A phosphorylated amino acid composite microsphere and its preparation and application

Abstract

This invention discloses phosphorylated amino acid composite microspheres, which comprise phosphorylated amino acids, a polymeric binder, a liquid-conducting agent, a pH adjuster, and a divalent metal salt. The mass ratio of (phosphorylated amino acids + liquid-conducting agent): polymeric binder: pH adjuster: divalent metal salt is (900-920):(20-40):(30-40):(20-40), and the mass ratio of phosphorylated amino acids to liquid-conducting agent is (930-980):(20-70). This invention also discloses its preparation method. Bone adhesive prepared by mixing the phosphorylated amino acid composite microspheres prepared according to this invention with hydroxyapatite exhibits optimal setting time and tested bond strength.

Description

Technical Field

[0001] This invention relates to a phosphorylated amino acid composite microsphere, its preparation, and its application. Background Technology

[0002] In surgical procedures involving tissue trauma, non-degradable materials such as nails and plates are often used, which negatively impacts healing and necessitates secondary surgery for removal. Soft tissue surgeries typically require sutures, which are time-consuming, create new wounds, and sutures are often insufficient to completely seal them. Postoperative leakage of air and bodily fluids, as well as exogenous infections, also hinder wound healing. High-quality medical adhesives, capable of directly bonding wounds together, represent an ideal solution.

[0003] Medical adhesives can be categorized according to their application, such as soft tissue adhesives and bone tissue adhesives. Soft tissue adhesives can be further classified according to their material properties into biological adhesives (such as fibrin derivatives, mussel adhesive proteins, and gelatin) and chemical adhesives (such as cyanoacrylates, polyethylene glycols, and polyurethanes). These adhesives are only suitable for soft tissue bonding.

[0004] Bone tissue adhesives maintain their bonding properties in humid environments and possess good biocompatibility and degradation resistance. Typically, bone tissue adhesives are composed of organic and inorganic materials. If the organic materials (such as starch, proteins, or other medical polymers) are not pretreated for liquid absorption and conduction, the outer layer will become sticky after absorbing liquid during use, while the inner dry layer cannot contact the liquid, significantly affecting the material's performance. Similarly, organic-inorganic composite bone adhesives require mixing before use, a process involving the uniform mixing of solid and liquid phases. Uneven mixing can negatively impact adhesive performance, such as difficulty in stirring and blending, and decreased adhesion. One method to address the issues of material reaction uniformity and sufficiency is pre-porous (liquid-conducting) treatment, including microsphere preparation and granulation. Emulsification processes can produce relatively ideal porous microspheres with significant advantages in particle size control; however, the process is complex, solvent removal is difficult, and solvent contamination is likely. While wet granulation or spray drying granulation methods are simple and effective, they require careful material design and selection to achieve a comprehensive effect in pore formation and granulation. Summary of the Invention

[0005] This invention was made to further expand the selection of bone adhesives and to provide a bone adhesive with better performance.

[0006] As one aspect of the present invention, a phosphorylated amino acid composite microsphere is disclosed, the phosphorylated amino acid composite microsphere comprising phosphorylated amino acids, a polymeric binder, a liquid-conducting agent, a pH adjuster, and a divalent metal salt, wherein the mass ratio of (phosphorylated amino acid + liquid-conducting agent): polymeric binder: pH adjuster: divalent metal salt is (900-920):(20-40):(30-40):(20-40), and the mass ratio of phosphorylated amino acids: liquid-conducting agent is (930-980):(20-70).

[0007] In at least one specific embodiment, the phosphorylated amino acid refers to phosphorylated threonine, phosphorylated tyrosine, phosphorylated serine, phosphorylated hydroxyproline, or any combination thereof.

[0008] In at least one specific embodiment, the polymeric adhesive refers to sodium carboxymethyl cellulose, hydroxyethyl cellulose, or any combination thereof.

[0009] In at least one specific embodiment, the liquid-conducting agent refers to sodium carboxymethyl starch, croscarmellose sodium, polyvinylpyrrolidone, or any combination thereof.

[0010] In at least one specific embodiment, the pH adjuster refers to sodium carbonate, sodium bicarbonate, or any combination thereof. The pH adjuster is alkaline and can undergo an acid-base neutralization reaction with acidic phosphorylated amino acids during granulation, increasing the pH value of the system, generating a small amount of carbon dioxide and water, while the remaining sodium salt remains in the system.

[0011] In at least one specific embodiment, the divalent metal salt refers to calcium citrate, calcium carbonate, calcium alginate, calcium glycerophosphate, or any combination thereof.

[0012] As another aspect of the present invention, a method for preparing the phosphorylated amino acid composite microspheres described above is provided, the method comprising:

[0013] 1) Weigh the phosphorylated amino acids and the liquid-conducting agent, add 75-95% ethanol solution, mix well, remove the liquid, add 80-90% ethanol solution, remove the liquid, dry, and obtain powder;

[0014] 2). Weigh out the polymer binder, pH adjuster, and divalent metal salt, and mix them with the powder obtained in step 1) to obtain a well-mixed powder;

[0015] 3) The mixed powder is added to a 60-75% ethanol solution at a volume / mass ratio of (45-55):100 (ml / g) for wet granulation;

[0016] 4) Drying to obtain dry granules;

[0017] 5) Sieve the particles to obtain particles between 50 and 80 mesh, which are phosphorylated amino acid composite microspheres.

[0018] As another aspect of the present invention, the application of the above-mentioned phosphorylated amino acid composite microspheres in the preparation of bone adhesives is involved.

[0019] As another aspect of the present invention, there is a bone adhesive comprising a mixture of the above-mentioned phosphorylated amino acid composite microspheres and a calcium phosphate compound.

[0020] In at least one specific embodiment, the calcium phosphate compound refers to calcium phosphate or hydroxyapatite.

[0021] This invention utilizes a wet granulation process to process phosphorylated amino acids, solving the problem of agglomeration upon contact with water during use. It allows for extremely rapid and uniform mixing and reaction with other materials in an aqueous environment, and also provides a solution for the rapid dissolution of phosphorylated amino acids. Wet granulation is low-cost, highly efficient, and environmentally friendly. An innovative composite binder and liquid-conducting agent balance the comprehensive needs of the granulation process and subsequent product applications, optimizing the adhesiveness of the granulation process. Pre-porous treatment of the raw materials by increasing the wetting liquid (ethanol) content increases the porosity of the microspheres. A pH adjuster containing carbonate is introduced during the granulation process; while adjusting the pH, the carbonate also decomposes in the acidic environment, releasing carbon dioxide and increasing the micropores of the material. This invention also introduces a small amount of inorganic material capable of coordination reactions, which, through pre-reaction, can regulate the curing speed during subsequent mixing and reaction with inorganic materials. Detailed Implementation

[0022] During the research process, the inventors discovered that when using amino acid granulation, there is a positive correlation between the concentration of ethanol used and the porosity of the product. However, if the ethanol concentration exceeds 70%, it will damage the adhesion of the material, making granulation impossible. By phosphorylating the amino acid and adding appropriate amounts of binder and liquid-conducting agent, the inventors prepared a porous composite microsphere product with high porosity that can quickly and uniformly absorb water, and thus filed this application.

[0023] In this application, unless otherwise stated, percentages are percentages by mass.

[0024] Example 1: A phosphorylated threonine composite microsphere for use as a component of bone adhesive and its preparation process

[0025] 1. Weigh 950g of phosphorylated threonine and 50g of croscarmellose sodium, and add 3000ml of 95% ethanol solution. Stir magnetically at 50rpm for 2 hours, and pass through a 200-mesh sieve. Add 2000ml of 80% ethanol solution to the retentate, and stir magnetically at 50rpm for 1 hour. Pass through a 200-mesh sieve. Dry the retentate at 50℃ for 3 hours until it becomes powder, pass through a 100-mesh sieve, and collect the filtrate.

[0026] 2. Weigh 20g of hydroxyethyl cellulose powder that has passed through a 100-mesh sieve, 40g of sodium bicarbonate powder that has passed through a 100-mesh sieve, and 40g of glycerophosphate powder that has passed through a 100-mesh sieve. Put them together with 900g of the filter material obtained in step 1 into a three-dimensional mixer and mix for 30 minutes to obtain a homogeneous powder.

[0027] 3. Granulation: Place the mixed powder in a wet granulator and add 65% ethanol solution at a volume / mass ratio of 45:100 (ml / g) to obtain wet granules. The granulation sieve is 50 mesh.

[0028] 4. Drying: Dry the obtained wet granules at 60℃ for 75 minutes to obtain dry granules;

[0029] 5. Granulation: Sieve the particles to obtain particles between 50 and 80 mesh, which are phosphorylated threonine composite microspheres.

[0030] 100g of the prepared phosphorylated threonine composite microspheres were tested for flowability using the fixed funnel method, and the angle of repose was 34°. 5g of the prepared phosphorylated threonine composite microspheres were measured using a rapid moisture analyzer, and the particle moisture content was 4.3%, with a saturated liquid absorption ratio of 2.6.

[0031] Method for determining the angle of repose: The fixed funnel method is used to determine the particle flowability. A glass funnel with a 5mm aperture is vertically fixed on an iron stand, and the lower opening of the funnel is adjusted to be 150mm away from the horizontal glass plate. 100g of the sample to be tested is slowly poured into the funnel, keeping the lower opening of the funnel completely open. The process is stopped when the particles naturally accumulate on the glass plate to form a cone and there is no particle flow. The angles formed by the bottom edge of the cone and the apex of the cone are measured with a protractor at three different azimuths. The measurements are performed in parallel three times, and the relative deviation should be less than 5%. The average value of 34° is taken as the measured value of the angle of repose.

[0032] Moisture content determination method: A halogen moisture analyzer was used for detection. 5.0±0.1g of sample was evenly spread on a sample tray. The test temperature was set to 105℃, and the automatic detection mode was turned on. When the sample mass change rate was <0.1% / min, it was determined to be constant weight. Three parallel determinations were performed and the average value was taken. The absolute difference between a single determination value and the average value should be ≤0.2%. The instrument automatically calculated and displayed the moisture content as 4.3%. Saturated liquid absorption ratio test: A 20ml test tube was weighed and tare. 5g of composite microspheres were poured into the bottom of the 20ml test tube, and purified water was added until the material was saturated with water. The glass test tube was tilted downwards, and the water that flowed out was absorbed with absorbent paper. The test tube was weighed. The saturated liquid absorption ratio was calculated as: (weight after absorption - 5) / 5.

[0033] 6. Weigh 5g of hydroxyapatite and 5g of the above-mentioned phosphorylated threonine composite microspheres, mix them, add 3g of water, and stir until a paste-like consistency is achieved. This is the bone adhesive, which begins to solidify after 6 minutes. The bond strength of the bone adhesive is tested to be 3.7MPa. The bond strength test method is as follows: In the bond strength test, select two bovine bones (100mm long, 25mm wide, and 1.6mm thick). While in a paste-like state, evenly apply the bone adhesive to one of the bovine bones to a thickness of 1mm, with a bonding surface 12.5mm long and 25mm wide. Fix the two bovine bones together using a universal clamp. Then, incubate the sample in PBS solution at 37°C for 72 hours before testing. Perform the bond strength test using a tensile testing machine with a crosshead speed of 1 mm / min. Test the sample until failure, and determine its bond strength based on the synthesized stress-strain curve. Test three times and take the average value.

[0034] The analysis and evaluation mainly focus on two aspects: particle physical properties and clinical applicability.

[0035] The physical properties of the granules were evaluated. Flowability was assessed with an angle of repose of 34°, indicating good flowability and allowing for better mixing of components during granulation. Stability was assessed with a moisture content of 4.3%, meeting the Chinese Pharmacopoeia's requirements for moisture control in solid dosage forms (≤5%), effectively preventing moisture absorption, clumping, or degradation during storage and ensuring better storage stability. A granulation ethanol concentration of 65% and a saturated liquid absorption ratio of 2.6 resulted in good porosity, allowing for better control of the granulation effect.

[0036] Clinical applicability evaluation, setting time and operability: The initial setting time of the bone adhesive is 6 minutes, which shortens the curing time while maintaining a clinically operable window to meet intraoperative shaping requirements. The bond strength is ≥2.0 MPa, meeting the tissue adhesion requirements in clinical practice.

[0037] In summary, this embodiment improves clinical operation efficiency by optimizing the coagulation time. Subsequent embodiments will be based on this, adjusting the content of phosphorylated amino acids, the selection of composite binders / liquid guiding agents, or process parameters (such as the ethanol concentration during granulation), or adjusting the proportion of carbonates to regulate pH, and comparing and analyzing their effects on flowability, coagulation time, and bonding strength.

[0038] Example 2: A phosphorylated tyrosine composite microsphere for use as a component of bone adhesive and its preparation process.

[0039] 1. Weigh 980g of phosphorylated tyrosine and 20g of polyvinylpyrrolidone, add 3000ml of 90% ethanol solution; stir magnetically at 60rpm for 1.5hrs, filter through a 200-mesh sieve; add 2000ml of 85% ethanol solution to the residue, stir magnetically at 50rpm for 1hr; spread the residue evenly in a dish, dry at 65℃ for 2hrs until it becomes powder, pass through a 100-mesh sieve, and collect the filtered material.

[0040] 2. Weigh 30g of hydroxyethyl cellulose that has passed through a 100-mesh sieve, 30g of sodium bicarbonate that has passed through a 100-mesh sieve, 20g of calcium citrate that has passed through a 100-mesh sieve, and 920g of the filtrate obtained in step 1, and put them into a three-dimensional mixer to mix them evenly to obtain a mixed powder.

[0041] 3. Granulation: Place the mixed powder in a wet granulator and add 60% ethanol solution at a volume / mass ratio (ml / g) of 50:100 to obtain wet granules. The granulation sieve is 50 mesh.

[0042] 4. Drying: Place the obtained wet granules in a forced-air drying oven and dry at 50℃ for 90 min to obtain dry granules;

[0043] 5. Granulation: Sieve the particles to obtain particles between 50 and 80 mesh, which are phosphorylated tyrosine composite microspheres.

[0044] 100g of the prepared phosphorylated tyrosine composite microspheres were tested for flowability using the fixed funnel method, with a repose angle of 35°. 5g of the prepared phosphorylated tyrosine composite microspheres were measured using a rapid moisture analyzer, with a particle moisture content of 4.5% and a saturated liquid absorption ratio of 2.7.

[0045] 6. Weigh 5g of tricalcium phosphate and 5g of the above-mentioned phosphorylated tyrosine composite microspheres, mix them, add 3g of water, and stir until a paste-like consistency is formed. This is the bone binder, which begins to solidify after 5 minutes. The bond strength of the bone binder is tested to be 3.6MPa.

[0046] Example 3: A phosphorylated serine composite microsphere for use as a component of bone adhesive and its preparation process.

[0047] 1. Weigh 960g of phosphorylated serine and 40g of sodium carboxymethyl starch, add 2000ml of 85% ethanol solution; stir magnetically at 80rpm for 1 hour, filter through a 200-mesh sieve; add 3000ml of 90% ethanol solution to the residue, stir magnetically at 60rpm for 1.5 hours. Spread the residue evenly in a dish, dry at 80℃ for 1 hour until it becomes powder, pass through a 100-mesh sieve, and collect the filter.

[0048] 2. Weigh 20g of sodium carboxymethyl cellulose that has passed through a 100-mesh sieve, 30g of sodium bicarbonate that has passed through a 100-mesh sieve, and 40g of calcium alginate that has passed through a 100-mesh sieve. Put them together with 910g of the filtered material obtained in step 1 into a three-dimensional mixer and mix them thoroughly to obtain a homogeneous powder.

[0049] 3. Granulation: Place the mixed powder in a wet granulator and add 60% ethanol solution at a volume / mass (ml / g) ratio of 55:100 to obtain wet granules. The granulation sieve is 50 mesh.

[0050] 4. Drying: Place the obtained wet granules in a forced-air drying oven and dry at 60℃ for 75 minutes to obtain dry granules;

[0051] 5. Granulation: Sieve the particles to obtain particles between 50 and 80 mesh, which are phosphorylated serine composite microspheres.

[0052] 50g of the prepared phosphorylated serine composite microspheres were tested using the fixed funnel method, and the angle of repose was 36°. 5g of the prepared phosphorylated serine composite microspheres were measured using a rapid moisture analyzer, and the particle moisture content was 4.8%, with a saturated liquid absorption ratio of 2.5.

[0053] 6. Weigh 5g of tricalcium phosphate and 5g of the above-mentioned phosphorylated serine composite microspheres, mix them, add 3g of water, and stir until a paste-like consistency is formed. This is the bone binder, which begins to solidify after 7 minutes. The bond strength of the bone binder is tested to be 3.4MPa.

[0054] Example 4: A method for rapidly dissolving phosphorylated threonine complex particles and its preparation

[0055] 1. Weigh 960g of phosphorylated threonine and 40g of sodium carboxymethyl starch, add 4000ml of 95% ethanol solution, stir magnetically at 60 rpm for 2 hours, and filter through a 200-mesh sieve; add 3000ml of 85% ethanol solution to the retentate, stir magnetically at 40 rpm for 1 hour. Spread the retentate evenly in a dish, dry at 60℃ for 2 hours until it becomes powder, pass through a 100-mesh sieve, and collect the filter.

[0056] 2. Weigh 20g of sodium carboxymethyl cellulose, 30g of sodium carbonate and 950g of the filter material obtained in step 1, crush and sieve them, and screen out the mixed powder that passes through a 100-mesh sieve.

[0057] 3. Granulation: Place the mixed powder in a wet granulator and add 60% ethanol solution at a volume / mass (ml / g) ratio of 40:100 to obtain wet granules. The granulation sieve is 50 mesh.

[0058] 4. Drying: Place the obtained wet granules in a forced-air drying oven and dry at 55℃ for 80 minutes to obtain dry granules;

[0059] 5. Granulation: Particles sieved to a mesh size of 50 to 80 are phosphorylated threonine composite microspheres. The angle of repose was 33° using the fixed funnel method; the moisture content was 4.1% measured using a rapid moisture meter, with a saturated liquid absorption ratio of 2.3.

[0060] 6. Pour the above-mentioned phosphorylated threonine composite microspheres into pure water using a spatula. The microspheres quickly absorb liquid on the water surface and sink to the bottom of the beaker without any white sticking. They gradually dissolve at the bottom of the beaker.

[0061] Example 5:

[0062] 1. Weigh 930g of phosphorylated threonine and 70g of croscarmellose sodium, and add 3000ml of 75% ethanol solution. Stir magnetically at 50rpm for 2 hours, then filter through a 200-mesh sieve. Add 2000ml of 80% ethanol solution to the residue, and stir magnetically at 50rpm for 1 hour. Filter through a 200-mesh sieve. Spread the residue evenly in a dish and dry at 50℃ for 3 hours until it becomes powder. Pass the powder through a 100-mesh sieve and collect the filtrate.

[0063] 2. Weigh 40g of hydroxyethyl cellulose, 40g of sodium bicarbonate, and 20g of calcium glycerophosphate that have passed through a 100-mesh sieve; put them together with 900g of the filtrate obtained in step 1 into a three-dimensional mixer and mix them thoroughly to obtain a homogeneous powder.

[0064] 3. Granulation: Place the mixed powder in a wet granulator and add 75% ethanol solution at a volume / mass (ml / g) ratio of 52 / 100 to obtain wet granules. The granulation sieve is 50 mesh.

[0065] 4. Drying: Place the obtained wet granules in a forced-air drying oven and dry at 56℃ for 90 min to obtain dry granules;

[0066] 5. Granulation: Sieve the particles to obtain those between 50 and 80 mesh; these are the phosphorylated threonine composite microspheres. The angle of repose was 33° using the fixed funnel method. The moisture content of the particles was measured to be 4.2% using a rapid moisture analyzer, with a saturated liquid absorption ratio of 2.4.

[0067] 6. Weigh 5g of hydroxyapatite and 5g of the above-mentioned phosphorylated threonine composite microspheres, mix them, add 3g of water, and stir until a paste-like consistency is formed. This is the bone binder, which begins to solidify after 6 minutes. The bond strength of the bone binder is tested to be 4.8MPa.

[0068] Example 6:

[0069] 1. Weigh 940g of phosphorylated threonine and 60g of croscarmellose sodium, and add 3000ml of 80% ethanol solution. Stir magnetically at 50rpm for 2 hours, then filter through a 200-mesh sieve. Add 2000ml of 80% ethanol solution to the residue, and stir magnetically at 50rpm for 1 hour. Filter through a 200-mesh sieve. Spread the residue evenly in a dish and dry at 50℃ for 3 hours until it becomes powder. Pass the powder through a 100-mesh sieve and collect the filter.

[0070] 2. Weigh 30g of hydroxyethyl cellulose, 20g of sodium bicarbonate, and 30g of calcium glycerophosphate that have passed through a 100-mesh sieve; put them together with 920g of the filtrate obtained in step 1 into a three-dimensional mixer and mix them thoroughly to obtain a homogeneous powder.

[0071] 3. Granulation: Place the mixed powder in a wet granulator and add 85% ethanol solution at a volume / mass (ml / g) ratio of 40 / 100 to obtain wet granules. The granulation sieve is 50 mesh.

[0072] 4. Drying: Place the obtained wet granules in a forced-air drying oven and dry at 60℃ for 90 minutes to obtain dry granules;

[0073] 5. Granulation: Sieve the particles to obtain those between 50 and 80 mesh; these are the phosphorylated threonine composite microspheres. The angle of repose was determined to be 36° using the fixed funnel method. The moisture content of the particles was measured to be 4.1% using a rapid moisture analyzer, with a saturated liquid absorption ratio of 2.8.

[0074] 6. Weigh 5g of hydroxyapatite and 5g of the above-mentioned phosphorylated threonine composite microspheres, mix them, add 3g of water, and stir until a paste-like consistency is formed. This is the bone binder, which begins to solidify after 8 minutes. The bond strength of the bone binder is tested to be 1.6MPa.

[0075] Example 7:

[0076] 1. Weigh 955g of phosphorylated threonine and 5g of croscarmellose sodium, and add 3000ml of 95% ethanol solution. Stir magnetically at 50rpm for 2 hours, then filter through a 200-mesh sieve. Add 2000ml of 80% ethanol solution to the residue, and stir magnetically at 50rpm for 1 hour. Filter through a 200-mesh sieve. Spread the residue evenly in a dish and dry at 50℃ for 3 hours until it becomes powder. Pass the powder through a 100-mesh sieve and collect the filtrate.

[0077] 2. Weigh 20g of hydroxyethyl cellulose that has passed through a 100-mesh sieve, 20g of sodium bicarbonate that has passed through a 100-mesh sieve, and 30g of calcium glycerophosphate that has passed through a 100-mesh sieve; put them together with 930g of the filtrate obtained in step 1 into a three-dimensional mixer and mix them thoroughly to obtain a homogeneous powder.

[0078] 3. Granulation: Place the mixed powder in a wet granulator and add 70% ethanol solution at a volume / mass (ml / g) ratio of 50 / 100 to obtain wet granules. The granulation sieve is 50 mesh.

[0079] 4. Drying: Place the obtained wet granules in a forced-air drying oven and dry at 65℃ for 60 minutes to obtain dry granules;

[0080] 5. Granulation: Sieve the particles to obtain those between 50 and 80 mesh; these are the phosphorylated threonine composite microspheres. The angle of repose is 35° using the fixed funnel method. A rapid moisture analyzer shows the particle moisture content to be 4.0%, with a saturated liquid absorption ratio of 2.6.

[0081] 6. Weigh 5g of hydroxyapatite and 5g of the above-mentioned phosphorylated threonine composite microspheres, mix them, add 3g of water, and stir until a paste-like consistency is formed. This is the bone binder, which begins to solidify after 7 minutes. The bond strength of the bone binder is tested to be 1.4MPa.

[0082] In summary, Example 4 primarily examined the solubilizing effect of phosphorylated amino acids. Since no inorganic materials were used, the saturated liquid absorption ratio of the prepared phosphorylated amino acid composite microspheres was only 2.3. Despite the low saturated liquid absorption ratio, it effectively promoted the dissolution of phosphorylated amino acids. In Example 6, the coagulation time of the bone adhesive was extended to 8 minutes, and the tested bond strength was 1.6 MPa, failing to meet the clinical bonding requirements (greater than 2 MPa). This was because an 85% ethanol concentration was used during granulation, resulting in loose particles and affecting the adhesive preparation effect. In Example 7, the coagulation time of the bone adhesive was extended to 7 minutes, and the tested bond strength was 1.4 MPa, also failing to meet the clinical bonding requirements (greater than 2 MPa). This was because the proportion of the cross-linked sodium carboxymethyl cellulose liquid-conducting agent was reduced, leading to loose particles and affecting the adhesive preparation effect. The above three examples did not meet the expectations of the invention, while the remaining examples met the expectations of the invention.

[0083] The phosphorylated amino acid composite microspheres prepared by this invention have excellent flowability (angle of repose ≤35°) and low hygroscopicity (moisture ≤5%), and good liquid absorption and conduction properties. When used to prepare bone adhesives, they can achieve rapid solidification (≤6 minutes) and bonding strength ≥2MPa, which can meet the clinical operation and bonding requirements of bone adhesives.

[0084] Summarizing Examples 1, 2, 3, and 5, the prepared phosphorylated amino acid composite microspheres contain phosphorylated amino acids, polymeric binders, liquid-conducting agents, pH adjusters, and divalent metal salts. When the mass ratio of (phosphorylated amino acids + liquid-conducting agent): polymeric binder: pH adjuster: divalent metal salt is (900-920):(20-40):(30-40):(20-40), and the mass ratio of phosphorylated amino acids to liquid-conducting agent is (930-980):(20-70), the prepared phosphorylated amino acid composite microspheres exhibit good repose angle, particle moisture content, and saturated liquid absorption ratio. Furthermore, the tested bonding strength of the bone adhesive formed by mixing with calcium phosphate compounds is also within a good range.

[0085] As can be summarized from Examples 1, 2, 3, and 5, the method for preparing phosphorylated amino acid composite microspheres includes:

[0086] 1) Weigh the phosphorylated amino acids and the liquid-conducting agent, add 75-95% ethanol solution, mix well, remove the liquid, add 80-90% ethanol solution, remove the liquid, dry, and obtain powder;

[0087] 2). Weigh out the polymer binder, pH adjuster, and divalent metal salt, and mix them with the powder obtained in step 1) to obtain a well-mixed powder;

[0088] 3) The mixed powder is added to a 60-75% ethanol solution at a volume / mass ratio of 45-55:100 (ml / g) for wet granulation;

[0089] 4) Drying to obtain dry granules;

[0090] 5) Sieve the particles to obtain particles between 50 and 80 mesh, which are phosphorylated amino acid composite microspheres.

[0091] The phosphorylated amino acid refers to phosphorylated threonine, phosphorylated tyrosine, phosphorylated serine, phosphorylated hydroxyproline, or any combination thereof.

[0092] The polymeric adhesive refers to sodium carboxymethyl cellulose, hydroxyethyl cellulose, or any combination thereof.

[0093] The liquid-conducting agent refers to sodium carboxymethyl starch (CMS-Na), cross-linked sodium carboxymethyl cellulose (CCMC-Na), polyvinylpyrrolidone, or any combination thereof.

[0094] The pH adjuster refers to sodium carbonate, sodium bicarbonate, or any combination thereof.

[0095] The divalent metal salts refer to calcium citrate, calcium carbonate, calcium alginate, calcium glycerophosphate, or any combination thereof.

Claims

1. Phosphorylated amino acid composite microspheres, characterized in that, The phosphorylated amino acid composite microspheres comprise phosphorylated amino acids, a polymeric binder, a liquid-conducting agent, a pH adjuster, and a divalent metal salt, wherein the mass ratio of (phosphorylated amino acid + liquid-conducting agent): polymeric binder: pH adjuster: divalent metal salt is (900-920):(20-40):(30-40):(20-40), and the mass ratio of phosphorylated amino acid: liquid-conducting agent is (930-980):(20-70). The polymeric adhesive refers to sodium carboxymethyl cellulose, hydroxyethyl cellulose, or any combination thereof; The liquid-conducting agent refers to sodium carboxymethyl starch, croscarmellose sodium, polyvinylpyrrolidone or any combination thereof; The pH adjuster refers to sodium carbonate, sodium bicarbonate, or any combination thereof; The divalent metal salts refer to calcium citrate, calcium carbonate, calcium alginate, calcium glycerophosphate, or any combination thereof; The preparation method of the phosphorylated amino acid composite microspheres includes: 1) Weigh the phosphorylated amino acids and the liquid-conducting agent, add 75-95% ethanol solution, mix well, remove the liquid, add 80-90% ethanol solution, remove the liquid, dry, and obtain powder; 2). Weigh out the polymer binder, pH adjuster, and divalent metal salt, and mix them with the powder obtained in step 1) to obtain a well-mixed powder; 3) The mixed powder is added to a 60-75% ethanol solution at a volume / mass ratio of (45-55) mL:100 g for wet granulation; 4) Drying to obtain dry granules; 5) Sieve the particles to obtain particles between 50 and 80 mesh, which are phosphorylated amino acid composite microspheres.

2. The phosphorylated amino acid composite microspheres according to claim 1, characterized in that, The phosphorylated amino acid refers to phosphorylated threonine, phosphorylated tyrosine, phosphorylated serine, phosphorylated hydroxyproline, or any combination thereof.

3. The application of the phosphorylated amino acid composite microspheres according to any one of claims 1-2 in the preparation of bone adhesives.

4. A bone adhesive, characterized in that, The bone adhesive is composed of phosphorylated amino acid composite microspheres as described in any one of claims 1-2 and a calcium phosphate compound.

5. The bone adhesive according to claim 4, characterized in that, The calcium phosphate compound refers to tricalcium phosphate or hydroxyapatite.