RU2806148C1 - Method for producing radiolabelled calcium carbonate particles using deferoxamine as chelating agent - Google Patents

Abstract

FIELD: biotechnology.

SUBSTANCE: present invention relates to a method for producing calcium carbonate particles with a radioisotope included in the structure, during which a solution is prepared with human serum albumin (HSA) and the chelating agent deferoxamine (DFO), after which the resulting solution is radiolabelled with an isotope and the resulting radiolabelled biomolecules are included in the structure of calcium carbonate, characterized in that, before being added to the solution, human serum albumin weighing 20 g is purified by mixing with 200 mcl of deionized water and 100 mcl of a saturated solution of diethylenetriaminepentaacetic acid, followed by incubation with stirring and heating to 37°C for 30 min, after which human serum albumin is purified from diethylenetriaminepentaacetic acid on a 0.5 ml regenerated cellulose ultrafiltration cell for 20 min at 10 rpm and washed 3 times with a 0.1 M aqueous solution of 4-( 2-hydroxyethyl)-1-piperazinethanesulfonic acid with a pH of 8.5, and then human serum albumin purified from impurities is diluted with a 0.1 M solution of 4-(2-hydroxyethyl)-1-piperazinethanesulfonic acid to a volume of 1.8 ml and 3 mg of chelating agent DFO is added in 75 mcl of 99.5% ethanol and 30 mcl of 2 M aqueous solution of Na₂CO₃, and the modification is carried out at 37°C for 30 minutes and at 4°C for 24 hours, and the resulting modified DFO-HSA solution in an ultrafiltration cell made of regenerated cellulose with a cell of 0.5 ml, after which the purified DFO-HSA solution is diluted with 0.05 M aqueous solutions of NH₄Ac with pH 7.5 to the concentration 3 mg/ml, after which the resulting solution is labelled with the radioisotope ⁸⁹Zr, after which the resulting radiolabelled biomolecules are included in the 6 structure of calcium carbonate particles by adding the resulting solution to an aqueous solution of calcium carbonate, stirring at 1000 rpm for 20 minutes until a precipitate forms and washed 1 time with a 95% ethanol solution and 2-3 times with deionized water, after which the surface of the resulting calcium carbonate particles with a radioisotope included in the structure is successively coated with 1 ml of an aqueous solution of human serum albumin at a concentration of 6 mg/ml, followed by washing with 1 ml water and centrifugation, after which the procedure, from the moment the surface of the resulting calcium carbonate particles with the radioisotope included in the structure is covered with solutions, is repeated 6-7 times until a stable polymer shell is formed, including at least 7 layers.

EFFECT: making radiolabelled calcium carbonate particles suitable for delivering a combination of biologically active substances and radioisotopes to the site of interest.

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Description

The present invention relates to the production of biologically inert and biodegradable nano- and microstructures of a hybrid composition (inorganic and polymer nano- and microstructures), including chelating compounds and substances that ensure the retention of radioisotopes and their decay products, and can be used in radionuclide therapy and cancer imaging diseases.

The most current developments in the field of creating radiopharmacological drugs use molecular vectors, such as monoclonal antibodies, small molecule peptides; nanoparticles of organic or inorganic composition, liposomes and microspheres [Peltek OO, Muslimov AR, Zyuzin MV, Timin AS. Correction to: Current outlook on radionuclide delivery systems: from design consideration to translation into clinics. J Nanobiotechnology. 2020 Jan 2;18(1):2. doi: 10.1186/s12951-019-0558-z] as an agent delivering a therapeutic/diagnostic radionuclide to the site of interest.

Molecular vectors can be substances of a protein nature: antibodies, peptides (analogs of somatostatin, bombesin) or small molecules (urea derivatives - inhibitors of Glutamate carboxypeptidase II) that interact with antigens and receptors on the surface of tumor cells, or imitate substances involved in tissue and cellular metabolism [Vorontsova M.S. Studying the effectiveness of modular nanotransporters for radionuclide therapy of malignant tumors (experimental study). 2019]. The present invention relates to hybrid biodegradable nano- and microstructures intended for use in radioisotope therapy and diagnostics of physiological and pathological processes.

The following examples in the literature are examples of relevant prior art publications, which should in no way be construed as being within the scope of the present invention. For example, Ibritumomab tiuxetan is an anti-CD20 monoclonal antibody conjugated to radioactive Yttrium-90 [

WO 2004054615, publ. 07/01/2004]. The composition [Ac-225]-p-SCN-Bn-DOTA/HuM195K, which is a monoclonal antibody conjugated with actinium, is also described [WO 2011011592, 01/27/2011]. Also described is a protocol for labeling recombinant humanized mini-antibodies specific to the cancer-associated antigen HER2/neu with a diagnostic γ-emitting radioisotope or short-lived α-emitting radioisotopes [RU 2537175, publ. 12/27/2014].

The disadvantage of using this type of targeting molecules is the features associated with the method of attaching the radioactive label. The use of chelating agents whose chemical binding energy with the radionuclide is less than the recoil energy generated after the first decay; make it impossible to effectively use monoclonal antibodies for the delivery of a number of radionuclides capable of a decay cascade, since daughter isotopes fly out of the structure of the chelating agent of the monoclonal antibody and have a toxic effect on cells and tissues outside the focus of interest.

The concept of a molecular vector also includes peptides that are ligands for cellular receptors. They are successfully used for receptor imaging and targeted radionuclide therapy and have a number of advantages over monoclonal antibodies. The low molecular weight of the compounds in question allows them to be quickly removed from non-target tissues; in addition, due to their size, the peptides penetrate more easily into organs, demonstrating better pharmacokinetics, and are also predominantly non-immunogenic. As an example for the described compounds, one can specify a mixture of iodide and alpha-fetoprotein [RU 2404812, publ. November 27, 2010]. The composition of 18FcMet-binding peptides is also described [WO 2012022676, publ. 02.23.2012] and new methods of adding a radioisotope to polypeptides [RU 2537175, publ. 12/27/2014].

Among the disadvantages of these compounds, it is necessary to note their low potential resistance to destruction during metabolism [Richter S. and Wuest F. 18F-Labeled Peptides: The Future Is Bright. Molecules, 2014, 19, 12, 20536-20556.]. At the moment, there are drugs based on lutetium-177 [Benešová M., Schafer M., Bauder-Wust U., et al. Preclinical evaluation of a tailor-made DOTA-conjugated PSMA inhibitor with optimized linker moiety for imaging and endoradiotherapy of prostate cancer. The Journal of Nuclear Medicine, 2015, 56, 914-920]; [Weineisen M., Schottelius M., Simecek J., et al. ⁶⁸ Ga- and ^l77 Lu-labeled PSMA I&T: optimization of a PSMA-targeted theranostic concept and first proof-of-concept human studies. The Journal of Nuclear Medicine, 2015, 56, 1169-1176].

In addition, the use of chelating agents whose chemical binding energy with the radionuclide is less than the recoil energy generated after the first decay; make it impossible to effectively use this type of molecular targeting vectors for the delivery of radionuclides capable of decay cascades, since daughter isotopes fly out of the structure of the chelating agent and have a toxic effect on cells and tissues outside the focus of interest. Radiopharmacological drugs based on bombesin, an amphibian peptide that is a homologue of gastrin-releasing peptide in animals, are also being developed. However, further research is needed to examine the correlation between data from preclinical studies on in vivo cancer models and the potential effectiveness of drugs under development in clinical trials [Ferreira C, Fuscaldi L. L., Townsend D. M., Rubello D., Barros A. L. B. Radiolabeled bombesin derivatives for preclinical oncological imaging. Biomedicine & Pharmacotherapy, 2017, 87, 58-72].

Liposomal delivery systems, which are phospholipid vesicles with one or more bilipid layers, are actively used for the encapsulation and delivery of various biologically active substances, including radionuclides. The sizes of these carriers can vary widely: from <100 nanometers to >1000 nanometers, depending on the chosen synthesis method. In the case of nanosized liposomes, their important feature is the tendency to accumulate in tumor sites, providing passive delivery of the drug [Greish, K. Enhanced permeability and retention (EPR) effect of anticancer nanomedicine drug targeting. Methods in Molecular Biology, 2010, 624, 25-37]. In addition, targeting can be achieved by modifying the surface of liposomes with various molecular vectors, however, these modification methods are often labor-intensive and difficult to reproduce [Sercombe L., Veerati T., Moheimani F., Wu SY, Sood AK, and Hua S. Advances and Challenges of Liposome Assisted Drug Delivery. Frontiers in Pharmacology, 2015, 6, 286]. There are approaches that allow the incorporation of radioactive isotopes into liposomal systems. Lipids in the inner bilipid layer can be modified with chelating agents and radiolabeling occurs during the synthesis step [Kim J., Pandya DN, Lee W., Park j. W., Kim YJ, Kwak W., et al. Vivid tumor imaging utilizing liposome-carried bimodal radiotracer. ACS Medicinal Chemistry Letters. 2015, 5, 390-394]. Also, the radionuclide can be included in the already formed liposome structure through the use of lipophilic chelating agents (BMEDA, HMPAO), which facilitate penetration through the lipid bilayer [Goins B., Bao A., Phillips W. T. Techniques for Loading Technetium-99m and Rheniuml86 /188 Radionuclides into Preformed Liposomes for Diagnostic Imaging and Radionuclide Therapy. Methods in Molecular Biology, 2017, 1522, 155-178]. The main disadvantage of liposomal systems is the instability of the liposomes themselves inside the body; most of the drugs being developed only reach the preclinical testing phase. However, some radiopharmaceuticals based on liposomal targeted delivery systems are being studied in clinical trials. One of these drugs includes Rhenium-188 ( ¹⁸⁸ Re) as both a therapeutic and diagnostic isotope associated with BMEDA, acting as a chelating agent [Schmid G. Nanoparticles: From Theory to Application. 2nd ed: John Wiley & sons, 2011].

The next type of carriers for the delivery of radionuclides are nanoparticles and microparticles of organic, inorganic composition and complex composition, which include the invention described in this application. Nanoparticles consist of various types of materials, the size of which varies, and they themselves exhibit properties different from the properties of the substances from which they are made [Yang M., Cheng K., Qi S., Liu H., Jiang Y., Jiang H. , et al. Affibody modified and radiolabeled gold-iron oxide heteronanostructures for tumor PET, optical and MR imaging. Biomaterials, 2013, 34, 2796-2806]. Nanoparticles can be distinguished whose cores consist of synthetic and natural polymers, metals, and non-metals. An example of metal nanoparticles are the previously described composite carriers of radionuclides [RU 2013132610, 01/20/2015]. Among inorganic nanoparticles of non-metallic nature, nanosized (<10 nm) particles of silicon oxide containing the fluorescent dye Cy5 and the diagnostic isotope iodine-124 should be distinguished. These particles were not toxic in a small group of patients with metastatic melanoma [Phillips E., Penate-Medina O., Zanzonico R. V. Clinical translation of an ultrasmall inorganic optical-PET imaging nanoparticle probe. Science Translational Medicine, 2014, 6, 260, 149]. There are also a number of developments on the use of microspheres for targeted delivery of radionuclides. They mean spherical structures from 20 to 100 microns, into the cavity of which a radionuclide is placed; at the moment, only two drugs are registered and approved for clinical use: TheraSphere and SIR-Sphere [Allison C.Yttrium-90 microspheres (TheraSphere and SIR-Spheres) for the treatment of unresectable hepatocellular carcinoma. Issues in Emerging Health Technologies, 2007, 102, 1-6].

Both drugs contain Yttrium-90 ( ⁹⁰ Y) as a radionuclide and consist of an indestructible shell that prevents the release of yttrium. TheraSphere are spheres whose shell is made of glass, and SIR-Sphere is made of resin. Their size ranges from 20 to 30 microns for TheraSphere and from 20 to 60 microns for SIR-SPHERE.

Of the organic carriers of radionuclides, it is worth noting the previously described polymer nanostructures labeled with rhenium-188, obtained by suspending organic polymer particles in a solution containing water-soluble salts of tin (II) and Re-188 [US 2008219923, 09/11/2008], polymer nanoparticles chelating radioactive isotopes and having a surface modified with specific molecules targeting the Glutamate carboxypeptidase II receptor [WO 2020188318, 09.24.2020], as well as particles having a hydrodynamic diameter of 8-40 nm and forming a chelate complex, the central part of which contains a cross-linked polymer framework structure and/or branched polymer frame structure of monomer units [WO 2015144891, 10/01/2015]. These carriers can be of a size that allows them to be used for local and systemic radionuclide therapy, can be modified with targeting ligands described earlier and, depending on the chosen chelating agent, allow the inclusion of various radionuclides in their structure, including alpha emitters, however, The disadvantage of this class of carriers is the inability to retain daughter isotopes that are detached from the chelating agent in the nanoparticle. These breakdown products have a toxic effect on cells and tissues outside the focus of interest, thereby significantly limiting the breadth of use of these carriers in real clinical practice.

The closest analogue to the claimed invention is the previously described technology for producing microparticles of calcium carbonate (CaCO ₃ ), radioactively labeled with ²²⁴ Ra [WO 2017005648, 01/12/2017], which is beyond the scope of the present invention, the advantage of which is the use of a porous inorganic matrix as a core coated polymer biodegradable layers forming a core-shell structure. The biologically active substance and/or radionuclide are included in the structure of the core, the size and shape of the pores of which can be specified by changing the synthesis conditions, and can also be included in the composition of the polymer layers in pure form or as part of complex compounds. The use of the technology of the claimed invention makes it possible to achieve monodisperse and polydisperse fractions of the resulting carriers in a wide range; in addition, these carriers have aggregative stability and biocompatibility. The time and nature of degradation of the resulting nano- and microstructures can be set at the synthesis stage. Also, by modifying the surface of carriers with molecular vectors, it becomes possible to use them for targeted delivery, and the inclusion of various organic and inorganic agents makes it possible to remotely and controlled activation of degradation of carriers using various internal and external chemical stimuli (including, but not limited to pH, temperature ) and electromagnetic (including, but not limited to ultrasound, magnetic field) stimuli.

The disadvantages of the closest analogue include the inability to deliver a combination of biologically active substances and radioisotopes to the site of interest to implement an integrated approach in the diagnosis and correction of various physiological and pathological processes in vitro, ex vivo and in vivo. This is due to the absence of the stage of creating a “core-shell” structure in the technology of the analogue in question. The process of forming a stable polymer shell makes it possible to modify carriers and use them both for loading biologically active substances and radioisotopes. Thanks to this technology, the present invention is applicable for an integrated approach to diagnosis and therapy.

The technical problem is the need to develop a method for producing radiolabeled carbonate particles that is devoid of the above disadvantages.

The technical result consists in providing the possibility of obtaining radiolabeled calcium carbonate particles suitable for delivering a combination of biologically active substances and radioisotopes to the site of interest.

The technical result is achieved by the fact that in the method for producing calcium carbonate particles with a radioisotope included in the structure, during which a solution is prepared with human serum albumin and the chelating agent DFO, after which the resulting solution is radiolabeled with an isotope and the resulting radiolabeled biomolecules are included in the structure of calcium carbonate, according to the invention Before adding to the solution, human serum albumin weighing 20 g is purified by mixing with 200 μl of deionized water and 100 μl of a saturated solution of diethylenetriaminepentaacetic acid, followed by incubation with stirring and heating to 37 ° C for 30 minutes, after which the human serum albumin is purified from diethylenetriaminepentaacetic acid acid on an ultrafiltration cell made of regenerated cellulose with a cell of 0.5 ml for 20 min at 10 rpm and washed 3 times with 0.1 M aqueous buffer solutions with a solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid with pH 8.5 , and then the human serum albumin purified from impurities is diluted with a 0.1 M solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid to a volume of 1.8 ml and 3 mg of the chelating agent DFO is added, in 75 μl of 99.5% ethanol and 30 μl of a 2 M aqueous solution Na ₂ CO ₃ , and the modification is carried out at 37°C for 30 minutes and at 4°C for 24 hours, and the resulting modified solution of DFO-HSA on an ultrafiltration cell made of regenerated cellulose with a cell of 0.5 ml, after which the purified solution DFO-HSA is diluted with 0.05 M aqueous solutions of NH ₄ Ac with pH 7.5 to a concentration of 3 mg/ml, after which the resulting solution is labeled with the radioisotope ⁸⁹ Zr, after which the resulting radiolabeled biomolecules are included in the structure of calcium carbonate particles by adding the resulting solution to aqueous calcium carbonate solution, stirring at 1000 rpm for 30 s until a precipitate forms and washed 1 time with a 95% ethanol solution and 2-3 times with deionized water, after which the surface of the resulting calcium carbonate particles with a radioisotope included in the structure is successively covered with 1 ml of aqueous solutions of human serum albumin at a concentration of 6 mg/ml and DC at a concentration of 4 mg/ml, followed by washing with 1 ml water and centrifugation, after which the procedure from the moment the surface of the resulting calcium carbonate particles with the radioisotope included in the structure is covered with solutions is repeated 6-7 times until formation of a stable polymer shell, including at least 7 layers.

The particles obtained within the framework of the claimed product can be used to implement an integrated approach in the diagnosis and correction of various physiological and pathological processes in vivo to ensure the ability to deliver a combination of biologically active substances and radioisotopes to the site of interest. For oncological diseases that manifest themselves in the form of malignant solid formations (carcinoma and sarcoma), the most effective approach to therapy is brachytherapy. Brachytherapy is a high-precision contact method of radiation therapy using a radioactive source that is introduced into the focus of a malignant tumor, destroying it from the inside.

The use of the claimed invention as a radioactive source makes it possible to concentrate the entire therapeutic potential directly inside the formation, which leads to the maximum effect of therapy with minimal impact on surrounding healthy tissue. There are several clinically relevant examples:

1) Soft tissue sarcoma. The leading role in the treatment of this disease is given to surgical intervention, but in 37-57% of cases a residual tumor remains. The introduction of irradiation of the tumor bed into therapy by the method of direct introduction of radiation sources based on the proposed invention helps to increase the effectiveness of therapy;

2) Prostate carcinoma. Routine treatments (surgery, external beam radiation and hormonal therapy) for prostate cancer are characterized by many side effects (intraoperative blood loss, erectile dysfunction, risk of damage to surrounding tissues, development of severe liver dysfunction), which significantly affect the patient’s quality of life after therapy. The use of the proposed invention in brachytherapy in this case is the most gentle approach that does not tend to cause complications;

3) Cervical carcinoma. Today, cervical cancer is a disease that can be completely cured by supplementing external beam radiation with brachytherapy. The introduction of radiation sources in the form of calcium carbonate is possible both directly into the tumor and into the uterine cavity, depending on the location of the malignant formation

The use of calcium carbonate-based carriers instead of classic plastic catheters or metal needles for brachytherapy offers the advantage of its controlled biodegradation.

The essence of the claimed invention is the development of technology for creating micro- and submicron carriers of therapeutic and diagnostic radionuclides for biomedical use. The developed carriers are hybrid spherical particles and have a “core-shell” structure, where the core is a porous matrix of calcium carbonate (CaCO ₃ ) containing a radioisotope conjugate, and the shell consists of biodegradable polymer layers. Using the described technology, it is possible to vary the size of the resulting particles in a wide range (100-3000 nm) and include various alpha, beta and gamma emitters in the structure of the resulting carriers for the needs of radiation therapy and visualization of physiological and pathological processes in vivo using single-photon emission computed tomography methods (SPECT) / positron emission tomography (PET).

To synthesize the cores of hybrid particles (CaCO) ₃ , the method of co-precipitation of aqueous solutions of inorganic salts (CaCl ₂ , Na ₂ CO ₃ ) in the presence of radiolabeled biomolecules or radioisotopes in individual form is used, followed by layer-by-layer formation of a biodegradable shell on the surface of the resulting particles.

In the case of using radionuclides, which are characterized by a cascade two-stage decay, the properties of the carriers obtained using the declared technology make it possible to retain at least 50-70% of the daughter nuclei and decay products of a given isotope.

The developed surface of the particles, containing reactive groups, allows the carriers to be modified with various molecular ligands (antibodies, peptides, DARPin, etc.) for targeted delivery of radioisotopes to specific tissues and cells.

The particles obtained by the claimed method were tested on several models of tumor diseases, which demonstrated the possibility of the developed drug influencing pathological processes of various localizations. The effectiveness of systemic administration was studied in a model of metastatic lung cancer. Combination therapy with calcium carbonate particles with the ¹⁷⁷ Lu isotope included in the structure and an antitumor drug demonstrated a specific accumulation of particles in the focus of interest (lungs), and also proved an increase in the effectiveness of combination therapy compared to monotherapy. The ability to ensure delivery and retention at the site of interest when administered locally was proven in the B16-F10 melanoma model. Local administration of a drug loaded with a ²²⁵ Ac alpha emitter into a solid formation showed the effectiveness of this type of therapy due to the retention of therapeutic activity in the tumor volume.

The inventive method is carried out as follows.

Human serum albumin weighing 20 g is purified by mixing with 200 μl of deionized water and 100 μl of saturated diethylenetriaminepentaacetic acid solution, followed by incubation with stirring and heating at 37°C for 30 minutes. Next, human serum albumin is purified from diethylenetriaminepentaacetic acid on an ultrafiltration cell made of regenerated cellulose with a 0.5 ml cell for 20 minutes at 10 rpm and washed 3 times with a 0.1 M aqueous buffer solution with a solution of 4-(2-hydroxyethyl)- 1-piperazineethanesulfonic acid with pH 8.5. Then human serum albumin, purified from impurities, is diluted with a 0.1 M solution of 4-(2-hydroxyethyl)-1-piperazinethanesulfonic acid to a volume of 1.8 ml and 3 mg of the chelating agent DFO is added, in 75 μl of 99.5% ethanol and 30 μl of a 2 M aqueous solution of Na ₂ CO ₃ . Moreover, the modification is carried out at 37°C for 30 minutes and at 4°C for 24 hours. The resulting modified DFO-HSA solution is placed on an ultrafiltration cell made of regenerated cellulose with a 0.5 ml cell, after which the purified DFO-HSA solution is diluted with 0.05 M aqueous solutions of NH ₄ Ac with pH 7.5 to a concentration of 3 mg/ml. Next, the resulting solution is labeled with the radioisotope ⁸⁹ Zr. Then the resulting radiolabeled biomolecules are incorporated into the structure of calcium carbonate particles by adding the resulting solution to an aqueous solution of calcium carbonate, stirring at 1000 rpm for 30 s until a precipitate forms. Afterwards, they are washed 1 time with a 95% ethanol solution and 2-3 times with deionized water, and then the surface of the resulting calcium carbonate particles with a radioisotope included in the structure is successively coated with 1 ml of aqueous solutions of human serum albumin at a concentration of 6 mg/ml and DC at a concentration of 4 mg/ml. ml followed by washing with 1 ml water and centrifugation. Then, from the moment the surface of the resulting calcium carbonate particles with the radioisotope included in the structure is covered with solutions, the procedure is repeated 6-7 times until a stable polymer shell is formed, including at least 7 layers.

The claimed invention is illustrated by examples.

Example 1. Purification of HSA from impurities

Before modification, 20 mg of HSA (200 mg/mL solution; 100 μL) was mixed with 200 μL of deionized water and 100 μL of saturated diethylenetriaminepentaacetic acid (DTPA) solution. The mixture was incubated with stirring and heating to 37°C for 30 min. HSA was purified from DTPA in an ultrafiltration cell with a regenerated cellulose membrane (0.5 ml cell, 20 min, 10.0 rpm) and washed 3 times with a 0.1 M aqueous solution of HEPES buffer (pH 8.5).

Example 2. Modification of HSA with the chelating agent 1-(4-isothiocyanatophenyl)-3-[6,17-dihydroxy-7,10,18,21-tetraoxo-27-(N-acetylhydroxyamino)-6,11,17,22- tetraashhepraeicosine] thiourea (DFO).

HSA purified from impurities was diluted with a 0.1 M aqueous solution of HEPES, pH 8.5, to a volume of 1.8 ml, and 3 mg of the chelating agent DFO was added in 75 μL of ethanol (99.5%) and 30 μL of a 2 M aqueous solution of Na ₂ CO ₃ . The modification was carried out at 37°C for 30 minutes and at 4°C for 24 hours. The modified DFO-HSA was purified in an ultrafiltration cell with a regenerated cellulose membrane (0.5 ml cell, 20 min, 10.0 rpm) and washed 3 times with a 0.05 M aqueous solution of _NH4Ac (pH 7.5). Purified DFO-HSA was diluted with a 0.05 M aqueous solution of _NH4Ac (pH 7.5) to a concentration of 3 mg/ml.

Example 3. Radiolabeling of DFO-HSA with the ⁸⁹ Zr isotope.

100 μl of a DOTA-HSA solution (3 mg/ml solution, 300 μg) in a 0.05 M aqueous solution of NH ₄ Ac (pH 7.5) was mixed with 500 μl of a 0.5 M aqueous solution of HEPES (pH 7.2) and 25 μl of a [ ⁸⁹ Zr]ZrCl solution ₄ in 1 M hydrochloric acid. The mixture was incubated at 37°C for 30 min. Modified [ ⁸⁹ Zr]Zr-DFO-HSA was used without additional purification to form calcium carbonate (CaCO ₃ ) particles of micron (1-2 μm) and/or submicron (300-600 nm) sizes.

Example 4. Incorporation of radiolabeled biomolecules ([ ⁸⁹ Zr]Zr-DFO-HSA) into the structure of micron-sized (1-2 μm) calcium carbonate (CaCO ₃ ) particles

1 ml of a 1 M aqueous solution of CaCl ₂ was mixed with 1 ml of a 1 M aqueous solution of Na ₂ CO ₃ and 0.625 ml of [ ⁸⁹ Zr]Zr-DFO-HSA. The reaction mixture was vigorously stirred at 1000 rpm for 30 s at room temperature until a precipitate formed. The resulting sediment was centrifuged (4000 g) for 1-2 minutes. and washed several times (2-3 times). Then, the surface of the resulting CaCO ₃ particles with the radioisotope incorporated into the structure was successively coated with aqueous solutions of HSA (6 mg/ml) and DC (4 mg/ml) in a volume of 1 ml and incubated with stirring in a thermal shaker (10 min, 900 rpm). followed by washing twice with water (1 ml) and centrifugation (1 min, 400g). This procedure was repeated several times (6-7 times) until a stable polymer shell was formed (at least 7 layers). The radiochemical yield was wt( ⁸⁹ Zr) ~ 70%.

Example 5. Incorporation of radiolabeled biomolecules ([ ⁸⁹ Zr]Zr-DFO-HSA) into the structure of calcium carbonate (CaCO ₃ ) particles of submicron (300-600 nm) sizes

5 ml of 0.33 M CaCl ₂ solution (ethylene glycol/water = 5:1) was mixed with 0.965 ml of 0.33 M Na ₂ CO ₃ solution (ethylene glycol/water = 5:1) and 0.625 ml of [ ⁸⁹ Zr]Zr-DFO-HSA. The reaction mixture was vigorously stirred at 1000 rpm for 20 min at room temperature until a precipitate formed. The resulting precipitate was centrifuged (10,000 rpm) for 1-2 minutes, washed once with a 95% ethanol solution and 2-3 times with deionized water. Then, the surface of the resulting CaCO ₃ particles with the radioisotope incorporated into the structure was successively coated with aqueous solutions of HSA (6 mg/ml) and DC (4 mg/ml) in a volume of 1 ml and incubated with stirring in a thermal shaker (10 min, 900 rpm). followed by washing twice with water (1 ml) and centrifugation (1 min, 10,000 rpm). This procedure was repeated several times (6-7 times) until a stable polymer shell was formed (at least 7 layers). The radiochemical yield was wt( ⁸⁹ Zr) ~ 70%.

Claims (1)

A method for producing calcium carbonate particles with a radioisotope included in the structure, during which a solution is prepared with human serum albumin (HSA) and the chelating agent deferoxamine (DFO), after which the resulting solution is radiolabeled with an isotope and the resulting radiolabeled biomolecules are included in the structure of calcium carbonate, characterized in that that before adding to the solution, human serum albumin weighing 20 g is purified by mixing with 200 μl of deionized water and 100 μl of a saturated solution of diethylenetriaminepentaacetic acid, followed by incubation with stirring and heating to 37 ° C for 30 minutes, after which the human serum albumin is purified from diethylenetriaminepentaacetic acid on a 0.5 ml regenerated cellulose ultrafiltration cell for 20 min at 10 rpm and washed 3 times with a 0.1 M aqueous solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer pH 8, 5, and then the human serum albumin purified from impurities is diluted with a 0.1 M solution of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid to a volume of 1.8 ml and 3 mg of the chelating agent DFO is added in 75 μl of 99.5% ethanol and 30 μl of a 2 M aqueous solution of Na ₂ CO ₃ , and the modification is carried out at 37 ° C for 30 minutes and at 4 ° C for 24 hours, and the resulting modified solution of DFO-HSA on an ultrafiltration cell made of regenerated cellulose with cell 0, 5 ml, after which the purified DFO-HSA solution is diluted with 0.05 M aqueous solutions of NH ₄ Ac with pH 7.5 to a concentration of 3 mg/ml, after which the resulting solution is labeled with the radioisotope ⁸⁹ Zr, after which the resulting radiolabeled biomolecules are included in 6 structure of calcium carbonate particles by adding the resulting solution to an aqueous solution of calcium carbonate, stirring at 1000 rpm for 20 minutes until a precipitate forms and washed 1 time with a 95% ethanol solution and 2-3 times with deionized water, after which the surface of the resulting calcium carbonate particles with a radioisotope included in the structure, sequentially cover with 1 ml of an aqueous solution of human serum albumin at a concentration of 6 mg/ml, followed by washing with 1 ml of water and centrifugation, after which the procedure is repeated 6-7 from the moment the surface of the resulting calcium carbonate particles with the radioisotope included in the structure is covered with solutions times until a stable polymer shell is formed, including at least 7 layers.