JP2009234929A - Hemoglobin-containing liposome suspension effective in oxygen delivery to hypoxic cell and tissue and production method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hemoglobin-containing liposome suspension with high oxygen affinity, which efficiently delivers oxygen to hypoxic parts such as sites of infarction, cancer, etc., and drastically improves hemoglobin yield. <P>SOLUTION: The hemoglobin-containing liposome suspension comprises a hemoglobin solution free of allosteric factors as an inner aqueous phase. Lipids forming a liposome membrane comprises stearic acid, and the concentration of hemoglobin, the lipids forming the liposome membrane and stearic acid in the liposome suspension are appropriately adjusted. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hemoglobin-containing liposome suspension as an artificial oxygen carrier. Specifically, oxygen can be selectively transported and supplied to hypoxic sites such as cells, tissues or cancer cells, cancer tissues, etc., where blood flow has been inhibited by thrombus, plugging, etc. The liposome suspension.

In order to make it easier to supply oxygen to hypoxic sites from normal tissue ends (oxygen partial pressure: 40 mmHg), such as infarcted sites and cancer sites, using hemoglobin-containing liposome suspensions as artificial oxygen carriers, The present inventors have intensively studied a hemoglobin-containing liposome suspension in which the oxygen releasing ability is controlled (Japanese Patent Laid-Open No. 2001-348341). Factors that shift the oxygen dissociation curve to the right and left and control the oxygen release ability are allosteric factor (detailed in 0011) and the pH of the aqueous phase hemoglobin in the liposome. It is not the pH of hemoglobin before operation (before mixing hemoglobin and liposome membrane-forming lipid), but the pH of internal aqueous phase hemoglobin after liposome formation. Depending on the type and composition ratio of the liposome membrane-forming lipid, the neutralization operation, etc., the “pH of hemoglobin before the liposome formation” differs from the “pH of the internal aqueous phase hemoglobin after the liposome formation”. Since the study of controlling the oxygen release ability was not sufficient after setting the factors affecting the pH of the inner aqueous phase hemoglobin and setting the appropriate numerical value of the pH of the inner aqueous phase hemoglobin, the present inventors , Low oxygen affinity (Oxygen dissociation curve shifts to the right compared to natural red blood cells: Compared with natural red blood cells, it is easy to separate oxygen between the oxygen partial pressure 100mmHg and oxygen partial pressure 40mmHg sites ) In the hemoglobin-containing liposome suspension (Japanese Patent Application No. 2006-308816). However, the high oxygen affinity targeted by the present invention (the oxygen dissociation curve is shifted to the left as compared with natural red blood cells: compared with natural red blood cells, it is easy to release oxygen at a site where the oxygen partial pressure is 40 mmHg or less) In the hemoglobin-containing liposome suspension, examination from the above viewpoint was not sufficient.
JP 2001-348341 A Artificial blood 2003; 11 (3): 179-184

Hemoglobin-containing liposomes are suspended in an external aqueous phase medium such as physiological saline and used as an artificial oxygen carrier. The factors involved in setting the oxygen carrying amount per unit amount of the liposome suspension are as follows. (1) hemoglobin concentration in the liposome suspension (2) pH of the inner aqueous phase hemoglobin (3) allosteric factor concentration, and the present inventors conducted an oxygen transport amount control method by optimal numerical setting of these factors. I have been studying earnestly. However, the hemoglobin pH setting prior to the liposomal operation was studied, but it was not the hemoglobin pH prior to the liposomal operation that was directly related to the oxygen carrying amount setting, but the final liposome water. The pH of the phase hemoglobin has not been fully investigated from this point of view. Depending on the type, composition ratio, neutralization operation, etc. of the liposome membrane-forming lipid membrane to be used, the `` pH of hemoglobin before liposome formation '' and the `` pH of internal aqueous phase hemoglobin after liposome formation '' are different. In the hemoglobin-containing liposome suspension with low oxygen affinity, the “pH of the inner aqueous phase hemoglobin after the formation of the liposome” is controlled within a certain range, and (1) hemoglobin concentration (2) allosteric factor concentration in the liposome suspension. (3) The optimal numerical value of the hemoglobin methotonization rate has been limited, and studies have been conducted in combination with these factors (Japanese Patent Application 2006-308816).
On the other hand, the average particle size of hemoglobin-containing liposomes as artificial oxygen carriers is around 0.2 μm, which is very small compared to natural red blood cells (7-8 μm). (Partial pressure is lower than the normal tissue oxygen partial pressure of 40 mmHg), and oxygen is passed through stenotic sites that are difficult for natural red blood cells to pass through, or through collateral blood vessels and surrounding capillaries. It is also possible to supply (Circulation, 2004; 100 (Suppl-I): 483, Circulation J., 2004: 68 (Suppl-I): I-133). In cancer tissue, there is sometimes no angiogenesis commensurate with the growth of cancer cells, so the vascular network is disordered and fragile, the blood flow of cancer tissue is unstable, and temporary blood Repeated flow interruption. For this reason, the cells inside the cancer tissue are exposed to hypoxia. Because of this hypoxic state, it is resistant to radiation for cancer treatment. A hemoglobin-containing liposome suspension as an artificial oxygen carrier may be able to supply oxygen to a hypoxic tissue site in cancer tissue that cannot be reached by natural erythrocytes (ASAIOJ., 2004: 50: 164).
In the present invention, in order to achieve high oxygen affinity so that oxygen can be efficiently transported to hypoxic sites such as infarcted sites or cancer tissues, it is a factor that affects oxygen transporting efficiency in hemoglobin-containing liposome suspensions. Intensive study was conducted on “pH of hemoglobin in the inner aqueous phase after liposome formation” and “allosteric factor”. As a result, the following facts were found. In conventional studies, in order to achieve low oxygen affinity, in hemoglobin-containing liposome suspensions to which allosteric factors have been added, the pH of the inner aqueous phase hemoglobin after liposome formation has an effect on oxygen transport efficiency, resulting in oxygen Involved in transport control. On the other hand, in the present invention, in order to achieve high oxygen affinity, in the hemoglobin-containing liposome suspension to which no allosteric factor is added (detailed in 0011), “the pH of the inner aqueous phase hemoglobin after the formation of liposome” is related to the oxygen carrying efficiency. It has little effect and as a result it is not substantially involved in oxygen transport control. And when allosteric factor is not contained, the hemoglobin yield (ratio (%) of the amount of hemoglobin in the form of liposome to the amount of charged hemoglobin) is improved. Further, higher saturated fatty acids such as stearic acid are preferably used as one of the components of the liposome membrane-constituting lipid, and the stearic acid composition ratio is related to the hemoglobin yield (detailed in 0014). As described above, in the present invention, even if the "pH of hemoglobin in the aqueous phase in the liposome" is not specified, the combination of "not adding allosteric factor" and "appropriate stearic acid composition ratio" allows the infarct site or cancer Provided is a high oxygen affinity hemoglobin-containing liposome suspension that can efficiently transport oxygen to a hypoxic site such as a tissue and that has a dramatically improved hemoglobin yield.

  Without adding allosteric factor, by setting appropriately the hemoglobin concentration, liposome membrane-forming lipid concentration, and stearic acid concentration in the hemoglobin-containing liposome suspension, it can be efficiently applied to hypoxia sites such as infarcted sites or cancer tissues A high oxygen affinity hemoglobin-containing liposome suspension capable of transporting oxygen and having dramatically improved hemoglobin yield is provided as follows.

(1) A liposome suspension having a hemoglobin solution containing no allosteric factor as an inner aqueous phase, wherein the liposome membrane-forming lipid contains stearic acid, and the hemoglobin concentration in the liposome suspension is 5.6 to 6.7 w / The liposome suspension characterized in that it is v%, the concentration of liposome membrane-forming lipid is 3.05 to 5.10 w / v%, and the stearic acid concentration is 0.45 to 0.73 w / v%.

(2) The liposome suspension according to claim 1, wherein a hemoglobin metration rate in the liposome suspension is 10% or less.

  As described above, in the present invention, in the hemoglobin-containing liposome suspension, (1) no allosteric factor is added (2) hemoglobin concentration (3) liposome membrane-forming lipid concentration and stearic acid concentration are appropriately set. Thus, a high oxygen affinity hemoglobin-containing liposome suspension capable of efficiently providing oxygen to a hypoxic site such as an infarct site or a cancer tissue and a hemoglobin yield has been dramatically improved, and a method for producing the same. Provided.

Hereinafter, the present invention will be described more specifically.
<Liposome membrane-forming lipid>
The liposome membrane-forming lipid in the present invention can be a natural or synthetic lipid. In particular, phospholipids are preferably used, and those obtained by hydrogenation according to a conventional method can be mentioned. Furthermore, a membrane-strengthening agent such as sterol or a higher saturated fatty acid as a charged substance is added to the liposome membrane-forming lipid as desired. Hydrogenated soybean phospholipid is preferably used as the phospholipid, cholesterol as the membrane strengthening agent, and stearic acid as the charged substance.

<Hemoglobin contained in liposome aqueous phase>
The hemoglobin contained in the aqueous phase of liposome of the present invention is obtained by removing leukocytes, platelets, plasma and erythrocyte membrane from a human expired concentrated erythrocyte preparation by a known method, and then hemolyzed, purified and concentrated human-derived concentrated hemoglobin is obtained. .

<Liposome surface modifier>
It has a hydrophobic part at one end and high hydrophilicity at the other end for the purpose of preventing protein adsorption inhibition or liposome aggregation inhibition on the liposome surface and improving blood stability after intravascular administration of liposomes. Compounds having molecules are used for the surface modification of liposomes. A polyethylene glycol-linked phospholipid in which polyethylene glycol and phospholipid are covalently bonded is preferably used.

<Allosteric factor and oxygen dissociation curve>
The allosteric factor described in the present invention is a factor that affects the oxygen dissociation curve (a curve showing the relationship between the oxygen saturation of hemoglobin and the oxygen partial pressure. See FIG. 1 for the oxygen dissociation curve of human erythrocytes). Allosteric factors shift the oxygen dissociation curve to the right, resulting in higher oxygen carrying efficiency. The oxygen carrying efficiency in natural erythrocytes indicates the difference in oxygen saturation of hemoglobin between 100 mmHg, which is the normal partial pressure of oxygen in the lung, and 40 mmHg, which is the oxygen partial pressure at the end of the tissue to which oxygen is supplied. As Figure 1 shows, human natural blood has about 100% oxygen saturation in the lung (oxygen partial pressure 100mmHg), and vein (tissue end, oxygen partial pressure 40mmHg) has oxygen saturation about 75%. Between the ends, about 25% of the oxygen saturation is supplied to the tissue. In a hemoglobin-containing liposome suspension as an artificial oxygen carrier, when human blood is used as a raw material, 2,3-DPG (allosteric factor originally present in human erythrocytes is used to regulate oxygen affinity in the process of taking out hemoglobin from erythrocytes. The working phosphoric acid compound) is lost. As a result, the oxygen dissociation curve shifts to the left, and there is a problem that the efficiency of oxygen transport to the normal tissue is lowered. As a countermeasure against this phenomenon, a method for solving this problem has been intensively studied by dissolving allosteric factor in a hemoglobin solution in advance and making it into liposomes (Japanese Patent Publication No. 4-66456). However, in a hypoxic region such as an infarcted region or a cancer tissue, the oxygen partial pressure is lower than a normal tissue partial oxygen partial pressure (= venous oxygen partial pressure) of 40 mmHg. For the purpose of supplying oxygen to these regions, the amount of oxygen that can be transported to a low oxygen region with an oxygen partial pressure of 40 mmHg or less is important, and the oxygen dissociation curve is shifted to the left as compared to red blood cells. Is more advantageous. In order to increase the amount of oxygen that can be transported to the low oxygen region, it is advantageous that the amount of allosteric factor added to act to shift the oxygen dissociation curve to the right is reduced or not added. It has also been found that when allosteric factor is added to hemoglobin, the yield of hemoglobin tends to decrease during liposome formation, and high oxygen affinity hemoglobin-containing liposome suspension for the purpose of supplying oxygen to hypoxic tissue is found. In the suspension, it was found that it is better not to add allosteric factors in terms of oxygen carrying amount and hemoglobin yield.

<Oxygen transport amount of hemoglobin-containing liposome suspension>
The artificial oxygen carrier according to the present invention can be obtained by liposome-forming hemoglobin from which the erythrocyte membrane has been removed from human natural erythrocytes. In the present invention, 1 mL of a liposome suspension having a hemoglobin solution containing no allosteric factor as an inner aqueous phase can be transported to a low oxygen region having an oxygen partial pressure of 40 mmHg or less. (1) Hemoglobin concentration (hemoglobin plays a major role in oxygen transport) (2) hemoglobin metration rate in the liposome suspension (has lost oxygen transport capacity when hemoglobin is oxidized to methemoglobin) (3) the liposome suspension Theoretically calculated from the oxygen transport efficiency. The oxygen transport efficiency in the present invention describes oxygen transport to a low oxygen region having an oxygen partial pressure of 40 mmHg or less. In the oxygen dissociation curve of a liposome suspension having hemoglobin that does not contain allosteric factor of the present invention as an inner aqueous phase, It is shown as the difference in oxygen saturation of hemoglobin between oxygen partial pressure of 40 mmHg and oxygen partial pressure of 0 mmHg. The oxygen carrying efficiency in the present invention increases as the oxygen dissociation curve shifts to the left. In the low oxygen affinity hemoglobin-containing liposome suspension, the oxygen transport efficiency (low oxygen affinity setting: oxygen partial pressure set between 100 mmHg and 40 mmHg) is related to the pH of the internal aqueous phase hemoglobin. In the lipophilic suspension containing oxygen affinity hemoglobin, the pH of the inner aqueous phase hemoglobin was found to have no effect on oxygen transport efficiency (high oxygen affinity setting: oxygen partial pressure set between 40 mmHg and 0 mmHg). Therefore, the stearic acid composition ratio, which is a factor affecting the inner aqueous phase hemoglobin pH, is selected only from the viewpoint of improving the hemoglobin yield. Hemoglobin concentration in the liposome suspension: Aw / v%, hemoglobin metration rate in the liposome suspension: B%, oxygen transport efficiency of the liposome suspension (in the present invention, oxygen partial pressure of 40 mmHg and oxygen Difference in oxygen saturation at partial pressure of 0 mmHg): Assuming C%, the amount of oxygen transport DmL (37 ° C, 1 mL of liposome suspension) that can be transported between the site of oxygen partial pressure of 40 mmHg and the site of oxygen partial pressure of 0 mmHg 1 atm) is calculated theoretically as follows.
Since the number of oxygen molecules that can bind to hemoglobin (moL) in 1 mL of liposome suspension is four oxygen molecules that can bind to hemoglobin,
{A (1-B / 100) × 4/64500} / 100 → (1)
Furthermore, since the oxygen carrying efficiency is C%, the number of oxygen molecules (moL) that can be released by 1 mL of liposome suspension is (1) × (C / 100) → (2).
Also, from the equation of state of gas PV = nRT · R (atm · 1 / K · moL) · = 0.082,
D (mL) = (2) x 0.082 x (37 + 273) x 1000 → (3)

<Hemoglobin concentration in liposome suspension>
The main role of oxygen transportation of the liposome suspension as artificial red blood cells in the present invention is hemoglobin. If the concentration of hemoglobin in the liposome suspension is too high, the concentration of liposome-forming lipids for converting hemoglobin into liposomes will inevitably increase, and the total lipid concentration administered to the living body will increase, raising concerns regarding safety. There is. On the other hand, if the hemoglobin concentration in the liposome suspension is too low, the absolute amount of hemoglobin, which is the main oxygen transporter, is insufficient, which is disadvantageous in setting the oxygen transport amount. Therefore, the hemoglobin concentration in the liposome suspension is 5.6 to 6.7 w / v%, more preferably 5.7 to 6.6 w / v%.

<Liposome membrane-forming lipid concentration in liposome suspension>
If the concentration of liposome membrane-forming lipid in the liposome suspension is too high, the viscosity of the liposome suspension will increase, and if administered into blood vessels, it will place a burden on the circulatory system and the total amount administered. There is a concern in terms of safety because the amount of resources increases. On the other hand, if the concentration of the liposome membrane-forming lipid is too low, the concentration of the drug or physiologically active substance that is inevitably contained also decreases, so that the effect on the use cannot be expected. Therefore, the appropriate value of the concentration of the liposome membrane-forming lipid in the liposome suspension set in the present invention is 3.05 to 5.10 w / v%, preferably 3.25 to 4.87 w / v%.

<Stearic acid concentration in liposome suspension>
As one of the components of the liposome membrane-forming lipid, stearic acid which is a charged substance is preferably used. When the composition ratio of stearic acid in the liposome membrane-forming lipid increases (the stearic acid concentration in the hemoglobin-containing liposome suspension increases), the hemoglobin yield tends to improve, while hemoglobin leakage from the liposome is observed. It becomes like. Moreover, when the composition ratio of stearic acid in the liposome membrane-forming lipid is lowered (the stearic acid concentration in the hemoglobin-containing liposome suspension is lowered), not only the hemoglobin yield is lowered, but also the liposome membrane-constituting lipid other than stearic acid. The composition ratio of phosphatidylcholine, which is one of the above, will be increased. Since phosphatidylcholine is expensive, it leads to an increase in cost. As described above, the appropriate stearic acid concentration in the hemoglobin-containing liposome suspension is 0.45 to 0.73 w / v%, more preferably 0.47 to 0.71 w / v%.

<Hemoglobin methaization rate in liposome suspension>
When hemoglobin is oxidized to methemoglobin, it loses its ability to carry oxygen. Therefore, in hemoglobin-containing liposomes as an artificial oxygen carrier, antioxidation of hemoglobin (prevention of hemoglobin methation) is one of the important issues. If the pH of hemoglobin decreases excessively, the oxidation of hemoglobin is promoted. Therefore, in the production process, while maintaining low temperature conditions, the pH of hemoglobin is controlled and deoxygenation is performed by a known method (Japanese Patent Laid-Open No. 2006-104069). After aseptically filling the preparation bag in the deoxygenated and deoxygenated state using the agent, outer packaging is performed so that the deoxygenated state can be maintained. Immediately after the preparation of the liposome suspension and during the effective storage period, the hemoglobin metation rate is 10% or less. If the hemoglobin metration rate is higher than this, it is disadvantageous in terms of the oxygen carrying efficiency of the liposome suspension.

  EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In addition, the manufacturing process of the said liposome suspension was made into operation in aseptic environment.

An example in which the oxygen dissociation curve is shifted to the left compared to natural red blood cells without adding allosteric factor (high oxygen affinity)
317 g of water was added to a uniformly mixed lipid composed of 182 g of hydrogenated soybean phosphatidylcholine, 89 g of cholesterol and 46 g of stearic acid, and heated at 85 ° C. for 30 minutes to prepare a hydrated and swollen uniformly mixed lipid. Hemoglobin was purified and concentrated from the expired concentrated red blood cell preparation to prepare concentrated hemoglobin having a hemoglobin concentration of 42.0 w / w%. Add 2264 g of the concentrated hemoglobin solution to 634 g of the hydrated and swollen uniformly mixed lipid and add sodium hydroxide in an amount to neutralize the stearic acid in the hydrated and swollen uniformly mixed lipid while stirring uniformly to pre-emulsify. went. After the pre-emulsification, the emulsification was carried out by a stronger stirring. The mixed solution after the main emulsification was diluted with physiological saline, and the particle size was controlled by circulating filtration using a 0.45 μm membrane. Next, 10 mg / mL sodium sulfite physiological saline solution was used, and after deoxygenation with sodium sulfite, a 0.5 mg / mL sodium sulfite physiological solution was used using an ultrafiltration membrane with a molecular weight cut off of 300,000. The hemoglobin that had not been converted to liposomes was removed by hydrofiltration concentration using a saline solution, and a human-derived concentrated hemoglobin-containing liposome suspension was prepared. A PEG-linked phospholipid physiological saline solution in which DSPE-PEG5000 (manufactured by NOF Corporation) was dissolved in physiological saline was added to the liposome suspension as a PEG-conjugated phospholipid. After adjusting the liposome membrane-forming lipid concentration in the liposome suspension containing the liposome and PEG-bound phospholipid to 4.05 w / v% and adjusting the PEG-bound phospholipid concentration to 0.31 w / v%, After treatment at 37 ° C. for 24 hours, 8000 mL of the above-described liposome suspension in which PEG-linked phospholipid was immobilized on the liposome surface was obtained.
The hemoglobin concentration in the liposome suspension was 6.3 w / v%, the stearic acid concentration was 0.58 w / v%, and the hemoglobin yield was 53.0% . The hemoglobin metation rate in the liposome suspension immediately after production was 4.0%. The oxygen carrying efficiency (set for low oxygen tissues. Difference in oxygen saturation between oxygen partial pressure 40 mmHg and oxygen partial pressure 0 mmHg) determined from the oxygen dissociation curve (37 ° C) of the liposome suspension was 97%. It was. When the hemoglobin concentration in the liposome suspension: 6.3 w / v%, the hemoglobin metation rate: 4.0%, and the oxygen transport efficiency of the liposome suspension: 97% are applied to the formula (3) described in the above 0015, The amount of oxygen transport (37 ° C., 1 atm) that can be carried by 1 mL of the liposome suspension between an oxygen partial pressure of 40 mmHg to 0 mmHg was calculated to be 0.092 mL .
(Comparative example)

Example of adding allosteric factors and shifting the oxygen dissociation curve to the right compared to natural red blood cells (low oxygen affinity)
317 g of water was added to a uniformly mixed lipid composed of 182 g of hydrogenated soybean phosphatidylcholine, 89 g of cholesterol and 46 g of stearic acid, and heated at 85 ° C. for 30 minutes to prepare a hydrated and swollen uniformly mixed lipid. Hemoglobin was purified and concentrated from the expired concentrated erythrocyte preparation, and concentrated hemoglobin having a hemoglobin concentration of 42.6 w / w% was prepared by adding equimolar amounts of 12 sodium phytate to hemoglobin as an allosteric factor. Add 2264 g of the concentrated hemoglobin solution with 12 sodium phytate to 634 g of the hydrated and swollen uniformly mixed lipid, and stir uniformly while adding sodium hydroxide in an amount to neutralize the stearic acid in the hydrated and swollen uniformly mixed lipid. And pre-emulsified. After the pre-emulsification, the emulsification was carried out by a stronger stirring. The mixed solution after the main emulsification was diluted with physiological saline, and the particle size was controlled by circulating filtration using a 0.45 μm membrane. Next, 10 mg / mL sodium sulfite physiological saline solution was used, and after deoxygenation with sodium sulfite, using a ultrafiltration membrane with a molecular weight of 300,000, a 0.5 mg / mL sodium sulfite physiological solution The hemoglobin and 12 sodium phytate that had not been made into liposomes were removed by hydrofiltration concentration using a saline solution, and a human-derived concentrated hemoglobin and allosteric factor-containing liposome suspension was prepared. To the liposome suspension, an aqueous PEG-conjugated phospholipid solution in which DSPE-PEG5000 (manufactured by NOF Corporation) was dissolved in physiological saline was added as a PEG-conjugated phospholipid. The liposome membrane-constituting lipid concentration in the liposome suspension containing the liposome and PEG-bound phospholipid is 4.04%, and adjusted so that the PEG-bound phospholipid concentration is 0.33 w / v%, then at 37 ° C., The liposome suspension was treated for 24 hours to obtain 1991 mL of the liposome suspension having the PEG-linked phospholipid immobilized on the liposome surface.
The hemoglobin concentration in the liposome suspension was 6.2 w / v%, the stearic acid concentration was 0.60 w / v%, and the hemoglobin yield was 12.8% . The hemoglobin metation rate in the liposome suspension immediately after production was 4.5%. The oxygen transport efficiency (set for low oxygen tissues. Difference in oxygen saturation between oxygen partial pressure of 40 mmHg and oxygen partial pressure of 0 mmHg) determined from the oxygen dissociation curve (37 ° C) of the liposome suspension was 41%. It was. When the hemoglobin concentration in the liposome suspension is 6.2%, the hemoglobin metation rate is 4.5%, and the oxygen transport efficiency of 41% is applied to the formula (3) described in the above 0016, 1 mL of the liposome suspension is obtained. The oxygen carrying amount (37 ° C., 1 atm) that can be carried between oxygen partial pressures of 40 mmHg and 0 mmHg was calculated to be 0.038 mL , which was less than 1/2 of the example.

The oxygen dissociation curve of human natural blood is shown.

Claims (2)

A liposome suspension having a hemoglobin solution containing no allosteric factor as an inner aqueous phase, wherein the liposome membrane-forming lipid contains stearic acid, and the hemoglobin concentration in the liposome suspension is 5.6 to 6.7 w / v% The liposome suspension characterized in that the liposome membrane-forming lipid concentration is 3.05 to 5.10 w / v% and the stearic acid concentration is 0.45 to 0.73 w / v%.
  2. The liposome suspension according to claim 1, wherein a hemoglobin metration rate in the liposome suspension is 10% or less.

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