Method for preparing hydroxyapatite nanoparticles by high-speed shearing and synergic double-inversion miniemulsion

Abstract

The application relates to a method for preparing hydroxyapatite nanoparticles through high-speed shearing and synergic double reverse-phase fine emulsion, which continuously acts on the emulsification, mixing and homogenization process of a weakly alkaline precursor solution containing a calcium salt and an oil phase system and a precursor solution containing a phosphate and an oil phase system (constituting double reverse-phase fine emulsion droplets), and the collision-mixing reaction process of the calcium salt in the subsequent dispersed phase emulsion droplet (water droplet) and the phosphate in another dispersed phase emulsion droplet (water droplet), realizes the continuous operation of the high-speed shearing effect to intensify the physical emulsification mixing process and the chemical reaction mixing process, and achieves the purpose of preparing nHAP with good dispersity, small size and narrow particle size distribution; the method has simple preparation process, low equipment requirement, low cost, mild reaction condition, easy control in the preparation process, and is easy to enlarge, effectively solves the problems of low yield, high cost, use of a large amount of solvent in the process, easy harm to human body and environment, and difficulty in realizing large-scale production in the prior art.

Description

Technical Field

[0001] This invention relates to a method for preparing hydroxyapatite nanoparticles, and more particularly to a method for preparing hydroxyapatite nanoparticles by high-speed shear synergistic double reverse phase emulsion. Background Technology

[0002] Hydroxyapatite (HAP, Ca) 10 (PO4)6(OH)2 is a slightly soluble, weakly alkaline (pH=7-9) calcium phosphate salt, and an important component of human and animal bones and teeth, possessing superior bioactivity, biocompatibility, and tissue compatibility. In the pharmaceutical field, the size of nanoparticles is defined as between 1 and 1000 nm. Compared with ordinary hydroxyapatite, hydroxyapatite nanoparticles (nHAP) have superior physicochemical properties, such as higher specific surface area, higher drug adsorption and carrying capacity, and stronger bioactivity. They can be used as drug carriers for disease treatment, as fillers for bone repair, or as adsorbents for environmental protection, and for the separation and purification of biomacromolecules such as nucleic acids. Therefore, it is a promising biomineral material.

[0003] Currently, the main methods for preparing nHAP include solid-phase grinding, hydrothermal methods, sol-gel methods, chemical precipitation methods, and microemulsion methods. Solid-phase grinding involves grinding solid calcium and phosphate salts in a ball mill, introducing steam at high temperature to replenish OH- ions, and utilizing diffusion to replenish Ca2+. 2+ The preparation of HAP crystals is a simple method that produces highly crystallized products, but the reaction is slow, time-consuming, and energy-intensive, and the resulting product has a large and uneven particle size. The hydrothermal method uses water or other aqueous solutions as the heating medium in a closed, high-temperature, and high-pressure vessel, with temperature and pressure controlled to dissolve and recrystallize sparingly soluble or insoluble substances. This method produces products with small particle size and uniform dispersion, but it requires sophisticated equipment, is prone to side reactions, and is unsuitable for large-scale production. The sol-gel method involves dropping Ca sol into PO4. 3- In the sol method, NH4HCO3 is added, and the pH is adjusted with ammonia. The gel is then aged, washed, dried, and calcined to obtain nHAP. This method is simple, and the product has small and uniform particle size, but it is costly, time-consuming, and has low yield. In the chemical precipitation method, a phosphorus source is added to a calcium source under stirring, and the pH is adjusted with ammonia. The precipitate is then aged, washed, dried, and calcined to obtain nHA crystals. This method is simple, easy to implement, and low in cost, but the product has poor uniformity and is prone to agglomeration. In the microemulsion method, surfactants and co-surfactants are added to the Ca... 2+ PO4 3-In this process, water and organic additives react to form an emulsion, from which HAP precipitates. This method is simple and the particle size is controllable, but the yield is low, and it uses a large amount of solvent, which can easily cause harm to human health and the environment, and the cost is high. At the same time, the microemulsion method is still in the experimental research stage and cannot be mass-produced and used yet.

[0004] Therefore, how to efficiently prepare nHAP with good dispersibility, stable performance, controllable size and morphology, and narrow particle size distribution under favorable conditions remains an important research hotspot in the industry. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide a method for preparing hydroxyapatite nanoparticles by high-speed shear synergistic dual-phase reverse microemulsion. This method continuously applies high-speed shear effect to the emulsification, mixing and homogenization process of a weakly alkaline precursor aqueous solution containing calcium salt and an oil phase system, and a precursor aqueous solution containing phosphate and an oil phase system (forming dual-phase reverse microemulsion droplets), as well as the collision-mixing reaction process of calcium salt in the subsequent dispersed phase droplets (water droplets) and phosphate in the other dispersed phase droplets (water droplets). This achieves continuous operation of the physical emulsification and mixing process and chemical reaction mixing process enhanced by high-speed shear effect, and achieves the goal of producing nHAP with good dispersibility, small size and narrow particle size distribution. The preparation process of this method is simple, requires low equipment, is low in cost, has mild reaction conditions, is easy to control, and is easy to scale up. It effectively solves the problems of low yield, high cost, large amount of solvent used in the preparation process of existing technologies, especially microemulsion methods, which are prone to causing harm to human health and the environment, and are difficult to achieve large-scale production.

[0006] The technical solution to the above-mentioned technical problems is: a method for preparing hydroxyapatite nanoparticles by high-speed shear synergistic dual-phase reverse emulsion, comprising the following steps: (1) Preparation of precursor aqueous solution I and precursor aqueous solution II: Dissolve an appropriate amount of calcium salt in deionized water, and adjust the pH of the calcium salt solution to 9-11 with an appropriate amount of alkaline reagent to form an alkaline solution with a calcium salt content of 0.1-2.0 mol / L as precursor aqueous solution I; the calcium salt is one of calcium chloride, calcium nitrate, and calcium acetate. An appropriate amount of phosphate is dissolved in deionized water to form a phosphate solution with a concentration of 0.1–1.0 mol / L as precursor aqueous solution II; the phosphate is one of the following soluble disodium hydrogen phosphate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium phosphate, potassium phosphate, and ammonium phosphate. (2) Preparation of oil phase: A certain amount of surfactant is fully dissolved in vegetable oil to form the oil phase; the surfactant is Span-80 or Span-60; the amount of surfactant is 2.0 to 8.0% (v / v) of the volume of vegetable oil. (3) Preparation of reversed-phase precursor crude emulsion I and reversed-phase precursor crude emulsion II: Take an appropriate amount of precursor aqueous solution I from step (1) and add it to the oil phase of step (2) under stirring at 40-60℃ to form reversed-phase precursor crude emulsion I; take an appropriate amount of precursor aqueous solution II from step (1) and add it to the oil phase of step (2) under stirring at 40-60℃ to form reversed-phase precursor crude emulsion II; the calcium / phosphorus molar ratio in the precursor aqueous solution I and precursor aqueous solution II is 1.6-2.0; the volume ratio of the precursor aqueous solution I, precursor aqueous solution II and oil phase is 15-30% (v / v). (4) High-speed shear mixing preparation of reverse precursor fine emulsion I and reverse precursor fine emulsion II: At the same temperature as the preparation of reverse precursor crude emulsion I in step (3), reverse precursor crude emulsion I and reverse precursor fine emulsion II in step (3) are simultaneously treated by a high-speed shear homogenizer at a certain high shear rate for 12 to 30 min to obtain reverse precursor fine emulsion I and reverse precursor fine emulsion II with emulsion particle size in the nanometer range. (5) Preparation of hydroxyapatite nanoparticles by high-speed shear mixing and synergistic two-phase reversed-phase fine emulsion: At the same temperature as the preparation of reversed-phase precursor fine emulsion I in step (4), reversed-phase precursor fine emulsion II in step (4) was added dropwise to reversed-phase precursor fine emulsion I under uninterrupted high-speed shear homogenization at a rate of 5-15 mL / min. The mixture was continuously high-speed shear mixing and homogenization was carried out at the same high shear rate as in step (4) for 60-150 min. The mixture was then rapidly cooled to 10-25 °C at a cooling rate of 8-12 °C / min, centrifuged, washed, dried, and calcined at a certain temperature to obtain hydroxyapatite nanoparticles.

[0007] Preferably, in step (1), the alkaline reagent is triethanolamine.

[0008] Preferably, in step (2), the vegetable oil is palm oil, corn oil, soybean oil, rapeseed oil, olive oil, or sunflower oil.

[0009] Preferably, the high shear rate in steps (4) and (5) is 8000 to 16000 r / min.

[0010] Preferably, the calcination temperature in step (5) is 400-600℃.

[0011] High-speed shear mixing, as a high-energy emulsification and homogenization technology, relies on the shear chamber formed by the high-speed rotating rotor and stator to generate synergistic effects of turbulent inertial forces and viscous shear forces, achieving rapid homogenization and mixing between immiscible liquid materials. When the rotor rotates at high speed, it drives the liquid material to form strong turbulence. The turbulent inertial forces create dramatic velocity gradients and pressure fluctuations within the material, enhancing the mixing between immiscible liquids and causing large droplets to break down into smaller droplets. Simultaneously, the liquid material is compressed and impacted within the gap between the rotor and stator, and the viscous shear forces further tear and refine the droplet size, promoting thorough mixing between different phases of liquid material. Furthermore, the high-speed motion of the liquid material has a certain probability of generating cavitation effects. The resulting microbubbles burst instantaneously, generating localized high pressure, microjets, and intense turbulence, which further enhance the mixing and homogenization effect, ultimately achieving a uniform and stable dispersion state between the two phases of liquid material.

[0012] This invention discloses a novel method for preparing hydroxyapatite nanoparticles using high-speed shear-coordinated dual-phase reverse emulsions. The main technical principles include: (1) The strong turbulent inertial force and viscous shear force generated between the rotor and stator of the high-speed shear mixing homogenizer promote the cutting and breaking of large-sized precursor calcium salt water (emulsion) droplets and large-sized precursor phosphate salt water (emulsion) droplets suspended in the vegetable oil phase, so that the suspended water (emulsion droplets) in the vegetable oil phase are continuously refined. A double reverse phase fine emulsion with a water (emulsion) droplet size of 100-500 nm can be prepared, forming an emulsion system with small droplet size, narrow distribution and high stability. This provides a nanoscale "template" reaction microsystem for obtaining ultrafine particle size, narrow distribution and good dispersibility of hydroxyapatite nanoparticles.

[0013] (2) Before the two-phase reverse water (emulsion) reaction, the emulsion system composed of vegetable oil, surfactant and aqueous solution will reach "approximate thermodynamic equilibrium" under the action of high-speed shear effect. The aggregation (flocculation) between the precursor weakly alkaline calcium-containing water (emulsion) droplets I suspended in the oil phase and its breakup into fine water (emulsion) droplets will reach "approximate thermodynamic equilibrium". Similarly, the aggregation (flocculation) between the precursor phosphate-containing emulsion droplets II and its breakup into fine water (emulsion) droplets will also reach "approximate thermodynamic equilibrium". This provides a favorable microenvironment for the generation of ultrafine-sized and narrowly distributed hydroxyapatite nanoparticles when the two collide, contact and react.

[0014] (3) In the process of double-phase fine emulsion reaction, the water (emulsion) droplet space of the fine emulsion can be regarded as a series of micro-element reaction spaces. Therefore, under the combined action of high-speed shear effect, including turbulent inertial force and viscous shear force, as well as a certain probability of cavitation effect, the reaction probability of the precursor weakly alkaline calcium-containing salt water (emulsion) droplet I suspended in the oil phase and the precursor phosphate-containing emulsion droplet II is increased, the reaction time is shortened, and the production efficiency of hydroxyapatite nanoparticles is effectively improved.

[0015] (4) The generation of two reverse phase fine water (emulsion) droplets is an important basis for preparing hydroxyapatite nanoparticles with good dispersibility, controllable size and morphology and narrow particle size distribution. The high-speed shear mixing effect is an important guarantee for generating water (emulsion) droplet sizes of 100-500 nm two reverse phase fine emulsions. The cooperation and complementarity of the two are the key to obtaining hydroxyapatite nanoparticles with good dispersibility, controllable size and narrow distribution by this method.

[0016] The beneficial effects of this invention are as follows: (1) The hydroxyapatite nanoparticles prepared by the present invention are nearly elliptical, have good dispersibility, and the particle size is controllable between 300 and 1000 nm, and the polydispersity index (PDI) is controllable between 0.3 and 0.7.

[0017] (2) Compared with conventional microemulsion methods, the present invention does not require co-surfactants, and reduces the amount of surfactant used by nearly 3 to 12 times, and is easier to scale up for mass production.

[0018] (3) Compared with conventional chemical precipitation methods, the hydroxyapatite nanoparticles obtained by the present invention have a narrow size distribution, good uniformity, and are not prone to agglomeration, resulting in good particle dispersibility.

[0019] (4) The preparation process provided by the present invention realizes the physical preparation process of reverse emulsification of precursor aqueous solutions I and II by high-speed shear mixing and continuous operation of subsequent chemical reaction granulation process, which simplifies the operation process.

[0020] (5) The preparation process of this invention does not use conventional pH adjusters such as ammonia water which are highly toxic. Instead, it uses triethanolamine which has low toxicity. Furthermore, the emulsification process uses food-grade surfactants and vegetable oils, which improves the safety of the entire process and greatly reduces the potential harm to the human body and the environment caused by reagent residues in hydroxyapatite nanoparticle products.

[0021] (6) The preparation process provided by the present invention can easily adjust the droplet size and distribution formed by the reverse precursor microemulsions I and II by controlling the high-speed shearing operation conditions and process parameters, thereby controlling the size and distribution of the generated hydroxyapatite composite microparticles. This effectively avoids the problem of difficulty in controlling the size and distribution of hydroxyapatite composite microparticles obtained in the conventional chemical precipitation method.

[0022] (7) The preparation process of the present invention is simple to operate, short in time, and has good repeatability. The high-speed shear mixing and homogenizing device is inexpensive and easy to control, which has the advantage of large-scale industrial application. Attached Figure Description

[0023] Figure 1Example 1 of this invention provides a process flow diagram of a method for preparing hydroxyapatite nanoparticles using high-speed shear synergistic dual-phase fine emulsion.

[0024] Figure 2 SEM image of the hydroxyapatite nanoparticles prepared in Example 1 of this invention.

[0025] Figure 3 SEM image of the hydroxyapatite nanoparticles prepared in Example 2 of this invention.

[0026] Figure 4 SEM image of the hydroxyapatite nanoparticles prepared in Example 3 of this invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention. Example 1

[0028] A method for preparing hydroxyapatite nanoparticles using high-speed shear-coordinated dual-phase reverse emulsion is described in the following flowchart: Figure 1 As shown, it includes the following steps: (1) Preparation of precursor aqueous solutions I and II: Weigh 5.55 g of anhydrous calcium chloride and dissolve it in deionized water, add 70 mL of triethanolamine, and then make up to 250 mL with deionized water to obtain a calcium chloride aqueous solution with a pH of about 10.4 and use it as precursor aqueous phase I. Weigh 5.28 g of diammonium hydrogen phosphate and dissolve it in deionized water, then make up to 250 mL to obtain a 0.16 mol / L diammonium hydrogen phosphate solution, which will be used as the precursor aqueous phase II. (2) Preparation of the oil phase: Dissolve 12 mL of surfactant Span-80 completely in 200 mL of palm oil to form the oil phase; (3) Preparation of reversed-phase precursor crude emulsions I and II: Take 22.8 mL of aqueous phase I from step (1) and add it to 114 mL of oil phase from step (2), and stir at 50 °C to form crude emulsion I; take 17.2 mL of aqueous phase II from step (1) and add it to 86 mL of oil phase from step (2), and stir at 50 °C to form crude emulsion II; (4) Preparation of reverse precursor fine emulsion I and II by high-speed shear mixing: At 50 °C, the precursor crude emulsion I and II from step (3) were simultaneously treated by a high-speed shear homogenizer at 14000 r / min for 15 min to obtain reverse precursor fine emulsion I and reverse precursor fine emulsion II with a particle size of nanometers. (5) Preparation of hydroxyapatite nanoparticles by high-speed shear mixing synergistic double reverse-phase fine emulsion: Under the condition of 50℃ and uninterrupted high-speed shear homogenization, the precursor fine emulsion II from step (4) was added dropwise to the reverse-phase fine precursor aqueous solution I from step (4) at a rate of 10 mL / min. The mixture was then treated with a high-speed shear homogenizer at a speed of 14000 r / min for 60 min (timing started when the reverse-phase precursor fine emulsion II was added). The mixture was then rapidly cooled to 15℃ at a cooling rate of 10℃ / min, centrifuged, washed and dried, and calcined at 500℃ to obtain hydroxyapatite nanoparticles. The surface morphology of the nanoparticles is shown in the figure. Figure 2 .

[0029] Table 1 compares the physicochemical properties and performance of hydroxyapatite nanoparticles (nHAP) prepared by high-speed shear synergistic dual-phase microemulsion method of the present invention with those prepared by conventional microemulsion method and conventional chemical precipitation method. The conventional microemulsion method refers to the microemulsion method described in "Preparation and Characterization of Nano-Hydroxyapatite by Reverse-Phase Microemulsion Method" by Zhu Minying, Li Hong, Li Lihua, and Zhou Changren; the conventional chemical precipitation method refers to the chemical precipitation method described in "Influence of Temperature and pH on the Synthesis of Hydroxyapatite Powder" by Song Yunjing, Li Musen, Wen Shulin, Jiang Qinghui, and Su Qingcai.

[0030]

[0031] From Table 1 and Figure 2 It can be seen that the nHAP prepared by high-speed shear mixing synergistic double reverse phase emulsion has good dispersibility, near-elliptical morphology, no adhesion, ultra-fine particle size and narrow distribution. The size of the obtained nHAP is 314.5 nm and the PDI is 0.310.

[0032] Compared to conventional microemulsion methods, although the nHAP prepared by the microemulsion method has a smaller size, it requires a large amount of n-pentanol co-surfactant (accounting for 16.5% of the oil phase volume), and the total amount of surfactant used is also significantly increased, reaching 5.9 times the total amount of surfactant used in high-speed shear mixing synergistic double reverse phase fine emulsion. Furthermore, the final product grinding is required, reducing the efficiency of the preparation process and increasing energy consumption. This result indicates that, compared to conventional microemulsion methods, high-speed shear mixing synergistic double reverse phase fine emulsion preparation of nHAP significantly reduces the amount of surfactant used and eliminates the need for co-surfactants, greatly reducing surfactant residue on nHAP and production costs. Simultaneously, the absence of grinding in the preparation process helps improve production efficiency and reduce energy consumption. Compared to conventional chemical precipitation methods, the nHAP prepared by this method has a size of 200–400 nm, exhibiting needle-like or strip-like shapes with a wide distribution, poor uniformity, and particle agglomeration. The final product grinding is also required, reducing the efficiency of the preparation process and increasing energy consumption. This result shows that, compared with conventional chemical precipitation, the size of nHAP prepared by high-speed shear mixing synergistic dual reverse phase fine emulsion is comparable to that of nHAP prepared by conventional chemical precipitation, but with better dispersibility, no adhesion, and ultra-fine particle size and narrow distribution; at the same time, the preparation process does not require grinding, which helps to improve production efficiency and reduce energy consumption in the production process. Example 2

[0033] A method for preparing hydroxyapatite nanoparticles using high-speed shear-coordinated dual-phase reverse emulsion includes the following steps: (1) Preparation of precursor aqueous solutions I and II: Weigh 8.2 g of anhydrous calcium nitrate and dissolve it in deionized water, add 65 mL of triethanolamine, and then make up to 250 mL with deionized water to obtain a calcium nitrate aqueous solution with a pH of about 10.0 and a concentration of 0.25 mol / L, which is used as precursor aqueous phase I. Weigh 4.8 g of disodium hydrogen phosphate and dissolve it in deionized water, then make up to 250 mL to obtain a 0.16 mol / L diammonium hydrogen phosphate solution, which is used as the precursor aqueous phase II. (2) Preparation of the oil phase: Dissolve 12.5 ml of surfactant Span-80 completely in 250 mL of soybean oil to form the oil phase; (3) Preparation of reversed-phase precursor crude emulsions I and II: Take 25.0 mL of aqueous phase I from step (1) and add it to 120 mL of oil phase from step (2), and stir at 45 °C to form crude emulsion I; take 20 mL of aqueous phase II from step (1) and add it to 96 mL of oil phase from step (2), and stir at 45 °C to form crude emulsion II; (4) High-speed shear mixing preparation of reverse precursor microemulsions I and II: At 45 °C, the precursor crude emulsions I and II from step (3) were treated by a high-speed shear homogenizer at 15000 r / min for 20 min to obtain reverse precursor microemulsions I and II with a particle size of nanometers. (5) Preparation of hydroxyapatite nanoparticles by high-speed shear mixing and synergistic two-phase reverse fine emulsion: Under the condition of 45 °C and uninterrupted high-speed shear homogenization, the precursor fine emulsion II from step (4) was added dropwise to the reverse fine precursor aqueous solution I from step (4) at a rate of 15 mL / min. The mixture was then treated with a high-speed shear homogenizer at a speed of 15000 r / min for 80 min. The mixture was then rapidly cooled to 20 °C at a cooling rate of 8 °C / min. After centrifugation, washing, and drying, the hydroxyapatite nanoparticles were obtained by calcination at 500 °C. The surface morphology of the nanoparticles is shown in the figure. Figure 3 .

[0034] Table 2 compares the physicochemical properties and performance of hydroxyapatite nanoparticles (nHAP) prepared by high-speed shear synergistic dual-phase reverse microemulsion of the present invention with those prepared by conventional microemulsion methods and conventional chemical precipitation methods. The conventional microemulsion method refers to the microemulsion method described in "Synthesis of Nano-hydroxyapatite using Triton X-100 / n-hexanol / cyclohexane Reverse Microemulsion System" by Xiao Fengjuan, Yang Huifang, and Xu Hua; the conventional chemical precipitation method refers to the chemical precipitation method described in "Orthogonal Experimental Design and Discussion of Precipitation Method for Ultrafine Hydroxyapatite Powder" by Hu Jilin, Liu Xin, Luo Chengjun, and Cao Yu.

[0035] From Table 2 and Figure 3 It can be seen that the nHAP prepared by high-speed shear mixing synergistic double reverse phase emulsion has good dispersibility, near-elliptical morphology, no adhesion, ultra-fine particle size and narrow distribution. The size of the obtained nHAP is 301.6 nm and the PDI is 0.337.

[0036] Compared to conventional microemulsion methods, although the nHAP prepared by the microemulsion method has a finer size, it requires a large amount of hexanol co-surfactant (accounting for 16.5% of the oil phase volume), and the total amount of surfactant used is also significantly increased, reaching 7.1 times the total amount of surfactant used in high-speed shear mixing synergistic biphase reverse-phase microemulsion. Furthermore, the final product grinding is required, reducing the efficiency of the preparation process and increasing energy consumption. This result indicates that, compared to conventional microemulsion methods, high-speed shear mixing synergistic biphase reverse-phase microemulsion preparation of nHAP significantly reduces the amount of surfactant used and eliminates the need for co-surfactants, greatly reducing surfactant residue and production costs. Simultaneously, the absence of grinding in the preparation process helps improve production efficiency and reduce energy consumption. Compared to conventional chemical precipitation methods, the nHAP prepared by this method has a size of 340–850 nm, is granular, has a wide distribution, poor uniformity, and exhibits particle agglomeration. Moreover, the preparation process requires a 24-hour settling period, resulting in low efficiency. This result indicates that, compared with conventional chemical precipitation, the high-speed shear mixing synergistic dual-phase fine emulsion method for preparing nHAP results in finer particle size, better dispersibility, no adhesion, and a narrower particle size distribution; at the same time, the preparation process does not require static aging, resulting in higher preparation efficiency.

[0037] Example 3 A method for preparing hydroxyapatite nanoparticles using high-speed shear-coordinated dual-phase reverse emulsion includes the following steps: (1) Preparation of precursor aqueous solutions I and II: Weigh 9.9 g of anhydrous calcium acetate and dissolve it in deionized water, add 75 mL of triethanolamine, and then make up to 250 mL with deionized water to obtain a calcium acetate aqueous solution with a pH of about 10.6 and a concentration of 0.25 mol / L, which is used as precursor aqueous phase I. Weigh 6.0 g of sodium dihydrogen phosphate and dissolve it in deionized water, then make up to 250 mL to obtain a 0.20 mol / L sodium dihydrogen phosphate solution, which will be used as the precursor aqueous phase II. (2) Preparation of the oil phase: After melting an appropriate amount of surfactant Span-60, take 10.0 mL and dissolve it completely in 250 mL of corn oil to obtain the oil phase; (3) Preparation of reversed-phase precursor crude emulsions I and II: Take 28.0 mL of aqueous phase I from step (1) and add it to 120 mL of oil phase from step (2), and stir at 55 °C to form crude emulsion I; take 20 mL of aqueous phase II from step (1) and add it to 87 mL of oil phase from step (2), and stir at 55 °C to form crude emulsion II; (4) High-speed shear mixing preparation of reverse precursor microemulsions I and II: At 55 °C, the precursor crude emulsions I and II from step (3) were treated by a high-speed shear homogenizer at 16000 r / min for 12 min to obtain reverse precursor microemulsions I and II with a particle size of nanometers. (5) Preparation of hydroxyapatite nanoparticles by high-speed shear mixing synergistic double reverse-phase fine emulsion: Under the condition of 55 °C and uninterrupted high-speed shear homogenization, the precursor fine emulsion II from step (4) was added dropwise to the reverse-phase fine precursor aqueous solution I from step (4) at a rate of 12 mL / min. The mixture was then treated with a high-speed shear homogenizer at a speed of 16000 r / min for 90 min. The mixture was then rapidly cooled to 16 °C at a cooling rate of 10 °C / min. After centrifugation, washing, and drying, the hydroxyapatite nanoparticles were obtained by calcination at 500 °C. The surface morphology of the nanoparticles is shown in the figure. Figure 4 .

[0038] Table 3 compares the physicochemical properties and performance of hydroxyapatite nanoparticles (nHAP) prepared by high-speed shear synergistic dual-phase reverse microemulsion method of the present invention with those prepared by conventional microemulsion method and conventional chemical precipitation method. The conventional microemulsion method refers to the microemulsion method described in "Preparation of Rod-shaped Hydroxyapatite Nanoparticles by Reverse Phase Microemulsion Method" by Guo Guangsheng, Sun Yuxiu, Wang Zhihua, and Guo Hongyou; the conventional chemical precipitation method refers to the chemical precipitation method described in "Influence of Process Factors on the Crystallization Morphology of Nano-hydroxyapatite" by Lü Kuilong, Zhou Yu, Meng Xiangcai, Li Xingyi, and Teng Liqun.

[0039]

[0040] From Table 3 and Figure 4 It can be seen that the nHAP prepared by high-speed shear mixing synergistic double reverse phase emulsion has good dispersibility, near-elliptical morphology, no adhesion, ultra-fine particle size and narrow distribution. The size of the obtained nHAP is 303.7 nm and the PDI is 0.326.

[0041] Compared to conventional microemulsion methods, although the nHAP prepared by the microemulsion method has a finer particle size, it requires a large amount of n-hexanol and n-butanol co-surfactants (totaling 18.7% of the oil phase volume), and the total amount of surfactant used is also significantly increased, reaching 9.9 times that of high-speed shear mixing synergistic double-phase fine emulsion. This result indicates that, compared to conventional microemulsion methods, high-speed shear mixing synergistic double-phase fine emulsion significantly reduces the amount of surfactant used and eliminates the need for co-surfactants, greatly reducing surfactant residue and production costs. Compared to conventional chemical precipitation methods, the nHAP prepared by this method has a size of 70–160 nm, exhibiting a near-spherical shape with varying particle sizes, wide distribution, poor uniformity, and particle agglomeration. This result indicates that, compared to conventional chemical precipitation methods, high-speed shear mixing synergistic double-phase fine emulsion prepares nHAP with better dispersibility, no adhesion, and a narrower particle size distribution.

Claims

1. A method for preparing hydroxyapatite nanoparticles using high-speed shear-coordinated dual-phase reverse emulsion, characterized in that, Includes the following steps: (1) Preparation of precursor aqueous solution I and precursor aqueous solution II: Dissolve an appropriate amount of calcium salt in deionized water, and adjust the pH of the calcium salt solution to 9-11 with an appropriate amount of alkaline reagent to form an alkaline solution with a calcium salt content of 0.1-2.0 mol / L as precursor aqueous solution I; the calcium salt is one of calcium chloride, calcium nitrate, and calcium acetate. An appropriate amount of phosphate is dissolved in deionized water to form a phosphate solution with a concentration of 0.1–1.0 mol / L as precursor aqueous solution II; the phosphate is one of the following soluble disodium hydrogen phosphate, sodium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium phosphate, potassium phosphate, and ammonium phosphate. (2) Preparation of oil phase: A certain amount of surfactant is fully dissolved in vegetable oil to form the oil phase; the surfactant is Span-80 or Span-60; the amount of surfactant is 2.0 to 8.0% (v / v) of the volume of vegetable oil. (3) Preparation of reversed-phase precursor crude emulsion I and reversed-phase precursor crude emulsion II: Take an appropriate amount of precursor aqueous solution I from step (1) and add it to the oil phase of step (2) under stirring at 40-60℃ to form reversed-phase precursor crude emulsion I; take an appropriate amount of precursor aqueous solution II from step (1) and add it to the oil phase of step (2) under stirring at 40-60℃ to form reversed-phase precursor crude emulsion II; the calcium / phosphorus molar ratio in the precursor aqueous solution I and precursor aqueous solution II is 1.6-2.0; the volume ratio of the precursor aqueous solution I, precursor aqueous solution II and oil phase is 15-30% (v / v). (4) High-speed shear mixing preparation of reverse precursor fine emulsion I and reverse precursor fine emulsion II: At the same temperature as the preparation of reverse precursor crude emulsion I in step (3), reverse precursor crude emulsion I and reverse precursor fine emulsion II in step (3) are simultaneously treated by a high-speed shear homogenizer at a certain high shear rate for 12 to 30 min to obtain reverse precursor fine emulsion I and reverse precursor fine emulsion II with emulsion particle size in the nanometer range. (5) Preparation of hydroxyapatite nanoparticles by high-speed shear mixing and synergistic two-phase reversed-phase fine emulsion: At the same temperature as the preparation of reversed-phase precursor fine emulsion I in step (4), reversed-phase precursor fine emulsion II in step (4) was added dropwise to reversed-phase precursor fine emulsion I under uninterrupted high-speed shear homogenization at a rate of 5-15 mL / min. The mixture was continuously high-speed shear mixing and homogenization was carried out at the same high shear rate as in step (4) for 60-150 min. The mixture was then rapidly cooled to 10-25 °C at a cooling rate of 8-12 °C / min, centrifuged, washed, dried, and calcined at a certain temperature to obtain hydroxyapatite nanoparticles.

2. The method for preparing hydroxyapatite nanoparticles by high-speed shear synergistic dual-phase reverse emulsion according to claim 1, characterized in that: In step (1), the alkaline reagent is triethanolamine.

3. The method for preparing hydroxyapatite nanoparticles by high-speed shear synergistic dual-phase reverse emulsion according to claim 1 or 2, characterized in that: In step (2), the vegetable oil is palm oil, corn oil, soybean oil, rapeseed oil, olive oil, or sunflower oil.

4. The method for preparing hydroxyapatite nanoparticles by high-speed shear synergistic dual-phase reverse emulsion according to claim 1 or 2, characterized in that: The high shear rate in steps (4) and (5) is 8000–16000 r / min.

5. The method for preparing hydroxyapatite nanoparticles by high-speed shear synergistic dual-phase reverse emulsion according to claim 1 or 2, characterized in that: The calcination temperature mentioned in step (5) is 400-600℃.

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