in order to convert the prothrombin to thrombin. Of course, the calcium can be part of the alkaline buffer. Calcium can be added in the form of, for S example, calcium chloride. The amount of calcium added should be sufficient to convert an amount of prothrombin to thrombin that is sufficient for the' intended medical use. Furthermore, the reaction should be permitted to occur for a period of time 10 sufficient to convert enough of the prothrambin to thrombin that is sufficient for the intended medical use. Generally, from about 5 millimolar to about 50 millimalar calcium chloride is sufficient.
Also, rather than adding a source of calcium 15 ions, prothrombin activating enzymes from snake venoms can be utilized. Far example, snake venom from Eccis carinatus or the Australian Tiger snake can be utilized.
As the thrombin forms, it converts the 20 fibrinogen to fibrin, which forms a fibrin clot. It is preferred to remove the fibrin clot, which can be carried out by, for example, wrapping the fibrin clot around a stirring rod or collecting the fibrin onto glass beads.
4.1.2. METHOD FOR PREPARATION OF THROMBIN BLOOD
FR~CTIDN BY DILUTING WFiOL~ BLOOD
In a preferred embodiment, the thrombin blood fraction can be prepared by initially preparing a Prothrombin blood fraction from whole blood comprising:
(a) diluting whole blood to an ionic strength of lass than about 100 millimalar ;
3s (b) separating plasma from said whole blood;

(c) lowering the pH of said plasma to precipitate a prothrombin blood fraction; and (d) separating said prothrambin blood fraction from said plasma.
The prothrambin blood fraction is then redissolved and converted to thrombin, i.e., the thrombin blood fraction of the subject invention is formed, which can then be utilized in a medical 1o procedure in an animal, e.g., as a component of a fibrin sealant. This method provides a thrombin blood fraction of the subject invention, which can be prepared in only about 45 minutes:
Specifically, whole blood is drawn from an ZS individual animal. the whole blood is then immediately (within about five minutes) diluted in order to lower the ionic strength to less than about 100 millimolar, preferably less than about 50 millimolar and preferably to from about 20 to about 40 2o millimolar. zt should be noted that since the whole blood is diluted immediately, there is no need for the use of an anticoagulant. Any physiologically acceptable solution at physiological osmotic pressure can be utilized to lower the ionic strength, e.g., a 25 glucose aqueous solution such as a 5.5% isotonic aqueous glucose so3ution.
The plasma is then separated from the whole blood. Any separation technique can be utilized, for example, sedimentation, centrifugation or filtration.
3o Centrifugation can be carried out at about 1,500 to about 3,000 g. for about 5 to about 10 minutes. The supernatant, which contains the plasma, can be removed by standard techniques.
The plasma fract3.on~ is then acidified, 35 thereby resulting in the formation of a prothrombin r WO 94/005G6 PCTIG B93l01323 - is -blood fraction, which is generally referred to as the euglobulin fraction, which is a precipitate. The plasma fraction can be acidified with, for example, citric acid, lactic acid or acetic acid. The pH
should be lowered to from about 4.5 to about 6 and preferably to from about 5 to about 5.5.
The excess fluid can then be separated from the prothrombin blood fraction by, for example, centrifugation, filtration or sedimentation.
l0 Centrifugation can be carried out at about 1,800 g far about 2 to about 5 minutes. This prothrombin blood fraction contains prothrombin, fibrinogen and many other blood proteins, but does not contain antithrambin III. The prothrombin blood fraction is then redissolved and the prothrambin is converted to thrombin. Any physiologically acceptable solution, e.g., saline, can be utilized to redissolve the prothrombin fraction. Furthermore, only a small volume of solution is required to redissolve the prathrombin fraction. It is believed that only from about 0.4 ml to about 1 ml of solution is required if about 17 ml of whole blood was initially drawn. An alkaline buffer can be added in an amount to raise the pH of the solution to about 6 to about 8 and preferably to about 6.5 to about ?.5. Nanlimiting examples of suitable alkaline buffers include sodium hydroxide, potassium hydroxide, calcium hydroxide, bicarbonate buffers such as sodium bicarbonate and potassium bicarbonate, tri-metal salts of citric acid, salts of acetic acid and salts of sulfuric acid.
Preferred alkaline buffers include: Sodium carbonate/bicarbonate pH 6-8, Sodium bicarbonate/NaOH
pH 6-8, Glycine/NaOH pH 6-8, Bis hydroxyethylaminoethane sulphonic acid (BES) pH 6-8, Hydraxyethylpiperazine propane sulphonic acid (EPPS) pH b-8, Tricine pH 6-8, Morpholino propane sulphonic acid (MOPS) pH b-8, Trishydroxymethyl aminoethane sulphonic acid (TES) pH 6-8 and Cyclohexylaminoethane sulphonic acid (CHES) pH 6-8; with Sodium 5 carbonate/bicarbonate pH 6-8 Bis hydroxethylaminoethane sulphonic acid (BES) pH 6-B, Hydroxyethylpiperazine propane sulphonic acid (EPPS) pH 6-8 and Trishydroxymethyl aminoethane sulphonic acid (TES) pH 6-8 being most preferred.
to Calcium is added to the neutral solution in order to convert the prothrombin to thrombin. Of course the calcium can be part of the alkaline buffer.
Calcium can be added in the form of farm of, for example, calcium chloride. The amount of calcium l5 added should be sufficient to convert an amount of prothrombin to thrombin that is sufficient for the intended medical use. Furthermore, the reaction should be permitted to occur for a period of time sufficient to convert enough of the prothrombin to 20 thrombin that is sufficient f ~r the intended medical use. Generally, from about 5 millimolar to about 50 millimolar calcium chloride is sufficient. It has been observed that at about 25 minutes of reaction sufficient amounts of thrombin are formed for mast 25 medical uses of the thrombin blood fraction of the subject invention.
Also, rather than adding a source of calcium ions, prothrom?ain activating enzymes from snake venoms can be utilized. For example, snake venom from Eccis 30 carinatus or the Australian Tiger snake can be utilized.
As the thrombin forms, it converts the fibrinogen to fibrin,-which forms a fibrin clot. It is preferred to remove the fibrin clot, which can be 35 carried out by, for example, wrapping the fibrin clot around a stirring rod or collection of the fibrin onto glass beads.
4.1.3. PREPARATION OF THROMBIN BLOOD
FRACTION HX REMOVING OR INACTIVATING
ANTITHROMBIN III FROM PLASH
In an alternative method, the thrombin blood Fraction of the subject invention can be prepared by withdrawing whole blood from an individual animal, e.g., a human, and preferably in the presence of an =o anticoagulant. Any anticoagulant can be utilized.
Suitable anticoagulants are heparin, EDTA, citrate or any other agent that can, directly or indirectly, prevent the formation of thrombin, with citrate being preferred.
The plasma, which contains the prathrombin, is then separated from the whole blood. Any separation technique can be utilized, for example, sedimentation, centrifugation or filtration.
Centrifugation can be carried out at about 3,000 g:
2o for abaut 10 minutes. The supernatant, which contains the plasma, can be removed by standard techniques.
Antithrombin III is then removed from the plasma or is inactivated. For example, the pH of the plasma can be lowered to at least to about 5. Such 25 lowering of pH inactivates antithrombin III; otherwise antithrombin III would prevent the conversion of prothrombin to thrombin. Antithrombin III can be inactivated by any technique. Far example, by the addition of 0.05 ml of 5 mol./liter HC1 per l.0 ml 3o plasma. After about to to about 2o minutes of incubation, the plasma can be neutralized with 0.05 ml of 5 mol./liter NaOH per ml of plasma.
Rather than inactivating the antithrombin III, the antithrombin III can be removed from the ss plasma by passing the plasma through a column that WO 9~l/00566 PCT/G893/01323 - 1~ -binds antithromlain III, e.g., a heparin column or a column with antibodies to antithrombin III.
The plasma fraction, which contains prothrombin, is then treated to convert prothrombin to thrombin. This can be carried out by, for example, the addition of a source of calcium ions, as described above, or by the addition of 0.1 ml CaCl: of 0.36 mol.Jliter per ml of plasma. Also, rather than adding a source of calcium ions, prothrombin activating l0 enzymes from snake venoms can be utilized. For example, snake venom from Eccis carinatus or the Australian Tiger snake.
As the thrombin farms, it converts the fibrinogen to fibrin, which forms a fibrin clot. It is preferred to remove the fibrin clot, which can be carried out by, for example, wrapping the fibrin clot around a stirring rod or collection of the fibrin onto glass beads.
The resulting plasma is a thrombin blood Zo fraction of the subject invention.
4.1.4. METHOD F4R THE PREPARATION OF A

WITLi AN ACID SOLUTION DIRECTLY
By the known process for preparing thrombin from plasma, plasma is diluted in the ratio 1:10 with Water, whereafter a pH-reducing acid is added, such as acetic acid, with the result that~the pH-value is about 5.0 to 5.3. The mixture is then centrifuged Par 20 min. at 2,000 g. The resulting precipitate 3o contains different coagulation factors, such as inter olio prothrombin and fibrinogen. When the excess fluid has been removed, the precipitate is dissolved in a physiological solution, preferably a 0.9% sodium chloride solution, whereafter.a pH-value-increasing ss agent, such as sodium carbonate, is added until the r pH-value is about ?.9. When the precipitate has been dissolved, calcium chloride is added and causes the conversion of the prothrombin into thrombin by a conventional, so-called coagulation cascade. The s resulting thrombin causes a conversion of fibrinogen into fibrin, whereafter the thrombin is separated by centrifuging and then subjected to a succeeding purification (column purification).
Another aspect of the subject invention is that the diluting step is performed directly with a diluted acid solution, e.g., 0.4% acetic acid, by the centrifuging step being performed in a container with a relatively large flat precipitation surface, by the physiological solution, with. the~agent for increasing i5 pH, and the calcium chloride being added at the same time to the precipitate as a mixture, whereby said precipitate is dissolved and then coagulates while forming fibrin, and by the thrombin then being reatoved.
As a result, it is now possible to prepare thrombin from plasma of autologous blood in a relatively quick way, which is in particular due to the fact that the precipitation is performed in a container with a relatively large flat precipitation surface. A quick and complete dissolution is thereby ensured of the precipitate containing prathrombin and fibrinogen. The complete dissolution is important before the presence of calcium chloride causes the conversion of prothrombin to thrombin. A too early thrombin formation leads tv fibrin formation and the fibrin will bind the added fluid, whereby the dissolution of the precipitate stops and cannot continue until said fluid has again been gassed out of the fibrin. The relatively small precipitate with a relatively large surface area relative to the amount PCTlG B93/01323 WO 94!00566 causes a complete dissolving of said precipitate by addition of the combined mixture of physiological solution, with the agent for increasing pH, and calcium chloride before the thrombin has been formed through said coagulation cascade and starts the formation of fibrin.
Moreover according to the invention, the mixture may be admixed with a plasminogan catalyst, such as atreptokinase, before being added to the to precipitate with the effect that the following separation of thrombin from fibrin is promoted.
According to the invention, the mixture added to the precipitate can advantageously be set to increase the pH-value to 6.5, whereby the resulting active thrombin is found to obtain the best keeping gualities as the thrombin has a tendency to became inactive on standing, which is usually the case in connection with enaymes. In addition, the dissolved precipitate can be transferred to a flexible material before the coagulation starts, said flexible material presenting a relatively large surface upon which the fibrin resulting from the coagulation can be deposited, whereafter the thrombin may be pressed ouz of the fibrin by the flexible material being subjected to a compaction. Exactly the obtained complete dissolving of the precipitate prior to formation of fibrin turned out to allow a quick transfer of the solution to a flexible material prior to said formation of fibrin. The flexible material ensures that the fibrin is deposited across a particularly large surface, the compaction of which facilitates the separation of thrombin from fibrin.
It is particularly preferred when the flexible material is a sponge with open pores.

The flexible material can be placed in a syringe, into which the dissolved precipitate can be absorbed and from which the thrombin can be squeezed out by an activation of the piston of the syringe. In 5 this manner, a particularly easy separation of the thrombin from the flexible material is ensured.
Moreover, the centrifuging may according to the invention suitably be performed at about 1,50o g for about 5 min, which also accelerates the preparing to of thrombin.
Thus, the subject invention comprises a process for preparing thrombin from human blood plasma, whereby the blood plasma is diluted to about 10 to 17%.with water or another ion-intensity-reducing 1s fluid arid an acid to reduce pH to about 5.0 to 5.3, whereafter the,mixture is centrifuged, and whereby the precipitate resulting from the centrifuging is admixed a physiological solution and calcium chloride, said physiological solution increasing pH to about 6 tv 8, 20 characterized by the diluting step being performed directly With a diluted acid solution, by the centrifuging step being performed in a container. with a relatively large plane precipitation surface, by trie physiological solution, with the agent for increasing pH, and the calcium chloride being added at the same time to the precipitate as a mixture, whereby said - precipitate is dissolved and then'coagulates while forming fibrin, and by the thrombin then being removed from the fibrin.

4.2. ACCELERATION OF THROMEIN FORMATION
BY CONTACTING BLOOD OR PLASMA WITH
A SURFACE THAT ACTIVATES BLOOD
COAGULATIOj~1 FACTORS XI AND XII
Another aspect of the sub~act invention is the preparation of a thrombin blood fraction wherein whole blood or plasma is contacted with a surface that activates blood coagulation factors XI and XII. It is believed that a negatively charged surface such as glass or kaolin, with glass being preferred, can provide such activation. Nonlimiting examples of glass surfaces are glass beads, glass wool, glass filters and glass capillary tubes.
The whole blood or plasma should contact the surface for a period of time sufficient tv activate such blood coagulation factors, e.g., for about 5 to about 10 minutes. If the whole blood or plasma has not been treated with an a:~...icoagulant, then the whole blood or plasma should be in contact with such a surface for not more than about 60 seconds, preferably 2a less than about 30 seconds and more preferably about 15 seconds. Without the anticoagulant, and if the contact of the whole blood or plasma with the surface is too long, then fibrin clots will form prematurely.
It is preferred that plasma be exposed to a surface of about 4 cm2 to about 60 cm', preferably from about 10 cm to about 30 cmZ and most preferably about 20 cm2 of such surface for each milliliter of plasma.
Also, it is preferred that whole blood be exposed to a surface of from about 2 cm= to about 3o cm=, preferably 3Q from about 5 cm~ to about 15 cm2 and most preferably about 10 cm= of such surface for each milliliter of whole blood.
It is believed that the contacting of the plasma or whole blood With a surface that can activate factors XI and XII accelerates the conversion time of prathrambin to thrombin. Thus, a thrombin blood fraction can be prepared in an extremely short period of time.
This activation of factors XI and XII can be utilized to accelerate the preparation, of any thrombin blood fraction, regardless of how the fraction is made and regardless of its purity and specific activity.
However, it is essential that the thrombin blood fraction be substantially free of active antithrambin 1o III. It is essential that the antithrombin III either be removed from or inactivated in the thrombin blood fraction prior to converting the prothrombin to thrombin. Otherwise, antithrombin III will prevent the conversion of the prothrombin to thrombin andJor 15 inactivate the thrombin. It is else preferred that the thrombin blood fraction be substantially free of fibrinogen and fibrin. For example, with respect to the activation when the thrombin blood fraction is prepared by means of the euglobulin fraction as 20 described in Section 4.1.1., the contacting of the plasma should be carried out immediately prior to the dilution of the plasma. When a thrombin blood fraction is prepared by diluting whole blood, as described in Section 4.1.2., the contacting of the 25 whole blood should be carried out immediately prior to the dilution of the whole blood. For example, this contacting step can be carried out by withdrawing whole blood into a syringe that contains, for example, glass beads. After net more than about 60 seconds, 30 the whole blood is discharged from the syringe and the thrombin blood fraction of the subject invention is then prepared, as described above.

WO 94IOOSb6 PCTIGB93/01323 4.3. THE USES OF THE THROMBIN BLOOD
FRACTION OF THE SUBJECT INVE.,~1TION
The thrombin blood fraction of the subject invention can be utilized in any medical procedure, known or to ba developed, in an animal, including vetinary praceduras. Any species of animal is suitable, but, of course, humans are preferred.
The thrombin blood fraction can be employed as a component of a fibrin sealant or can be employed 1o alone just as conventional thrombin preparations have been employed. The thrombin blood fraction is utilized by contacting the desired site of the animal with the thrombin blood fraction. For the purpose of the subject invention, the "desired site" is that 15 location in or an an animal where one desires to form a fibrin clot. What or where the desired site is depends on the use of the thrombin blood traction of the subject invention.
The use of the thrombin bland fraction as a 2o component of a fibrin sealant, can be utilized for connecting tissues or organs, stopping bleeding, healing wounds, sealing a surgical wound, use in vascular surgery include providing hemostasis for stitch hole bleeding of distal coronary artery 25 anastomoses; left ventricular suture lines; aortotomy and cannulation sites; diffuse epimyocardial bleeding . seen in reoperations; and oozing_from venous bleeding sites, e.g. at atrial, caval, or right ventricular levels. The subject invention is also useful for 3o sealing of dacron artery grafts prior to grafting, sealing tissues outside the body, producing fibrin rafts for cell growth, stopping bleeding from damaged spleens (thereby saving the organ), livers, and other parenchymatous organs; sealing tracheal and bronchial 3s anastomoses and air leaks or lacerar.ions of the lung, sealing bronchial stumps, bronchial ffistulas and CVO 94/00566 PCTIGB93l01323 esophageal fistulas; for sutureless seamless healing ("Zipper" technique), and embolization in vascular radiology of intracerebral AVM's, liver AVM's, angiodysplasia of colon, esophageal varices, "pumping"
GI bleeders~secondary to peptic ulcers, etc. The subject invention is further useful for providing hemostasis in corneal transplants, nosebleeds, past tonsillectomies, teeth extractions and other applications. See G.F. Gestring and R. Leaner, Vascular Surgery, 294-304, Sept./Oct. 1983.
The thrombin blood fraction of the subject invention can be employed alone to staunch oozing hemorrhages or hemorrhages in hollow organs. The thrombin blood fraction can also be utilized in the treatment of damaged live animal tissue by utilizing the fraction to activate the release of the materials, i.e., plated-derived factors, Prom platelets, wherein such materials can be utilized to heal damaged tissue.
See United States Patent No. 5,165,938. The thrombin 2o blood fraction can also be utilized to assist in the cell culture growth of keratinecytes and to assist in the autologous transplantation of keratinocytes, or any other skin-derived calls, e.g., fibroblaszs. See V. Ronfard et al., Burns 17:181-38~ (1991); H. Sroiy, Canadian Patent No. 2,018,020 and ~. Hunyadi et al., J. Dermatol. Surg. oncol. 1:?S-?8.(1988).
Also, the thrombin blood fraction can be placed on a selid support, e.g., bandage, suture, prosthesis., or dressing, that will be in contact :pith 3o the desired site. Such support is then placed in contact with the desired site until, for example, the fibrin clot forms.

CVO 94!00566 PCT/G B93/01323 The dosage of the thrombin blood fraction depends on its particular use, but the dosage should be an effective amount for the composition to perform its intended use. Generally, it is believed that from 5 about 0.5 ml to about 5 ml of the thrombin blood fraction is sufficient. However, depending on the use, the dosage can range from about 0.05 ml to about 40 ml.
If the thrombin blood fraction is utilized 1o as a component of a fibrin sealant, then the fibrin sealant can be applied to the desired site with, for example, a double-barrelled syringe. The double-barrelled syringe can be Y-shaped, thereby permitting the mixing of fibrinogen and the thrombin 15 blood Fraction immediately prior to the contacting step. Also, rather than a Y-shaped double-barrelled syringe a double-barrelled syringe with two openings can be utilized. This permits the si:aultaneous contacting of the desired site. Also, the 2o compositions of the double-barrelled syringe can be sprayed onto the desired site. See H.B. Kram et al., The American Surgeon, 57:381 (1991), Also, if the blood fraction is employed as a component of a fibrin sealant, then autologous fibrinogen can be utilized, 25 thereby rendering the entire fibrin sealant autoiogous. Also, if the thrombin blood fraction is employed alone, then the fraction can be applied to the desired site with a single-barrelled syringe.
It should also be noted that the thrombin 30 blood fraction of the subject invention can further comprise a source of calcium ions, e.g., calcium chloride. The source of calcium ions assists in the conversion of Fibrinogen to the fibrin clot. The amount of calcium ions should be the same as that 35 utilized in conventional fibrin sealants. However, WO 9d!00566 PCT/GB93I01323 since the thrombin blood fraction may contain a source of calcium ions already due to the conversion of prothrombin to thrombin, an additional source of calcium ions may not be required. But, if more S calcium is needed to form the (fibrin clot than to form thrombin, then, as an option, excess calcium from what is required to form thrombin can be utilized so that no additional calcium need ba added when the thrombin blood fraction is utilized in the medical procedure, to e.g., as a component of a (fibrin sealant.
5. EX~~~ES
EXAMPLE I
Preparation of a Composition Captaining a =5 Thrombin Blood Fraction Obtained From 17 ml of Fresh Blood From a Human Adult Donor A puncture of the vein of a human was performed by a needle and 17 ml of blood was drawn into an empty 30 m1 syringe. Immediately after 20 .awing the blood, it was transferred to a 50 ml test tube containing 34 ml of a solution containing 5.5~
glucose. The 50 ml test tube was placed in a centrifuge and centrifuged for 5 minutes at 1,500 x g at room temperature. After centrifugation, 4o ml of 25 ~e supernatant plasma/glucose solution was removed by a syringe, and transferred to a new 50 ml test tube.
By means of 1.07 ml of~a 2.8~ citric acid solution, the pH in the plasma/glucose solution was lowered to 5.2 and after a period of l0 minutes at 3o roam temperature, the solution was centrifuged at I8~C
at 1,500 x g for 5 minutes. After centrifugation, the supernatant was drained off and the precipitate was dissolved in 0.424 ml of a solution containing 14 mmole/L of NaHCO~ and 8 gram/L of NaCl. This 35 precipitate contains fibrinogen, prothrombin and other c WO 94100566 PCTlGB93/01323 blood proteins, but is substantially free of antithrombin III. The pH of this dissolved prothrombin containing euglabulin solution was 7.35.
Activation of the prothrombin was performed by the addition of 0.027 ml of a solution containing CaCl2, 0.5 mole/L. From 12 to 17 minutes after the addition of the CaCh, the fibrinogen in the solution started to coagulate, and the fibrin thus formed-was removed by means of a polystyrene spatula. small to samples were removed at different intervals and the thrombin concentration was measured. The results from the example are shown in Tabie I.
Table I

time after 10 20 30 60 120 27 Ca-addition min min min min min hour NIH u/ml 0 180 368 540 600 737 2o E~LE II
Preparation of a Composition Containing a Thrombin Blovd Fraction Obtained From 17 ml of Fresh Glass Activated Blood From a Human adult Donor In this experiment, the donor and the day for the performance was the same as used in Example I.
A puncture of the vein of a human was performed by a needle and 20 ml of blood was dratan into a 30 ml syringe containing ZO grams of glass beads witY: a 3o diameter of approximately 2 mm. The total surface area of the beads was approximately 23o cm~ and, therefore, the surface area was about 11.5 cm' per ml of whole blood.
hamediately after drawing the blood, the 3s syringe was turned gently for 10 to 15 seconds before i7 ml of the blood was transferred to a 50 ml test a tube containing 34 ml of a solution containing 5.5%
glucose. The 50 ml test tube was placed in a centrifuge and centrifuged for 5 minutes at 1,500 x g at room temperature. After centrifugation, 40 ml of s the supernatant plasma/glucose solution was removed by a syringe, and transferred to another 50 m1 test tube.
By means of 1.07 ml of a 2.8% citric acid solution, the pH was lowered to 5.2 and after a period of 10 minutes at room temperature, the solution was 1o centrifuged at 18°C at 1,500 x g for 5 minutes.
After centrifugation the supernatant was drained off and the precipitate was dissolved in 0.424 ml of a solution containing 14 mmole/I, of HaHC03 and 8 gram/L of NaCl. This Precipitate contains 15 prothrombin, fibrinogen and other blood proteins, but is substantially free of antithrombin III. The pH of this dissolved prothrambin containing euglobulin solution was 7.35.
Activation of the prothrambin was performed 2o by the addition of a 0.027 ml of a solution co»taining CaCl2, 0.5 mole/L. From 4 to 9 minutes after the addition of the CaCI2, the fibrinogen in the solution started to coagulate, and the fibrin thus formed was removed by means af.a polystyrene spatula. Small Z5 samples were removed at different intervals and the thrombin concentration was measured. The results are shown in Table II. .
Table ?I

time after 10 20 30 60 120 27 Ca-addition min min min min min hour NIFi u/ml 130 444 560 720 695 880 3$ Thus, from Table II it is readily apparent that the glass activation accelerates the time WO 94!00566 PCT/GB93/O1323 required for the conversion of the prothrombin to thrombin. For example, at only 10 minutes after the addition or a source of calcium ions, 130.NIH units/ml of thrombin activity was measured. In contrast, without glass activation, as in Example I, at l0 minutes after the addition of a source of calcium ions, there was no detectable thrombin activity.
EXAMPLE III
Preparation of a Composition Containing a Thrombin Fraction Obtained From 17 ml of Fresh Blood From Human Adult Donors, Characterized by Low Specific Thrombin Actiyity In four experiments, performed as described in Example I, the thrombin concentration and the specific activity of throz~bin were measured. The results are given in Tables III and IV where the pH
value is the pH in the dissolved euglobulin fractions.

Table III
A thrombin measured from l5 min to 2 hours after dissolution~of the euglobulin fraction.
NIH u/ml donor pH E-280 15 min 30 min 60 min 2 hr~
( JH 6.96 25.8 142 483 661 779 HJS 6.35 26.7 0 56 942 1,238 LFC 6.98 19.5 30 249 430 562 KN 6.21 31.5 O 142 X 616 725 3d (E-280 is a measurement of the total protein concentration in mg/ml).

d WO 9x/00566 PCTJCB931013I,3 Table IV
8 specific activity of thrombin measured from 15 min to 2 hours after dissolution of the euglobulin fraction.
NII3 u/mg protein donor 15 min 30 min 6o min 2 hr JIi 5.5 19 26 3D

HJS 0 2.1 35 ~ 46 LK 1.5 13 22 29 iv xi~ o a.5 20 23 Thus, the preparation of a thrombin blood fraction as described in Example I results in a thrombin blood fraction of a concentration and 15 Specific activity of the subject invention.
~E IV
Preparation of Thrombin From Whole Blood Using the Device of W091/I7778 The device described in W091/17778 was used for the preparation of thrombin. Before the blood was introduced into the device. 40 rsl ef a ~.5%
glucose solution was introduced into zhe first chamber (14) through the filter (43) counted on the tubing (39) .
Blood, 10 ia3, was collected from human donors into a syringe and immediately thereafter transferred through the tubing (39) into the glucose solution. The device was placed in a centrifuge and centrifuged far 5 min at 1,5DD x g. after centrifugaz'_nn, the plasma/glucose solution was transferred into the second chamber (3D) With the red cells remaining in the chamber (1:). Through the sterile filter in tube (60) 0.6 M1 of 2.8% citric acid solution was introduced into the plasma/glucose s , WO 94/00566 PCTlGB93/O1323 solution. After 5 to 10 min, the device was placed in a centrifuge and centrifuged for 5 min at 1,500 x g.
After centrifugation the supernatant was transferred to the first chamber (14) and the precipitate, the eugiobulin fraction, remained in the second chamber (30). Through the sterile filter in tube (60) 0.85 ml of a solution containing 7.5 mM NaHC03, 52 mM NaGl and 30 mM CaCl2 was introduced into the second chamber (30). The euglobulin precipitate was dissolved within 1-2 minutes, and transferred to the syringe (51) connected to the second chamber (30). The syringe contained a polyurethane sponge facilitating the removal of the formed fibrin. Thrombin concentrations were measured after 30 min to 22 hours. The results are recited in Table V.
Table V
throabin concentration NIH
u/ml 2o Donor plasma 30 min l hour 2 hour 22 hour dilution RFC-A 11.9% 185 ~ 240 231 2?9 I

RH-B 12.3% ~ 54 ( 130 130 ~ 132 I

RH-C 11.7% ( 1?8 186 I 180 I 192 ~ I

~-D 12.5 ~ 104 120 92 123 l I

EXAMPLE V
Preparation of Thro:abin and Fibrinogen Frc.;.
Whole Hlood Using a Device System Made From Two Inter-Connected Devices of W091/17778, and the Use of Thrombin and Fibrinogen in a Fibrin Glue The device svste~: consists of two devices as described in W091/17778. The Two tubings (39) 3s from the too devices were connected to the sate r ' WO 94/00566 PCTlGB93/01323 cannula (40) by means of a three-way connector. In the devise used fox tha thrombin precipitation 5 glass beads, 3 num in diameter, were placed in the second chamber (30). The syringe in the thrombin device was s changed ,from being a 3 ml syringe in the fibrinogen device to a 1 zal syringe.
Before the blood was collected from the donor, citrate and glucose solutions were filled into the two devices. Citrate, 5 ml of a 3.8% solution, 1o was introduced into the first chamber (14) of the fibrinogen device (hereafter named Device-F) through the filter (43) mounted on the tubing (39). Glucose, 34 ml of a 5.5% solution was introduced into the ffirst chamber (14) of the thrombin device (hereafter named 15 Device-T) through the filter (a3) mounted on the tubing (39).
Blood, 45 ml was collected through the cannula into the first chamber (14) in Device-F
containing the citrate solution, and I7 ml was 20 collected into the first chamber (14) in the Device-T
containing the glucose solution. After collection of the blood, the separator-system was disconnected from the donor, and the tubing (39) was sealed close~to inlet (38). Both devices were placed in a centrifuge 25 and centrifuged for 10 min at 1,500 x g.
The separated plasma in Device-F was transferred to the second chamber,(30) and 2.5 ml of a 96% ethanol solution was introduced into the second chamber (30) through the sterile filter in tube (60).
3o The device was now placed into a ice-water bath far 20 minutes to reduce the temperature in the plasma/ethanol solution to approximately 0 to 4~C. At this te~uperature, 85% of the fibrinogen in plasma was precipitated. The device was now placed in a 35 centrifuge and centrifuged far 5 min at 1,500 x g.

A i The supernatant serum was transferred to the (first chamber (14), and the solid fibrinogen was dissolved by incubation for 5 minutes at 37°C. The dissolved solution was transferred to the sterile syringe (51).
The concentration of fibrinogen was measured to be 31 mg/ml.
The separated plasma/glucose in Device-T was transferred into the second chamber (30) with the red cells remaining in the first chamber (14). Through to the sterile filter in tube (60) 1.2 ml of a 2.8%
citric acid solution was introduced into the plasma/glucose solution. After 5 to 10 min the device was placed in a centrifuge and centrifuged f or 5 min at 1,500 x g. After centrifugation, the supernatant is was transferred to the first chamber (14) and the precipitate, the euglabulin fraction, remained in the second chamber (30). Through the sterile filter in the tube (60), 0.85 ml of a solution containing 7.5 mM
NaIiC03, 52 mM NaCi and 30 mM CaCl= was introduced into 2o the second chamber (30). The euglobulin precipitate was dissolved within 1-2 minutes, and the fibrin formed during the activation of prathrombin to thrombin was collected onto 5 glass beads placed in the second chamber (30}. After 15 minutes the.
25 thrombin solution was transferred to the syringe (51) connected to the second chamber (30). Thrombin '- concentration was measured to be 248-340-372 NIH ujml after 15-30-6o minutes, respectively.
The two syringes containing the fibrinogen 3o and the thrombin were used as a double barrelled syringe. The two solutions ware expelled from the syringes and formed immediately a firm fibrin clot.
s5 EXAMPLE VI
54 m1 of 0.o4% FIAc were added to 6 ml of plasma. This mixture was placed in a flat-bottomed container of the type known from the above 5 PCT/DK91/08131. The container is of a circular Cross section with an inner diameter of 4.5 cm. The pH-value was 5.3. Tha pH-value and the relatively low concentration of ions in the provided mixture ensure the following precipitation of the coagulation factors, inter olio prothrombin, as a precipitate by a centrifuging. The centrifuging was performed at 1,500 g f or 5 min. Thus the centrifuging was relatively quickly terminated, which is due to the relatively short falling height and large precipitation surface.
15 After removal of excess fluid, an 0.75 ml aqueous solution of 0.9% NaCl, 0.03% NarC03 and 25 mM CaCl2 was added to the precipitate. After dissolving of the precipitate, the solution was sucked into a 2.5 ml syringe containing a polyurethane sponge. The 20 formation of fibrin did not start until about 1 to 2 min. after the precipitate had become completely dissolved, and accordingly more than enough time for the sucking procedure. After termination of the fonaation of fibrin in the syringe, the thrombin 25 solution could be expelled by squeezing the sponge by means of the piston of the syringe, the fibrin remaining depositing on the large surface of the sponge.
The dissolved precipitate had a pH-value of 30 6.5. Other amounts of Na,C03 or another base or a buffer system car be used provided the pH-value is between 6.0 and 2:5, but an optimum balance between the keeping qualities of the thrombin and the capacity of the thrombin to accelerate the coagulation process 35 is found at 6.5.

CVO 94!00566 PCTJGB93JOt323 -~ 3 5 The thrombin was expelled from the syringe after 30 min, and a concentration of 256 NIH units per ml was obtained. The thrombin concentration increased by time, but after 30 to 60 min a sufficient amount of thrombin was obtained year a conventional use in a fibrin sealant.
The preparation of thrombin was in the present Example produced from 12 ml as autologous blood and was terminated over a period of 45 to 60 to min, i.e., almost simultaneously With the termination of the preparation of fibrinogen. The produced amount of thrombin was sufficient far being used in combination with fibrinogen produced from 45 gal of autologous blood in the manner described in i5 w091/17778.
The fibrin f ormed during the ttirambin preparation has always a tendency to bind the thrombin. The release of this thrombin can, however, be promoted by the addition of a piasminogen catalyst, 2o such as stxeptokinase, urokinase or t-PA (tissue plasminogen catalyst) optionally adaixed with a physiological solution.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for preparing a composition comprising platelet derived factors by activating platelets to release said platelet derived factors by contact with thrombin that is derived from the same individual animal as said platelets, wherein said thrombin is a thrombin blood fraction comprising:
(a) a thrombin concentration of from 1 NIH unit/ml to 2,000 NIH units/ml; and (b) a specific activity of thrombin of from 1 NIH
unit/mg of blood protein to 200 NIH units/mg of blood protein;
and wherein said thrombin blood fraction contains less than 50% activity of antithrombin III in normal plasma per unit volume.