Hybrid particle dispersion and method for manufacturing the same

Abstract

To provide a hybrid particle dispersion capable of achieving a gel state while containing inorganic materials, and a method for manufacturing the same.SOLUTION: A hybrid particle dispersion of the present invention is made by dispersing hybrid particles, in which organic acid ions coordinate with metal ions of inorganic nanoparticles, into a dispersion medium. Another aspect of the present invention relates to a method for producing a hybrid particle dispersion, wherein inorganic acids, organic acids, and metal ions are mixed at a low temperature to produce a hybrid particle dispersion in which organic acid ions coordinate with the metal ions of inorganic nanoparticles, and the hybrid particle dispersion is dispersed into a dispersion medium. A medium for cell culture according to another aspect of the present invention comprises hybrid particles in which organic acid ions coordinate with metal ions of inorganic nanoparticles, into a dispersion medium. Another aspect relates to a transporter comprising a transport object and a packaging body enclosing the transport object, wherein the packaging body disperses hybrid particles, formed by the coordination of organic acid ions to metal ions of inorganic nanoparticles, into a dispersing medium.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a hybrid particle dispersion and a method for producing the same. [Background technology]

[0002] In a dispersion system in which fine particles are dispersed in a dispersion medium, a state in which the dispersion medium has fluidity is called a sol state, and a state in which the dispersion medium has lost fluidity and is highly viscous is called a gel state. In particular, the gel state can maintain the dispersion medium in a liquid state while maintaining high viscosity, so it is widely used in various daily necessities such as air fresheners, contact lenses, and disposable diapers. In particular, in recent years, it has been expected to be applied to regenerative medicine, such as cell culture media.

[0003] The property of a dispersion system that can change from a gel state to a sol state and from a sol state to a gel state is called thixotropy, and technologies relating to physical gels that exhibit this thixotropy are described, for example, in the following Patent Documents 1 and 2. Furthermore, the following Patent Document 3, for example, is an example of a document that examines the application of this thixotropy to the above-mentioned regenerative medicine. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-178318 [Patent Document 2] Japanese Patent Application Publication No. 2023-10064 [Patent Document 3] Japanese Patent Publication No. 2019-041755 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, in today's aging society, the development of regenerative medical materials has become an urgent issue, and biocompatible ceramics such as hydroxyapatite have been implanted into living bodies as substitute materials for teeth and bones.

[0006] However, as mentioned above, hydroxyapatite is a ceramic material, and therefore lacks flexibility and dynamic functionality, and its use remains limited to hard tissues, with no further progress being made.

[0007] Furthermore, the materials used in the technology described in Patent Document 3 are only organic substances such as sodium alginate gel, and there are no examples of gels containing inorganic substances, particularly inorganic particles, such as ceramics. Of course, the same is true for Patent Documents 1 and 2.

[0008] In view of the above problems, an object of the present invention is to provide a hybrid particle dispersion that can contain inorganic particles and achieve a gel state, and a method for producing the same. [Means for solving the problem]

[0009] The present inventors have conducted extensive research into the above-mentioned problems and have discovered that by using inorganic nanoparticles containing metal ions and coordinating organic acid ions to the metal ions of these inorganic nanoparticles, gelation can be achieved and, in some cases, thixotropy can be imparted to the inorganic nanoparticles, thereby completing the present invention.

[0010] That is, the hybrid particle dispersion according to one aspect of the present invention is obtained by dispersing hybrid particles in a dispersion medium, in which organic acid ions are coordinated to metal ions of inorganic nanoparticles.

[0011] In addition, in this respect, although not limited thereto, it is preferable that the content of hybrid particles is 2.5% by weight or more.

[0012] In addition, in this respect, although not limited thereto, it is preferable that the average particle size of the inorganic nanoparticles is in the range of 5 nm to 1 μm.

[0013] In addition, in this respect, although not limited thereto, it is preferable that the inorganic nanoparticles are amorphous.

[0014] In addition, in this respect, although not limited thereto, it is preferable that a chelate is formed between an organic acid ion and a metal ion.

[0015] In addition, in this respect, although not limited thereto, the organic acid ion is preferably at least one of a carboxylate ion and a sulfonate ion.

[0016] Furthermore, in this aspect, although not limited thereto, the metal ion is preferably at least one of iron ion, gallium ion, copper ion, nickel ion, lead ion, zinc ion, cobalt ion, gadolinium ion, cesium ion, manganese ion, calcium ion, magnesium ion, strontium ion, barium ion, silver ion, lithium ion, sodium ion, europium ion, vanadium ion, and yttrium ion.

[0017] In addition, in this respect, although not limited thereto, it is preferable that the average coverage of the hybrid particles with organic acid ions is 30% or more.

[0018] In addition, in this respect, although not limited thereto, the organic acid ion is preferably at least one of isocitrate ion, gluconate ion, succinate ion, and aspartate ion.

[0019] In addition, in this aspect, although not limited thereto, the inorganic nanoparticles are preferably particles of at least one of calcium phosphate, calcium carbonate, and calcium hydroxide.

[0020] In addition, in this respect, although not limited thereto, it is preferable that the gel is formed by heating.

[0021] In addition, in this respect, although not limited thereto, it is preferable that the material has thixotropy, that is, it gels when heated and turns into a sol when stress is applied.

[0022] In addition, a method for producing a hybrid particle dispersion according to another aspect of the present invention comprises mixing an inorganic acid, an organic acid, and metal ions at a low temperature to produce a hybrid particle dispersion in which organic acid ions are coordinated to metal ions of inorganic nanoparticles, and dispersing the hybrid particle dispersion in a dispersion medium.

[0023] Furthermore, a cell culture medium according to another aspect of the present invention comprises a hybrid particle dispersion in which hybrid particles in which organic acid ions are coordinated to metal ions of inorganic nanoparticles are dispersed in a dispersion medium.

[0024] Furthermore, a transporter according to another aspect of the present invention has an object to be transported and a packaging body that encases the object to be transported, and the packaging body is a hybrid particle dispersion in which hybrid particles in which organic acid ions are coordinated to metal ions of inorganic nanoparticles are dispersed in a dispersion medium. [Effects of the Invention]

[0025] As described above, the present invention can provide a hybrid particle dispersion that can contain inorganic particles and achieve a gel state, and a method for producing the same. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 2 is a photograph of an example of a hybrid particle dispersion in a gel state according to an embodiment. [Figure 2] FIG. 2 is a photograph of an example of a hybrid particle dispersion in a sol state according to an embodiment. [Figure 3] FIG. 1 is an image diagram of a hybrid particle according to an embodiment. [Figure 4] FIG. 10 is an image diagram illustrating calculation of the coverage of hybrid particles according to the embodiment. [Figure 5] FIG. 2 is a diagram showing a flow of a method for producing a hybrid particle dispersion according to an embodiment. [Figure 6] 1A to 1C are diagrams illustrating application examples of a hybrid particle dispersion according to an embodiment. [Figure 7] 1A to 1C are diagrams illustrating application examples of a hybrid particle dispersion according to an embodiment. [Figure 8] 1A to 1C are diagrams illustrating application examples of a hybrid particle dispersion according to an embodiment. [Figure 9] 1A to 1C are diagrams illustrating application examples of a hybrid particle dispersion according to an embodiment. [Figure 10] 1 is a photograph of a hybrid particle dispersion (Sample 1:4-4) prepared in an example. [Figure 11] 1 is a photograph of a hybrid particle dispersion (Sample 2:4-40) prepared in an example. [Figure 12] FIG. 1 is a photograph of a hybrid particle dispersion (Sample 3:40-4) produced in an example. [Figure 13] 1 is a photograph of a hybrid particle dispersion (Sample 4: 40-40) prepared in an example. [Figure 14] 1 is a photograph showing the experimental results of the hybrid particle dispersion produced in the examples. [Figure 15] 1 is a photograph showing the experimental results of the hybrid particle dispersion produced in the examples. [Figure 16] 1 is a photograph showing the experimental results of the hybrid particle dispersion produced in the examples. [Figure 17] 1 is a photograph showing the experimental results of the hybrid particle dispersion produced in the examples. [Figure 18] FIG. 1 shows TG-DTA curves of hybrid particle dispersions produced in the examples. [Figure 19] 1 is an image of calculation of peak areas in DTA analysis of hybrid particle dispersions produced in Examples. [Figure 20] FIG. 1 shows the results of TG analysis of the hybrid particle dispersion produced in the examples. [Figure 21] FIG. 1 shows an FT-IR spectrum of a hybrid particle dispersion produced in an example. [Figure 22] FIG. 1 shows data on peak area ratios in FT-IR of hybrid particle dispersions produced in the examples. [Figure 23] FIG. 1 shows data on peak area ratios in FT-IR of hybrid particle dispersions produced in the examples. [Figure 24] FIG. 1 is a diagram showing the results of BJH pore size distribution analysis of the hybrid particle dispersions produced in the examples. [Figure 25] FIG. 1 is an image diagram showing the determination of half-value width in BJH pore size distribution analysis of the hybrid particle dispersion produced in the examples. [Figure 26] FIG. 1 is a diagram showing the results of absorbance measurement of the hybrid particle dispersions produced in the examples using an ultraviolet-visible spectrophotometer. [Figure 27] FIG. 1 is a diagram showing analytical data of absorbance measurement of a hybrid particle dispersion produced in an example. [Figure 28] FIG. 1 shows the results of TEM observation of a hybrid particle dispersion produced in an example. [Figure 29] FIG. 1 is a data diagram relating to particle sizes of hybrid particle dispersions produced in the examples. [Figure 30] FIG. 1 shows the results of XRD measurement of the hybrid particle dispersions produced in the examples. [Figure 31] FIG. 1 is a data diagram showing the results of XRD measurement of the hybrid particle dispersions produced in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention can be embodied in many different forms, and is not limited to the specific examples of the embodiments and examples shown below.

[0028] (Embodiment) (Hybrid particle dispersion) The hybrid particle dispersion according to this embodiment (hereinafter referred to as "the present dispersion") is a dispersion in which hybrid particles in which organic acid ions are coordinated to metal ions of inorganic nanoparticles are dispersed in a dispersion medium. Fig. 1 shows a photograph of an example of the present dispersion in a gel state, and Fig. 2 shows a photograph of the same dispersion in a sol state.

[0029] As shown in these figures, the present dispersion can be changed from a sol state to a gel state and from a gel state to a sol state, and has so-called thixotropy. The present dispersion can change from one state (sol state or gel state) to another state (gel state or sol state) in response to an external stimulus. However, as will be described later, in light of the fact that gelation of substances containing inorganic particles has not been achieved in the past, a case in which only one of the changes from a sol state to a gel state or from a gel state to a sol state can also be considered an example of the present dispersion.

[0030] As described above, the present dispersion has a configuration in which hybrid particles are dispersed in a dispersion medium. Here, the "dispersion medium" refers to a medium for dispersing the hybrid particles, and is not limited as long as it can perform the functions of the present dispersion. Examples of the dispersion medium include liquid polar solvents that interact with the hybrid particles, such as water, alcohol, and dimethylformamide (DMF).

[0031] As mentioned above, the "hybrid particles" in this dispersion are inorganic nanoparticles in which organic acid ions are coordinated with metal ions. Details are as follows, but will be explained using the image of hybrid particles in Figure 3.

[0032] First, the "inorganic nanoparticles" constituting part of the hybrid particles are particles made of an inorganic substance. Furthermore, the inorganic nanoparticles are not limited as long as they can realize a gel state for the dispersion, but are preferably amorphous particles. Being amorphous allows the adsorption of organic acid ions to be adjusted within a preferred range, making it possible to realize a gel state including the inorganic particles.

[0033] Furthermore, it is believed that the size (particle diameter) of inorganic nanoparticles determines the particle structure that can realize a gel state. It is believed that a small particle diameter, combined with the effects of electrostatic repulsion or attraction (described below), makes this possible. The average particle diameter of inorganic nanoparticles that can realize a gel state is preferably nano-level. Here, "nano-level" refers to a size less than a micrometer, although a certain degree of variation is acceptable. For example, it is within the range of 5 nm to less than 1 μm, preferably within the range of 500 nm or less, more preferably 200 nm or less, even more preferably 100 nm or less, and particularly preferably 80 nm or less. Here, "average particle diameter" can be measured by adding the minor and major axes of N inorganic nanoparticles observed with a transmission electron microscope and dividing the sum by two to obtain the number average particle diameter (primary particle diameter) of N particles. The number of particles N observed may be any number that can determine the average size of all inorganic nanoparticles in the hybrid particle dispersion. N = 100 sufficiently satisfies this condition, and N = 50 can also satisfy the condition.

[0034] Furthermore, the shape of inorganic nanoparticles is not limited, but is preferably isotropic, i.e., with an aspect ratio close to 1. Although this principle is speculative, it is believed that in particle structures, electrostatic repulsion or attraction occurs on each surface, and therefore it is important to maintain the balance between these electrostatic repulsion and attraction as close to 1 as possible. In other words, if the particles are stretched too far in one direction, the balance of these forces will be disrupted, making it difficult to maintain the desired sol or gel state, whereas isotropy will achieve this balance. Therefore, the aspect ratio of inorganic nanoparticles is preferably such that, when the shortest length of the particle (also referred to as the minor axis or short diameter) is 1, the longest length of the particle (also referred to as the major axis or long diameter) is 1 or more and less than 3.4. The minor axis, major axis, and aspect ratio can be determined by observation with a microscope, as described above.

[0035] Furthermore, as described above, the material for the inorganic nanoparticles is not limited as long as it can achieve a gel state, but is preferably an inorganic salt composed of a metal ion (cation) and an anion. Examples of metal ions include, for example, iron ions, gallium ions, copper ions, nickel ions, lead ions, zinc ions, cobalt ions, gadolinium ions, cesium ions, manganese ions, calcium ions, magnesium ions, strontium ions, barium ions, silver ions, lithium ions, sodium ions, europium ions, vanadium ions, and yttrium ions, and more preferably calcium ions, magnesium ions, and zinc ions. On the other hand, examples of anions include, for example, phosphate ions, carbonate ions, and hydroxide ions, and more preferably phosphate ions and hydroxide ions. Furthermore, specific examples of inorganic salts include, but are not limited to, calcium phosphate, calcium carbonate, and calcium hydroxide.

[0036] As described above, the hybrid particles are formed by coordinating organic acid ions to the metal ions of the inorganic nanoparticles. More specifically, the hybrid particles form a network structure by coordinating organic acid ions to the metal ions present on the surface of the inorganic nanoparticles, thereby enabling the formation of a gel state. The organic acid ions are not limited as long as they enable the dispersion to achieve a gel state, but examples include carboxylate ions having a carboxyl group, sulfonate ions having a sulfo group, and borate ions. More specifically, the carboxylate ions are preferably at least one of citrate ions, isocitrate ions, gluconate ions, succinate ions, and aspartate ions, but are not limited thereto. Furthermore, examples of other organic acids include preferably at least one of orthophosphate ion, pyrophosphate ion, arsenate ion, selenate ion, tellurite ion, and iodate ion, and more preferably at least one of citrate ion, isocitrate ion, gluconate ion, succinate ion, aspartate ion, orthophosphate ion, pyrophosphate ion, borate ion, and sulfonate ion.

[0037] Furthermore, the present dispersion preferably contains 2.5 wt% or more of hybrid particles, although this is not a limitation. By containing 2.5 wt% or more of hybrid particles in the present dispersion, a network of the hybrid particles can be formed, resulting in a gel state. On the other hand, there is no particular upper limit, but as a practical manufacturing range, it is preferably 50 wt% or less, more preferably 40 wt% or less, even more preferably 35 wt% or less, and particularly preferably 30 wt% or less.

[0038] In addition, in the present dispersion, although not limited thereto, it is preferable that a chelate is formed between the organic acid ion and the metal ion. By forming a chelate, the inorganic nanoparticles are covered with the organic acid ion and polar solvent molecules such as water molecules are adsorbed around the inorganic nanoparticles, thereby forming a network between the hybrid particles.

[0039] Furthermore, in the present dispersion, although not limited thereto, it is preferable that the average coverage of the inorganic nanoparticles with the organic acid ions of the hybrid particles is 30% or more. In the examples described below, it has been confirmed that when the average coverage is at least 30% or more, the property of forming a stable gel upon heating is exhibited. Here, the "average coverage" refers to the percentage of the area of ​​the inorganic nanoparticle surface that is covered with organic acid ions.

[0040] The average coverage can be calculated, for example, by the following formula (1): A is Avogadro's number (6.02214×10 23 / mol), M is the organic acid ion content (mol / g), A acid is the cross-sectional area of ​​the organic acid ion (m 2 ), A iop is the BET specific surface area (m 2 ) respectively. The following formulas are based on the assumption that the organic acid ions are adsorbed onto the surface of the inorganic nanoparticles in the direction shown in FIG.

number

[0041] In the above formula (1), the cross-sectional area A of the organic acid ion acid is a unique value determined for each organic acid ion. For example, for citric acid, the cross section is 4.6 × 10 -10 (m) cross-sectional area of ​​a circle 1.666×10 -19 (m 2 ) is calculated as

[0042] In addition, the organic acid ion content M in the above formula (1) can be determined by various methods, for example, by measuring absorbance using a calibration curve. Specifically, a calibration curve can be created in advance by preparing a plurality of solutions with different organic acid ion concentrations and measuring the absorbance, and then completely dissolving the hybrid particles whose coverage is to be determined in acid to liberate the organic acid, and comparing the absorbance of this liberated organic acid with the above calibration curve.

[0043] In addition, in the above formula (1), A iop is the BET specific surface area as described above, and can be determined by the BET method. Specifically, it can be calculated using the following formula (2). In the following formula (2), V m is the monomolecular adsorption amount (cm), which is the adsorption amount per unit mass of the sample converted to standard conditions. 3 (STP) / g), where S is the molecular cross-sectional area, which is the area occupied by the adsorbed gas molecules on the solid surface. A As in the above formula (1), means Avogadro's number.

number

[0044] More specifically, the BET method is an extension of the Langmuir monolayer adsorption theory to monolayer adsorption, and can be expressed by the following formula (3): In formula (3), P is the sample pressure, P0 is the saturated vapor pressure, V is the total gas adsorption amount, and C is the BET constant.

number

[0045] According to the above formula (3), the adsorption amount V at a certain relative pressure can be calculated from the actual adsorption isotherm. a If we plot P / P0 on the horizontal axis and P / Va (P0-P) on the vertical axis, the slope will be (C-1) / V m C, intercept is 1 / V m A straight line (BET plot) of C can be obtained. And the obtained V mBy substituting into the above equation (2), S BET can be obtained.

[0046] Furthermore, in this dispersion, for example, when the dispersion medium is water, the hybrid particles are in a state in which water molecules are adsorbed around the organic acid ions, i.e., in a hydrated state. Although this is also speculation, it is thought that in this dispersion, the presence of water molecules between the hybrid particles forms a nanoparticle network structure with these as crosslinking points, allowing the dispersion to become gel-like. On the other hand, depending on the state of the hybrid particles, it is thought that this network can be broken and returned to a sol state by an external stimulus.

[0047] As described above, the present dispersion changes from a sol state to a gel state or from a gel state to a sol state in response to an external stimulus, such as, but not limited to, heat (temperature), light, an electric field, a magnetic field, or stress applied by vibrations such as sound or ultrasonic waves.

[0048] For example, although not limited to, the dispersion is preferably in a state in which it gels upon heating. Heating is a stimulus that can be applied relatively easily by heat transfer, radiation, microwaves, etc., and this makes it possible to easily gel.

[0049] Furthermore, although not limited thereto, the present dispersion is preferably gelled by heating and liquefied or soled by application of stress. Specifically, a method of applying stress to the gelled dispersion can break the network formed in the dispersion and sole it, for example, by tapping the container containing the gelled dispersion lightly from the outside, which can easily sole it.

[0050] (Method of manufacturing hybrid particle dispersion) Here, a method for producing the present dispersion (hereinafter referred to as "the present method") will be described. The present method is not limited as long as it can produce the present dispersion, but involves mixing an inorganic acid, an organic acid, and metal ions at a low temperature to produce a hybrid particle dispersion in which organic acid ions are coordinated with the metal ions of inorganic nanoparticles, and dispersing the hybrid particle dispersion in a dispersion medium.

[0051] In more detail, this method includes, but is not limited to, the steps of (S1) mixing an inorganic acid and an organic acid to form an acid solution and adjusting the temperature of this acid solution, (S2) mixing a metal salt solution serving as a source of metal ions with the acid solution to form hybrid particles, and (S3) dispersing the hybrid particles in a dispersion medium. The flow in this case is shown in Figure 5.

[0052] First, this method includes a step (S1) of mixing an inorganic acid and an organic acid to form an acid solution and adjusting the acid solution to a low temperature. In this method, the inorganic acid and the organic acid are mixed in advance before mixing with the metal salt solution. This allows the formation of inorganic nanoparticles and the coordination of organic acid ions to be carried out in parallel in a later step. However, this step can also be performed using only an inorganic acid without mixing with an organic acid, and then coordinating organic acid ions after the formation of hybrid particles in a later step, as long as hybrid particles that can achieve the effects of this dispersion can be formed.

[0053] Here, the inorganic acid is an acid containing the anion of the inorganic nanoparticles described above, and examples thereof include potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, and phosphates consisting of combinations thereof, as well as potassium bicarbonate, potassium carbonate, and carbonates consisting of combinations thereof.

[0054] The organic acid used here is preferably an organic acid that serves as a supply source of organic acid ions, as described above in detail.

[0055] In addition, it is preferable to adjust the pH in the preparation of this acid solution. Adjusting the pH not only promotes the formation of inorganic nanoparticles, but also makes it easier to expose metal ions on the surface of the inorganic nanoparticles, increasing surface reactivity and facilitating coordination of organic acid ions. In addition, it is preferable to use a base agent in this pH adjustment, and examples of such agents include, but are not limited to, tetramethylammonium hydroxide (TMAOH), potassium hydroxide, and sodium hydroxide.

[0056] Furthermore, after mixing the inorganic acid and the organic acid, it is preferable to lower the temperature. By lowering the temperature, excessive particle growth in the subsequent step can be suppressed, and the balance between electrostatic repulsion and attraction within the particles can be set within a preferred range. This temperature range is not limited, but is preferably 20°C or lower, more preferably 10°C or lower, and even more preferably 5°C or lower.

[0057] This method also includes a step (S2) of mixing the acid solution with a metal salt solution to form hybrid particles. In this step, the formation of inorganic nanoparticles by the reaction of the inorganic acid with metal ions from the metal salt solution and the coordination of organic acid ions with the metal ions present on the surface of the inorganic nanoparticles can be carried out in parallel. This allows the formation of hybrid particles while suppressing the growth of inorganic nanoparticles.

[0058] Here, the metal salt solution is a source of metal ions (cations of inorganic acids) for inorganic nanoparticles, and is preferably a solution in which a metal salt is dissolved. This allows the inorganic acid to react with the metal ions in the metal salt to produce particles. The metal salt used here is not particularly limited as long as it can supply metal ions, but examples include calcium chloride aqueous solutions.

[0059] Furthermore, in this step, a heating step may be added when mixing the acid solution and the metal salt solution. Heating makes it possible to adjust the behavior (characteristics) of the hybrid particles. For example, if the hybrid particle dispersion is gelled by stirring at a low temperature, the gel state can be maintained. On the other hand, if the hybrid particle dispersion is heated and stirred, it is possible to develop thixotropy, in which the hybrid particle dispersion returns to a sol state after having been gelled. Although this heating step is speculative, it is thought to be a so-called aging step that controls particle growth after the hybrid particle nuclei are formed by the reaction between the low-temperature acid solution and the metal salt.

[0060] The heating temperature for this mixing can be adjusted appropriately and is not particularly limited. On the other hand, when the temperature is low, it is preferably 20°C or lower, more preferably 10°C or lower, and even more preferably 5°C or lower.

[0061] The stirring time during mixing is not limited as long as it is within a range that allows the growth of preferred inorganic nanoparticles, but is preferably 5 minutes or more, more preferably 10 minutes or more, even more preferably 20 minutes or more, particularly preferably 40 minutes or more, and particularly preferably 1 hour or more. On the other hand, the upper limit is not particularly limited, but is preferably within a range of 5 hours or less.

[0062] In addition, in this step (S2), hybrid particles can be obtained as a result of mixing, but it is important to separate these hybrid particles from the solvent used for synthesis (separation treatment). Examples of this separation treatment include, but are not limited to, centrifugation followed by washing.

[0063] As described above, this method also includes the step (S3) of dispersing hybrid particles in a dispersion medium. Dispersion media that can be used in this dispersion step include water, alcohol, DMF, etc., as described above. In this dispersion step, the dispersion method is not limited as long as the hybrid particles can be easily dispersed in the dispersion medium. While simple stirring using a stirrer or the like is acceptable, ultrasonic dispersion or the like can be used to achieve more efficient dispersion.

[0064] In this step (S3), the proportion of the hybrid particles in the dispersion medium is as described above, and when the weight of the hybrid particle dispersion is taken as 100% by weight, the proportion of the hybrid particles is preferably 2.5% by weight or more.

[0065] As described above, the present method can provide a hybrid particle dispersion that can contain inorganic particles and achieve a gel state, and a method for producing the same.

[0066] (Application example 1: Cell culture medium) This dispersion can be used in a variety of applications, including, as mentioned above, in fields such as regenerative medicine. One example is its application as a cell culture medium. That is, a cell culture medium using this dispersion contains a hybrid particle dispersion in which hybrid particles, in which organic acid ions are coordinated to metal ions of inorganic nanoparticles, are dispersed in a dispersion medium. An image of this case is shown in Figure 6.

[0067] According to the example shown in this figure, the present dispersion in a sol state can be applied to a culture vessel such as a petri dish and gelled by, for example, heating. Cells to be cultured are then applied to this gel-state hybrid particle dispersion and cultured under specified conditions. After the cells to be cultured have been sufficiently cultured, an external stimulus is applied to return the hybrid particle dispersion to a sol state, allowing the cells to be isolated. Since the present dispersion is initially in a sol state, this method allows it to be applied to containers of various shapes, and the shape can then be stabilized by gelling. Another advantage of this method is that the culture medium itself can contain inorganic materials, such as hydroxyapatite, enabling the selective culture of only cells that can be cultured in the presence of inorganic materials.

[0068] (Application example 2: Droplet gel) The hybrid particle dispersion can also be used as a gel (droplet gel) that serves as a package for cell transport. For example, this dispersion can be used to create droplet gels (packages) with a diameter of approximately tens to hundreds of micrometers that encapsulate the cells to be transported. By transporting the gel as is, the encapsulated cells can be transported without losing their activity. After transport, the gel can be transformed into a sol by applying an external force such as vibration, allowing the cells to be extracted for observation or use. This particular example does not require chemical or heat treatment, making it a potentially gentle cell transport technique that does not damage the encapsulated cells. An image of this case is shown in Figure 7.

[0069] (Application 3: Regenerative medicine) Furthermore, the cell culture medium described above can be used in regenerative medicine. An example of this application is shown in Figure 8. The hybrid particle dispersion can be adjusted to a sol state at room temperature and a gel state when heated to about body temperature. This allows, for example, the sol state at room temperature containing a drug to be filled into a syringe and injected into a patient's affected area, such as a knee joint. On the other hand, since the dispersion becomes a gel when heated to about body temperature, it becomes a gel immediately after injection, allowing it to remain near the affected area for a long period of time. In particular, if an inorganic material necessary in the body, such as hydroxyapatite, is used, the hydroxyapatite itself can be advantageously used as a material for regenerative medicine.

[0070] (Application example 4: Gel ink) Furthermore, we will now describe an example of gel ink using a hybrid particle dispersion. Specifically, this hybrid particle dispersion can be used in inks for ballpoint pens and other devices. For example, a hybrid particle dispersion that is in a sol state at room temperature and becomes a gel state upon heating can be prepared. By mixing this with a colorant such as a pigment within a range that does not impair performance and using it as ink for a typical ballpoint pen, the sol state when filled in the ballpoint pen can be gelled by applying pressure and heat when the ball at the tip is pressed against a drawing object such as paper. The gelling process improves adhesion to paper and other materials, resulting in a ballpoint pen with high-performance ink. A conceptual diagram of this case is shown in Figure 9.

[0071] As described above, the present dispersion has a variety of applications and is industrially useful. [Example]

[0072] The hybrid particle dispersion described in the above embodiment was actually prepared, and its effects were confirmed. A detailed description will be given below.

[0073] (Sample 1:4-4) First, 0.01 mol of dipotassium hydrogen phosphate (K2HPO4) was dissolved in 70 mL of ultrapure water in a 200 mL beaker as an inorganic acid source, and 0.02 mol of citric acid was added as an organic acid. The solution was immediately adjusted to 4°C, after which a calibrated pH electrode (pH- / ORP / ION METER-D-73) was placed in the solution, and TMAOH (25 vol% tetramethylammonium hydroxide solution) was added as a base to adjust the pH to 12.5. This solution was used as an aqueous phosphoric acid solution (acid solution).

[0074] On the other hand, 0.02 mol of CaCl2·2H2O (calcium chloride dihydrate) was dissolved in 30 mL of ultrapure water in a sample container as a metal ion source. This solution was used as a calcium aqueous solution (metal salt solution).

[0075] The calcium aqueous solution was then added dropwise to the phosphoric acid aqueous solution at a rate of 1 mL / min using a constant volume pump (MP-2000). While maintaining the temperature at 4°C (temperature T1), the solution was stirred for 30 minutes using a magnetic stirrer ((OCTOPUS) S-11-4609-25) at a stirring speed of 500 rpm, and then further stirred for 3 hours at a temperature of 4°C (temperature T2).

[0076] After stirring, 50 mL of this solution was transferred to a centrifuge tube and centrifuged in a centrifuge (KUBOTA: Micro Refrigerated Centrifuge 3700) for separation. The centrifugation conditions were a centrifugation temperature of 4°C, a rotation speed of 12,000 rpm, and a time of 5 minutes. The supernatant was then discarded, and only the settled particle phase was collected. 120 mL of ultrapure water was added to the collected particles, and the particles were dispersed by applying vibrations of 60 Hz using a vortex mixer (VORTEX GENIC2). The dispersion was then placed in an ultrasonic cleaner (Branson Bransonic® CPXH Digital Cleaner 3800) and subjected to ultrasonic treatment for 5 minutes (ultrapure water cleaning).

[0077] The solution that had been dispersed and washed using ultrasonic waves was centrifuged, the supernatant was discarded, and the precipitated particles were collected. 120 mL of ethanol was then added. The particles were then dispersed using a vortex mixer at 60 Hz, and then ultrasonic treatment was performed (ethanol washing).

[0078] The solution was then centrifuged under the same conditions as those used for the ultrapure water washing. The particle dispersion concentration was then adjusted to approximately 10 wt%. The adjusted dispersion was placed in a screw tube, weighed, and then placed in a dryer at 120°C for at least 3 hours to completely dry (leaving only the solid phase). Finally, as a dispersion step, the weight of the sample after drying was measured, and the particle concentration in the dispersion was calculated from the weight of the solution before drying and the weight of the particles after drying. Ultrapure water was then added so that the final particle dispersion concentration was 6 wt%. After adding the ultrapure water, an ultrasonic dispersion process was further performed to completely disperse the particles and synthesize a sol. A photograph of the resulting sol (Sample 1) is shown in Figure 10.

[0079] (Sample 2:4-40) A sol was also synthesized under almost the same conditions as in the synthesis of Sample 1, except that the temperature T2 during additional stirring was set to 40° C. A photograph of the resulting sol (Sample 2) is shown in FIG.

[0080] (Sample 3:40-4) Furthermore, a sol was synthesized under almost the same conditions as in the synthesis of Sample 1 above, except that the initial stirring temperature T1 was set to 40° C. A photograph of the resulting sol (Sample 3) is shown in FIG.

[0081] (Sample 4:40-40) In addition, a sol was synthesized under almost the same conditions as in the synthesis of Sample 1 above, except that the initial stirring temperature T1 and the temperature T2 during additional stirring were set to 40° C. A photograph of the resulting sol (Sample 4) is shown in FIG.

[0082] (Sol status check) For each of the above samples 1 to 4, 0.2 mL was dropped onto a horizontally placed pure titanium plate (AS ONE, 150 mm wide x 150 mm high x 1 mm thick), and then the plate was turned upright at room temperature. It was confirmed that all samples 1 to 4 began to drip. Photographs of this situation are shown in Figures 14 and 15. Note that Figure 14 shows the plate placed horizontally, and Figure 15 shows the plate placed vertically. As a result, it was confirmed that all samples 1 to 4 were initially in a sol state.

[0083] (Gel formation confirmation) Next, for each of the above samples 1 to 4, 0.2 mL was dropped onto a horizontally placed pure titanium plate, which was then heated and left to stand in an incubator at 40°C and 100% RH for 1,800 seconds. The pure titanium plate was then placed vertically at room temperature and left to stand for 180 seconds. A photograph of this case is shown in Figure 16. As a result, samples 1 and 2 did not drip, while samples 3 and 4 began to drip, confirming that they were in a sol state. In other words, samples 1 and 2 were confirmed to gel upon heating. It was also confirmed that samples 1 and 2 had the property of gelling upon heating at approximately 37°C for 900 seconds.

[0084] (Confirmation of solization) Furthermore, the pure titanium plate was returned to a horizontal position, and a 60 Hz vibration was applied for 10 seconds. It was then immediately turned vertical and left to stand for 180 seconds. A photograph of this state is shown in Figure 17. As a result, it was confirmed that Sample 1 did not drip, but Sample 2 did drip. In other words, it was confirmed that Sample 2, even though it had gelled due to heating, was able to re-solate due to vibration.

[0085] As described above, the effects of the present invention were confirmed by this example. Next, various analyses were performed on each sample. Samples 1 to 4 in the sol state were used for TG-DTA analysis. Freeze-dried Samples 1 to 4 were used for infrared spectroscopy, nitrogen adsorption / desorption, absorbance, and XRD measurements. Diluted Samples 1 to 4 were used for TEM measurement.

[0086] (TG-DTA analysis) First, thermal analysis of the hybrid particles was carried out using Samples 1 to 4. For the thermal analysis of the particles, a simultaneous thermogravimetric and differential thermal analyzer (TG-DTA: Simultaneous Thermogravimetric Analyse TG8120, manufactured by Rigaku Corporation) was used.

[0087] Specifically, approximately 30 mg of the sample was placed in an aluminum pan and thermal measurements were performed simultaneously with the standard sample α-Al2O3. Specifically, the thermogravimetric and differential thermal changes of the hybrid particles were recorded at a heating rate of 5 K / min in a nitrogen atmosphere. Note that, because the influence of room temperature is present near room temperature, data above 40°C was analyzed.

[0088] (DTA analysis) The peak area was calculated using the trapezoidal rule. Regarding the integration region, the section up to the peak top of the DTA curve, which appears between 40 and 80°C, was integrated using the temperature value. Specifically, 40°C was used as the starting point, and the point at which the DTA became positive was used as the end point.

[0089] (TG analysis) The peak was differentiated and noise was removed by setting the number of moving averages to 10. TG analysis (DTG: thermogravimetric differential) was performed from the obtained data to estimate the weight of evaporated water.

[0090] The resulting TG-DTA curves are shown in Figure 18. As shown in this figure, the main endothermic peak was confirmed to appear around 80 °C (approximately ±2 °C) in Samples 1 and 2, whereas the main endothermic peak did not appear around 80 °C in Samples 3 and 4. In addition, a shoulder-like endothermic peak was also observed in Samples 1 and 2 on the low-temperature side of the main endothermic peak (around 60 °C). In other words, the presence of this shoulder may be able to determine whether gelation is possible. Furthermore, by calculating the area ratio of this shoulder endothermic peak, it may be possible to determine whether a material exhibits thixotropy in addition to whether gelation is possible.

[0091] In the above calculation of the shoulder endothermic peak area, the shoulder endothermic peak appearing in a graph having a main endothermic peak at around 80°C was taken as the gelation peak, and the baseline was subtracted to calculate the area, as shown in Figure 19. More specifically, the entire main endothermic peak was second-order differentiated, and the inflection points were calculated, and the line connecting the inflection points was taken as the baseline.

[0092] The results of the TG analysis are shown in Figure 20. This figure confirms that gelling sample 1 exhibits peaks at 59.4°C and 73.0°C, whereas non-gelling sample 3 exhibits peaks at 67.4°C and 78.7°C, and sample 4 exhibits peaks at 78.7°C. Sample 2, which is both gelling and thixotropic, exhibits a peak at 59.4°C, the same as sample 1, as well as small successive peaks at 73.0°C, the same as sample 1, and at 67.4°C and 78.7°C, the same as samples 3 and 4. As a result, the gelling and non-gelling samples exhibited peaks at separate positions. In particular, sample 2, which exhibited thixotropy, exhibiting both gelling and sol formation, exhibited peaks for both gelling and sol formation. These results suggest that it is possible to distinguish between samples that can form a gel, those that maintain a sol state, and those that can achieve both.

[0093] (Infrared spectroscopy) Next, the freeze-dried samples 1 to 4 were subjected to infrared spectroscopy (FT-IR: Fourier Transform Infrared Spectrophotometer).

[0094] The freeze-drying process will now be described. First, 0.2 mL of each of Samples 1 to 4 in sol state was dropped onto a horizontally placed pure titanium plate. The plate was then heated for 1,800 seconds in an incubator at 40°C and 100% RH, and then pre-frozen by immersion in liquid nitrogen for 1 minute. After pre-freezing, the plate was freeze-dried using a freeze dryer (Freeze Dryer FDU-1200 63-1397-07). The freeze dryer was initially set to a temperature of -50°C and the sample was placed inside. The pressure was then reduced until the internal pressure reached 3,000 Pa or less, after which the plate was heated to sublimate the water. After sublimation, the plate was pressurized, and the sample was removed when it returned to room temperature and pressure, and then crushed in a mortar.

[0095] A Fourier transform infrared spectrophotometer (JASCO, FT / IR-4600) was used to evaluate the chemical bonding state of the particles. The KBr powder method was used for FT-IR measurement. Specifically, the background was KBr powder, and the wave number range was 1600 cm. -1 ~800cm -1 , 128 integration times, resolution 2.0cm -1 The transmission spectrum of the particles was obtained using the above method. These results are shown in Figure 21. As a result, as shown in this figure, the peak position was 3350 cm -1 , 3500cm -1 The peak shape is 800 to 1800 cm -1 Differences were observed in the peak positions and shapes, and clear differences were observed between the samples that formed a gel (4-4, 4-40) and the samples that did not form a gel (40-4, 40-40).

[0096] From here, 800cm -1 1200cm from the point with the least absorption -1 Absorption peaks between 1200 and 1800 cm (phosphate group peaks) -1 Absorption peak between 2000cm and 2000cm (peak of organic acid ions) -1 ~4000cm -1The absorption peak range (hydration water peak) between 1200 and 1800 cm was separated and the peak area of ​​each peak was calculated. Furthermore, the ratio of the peak area of ​​the organic acid ions and the peak area of ​​the hydration water to the peak area of ​​the phosphate group was calculated. The results are shown in Figure 22 and Figure 23, respectively. Note that Figure 22 shows the absorption peak range between 1200 and 1800 cm -1 The results for the peak range of 2000 cm -1 ~4000cm -1 The results are shown for the peak ranges of phosphate groups and hydrated water. As a result, it was confirmed that gelation can be determined when the peak area of ​​organic acid ions and the peak area of ​​hydrated water relative to the peak area of ​​phosphate groups are equal to or greater than a certain value. For example, in the example of Fig. 22, it was confirmed that gelation can be determined when the peak area ratio of phosphate groups to organic acid ion peaks is greater than 0.85, more specifically 1 or greater, and even more preferably 1.2 or greater. Also, in the example of Fig. 23, it was confirmed that gelation can be determined when the peak area ratio of phosphate groups to hydrated water peaks is greater than 4.45, more specifically 5 or greater, and even more preferably 5.91 or greater.

[0097] (Nitrogen adsorption / desorption measurement) Nitrogen adsorption / desorption measurements were also performed on freeze-dried samples 1 to 4. Specifically, to measure the interparticle voids, nitrogen adsorption / desorption isotherms were measured using a nitrogen adsorption / desorption isotherm analyzer (Microtrack-Bell, BELSORP-miniII) and the Brunauer-Emmet-Teller (BET) specific surface area was calculated. Prior to the measurements, samples were pretreated by vacuum heating at 100°C for 2 hours using a pretreatment device (Microtrack-Bell, BELSORP-vacl).

[0098] The BET specific surface area S BET (m 2 / g) is the amount of adsorption Vm (monomolecular adsorption amount (cm)) sufficient to form a monolayer. 3 (STP) / g) and the area occupied by the adsorbed gas molecules in the solid state, S (molecular occupied cross section (m 2)) was calculated based on the above equations (2) and (3). The results are shown in Figure 24, along with the BJH pore size distribution. Note that this value, the monomolecular adsorption amount, means the adsorption amount per unit mass of the sample under standard conditions. In addition, in this case, when calculating the half-width, considering that the half-width can change significantly depending on the baseline selected, we decided to calculate it as is without drawing a baseline. After calculating the half-width, two points that fall between the half-values ​​were selected, a line was drawn between them, and the point at which the half-value was reached was calculated, and the half-width was then calculated from the two points. An image of this case is shown in Figure 25.

[0099] (Average coverage calculation) Here, the average coverage of citric acid on the hybrid particles was calculated. The citric acid content in freeze-dried samples 1 to 4 was determined by measuring absorbance using an ultraviolet-visible spectrophotometer (UV-Vis). First, to create a calibration curve, citric acid was dissolved in hydrochloric acid (1 mol / L) to prepare four citric acid / hydrochloric acid solutions with citric acid concentrations of 1.25 mg / mL, 0.50 mg / mL, 0.25 mg / mL, and 0.10 mg / mL. The absorbance was measured under conditions of a bandwidth of 1 nm and a scan speed of 200 nm / min (Figure 26). A calibration curve (R 2 =0.9997) was prepared (inset in Figure 26). Next, freeze-dried samples 1 to 4 were each dissolved in hydrochloric acid (1 mol / L), the absorbance was measured, and the citric acid content was calculated from the calibration curve. The results are shown in Figure 27.

[0100] Then, based on the above results and the above formula (1), the coverage of citric acid was calculated. The results are also shown in Figure 27. As a result, it was confirmed that when a gel is formed by heating and the gel state is maintained even when an external stimulus is applied, the average coverage is 30% or more.

[0101] (TEM measurement) The primary particle diameters of the samples were also observed using a transmission electron microscope (Hitachi HT7700) with an accelerating voltage of 120 kV. Samples 1 to 4 were diluted for TEM observation. For the dilution process, 0.2 mL of each of the sol-state samples 1 to 4 was dropped onto a horizontal pure titanium plate, heated for 1,800 seconds in an incubator at 40°C and 100% RH, and then diluted 10,000 times with ethanol. Each diluted sample was cast onto a carbon-coated Cu grid and then vacuum-dried at room temperature. The particle morphology was then observed. The minor and major diameters of 50 particles were measured and calculated. The results are shown in Figure 28. The gelling samples (4-4 and 4-40) were confirmed to contain connected amorphous and isotropic particles, while the non-gelling samples (40-4 and 40-40) contained connected acicular and anisotropic particles, confirming the differences in their shapes.

[0102] We also checked the aspect ratio and other values ​​of these particles. The results are shown in Figure 29. As shown in this figure, we discovered that there was a large difference in the aspect ratio of the particles between samples that gel and those that do not. That is, samples with an aspect ratio of 3.41 or more do not gel, while particles with an aspect ratio of less than 3.41, preferably 2 or less, and most definitely 1.62 or less, are presumed to gel.

[0103] (XRD measurement) XRD measurements were also performed on freeze-dried samples 1 to 4. The results are shown in Figures 30 and 31. A fully automated multipurpose X-ray diffractometer (XRD: X-ray diffraction, Rigaku Corporation, Smart Lab) was used to evaluate the particle structure in these measurements. The X-ray source used was CuKα radiation (λ = 1.5418 Å), with an output of 40 kV / 30 mA, a scan speed of 3.0° / min, a sampling width of 0.01°, and a continuous measurement mode. For samples 3 and 4, the diffraction line position, diffraction angle, and half-width were calculated using the software provided with the instrument (Rigaku Corporation, PDXI). The crystalline layers were identified by the Hanawalt method using the ICDD standard data collection. Because the (300) and (211) planes of HA overlap, only the (002) plane of HA was used to determine the crystallite size. In addition, the crystallite size D can be calculated from the Scherrer equation shown below using the diffraction angle and half-width of HA (002). hkl In the following formula, β is the half-width [rad], θ is the diffraction angle [rad], and K is the Scherrer constant, where K=0.9 was used.

number

[0104] As a result, there was a clear difference in the presence or absence of peaks between samples 1 and 2, which gel, and samples 3 and 4, which do not gel, and it was confirmed that samples 1 and 2 were amorphous. In other words, being amorphous is considered to be important for gelation.

[0105] As described above, the effects of the present invention were confirmed by this example. [Industrial Applicability]

[0106] INDUSTRIAL APPLICABILITY The present invention has industrial applicability as a hybrid particle dispersion and a method for producing the same.

Claims

1. A hybrid particle dispersion in which hybrid particles, in which organic acid ions are coordinated with metal ions of inorganic nanoparticles, are dispersed in a dispersion medium.

2. The hybrid particle dispersion according to claim 1, wherein the hybrid particle dispersion contains 2.5% by weight or more of the hybrid particles.

3. 2. The hybrid particle dispersion according to claim 1, wherein the inorganic nanoparticles have an average particle size in the range of 5 nm to 1 μm.

4. 2. The hybrid particle dispersion according to claim 1, wherein the inorganic nanoparticles are amorphous.

5. 2. The hybrid particle dispersion according to claim 1, wherein a chelate is formed between the organic acid ion and the metal ion.

6. 2. The hybrid particle dispersion according to claim 1, wherein the organic acid ions are at least one of carboxylate ions and sulfonate ions.

7. 2. The hybrid particle dispersion according to claim 1, wherein the metal ions are at least one of iron ions, gallium ions, copper ions, nickel ions, lead ions, zinc ions, cobalt ions, gadolinium ions, cesium ions, manganese ions, calcium ions, magnesium ions, strontium ions, barium ions, silver ions, lithium ions, sodium ions, europium ions, vanadium ions, and yttrium ions.

8. 2. The hybrid particle dispersion according to claim 1, wherein the average coverage of the hybrid particles with the organic acid ions is 30% or more.

9. 2. The hybrid particle dispersion according to claim 1, wherein the organic acid ions are at least one of citrate ions, isocitrate ions, gluconate ions, succinate ions, and aspartate ions.

10. 2. The hybrid particle dispersion according to claim 1, wherein the inorganic nanoparticles are particles of at least one of calcium phosphate, calcium carbonate, and calcium hydroxide.

11. The hybrid particle dispersion according to claim 1, which gels upon heating.

12. 2. The hybrid particle dispersion according to claim 1, which has thixotropy, being capable of gelling upon heating and of solizing upon application of stress.

13. A method for producing a hybrid particle dispersion, comprising mixing an inorganic acid, an organic acid, and metal ions at a low temperature to produce a hybrid particle dispersion in which organic acid ions are coordinated to the metal ions of inorganic nanoparticles, and dispersing the hybrid particle dispersion in a dispersion medium.

14. A cell culture medium comprising a hybrid particle dispersion in which hybrid particles in which organic acid ions are coordinated to metal ions of inorganic nanoparticles are dispersed in a dispersion medium.

15. A transporter having an object to be transported and a package that encases the object to be transported, The package is a transporter that is a hybrid particle dispersion in which hybrid particles in which organic acid ions are coordinated with metal ions of inorganic nanoparticles are dispersed in a dispersion medium.

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