Biodegradable radioactive microsphere as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of radioactive microspheres / radiopharmaceuticals, and particularly relates to biodegradable radioactive microspheres and a preparation method and application thereof. The preparation method comprises the steps of precursor preparation, two-phase solution preparation, micro-droplet preparation, microsphere curing, microsphere irradiation and the like. The preparation yield of the microspheres can be greater than 100mg / h, the particle size deviation of the microspheres can be controlled within + / -10%, and the breakage rate of the microspheres can be controlled below 10%.

Description

Technical Field

[0001] This invention belongs to the field of radioactive microspheres / radiopharmaceutical technology, specifically relating to a biodegradable radioactive microsphere, its preparation method, and its application. Background Technology

[0002] Radioactive microspheres are mainly used in transarterial radioembolization (TARE) therapy for liver cancer. Clinically, it is an effective method for treating unresectable liver cancer and metastatic liver cancer. It has also shown certain therapeutic effects on colorectal cancer, brain tumors, ovarian cancer and other diseases. Compared with traditional glass or resin-based microspheres, degradable radioactive microspheres have the following core advantages: (1) They have better biocompatibility and can effectively reduce immune rejection in TARE therapy; (2) They have biodegradable function. After treatment, the microspheres gradually degrade to free up embolization sites, allowing for multiple treatments on the same patient; (3) They are easy to mix with other effective therapeutic or imaging components, which is beneficial to increase the therapeutic and imaging effects of the microspheres. However, there are some problems to be solved in the preparation of degradable microspheres: (1) It is difficult to unify the uniformity of microsphere particle size and the yield of microspheres. The emulsion solvent evaporation method has a large yield and can be easily scaled up to achieve mass production. However, the microspheres prepared by this method have uneven particle size and need to be sieved to obtain microspheres with a suitable particle size. The microspheres prepared by the droplet microfluidic method have uniform particle size and the deviation can be controlled within 10%. However, conventional single-channel chips have low production yield due to flow rate limits. (2) Degradable polymers generally have very low glass transition temperatures, while the temperature of neutron activation process in reactors is usually above 60°C, resulting in a high microsphere breakage rate during irradiation. Summary of the Invention

[0003] The purpose of this invention is to solve problems such as uneven particle size, low yield, and irradiation damage during the preparation of biodegradable microspheres. The invention aims to accurately control the particle size uniformity and irradiation damage rate of the microspheres during the preparation process to ensure the effectiveness of microsphere therapy.

[0004] Therefore, a first aspect of the present invention provides a method for preparing biodegradable radioactive microspheres, the method comprising:

[0005] (1) Prepare a lipophilic crystal by mixing an inorganic metal compound with a ligand, dissolve the lipophilic crystal with a polymer matrix material in an organic solvent, add a functional material to prepare an organic phase solution, and optionally filter it;

[0006] (2) Dissolve the emulsifier in water to prepare an aqueous solution;

[0007] (3) In a multi-channel droplet microfluidic device, connect the sampler and adjust the flow rate of the two-phase solution to mix them and generate droplets;

[0008] (4) Allow the organic solvent to evaporate, optionally wash with water, then clean with alkaline solution or buffer solution, dry after cleaning, and load the dried microspheres into the irradiation target tube.

[0009] (5) Adjust the water temperature in the irradiation channel to control the temperature to 15-40℃, and place the irradiation target tube in the irradiation device of the pool reactor for irradiation.

[0010] The aforementioned preparation method precisely manipulates the dispersion behavior of droplets using a droplet microfluidic device, ensuring that the shearing action of the two-phase droplets occurs at a constant flow rate. This controls the uniformity of droplet dispersion, reducing droplet size deviation, and ultimately producing microspheres with a size deviation within 10%. The method also scales up the microsphere preparation process using a multi-channel microfluidic device, employing multiple droplet generation channels in parallel to increase microsphere production, overcoming the low yield limitation of single-channel microfluidic devices. When irradiating in the water channels of a pool reactor, the irradiation temperature is typically between 50 and 60°C. However, the glass transition temperature of biodegradable materials is usually very low; for example, the glass transition temperature of polylactic acid is 60°C. Therefore, it is difficult to guarantee a high breakage rate for microspheres irradiated using conventional processes. This method precisely controls the irradiation temperature in the pool reactor using an irradiation device, stabilizing it between 15 and 40°C, which significantly reduces the irradiation breakage rate of biodegradable microspheres.

[0011] In the above-mentioned method for preparing biodegradable radioactive microspheres, the mass ratio of the compound to the ligand in step (1) can be selected as needed.

[0012] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, in step (1), the inorganic metal is one or more of holmium (Ho), phosphorus (P), rhenium (Re), lutetium (Lu), and yttrium (Y). Holmium (Ho): can be used for radioactive labeling (e.g., 166 Ho has potential applications in tumor radioembolization therapy and radiation-induced synovectomy. Phosphorus (P): Although not radioactive itself, it can act as a carrier element (e.g., phosphate ligands) or bind with radionuclides (e.g.,... 32 P) binds to rhenium and is used in radiotherapy or imaging. Rhenium (Re): commonly used as... 99m Tc analogues are used in the development of radioactive diagnostic probes; their stable isotopes can also serve as models for studying radioactive behavior. Lutetium (Lu): an important source of therapeutic radionuclides, such as... 177 Lu (Lu) is widely used in targeted radiotherapy for neuroendocrine tumors and prostate cancer. Yttrium (Y): One of the most important medical radioactive metals, such as... 90 Y is used for radioembolization therapy of liver cancer.

[0013] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, in step (1), the compound is in the form of one or more of oxides, chlorides, sulfates, and nitrates. Oxides: stable but usually need to be converted into soluble salts for complexation. Chlorides: highly water-soluble, readily form complexes with ligands, and are commonly used precursors. Nitrates: readily soluble in water, but may introduce nitrate ions, requiring subsequent purification. Sulfates: rarely used directly, but can be used as intermediates. Soluble metal salts (such as chlorides and nitrates) are preferred, as they facilitate rapid complexation with ligands to form lipophilic organometallic compounds, which then dissolve in the organic phase.

[0014] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, in step (1), the ligand includes one or more of oleylamine, long-chain fatty acids, phospholipids, alkyl phosphates, and acetylacetone. Long-chain fatty acids (such as stearic acid and oleic acid): commonly used for coordination of rare earth metals to improve lipophilicity, but may have slightly poor biocompatibility. Phospholipids (such as phosphatidylcholine and DSPC): have good biocompatibility and can be used in biomimetic membrane structures or liposome-compatible systems, while also assisting in metal complexation. Alkyl phosphates (such as tributyl phosphate, TBP): have excellent extraction and complexation capabilities for lanthanides / actinides, improving the retention of metals in the organic phase. Acetylacetone: a classic β-diketone ligand that forms stable chelates with various metals, possessing both lipophilicity and thermal stability.

[0015] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, the polymer matrix material in step (1) includes one or more of poly(L-lactic acid) (PLLA), poly(lactic-co-glycolic acid) (PLGA), polyglycolic acid (PGA), polycaprolactone (PCL), lactic acid-caprolactone copolymer (PLCL), and polyethylene glycol (PEG). PLLA / PGA / PLGA: The most classic biodegradable medical polymers, whose degradation products are lactic acid / glycolic acid, are harmless to the human body and have been widely used in drug sustained-release and embolization microspheres. PCL: Degrades at a slower rate, suitable for scenarios requiring long-term release. PLCL: Has better flexibility and a moderate degradation time, suitable for improving the mechanical properties of microspheres. PEG (polyethylene glycol): A hydrophilic polymer that can improve the hydrophilicity of the microsphere surface, delay protein adsorption, and prolong in vivo circulation time.

[0016] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, step (1) includes one or more of the following functional materials: contrast agent, chemotherapeutic drug, immunomodulator, targeted drug, and photothermal material. Contrast agent: such as iodized oil, gold nanoparticles, superparamagnetic iron oxide (SPIO), near-infrared dyes (Cy5.5, ICG), used for image-guided precision treatment. Chemotherapy drug: such as doxorubicin (DOX), cisplatin, paclitaxel, to achieve synergistic radiotherapy and chemotherapy. Immunotherapeutic agent: such as PD-1 / PD-L1 inhibitors, cytokines (IL-2, IFN-γ), used to activate the immune response. Targeted drug: such as antibody-drug conjugates (ADC), folic acid, RGD peptide, to improve tumor targeting. Photothermal material: such as gold nanorods, copper sulfide, black phosphorus, used in combination with photothermal therapy (PTT) and radiotherapy.

[0017] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, the emulsifier in step (2) is polyvinyl alcohol and / or gelatin. Polyvinyl alcohol (PVA): the most commonly used polymeric emulsifier, safe, non-toxic, and with good film-forming properties, widely used in microsphere preparation. Gelatin: naturally sourced, with excellent biocompatibility, but may trigger an immune response, suitable for specific biological scenarios.

[0018] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, in step (1), the concentration of the organic phase solution is 5 wt% to 30 wt%, and more preferably, the concentration of the organic phase solution is 10 wt% to 20 wt%. In step (2), the concentration of the aqueous phase solution is 0.5 wt% to 5 wt%, and more preferably, the concentration of the aqueous phase solution is 1 wt% to 2 wt%.

[0019] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, in step (3), the flow rate ratio of the organic phase to the aqueous phase is 1:(1-100), and more preferably, the flow rate ratio of the organic phase to the aqueous phase is 1:(10-25). Flow rate ratio control: determines the droplet size and monodispersity; 1:(10-25) is the efficient range, which can produce microspheres with uniform particle size.

[0020] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, the number of channels in the multi-channel droplet microfluidic device in step (3) is 5 to 100, and more preferably, the number of channels in the multi-channel droplet microfluidic device is 20 to 50. Multi-channel design: 20 to 50 channels can significantly increase yield while ensuring uniformity, making it suitable for large-scale production.

[0021] As a preferred embodiment, in the above-mentioned method for preparing biodegradable radioactive microspheres, in step (4), the alkaline solution is 0.01–1 M NaOH; the buffer solution is NaH₂PO₄ buffer or PBS buffer. The purpose of the alkaline treatment is to remove surface PVA residue, improve the hydrophilicity of the microspheres, convert the metal complexes of the microspheres into metal hydroxides, and increase their stability. Buffer selection: PBS (pH 7.4) simulates the physiological environment, while NaH₂PO₄ buffer can be used for specific pH adjustment needs.

[0022] In the above-mentioned method for preparing biodegradable radioactive microspheres, in step (5), the temperature is controlled at 15-40℃ to: avoid polymer softening / melting or abnormal radionuclide decay caused by high temperature; and maintain the integrity of the physical structure of the microspheres.

[0023] A second aspect of the present invention provides a biodegradable radioactive microsphere, which is prepared by the above-described preparation method.

[0024] According to the present invention, the median particle size of the radioactive microspheres is between 20 and 50 μm; the particle size deviation of the radioactive microspheres is ±10%; and the half-degradation period of the radioactive microspheres is 1 to 24 months.

[0025] According to the present invention, the irradiation damage rate of the radioactive microspheres is not higher than 10%.

[0026] A third aspect of the invention provides an application of biodegradable radioactive microspheres in the preparation of radioembolization drugs or devices. This radioembolization drug or device is primarily used for radioembolization therapy of liver cancer, pancreatic cancer, etc.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects:

[0028] Degradable radioactive microspheres have better biocompatibility and biodegradability. However, particle size uniformity and yield cannot be effectively controlled simultaneously during the preparation process. During irradiation, the microspheres are easily damaged because the degradable polymers are not resistant to high temperatures.

[0029] This invention provides a method for preparing biodegradable radioactive microspheres. This method can produce cold microspheres with uniform particle size in large quantities. After neutron activation by isothermal irradiation in a reactor, multifunctional radioactive microspheres can be obtained. The irradiation time is typically 1 hour to 7 days, and the irradiation neutron flux is 1 × 10⁻⁶. 12 ~1×10 14 n·cm -2 s -1Specifically, the microsphere production rate can exceed 100 mg / h, the microsphere particle size deviation can be controlled within ±10%, and the microsphere breakage rate can be controlled below 10%.

[0030] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Detailed Implementation

[0031] The following description provides numerous specific details to offer a more thorough understanding of the technical solutions provided by this invention. However, it will be apparent to those skilled in the art that the technical solutions provided by this invention can be implemented without one or more of these details.

[0032] In this embodiment of the invention, the raw materials are commercially available, and the irradiation device used is an existing pool reactor irradiation device.

[0033] Example 1

[0034] 10g of holmium chloride hexahydrate was dissolved in water. 180g of acetylacetone was dissolved in 1L of water. Ammonia was added to adjust the pH to 8.5. The dissolved holmium chloride hexahydrate was then added to a beaker. After standing for 24–48 hours until crystals formed, the mixture was filtered, washed three times, and dried to obtain holmium acetylacetone crystals. Holmium acetylacetone was mixed with polylactic-co-glycolic acid (PLGA) at a 1:1 mass ratio. 5% (w / w) of doxorubicin liposomes was added, and 10 times the total mass of chloroform was added to dissolve the mixture, preparing an organic phase solution. The organic phase solution was filtered through a 0.8μm filter membrane and then loaded into the organic phase injection cell. 10.2g of polyvinyl alcohol 1788 was dissolved in hot water at 90℃. After cooling to room temperature, the volume was adjusted to 1000mL and loaded into the aqueous phase injection cell. Connect the sample inlet cell to the 20-channel microfluidic reactor using a pipeline. Adjust the flow rate ratio of the organic phase to the aqueous phase to 1:10. Turn on the pump to allow the liquid in the sample inlet cell to enter the 20-channel microfluidic reactor for reaction. The organic phase forms droplets under the constant shear of the aqueous phase, and the droplets are collected in a collection bottle. Stir at 45℃ for 24 hours to allow the organic solvent to evaporate. Filter and collect the microspheres, wash them three times, and dry them with nitrogen at a flow rate of 10 L / min. Add 0.1 M NaH2PO4 solution to the dried microspheres, shake for 1 hour, remove and filter, and collect the microspheres for vacuum drying at 40℃. Weigh an appropriate amount of microspheres and load them into the inner target tube. Adjust the temperature of the irradiation channel to 25℃ using a pore water circulation irradiation device. Load the target tube into the irradiation device and irradiate it into the active area. The neutron flux of the irradiated microspheres is 1~10×10⁻⁶. 12 n. cm -2 ·s -1After irradiation for 6 hours, the microspheres were removed, yielding activated holmium-166 biodegradable microspheres. The particle size of the obtained radioactive microspheres was 37±3 μm; the half-degradation period of the radioactive microspheres was 180 days, and the irradiation damage rate of the radioactive microspheres was 5.15%.

[0035] Example 2

[0036] 10g of anhydrous yttrium chloride was dissolved in water, and the insoluble matter was removed by filtration. 180g of acetylacetone was dissolved in 1L of water, and ammonia was added to adjust the pH to 8.5. The dissolved yttrium chloride solution was added to a beaker and left to stand for 24–48 hours until crystals formed. After filtration and washing three times, the solution was dried to obtain yttrium acetylacetone crystals. Yttrium acetylacetone was mixed with polycaprolactone (PCL) at a mass ratio of 1:1, and 2wt% sorafenib liposomes were added. Then, 10 times the total mass of dichloromethane was added to dissolve the mixture, preparing an organic phase solution. The organic phase solution was filtered through a 0.8μm filter membrane and then loaded into the organic phase injection cell. 10.2g of gelatin was dissolved in hot water at 90℃, cooled to room temperature, and then loaded into the aqueous phase injection cell. Connect the sample inlet cell to the 30-channel microfluidic reactor using a pipeline. Adjust the flow rate ratio of the organic phase to the aqueous phase to 1:20. Turn on the pump to allow the liquid in the sample inlet cell to enter the 30-channel microfluidic reactor for reaction. The organic phase forms droplets under the constant shear of the aqueous phase, and the droplets are collected in a collection bottle. Stir at 45℃ for 24 hours to allow the organic solvent to evaporate. Filter and collect the microspheres, wash them three times, and dry them with nitrogen at a flow rate of 10 L / min. Add 0.1 M NaH2PO4 solution to the dried microspheres, shake for 1 hour, remove and filter, and collect the microspheres for vacuum drying at 40℃. Weigh an appropriate amount of microspheres and load them into the inner target tube. Adjust the temperature of the irradiation channel to 25℃ using a pore water circulation irradiation device. Load the target tube into the irradiation device and irradiate it into the active area. The neutron flux of the irradiated microspheres is 1~10×10⁻⁶. 12 n. cm -2 ·s -1 After irradiation for 7 days, the samples were removed to obtain activated yttrium-90 biodegradable microspheres. The particle size of the obtained radioactive microspheres was 35±2 μm; the half-degradation period of the radioactive microspheres was 320 days, and the irradiation damage rate of the radioactive microspheres was 7.50%.

[0037] Example 3

[0038] 1g of lutetium chloride was weighed and dissolved in ethylene glycol along with 5g of oleylamine. The mixture was reacted in a high-pressure reactor at 180℃ for 24 hours until crystals formed. The resulting crystals were centrifuged, washed, and dried to obtain fat-soluble crystals. The crystals were mixed with lactic acid-caprolactone copolymer (PLCL) at a mass ratio of 1:2 and dissolved in chloroform. 1wt% of the chemotherapy drug doxorubicin was added to prepare an organic phase solution. A 0.5% gelatin solution was prepared as the aqueous phase solution. The reaction was carried out in a 50-channel microfluidic reactor with an organic phase to aqueous phase flow rate ratio of 1:5. The generated microdroplets were collected and continuously stirred for 24 hours to allow the organic solvent to evaporate. After the microspheres solidified, they were washed three times, dried under nitrogen for 24 hours, and then vacuum-dried at 40℃ for 24 hours. The resulting microspheres were loaded into an inner target tube and irradiated in a reactor at a temperature of 15℃. The neutron flux of the irradiated microspheres was 1–10 × 10⁻⁶. 12 n. cm -2 ·s -1 After irradiation for 7 days, the samples were removed to obtain activated Lu-177 microspheres. The particle size of the obtained radioactive microspheres was 40±3 μm; the half-degradation period of the radioactive microspheres was 320 days, and the irradiation damage rate of the radioactive microspheres was 7.50%.

[0039] Comparative Example 1

[0040] The difference from Example 1 is that the temperature of the irradiation channel in the pool reactor is not adjusted by the channel water circulation irradiation device, and the temperature is 64°C.

[0041] After irradiation, a large number of microspheres were damaged, with a damage rate of over 60%. The microsphere fragments damaged after irradiation affected the microsphere particle size, which was 3–40 μm.

[0042] Comparative Example 2

[0043] The difference from Example 2 is that the temperature of the irradiation channel in the pool reactor is not adjusted by the channel water circulation irradiation device, and the temperature is 51°C.

[0044] After irradiation, some microspheres were damaged and others agglomerated, with a damage rate of 20%. The microsphere particle size ranged from 10 to 80 μm.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing biodegradable radioactive microspheres, characterized in that, The preparation method includes: (1) Prepare a lipophilic crystal by mixing an inorganic metal compound with a ligand, mix the lipophilic crystal with a polymer matrix material, add a functional material, dissolve it in an organic solvent to prepare an organic phase solution, and optionally filter it. (2) Dissolve the emulsifier in water to prepare an aqueous solution; (3) In a multi-channel droplet microfluidic device, connect the sampler and adjust the flow rate of the two-phase solution to mix them and generate droplets; (4) Allow the organic solvent to evaporate, optionally wash with water, then clean with alkaline solution or buffer solution, dry after cleaning, and load the dried microspheres into the irradiation target tube. (5) Adjust the water temperature in the irradiation channel to control the temperature to 15-40℃, and place the irradiation target tube in the irradiation device of the pool reactor for irradiation.

2. The method for preparing biodegradable radioactive microspheres according to claim 1, characterized in that, In step (1), the inorganic metal is one or more of holmium, phosphorus, rhenium, lutetium, and yttrium; In step (1), the compound is in the form of one or more of oxides, chlorides, sulfates, and nitrates; In step (1), the ligand includes one or more of oleylamine, long-chain fatty acids, phospholipids, alkyl phosphates, and acetylacetone; In step (1), the polymer matrix material includes one or more of PLLA, PLGA, PGA, PCL, PLCL, and PEG; In step (1), the functional material includes one or more of the following: contrast agent, chemotherapeutic drug, immunomodulator, targeted drug, and photothermal material; In step (2), the emulsifier is polyvinyl alcohol and / or gelatin.

3. The method for preparing biodegradable radioactive microspheres according to claim 1, characterized in that, In step (1), the concentration of the organic phase solution is 5 wt% to 30 wt%. In step (2), the concentration of the aqueous solution is 0.5 wt% to 5 wt%. In step (3), the flow rate ratio of the organic phase to the aqueous phase is 1:(1~100); In step (3), the number of channels in the multichannel droplet microfluidic device is 5 to 100.

4. The method for preparing biodegradable radioactive microspheres according to claim 3, characterized in that, In step (1), the concentration of the organic phase solution is 10 wt% to 20 wt%. In step (2), the concentration of the aqueous solution is 1 wt% to 2 wt%. In step (3), the flow rate ratio of the organic phase to the aqueous phase is 1:(10-25); In step (3), the number of channels in the multichannel droplet microfluidic device is 20 to 50.

5. The method for preparing biodegradable radioactive microspheres according to claim 1, characterized in that, In step (4), the alkaline solution is 0.01–1 M NaOH; In step (4), the buffer solution is NaH2PO4 buffer or PBS buffer.

6. The method for preparing biodegradable radioactive microspheres according to claim 1, characterized in that, In step (5), the irradiation time is 1 hour to 7 days, and the irradiation neutron flux is 1 × 10⁻⁶. 12 ~1×10 14 n·cm -2 s -1 .

7. A biodegradable radioactive microsphere, characterized in that, The radioactive microspheres are prepared by the preparation method according to any one of claims 1-6.

8. The biodegradable radioactive microspheres according to claim 7, characterized in that, The median particle size of the radioactive microspheres is between 20 and 50 μm; The particle size deviation of the radioactive microspheres is ±10%; The radioactive microspheres have a half-degradation period of 1 to 24 months.

9. The biodegradable radioactive microspheres according to claim 7, characterized in that, The irradiation damage rate of the radioactive microspheres is no higher than 10%.

10. The application of a biodegradable radioactive microsphere, characterized in that, The application is in the preparation of radioembolization drugs or radioembolization devices.