METHOD AND APPARATUS FOR PURIFYING BLOOD

Abstract

A device and method for purifying blood. The method includes the steps of separating the blood plasma from the blood cells, adjusting the pH of the blood plasma to a pH close to an isoelectric point of at least one predetermined protein, treating the blood plasma by ion-exchange chromatography, neutralizing the pH of the blood plasma, and pooling of the blood plasma and blood cells.

Claims

1. A method for purifying blood comprising the steps of: separating blood plasma from blood cells; adjusting a pH of the blood plasma to a pH close to an isoelectric point of at least one predetermined protein; treating the blood plasma by ion-exchange chromatography; neutralizing the pH of the blood plasma; and pooling the blood plasma and the blood cells, wherein the pH to which the pH of the blood plasma is adjusted corresponds to the isoelectric point of the predetermined protein to within +1.5/+0.0 pH point.

2. (canceled)

3. (canceled)

4. The method according to claim 1, wherein the predetermined protein is a coagulation factor.

5. The method according to claim 1, wherein the pH of the blood plasma is adjusted to a pH which is lower than pH=5.5.

6. The method according to claim 1, wherein the adjustment of the pH of the blood plasma is carried out by supplying protons to the blood plasma and/or dialysis of the blood plasma with an acidic buffer.

7. The method according to claim 1, wherein neutralization of the pH of the blood plasma is carried out by supplying hydroxide ions to the blood plasma and/or dialysis of the blood plasma with a basic buffer.

8. The method according to claim 1, wherein treatment of the blood plasma is carried out by means of anion-exchange chromatography.

9. (canceled)

10. A blood treatment machine configured to perform the method according to claim 1, the blood treatment machine comprising: a plasma filter for separating blood into blood plasma and blood cells; a feed device/mixing pump for adjusting a pH of the blood plasma; and an ion exchanger.

11. The blood treatment machine according to claim 10, further comprising a dialyzer, wherein: the feed device/mixing pump is fluidically connected downstream of the plasma filter, the ion exchanger is connected downstream of the feed device/mixing pump, and the dialyzer is configured to carry out dialysis using acidic or basic dialyzing fluid.

12. The blood treatment machine according to claim 10, wherein the ion exchanger is a DEAE anion exchanger.

13. A method of purifying blood plasma comprising the step of using a DEAE anion exchanger to purify the blood plasma.

14. The method according to claim 1, wherein the pH of the blood plasma is adjusted to a pH in a range between pH=5.0 and pH=5.5.

Description

BRIEF DESCRIPTION OF THE DRAWING FIGURES

[0080] FIG. 1 shows an example of the adsorption of various coagulation factors on a DEAE anion exchanger at a physiological pH of the blood plasma.

[0081] FIG. 2 shows an example of the adsorption of various coagulation factors on a DEAE anion exchanger at a blood plasma pH of pH=5.1.

[0082] FIGS. 3a and 3b illustrate the pH-dependent adsorption of various coagulation factors on a DEAE anion exchanger.

[0083] FIG. 4 shows an example of a device according to the invention.

DETAILED DESCRIPTION

[0084] Examples of embodiments of the present invention are described below with reference to the accompanying figures.

[0085] FIG. 1 shows an example of the adsorption of various coagulation factors on a DEAE anion exchanger at a physiological pH of the blood plasma. In an in vitro experimental set-up, DEAE anion exchangers were flowed through with blood plasma with a physiological pH of pH=7.4 and the adsorption of coagulation factors was determined.

[0086] Factors II, IX and X of the blood coagulation cascade were effectively adsorbed by the DEAE anion exchanger and largely removed from the blood. At a time t1, the measurable amount of Coagulation Factors II, IX and X in the blood plasma is zero. The global coagulation status therefore dropped to a dangerously low level after treatment with the DEAE anion exchanger.

[0087] The amount of Coagulation Factor IX remained permanently low, whereas Coagulation Factors II and X were no longer adsorbed after a plasma volume (approx. 3 L, after a time t2 in FIG. 1) was passed through the DEAE anion exchanger. Therefore, the amounts of Coagulation Factors II and X increase after time t2 in FIG. 1.

[0088] FIG. 2 shows an example of the adsorption of various coagulation factors on a DEAE anion exchanger at a blood plasma pH of pH=5.1.

[0089] The amounts of Coagulation Factors II, IX and X remain stable and there is no adsorption to the DEAE anion exchanger. The dip of the curves at time t3 in FIG. 2 is an artefact and is due to a dilution effect of rinsing solution present in the system.

[0090] FIGS. 3a-b illustrate the pH-dependent adsorption of the coagulation factors Factor I, Factor II, Factor IV, Factor V, Factor VI, Factor VII, Factor VIIa, Factor VIII, Factor IX, Factor X, Factor XI and Factor XII to a DEAE anion exchanger. The position of the vertical arrows on the pH scale shows the isoelectric point of the respective coagulation factors. FIG. 3a shows the adsorption of the coagulation factors when the blood plasma has a pH of approx. pH 7.4. FIG. 3b shows the adsorption of the coagulation factors when the blood plasma has a pH of approx. pH 5.1.

[0091] As shown in FIG. 3a, at a blood plasma pH of approx. pH 7.4, Factors II, IX and X are adsorbed on the DEAE anion exchanger, while Factors V, I, VIIa, VII, VIII, XII and XI are not adsorbed. When the pH shifts from the neutral pH of pH 7.4 into the acidic range (lower pH), the negative charge of the proteins/molecules increases. When the pH shifts from the neutral pH of pH 7.4 into the basic range (higher pH), the positive charge of the proteins/molecules increases.

[0092] As shown in FIG. 3b, at a blood plasma pH of approx. pH 5.1, there is no adsorption of Factors II, IX, X, V, I, VIIa, VII, VIII, XII and XI on the DEAE anion exchanger. The pH of approx. 5.1 is close to the isoelectric point of Factor II, which is pH=4.4 and is 1.1 higher than the isoelectric point of Factor II.

[0093] When the pH shifts from the acidic pH of pH 5.1 further into the acidic range (lower pH), the negative charge of the proteins/molecules increases. When the pH shifts from the acidic pH of pH 5.1 to the basic range (higher pH), the positive charge of the proteins/molecules increases.

[0094] In both the case shown in FIG. 3a and in the case shown in FIG. 3b, non-amphoteric pathogenic substances such as endotoxins, viruses, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are bound by the DEAE anion exchanger with consistent effectiveness and therefore removed from the blood plasma.

[0095] By adjusting the pH of the blood plasma prior to ion-exchange chromatography, the adsorption or binding behaviour of amphoteric proteins/molecules such as coagulation factors can therefore be selectively influenced in such a way that these proteins/molecules are not adsorbed or removed from the blood plasma, while non-amphoteric proteins/molecules such as pathogens and endotoxins continue to be effectively adsorbed and therefore removed from the blood plasma.

[0096] FIG. 4 schematically shows the structure of a blood treatment machine according to the invention, which is designed/configured to perform a method according to the invention. The blood treatment machine is preferably an apheresis machine.

[0097] The blood machine is connected or connectable to a patient via a blood inflow line and a blood outflow line. The blood from the blood inflow line is conveyed by a first feed pump 5 and then flows further into a plasma filter 1 having two outlets, in which the blood is separated into blood plasma and blood cells, whereby the blood plasma flows out from one outlet of the plasma filter 1 and the blood cells flows out from another outlet of the plasma filter 1.

[0098] The blood plasma separated by the plasma filter 1 is further mixed in a feed device/mixing pump 2 with an acetate buffer having a pH of pH 4 provided by a fluid supply/source 6 to lower the pH of the blood plasma to approx. 5.

[0099] The blood plasma treated in this way is channeled by the feed device/mixing pump 2 to a valve/shut-off device for controlling the flow. From there it flows further into an ion exchanger 3, which in this embodiment is an anion exchanger, preferably an anion exchanger with tentacle technology.

[0100] Ion exchange with charges of the molecules takes place in the ion exchanger 3. If the pH of the blood plasma is close to the isoelectric point, the amphoteric coagulation factor is no longer adsorbed by ion exchanger 3. Non-amphoteric molecules such as LPS, LTA and viruses are further adsorbed in ion exchanger 3 regardless of the pH of the blood plasma.

[0101] After the ion exchanger 3, the blood plasma flows through a blood side of a dialyzer 4, in which the dialysate side of the dialyzer 4 is flowed through with a bicarbonate buffer provided from a further fluid supply/source 6 as dialysing fluid to restore a neutral physiological pH of the blood plasma, whereby a second feed pump 5 is arranged between the fluid supply/source 6 with bicarbonate buffer and an inlet of the dialyzer 4 to feed the bicarbonate buffer.

[0102] The purified blood plasma, which again has a physiological pH, is further conveyed by a third feed pump 5 downstream of the dialyzer 4 and then reunited with the blood cells from the plasma filter 1.

[0103] The treated blood then continues to flow through an air trap with an air detector, in which air bubbles are detected and removed, and flows to another downstream valve/shut-off device to control the flow which is connected to the blood discharge line. From there, the treated blood is returned to the patient.

[0104] In summary, the blood treatment machine comprises a plasma filter 1 for separating blood into blood plasma and blood cells, a feed device/mixing pump 2 fluidically connected downstream of the plasma filter 1 for adjusting the pH of the blood plasma, an ion exchanger 3, which is preferably an anion exchanger, connected downstream of the feed device/mixing pump 2, and a dialyzer 4, which is fluidically connected downstream of the ion exchanger 3 and by means of which dialysis can be carried out using acidic or basic dialysis fluid.

[0105] After the blood has been separated into blood plasma and blood cells in the plasma filter 1, the blood plasma is mixed with an acetate buffer with a pH of pH 4 provided by a fluid supply/source 6 by means of the feed device/mixing pump 2 to lower the pH of the blood plasma to approx. pH 5.

[0106] The blood plasma then flows through a valve/shut-off device into the ion exchanger 3, which in this embodiment is an anion exchanger, preferably an anion exchanger with tentacle technology.

[0107] After the ion exchanger 3, the blood plasma flows through the dialyzer 4. This is flowed through on the dialysate side with a bicarbonate buffer provided as dialysis fluid by another fluid supply/source 6 and conveyed by a second feed pump 5. In this way, the dialyzer 4 restores a neutral physiological pH of the blood plasma and removes additional fluid from the blood plasma.

[0108] The purified blood plasma is then reunited with the blood cells from the plasma filter 1 by a third feed pump 5. The combined and purified blood flows through an air trap with an air detector and another downstream valve/shut-off device and finally from the blood treatment machine back to the patient.