Use of a copt nanoparticle in treating akI transitioning to CKD

Abstract

The application provides application of COPT nanoparticles in treatment of AKI transformation into CKD. The COPT nanoparticles are of core-shell structure, the core is tricobalt tetraoxide, the tricobalt tetraoxide is wrapped with polyethylene glycol, the polyethylene glycol is covalently connected with triphenylphosphine, and the polyethylene glycol and triphenylphosphine form a shell. The COPT of the application can improve acute kidney injury and its transformation into chronic kidney disease, and the COPT is targeted to proximal tubular epithelial cells in the kidney, induces mitochondrial autophagy by up-regulating BNIP3 gene expression, and then maintains mitochondrial homeostasis, thereby playing a kidney protection role.

Description

Technical Field

[0001] This invention relates to the field of cobalt-containing compound technology, and in particular to the application of COPT nanoparticles in the treatment of AKI conversion to CKD. Background Technology

[0002] Acute kidney injury (AKI) is a clinical syndrome caused by a rapid decline in renal function, characterized by a decreased glomerular filtration rate (eGFR), accompanied by nitrogenous product retention and electrolyte and acid-base imbalances. It is a critical clinical condition with a high morbidity and mortality rate. Statistics show that the incidence of AKI in hospitalized patients is 10-15%, reaching as high as 50% in intensive care units, with approximately 41.2% of AKI patients still experiencing renal function failure upon discharge. Currently, there are no specific drugs for treating AKI. Furthermore, the misdiagnosis rate of AKI in my country is as high as 74.2%. Therefore, exploring novel diagnostic and treatment strategies for AKI is of significant clinical importance.

[0003] Studies have shown that renal tubular cells are rich in mitochondria, and mitochondrial damage is a typical feature of the development of acute kidney injury (AKI). Mitochondrial autophagy impairment is a key link in mitochondrial damage. On the one hand, increased oxidative stress and reactive oxygen species (ROS) can induce mitochondrial damage, leading to apoptosis; conversely, damaged mitochondria release large amounts of ROS, creating a vicious cycle. On the other hand, selectively clearing damaged mitochondria helps to remove ROS and maintain mitochondrial homeostasis, while nephrotoxins can inhibit mitochondrial autophagy and induce mitochondrial dysfunction. In this case, the accumulated damaged mitochondria in the kidney cannot be cleared, further aggravating mitochondrial damage and ultimately inducing renal tubular cell apoptosis. It is noteworthy that AKI primarily affects the proximal tubules of the kidney, and previous studies have shown that increased ROS production and apoptosis also occur more frequently in the proximal tubules. Therefore, mitochondrial damage and impaired mitochondrial autophagy are typical characteristics and important links in AKI. Therefore, inducing mitochondrial autophagy to alleviate kidney damage is a potential therapeutic strategy for AKI. However, while current ROS scavengers (such as N-acetyl-L-cysteine) and autophagy inducers (such as rapamycin) can scavenge ROS and induce autophagy, respectively, their broad range of action and tendency to produce side effects limit their clinical application. Therefore, there is currently a lack of kidney-targeted autophagy inducers for the treatment of AKI.

[0004] AKI frequently increases the risk of chronic kidney disease (CKD) and end-stage renal disease, often requiring hemodialysis and kidney transplantation to replace kidney function, placing a significant burden on patients and society. Therefore, timely intervention in the transition from AKI to CKD is crucial for protecting kidney function. Elucidating the molecular mechanisms of AKI-to-CKD transition has been a hot topic in kidney research, and increasing research has revealed the key role of mitochondrial dysfunction in this process. Mitochondrial dysfunction mainly consists of downregulation of mitochondrial biosynthesis, altered mitochondrial biodynamics, mitophagy, altered mitochondrial bioenergetics, and mitochondrial-endoplasmic reticulum crosstalk. However, the specific molecular mechanisms of these processes still require further investigation. Significant mitochondrial dysfunction exists in the transition from AKI to CKD, leading to persistent maladaptive repair after AKI and the development of CKD.

[0005] In recent years, although novel nanomaterials have shown a trend of widespread application in the fields of oncology and bacteria, they have not yet received sufficient attention in the field of kidney disease. Studies have shown that cobalt tetroxide (CO) possesses natural peroxidase activity and is widely used in industries such as lithium-ion battery material synthesis and ceramics, but its application in the biological field is rarely reported. Previous studies have confirmed that CO analogue iron tetroxide nanoparticles can reduce blood cell apoptosis mediated by the antitumor drug doxorubicin by inducing autophagy. Recent studies have shown that CO also has strong stability and can exert a protective effect by scavenging ROS, effectively inhibiting *Escherichia coli* and *Staphylococcus aureus*. Therefore, CO has significant clinical application prospects in the field of disease treatment. The paper "Cobalt oxide nanoparticle-synergized protein degradation and phototherapy for enhanced anticancer therapeutics" discloses the synergistic effects of cobalt oxide nanoparticles (Co3O4NPs) as autophagy regulators, chemosensitizers, and photosensitizers. Through protein degradation pathways and photothermal therapy, it enhances in vitro and in vivo anticancer treatments. The paper also points out that cobalt oxide nanoparticles can induce autolysomnography and lysosomal dysfunction by inhibiting lysosomal proteolytic activity and reducing intracellular ATP levels. However, to date, no research reports have been found on COPT (cobalt oxide nanoparticles) for the treatment of AKI (acute kilotons).

[0006] BNIP3 and NIX are autophagy regulators located on the outer mitochondrial membrane. Under hypoxic conditions, they are activated by hypoxia-inducible factor-1 and forkhead box transcription factor O, thereby inducing the clearance of damaged mitochondria through autophagy (Esteban-Martinez L, Boya P. BNIP3L / NIX-dependent mitophagy regulates cell differentiation via metabolic reporgramming. Autophagy, 2018, 14(5):915-917.). In addition, studies have confirmed that BNIP3-mediated mitophagy activation plays a key role in mitochondrial quality control and renal tubular cell protection during AKI (Tang C, et al. Activation of BNIP3-mediated mitophagy protects against renal ischemia-reperfusion injury. Cell Death Dis, 2019, 10(9):677.). Renal ischemic preconditioning is an effective way to delay renal tubular damage and renal interstitial fibrosis after AKI, and FUNDC1-mediated mitochondrial mitosis has been shown to be positively correlated with the renal protective effect of ischemic preconditioning after AKI (Wang J, et al. Fundc1-dependent mitophagy is obligatory to ischemic preconditioning-conferred renoprotection in ischemic AKI via suppression of Drp1-mediated mitochondrial fission. Redox Biol, 2020, 30:101415.). Therefore, autophagy, as a biological phenomenon widely present in organisms, presents a challenge in targeting and regulating this process to treat kidney diseases due to its dual nature. In the development and progression of AKI, mitophagy may play a positive role in maintaining mitochondrial function, but currently there are no specific and effective mitophagy activators that act on the kidney. Therefore, further exploration of the molecular mechanisms of mitophagy and the identification of its regulatory factors are urgent problems to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides an application of COPT nanoparticles in the treatment of AKI transforming into CKD, which provides an effective target for repairing mitochondrial dysfunction in acute kidney injury.

[0008] In one aspect, the present invention provides COPT nanoparticles, wherein the COPT nanoparticles have a core-shell structure, the core is cobalt tetroxide, the surface of the cobalt tetroxide is coated with polyethylene glycol, the polyethylene glycol is covalently linked with triphenylphosphine, and the polyethylene glycol and triphenylphosphine form a shell.

[0009] Furthermore, the COPT nanoparticles have a nanoparticle size of 27 nm and a Zeta point of 19.4 ± 2.01 mV.

[0010] In another aspect, the present invention provides a method for preparing COPT nanoparticles, comprising the following steps:

[0011] S1: Using divalent cobalt salt and polyethylene glycol as raw materials, under the action of oxidant and alkali, cobalt oxide encapsulated in polyethylene glycol is obtained;

[0012] S2: Add an activator to activate polyethylene glycol to obtain activated polyethylene glycol-encapsulated cobalt oxide;

[0013] S3: Add TPP and activated polyethylene glycol to undergo a coupling reaction to obtain COPT nanoparticles.

[0014] Further, in step S1, the divalent cobalt salt is cobalt acetate; the oxidant is hydrogen peroxide; and the alkali is ammonia.

[0015] Furthermore, step S1 includes one or more of the following features:

[0016] (1) The mass ratio of the divalent cobalt salt to polyethylene glycol is 3.75:1;

[0017] (2) The divalent cobalt salt is added in two parts. The ratio of the first addition of divalent cobalt salt to the second addition of divalent cobalt salt is 2:1. The first reaction time is 10 min and the temperature is 80℃.

[0018] The second reaction lasted 12 hours and was carried out at a temperature of 60°C.

[0019] Furthermore, step S2 includes one or more of the following features:

[0020] (1) The mass ratio of activator to polyethylene glycol is 2:5;

[0021] (2) The activators are EDC and Sulfo-NHS, and the mass ratio of EDC to Sulfo-NHS is 1:1.

[0022] (3) The activation time is 12 hours and the temperature is room temperature.

[0023] Furthermore, in step S3, the mass ratio of TPP to polyethylene glycol is 119:1, the reaction time is 12 hours, and the reaction temperature is room temperature.

[0024] In another aspect, the present invention provides the application of COPT nanoparticles in the preparation of a drug for treating acute kidney injury and its transformation into chronic kidney disease.

[0025] In another aspect, the present invention provides the use of cobalt oxide in the preparation of medicaments for treating acute kidney injury and its progression to chronic kidney disease.

[0026] Furthermore, the cobalt oxide is cobalt tetroxide.

[0027] The technical principle of this invention is as follows: The inventors discovered through experiments that linking CO with polyethylene glycol (PEG), which improves biocompatibility, and triphenylphosphine (TPP) groups, which target mitochondria, and reconstructing it into COPT nanoparticles, can improve acute kidney injury (AKI) and its conversion to chronic kidney disease (CKD). Further mechanistic studies revealed that COPT nanoparticles target and localize to proximal tubular epithelial cells of the kidney, inducing mitophagy by upregulating BNIP3 gene expression to clear damaged mitochondria, thereby maintaining mitochondrial homeostasis and improving acute kidney injury and its transformation to chronic kidney disease.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The COPT nanoparticles of this invention are novel COPT nanoparticles that can improve the conversion of AKI to CKD.

[0030] (1) The COPT nanoparticles provided by this invention can target and locate the proximal tubular epithelial cells of the kidney, and maintain mitochondrial homeostasis by upregulating the gene expression of BNIP3 and inducing mitochondrial autophagy, thereby reducing mitochondrial damage, thus alleviating acute kidney injury and delaying its progression to chronic kidney disease, providing a novel potential treatment strategy for the clinical treatment of ischemic acute kidney injury.

[0031] (2) The present invention synthesizes a novel COPT nanoparticle that can specifically target damaged kidneys and thus has potential diagnostic value.

[0032] (3) The COPT nanoparticles of the present invention have good biosafety: through toxicity test evaluation, after normal C57BL6 / J mice were intravenously administered 25mg / kg for 28 days, the main tissues and organs were taken for pathological sections, and serum samples were taken to test liver and kidney function and blood routine. No obvious toxic side effects were observed. Furthermore, the COPT nanoparticles did not affect the cell activity of renal tubular epithelial cells when incubated. Attached Figure Description

[0033] Figure 1The diagram shows the synthesis route and characteristic identification of COPT nanoparticles in Example 1 of this invention. In this diagram, a is the synthesis flowchart of COPT nanoparticles, b is the Zeta potential of the COPT nanomaterials, c and d are electron micrographs of COPT and their nanoparticle sizes, e is the DLS hydration size of COPT, f is the XPS valence of Co, g is the effect of different concentrations of COPT incubation for 48 hours on the activity of HK2 cells, h is the hemolytic properties of different concentrations of COPT, and water is used as a positive control. **P<0.01, ***P<0.001.

[0034] Figure 2 The images show the targeting effect of COPT nanoparticles in Example 2 of this invention. Image a shows fluorescence images of the main organs (heart, liver, spleen, lung, kidney, and intestine) of a control group and AKI mice after tail vein injection of 5 mg / kg COPT linked to Cy5. Image b shows fluorescence images of the kidneys of AKI mice after tail vein injection of 5 mg / kg COPT at different times. Image c shows fluorescence images of kidney tissue from AKI mice after tail vein injection of 5 mg / kg COPT, captured using a laser confocal microscope. Image d shows fluorescence images of primary renal tubular epithelial cells incubated with FITC-linked COPT, captured using a Mito-Tracker microscope. **P<0.01, ***P<0.001.

[0035] Figure 3 Figures show the effects of COPT nanoparticles on improving AKI and the conversion of AKI to CKD in mice in Examples 3 and 4 of this invention. Figure a shows AKI mice induced by tail vein administration of Sham and ischemia-reperfusion, respectively, with control and 5 mg / kg COPT administered. HE staining and PAS staining were used to assess renal tubular damage. Figures b and c show the serum creatinine and blood urea nitrogen levels of the mice in Figure a, respectively, detected using the kit. Figures d and e show the expression of Kim1 and Ngal mRNA in the kidney tissue of the mice in Figure a, respectively, detected by qPCR. Figures f and g show the degree of renal fibrosis in CKD mouse models induced by Sham, 30 min ischemia-reperfusion, and 35 min ischemia-reperfusion, respectively, with control and 5 mg / kg COPT administered via tail vein administration. HE staining and Masson staining were used to assess the degree of renal fibrosis. Figure h shows the protein expression levels of renal fibrosis markers (Fibronectin and α-SMA) in the kidney tissue of the mice in Figure f, detected by Western blot. ns: no statistically significant difference, ***P<0.001.

[0036] Figure 4Figure 5 shows the effect of COPT nanoparticles inducing mitophagy by inducing BNIP3 in Example 5 of this invention. a and b show the GO enrichment analysis and KEGG pathway classification results of RNA sequencing from primary renal tubular epithelial cells of AKI mice treated with control and COPT, respectively. c shows the RNA sequencing heatmap analysis of Figure a. d shows the expression levels of mitophagy-related proteins in HK2 cells treated with different concentrations of COPT by Western blot. e shows the expression levels of mitophagy-related proteins in HK2 cells treated with normoxic and hypoxia-reoxygenation (HR) models after treatment with control and COPT, respectively. f shows the BNIP3 protein expression levels in Sham and AKI mice after treatment with control and COPT, respectively. g shows the reversal effect of siRNA knockdown of BNIP3 expression in HK2 cells treated with HR model on COPT-induced mitophagy protein reversal. h shows the reversal effect of siRNA knockdown of BNIP3 expression in HK2 cells treated with HR model on COPT-inhibited apoptosis. ns: No statistically significant difference, *P<0.05, **P<0.01, ***P<0.001.

[0037] Figure 5 The following is a diagram showing the biosafety evaluation of COPT nanoparticles in Example 6 of this invention. Figure a shows the results of injecting different doses of COPT (control, 1 mg / kg, 5 mg / kg or 25 mg / kg) into normal C57BL / 6J mice via the tail vein. HE staining showed no significant damage to the major organs (heart, liver, spleen, lung, kidney and intestine) of the mice. Figure b shows the results of blood routine and liver and kidney function tests on the serum of the mice in Figure a.

[0038] Figure 6 A schematic diagram illustrating how COPT nanoparticles improve the conversion of AKI to CKD. Detailed Implementation

[0039] The technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] Example 1: Preparation of COPT Nanoparticles

[0041] Dissolve 0.125 g of cobalt acetate in 20 ml of deionized water, add 5 ml of 0.01 g / ml mPEG-NH2, and react at 80 °C for 10 minutes; then add 1 ml of NH3·H2O and 60 μl of H2O2 and react for 15 minutes; then add 0.0625 g of cobalt acetate and 10 ml of deionized water and react at 60 °C overnight; centrifuge at 10,000 rpm for 15 minutes, wash, and dissolve in 5 ml of deionized water; add 2 mg of EDC·HCl and 2 mg of Sulfo-NHS and react for 12 hours, then add 10 mg / mL of TPP and continue reacting for 12 hours; centrifuge at 10,000 rpm for 10 minutes, wash, and freeze-dry to obtain COPT nanoparticles.

[0042] like Figure 1 As shown in ah, Figure 1 a is the synthesis route diagram of COPT nanoparticles; from Figure 1 b shows that after TPP modification, the Zeta potential of the COPT nanomaterial is 19.4 ± 2.01 mV; transmission electron microscopy reveals that the COPT nanomaterial is spherical. Figure 1 c), the nanoparticle size is 27 nm ( Figure 1 d). The hydrated particle size of COPT detected by DLS is approximately 55.8 nm. Figure 1 e). XPS analysis revealed that Co exhibits both +2 and +3 oxidation states, indicating the successful synthesis of COPT containing Co3O4. Figure 1 f). The effect of different concentrations of COPT incubation for 48 hours on the viability of HK2 cells was detected using the CCK-8 assay. It was found that COPT had no significant cytotoxicity at concentrations not exceeding 100 μg / ml. Figure 1 g). Furthermore, hemolytic characterization experiments indicate that COPT concentrations below 100 μg / ml do not cause hemolysis. Figure 1 h). The above experiments successfully identified the physicochemical properties of COPT nanomaterials.

[0043] Example 2: In vivo distribution of COPT nanoparticles

[0044] 1. Establishment of a mouse model of renal ischemia-reperfusion induced AKI: After approval by the university's experimental animal ethics committee, 8-week-old male C57BL / 6J mice were anesthetized by intraperitoneal injection of sodium pentobarbital. The skin was incised with ophthalmic scissors along the spine and lower rib margin on the back, and muscle tissue was separated to expose the red kidneys. Both renal arteries were clamped with arterial clamps, causing the kidneys to change color from red to white and then to dark purple. Ischemia was maintained for 35 minutes while the mice's body temperature was kept at 37°C. The arterial clamps were then released, and the recovery of renal blood flow was observed. The muscle and skin tissues were sutured separately. After the animals recovered, they were returned to the animal facility for continued rearing. Blood flow perfusion was maintained for 24 hours, thus establishing the AKI model. Mice whose kidneys were exposed only through abdominal incision, but whose renal arteries were not clamped, were designated as the Sham group (sham surgery treatment).

[0045] 2. Mouse organs (heart, liver, spleen, lungs, kidneys, intestines) were observed and photographed using a small animal imaging system after being injected via tail vein with either the control or the preparation of 5 mg / kg COPT nanoparticles prepared in Example 1. Figure 2 a) At 0h, 1h, 3h, 6h, 12h, and 24h after successful AKI modeling and injection of COPT nanoparticles, mouse kidneys were removed and observed and photographed using a small animal imaging system. It was found that COPT specifically accumulated in the kidney tissue of AKI-treated mice, reaching a peak at 6h after injection, and then gradually decreased. Figure 2 b). Kidney tissue sections were obtained, and the renal tubular marker LTL antibody was incubated using immunofluorescence assay followed by FITC secondary antibody staining. Finally, the cell nuclei were stained with DAPI, and observation using laser confocal microscopy revealed COPT accumulation in the renal tubules of AKI mice. Figure 2 c). Furthermore, primary renal tubular epithelial cells were incubated with COPT nanoparticles linked to FITC, and after incubation with Mito-Tracker, laser confocal microscopy revealed that COPT was localized in the mitochondria of the renal tubular epithelial cells. Figure 2 d).

[0046] Example 3: Evaluation of the effect of COPT nanoparticles on AKI

[0047] Sham and ischemia-reperfusion induced AKI mice were administered COPT nanoparticles via tail vein, with control mice receiving saline and mice receiving COPT nanoparticles at 5 mg / kg. Renal tubular injury was assessed using HE and PAS staining, and the renal tubules were observed and scored using an inverted microscope. The results showed that COPT significantly alleviated AKI. Figure 3 a).

[0048] Serum from the above-mentioned mice was collected, and serum creatinine and blood urea nitrogen levels were measured using a kit purchased from Nanjing Jiancheng Company. The results indicated that COPT could significantly inhibit creatinine levels in AKI mice. Figure 3 b) Blood urea nitrogen ( Figure 3 c) The elevated levels of these markers were detected. RNA was extracted from mouse kidney tissue using the Trizol method and reverse transcribed into cDNA using a reverse transcription kit. The expression of AKI markers Kim1 and Ngal mRNA was then detected using qPCR. PCR primers for Kim1 and Ngal were synthesized by Qingke Biotechnology Co., Ltd. The results showed that COPT significantly inhibited the expression of Kim1 (cDNA) in AKI mice. Figure 3 d) Ngal ( Figure 3 The expression level of e) was observed. This indicates that COPT nanoparticles have a significant effect on improving AKI.

[0049] Example 4: Evaluation of the role of COPT nanoparticles in improving the conversion of AKI to CKD

[0050] AKI-to-CKD model mice induced by tail vein administration of Sham, 30 minutes of ischemia-reperfusion, and 35 minutes of ischemia-reperfusion were injected with either the control group or 5 mg / kg COPT. Kidney tissue was harvested 28 days later, and the degree of renal fibrosis was assessed using HE staining and Masson staining. Observation under an inverted microscope revealed that COPT could alleviate renal fibrosis in AKI-to-CKD model mice. Figure 3 f, 3g). A schematic diagram illustrating how COPT nanoparticles improve the conversion of AKI to CKD is shown below. Figure 6 As shown. By Figure 6 It is known that COPT nanoparticles target and localize to the proximal tubular epithelial cells of the kidney, induce mitophagy by upregulating the expression of the BNIP3 gene to clear damaged mitochondria, thereby maintaining mitochondrial homeostasis and improving the transformation of acute kidney injury into chronic kidney disease.

[0051] Fresh kidney tissue from mice was collected, and proteins were extracted using a protein extraction kit from Beyotime Biotechnology Co., Ltd. Protein concentration was determined using a BCA kit. 30 μg of protein was loaded onto a PVDF membrane and subjected to SDS-PAGE electrophoresis. The membrane was then wet-transferred and incubated for 1 hour. The membrane was then incubated overnight at 4°C with diluted primary antibody antibodies (Fibronectin and α-SMA) or internal control β-Actin. The next day, the membrane was incubated with the corresponding secondary antibody, and the images were developed using chemiluminescence. Images were taken using a Bio-Rad gel imaging system, and grayscale scanning and data analysis were performed using ImageJ software. The results confirmed that COPT could alleviate the expression levels of kidney fibrosis-related proteins in AKI-to-CKD model mice. Figure 3 h).

[0052] Example 5: Molecular mechanism by which COPT nanoparticles alleviate the conversion of AKI to CKD

[0053] 1. RNA sequencing and bioinformatics analysis

[0054] Primary renal tubular epithelial cells from control and COPT-treated AKI mice were collected, flash-frozen in liquid nitrogen, and total RNA was extracted using the Trizol method. cDNA libraries were constructed and sent to BGI Genomics for RNA sequencing. In-depth bioinformatics analysis was performed on the obtained data, including gene function identification, GO enrichment analysis, and significance analysis of the KEGG signaling pathway. Heatmaps were generated, and the raw sequencing data were finally uploaded to an online database. Figure 4 As shown in ac.

[0055] 2. Screening for COPT target genes

[0056] The Western blot experiment was performed as described in Example 4. HK2 cells were treated with different concentrations of COPT for 24 hours, and the expression levels of mitophagy-related proteins (Nix, BNIP3, Pink1, Parkin) were detected using Western blot. Figure 4 d). HK2 cells were treated with normoxic and hypoxia-reoxygenation (HR) models, and then subjected to control or COPT treatment, respectively. Proteins were extracted, and Western blot experiments were used to detect the expression levels of mitophagy-related proteins (Nix, BNIP3, Pink1, Parkin). Figure 4 e). Total protein was extracted from Sham and AKI mice after treatment with control and COPT, respectively, and the expression level of BNIP3 protein was detected by Western blot. Figure 4 f). Based on the above screening, it was found that COPT can induce BNIP3 protein expression.

[0057] 3. COPT Functional Verification Experiment

[0058] In HK2 cells treated with normoxic or HR models, BNIP3 expression was knocked down using siRNA, and the expression levels of mitophagy-related proteins (LC3, P62, COXIV) were detected using Western blot. Figure 4 g), and after incubating HK2 cells with an apoptosis kit, the level of apoptosis was detected by flow cytometry. Figure 4 h), thereby confirming the reversal effect of COPT-induced mitophagy and inhibition of apoptosis.

[0059] Example 6: Biosafety of COPT Nanoparticles

[0060] Different doses of COPT (control, 1 mg / kg, 5 mg / kg, or 25 mg / kg) were injected into normal C57BL / 6J mice via the tail vein. After 28 days, the major organs (heart, liver, spleen, lung, kidney, intestine) of the mice were collected, fixed, stained with hematoxylin and eosin (HE), and observed under an inverted microscope to confirm that no significant damage was observed in the major organs of the mice after COPT treatment. Figure 5 a). Serum from the above-mentioned mice was collected, and blood routine tests, liver function (alanine aminotransferase and aspartate aminotransferase), and kidney function (creatinine and blood urea nitrogen) were detected using a kit. The results confirmed that COPT had no significant effect on the blood routine tests and liver and kidney function of the mice, indicating that COPT did not have obvious toxic side effects. Figure 5 b).

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A COPT nanoparticle for treating the transformation of AKI into CKD, characterized in that: The COPT nanoparticles have a core-shell structure, with the core being cobalt tetroxide and the surface of the cobalt tetroxide coated with polyethylene glycol. The polyethylene glycol is covalently linked to triphenylphosphine, and the polyethylene glycol and triphenylphosphine form a shell.

2. The COPT nanoparticles for treating AKI conversion to CKD as described in claim 1, characterized in that: The COPT nanoparticles have a nanoparticle size of 27 nm and a Zeta point of 19.4 ± 2.01 mV.

3. A method for preparing COPT nanoparticles for treating AKI conversion to CKD, characterized in that: Includes the following steps: S1: Using divalent cobalt salt and polyethylene glycol as raw materials, under the action of oxidant and alkali, cobalt oxide encapsulated in polyethylene glycol is obtained; S2: Add an activator to activate polyethylene glycol to obtain activated polyethylene glycol-encapsulated cobalt oxide; S3: Add TPP and activated polyethylene glycol to undergo a coupling reaction to obtain COPT nanoparticles.

4. The method for preparing COPT nanoparticles for treating AKI conversion to CKD as described in claim 3, characterized in that: In step S1, the divalent cobalt salt is cobalt acetate; the oxidant is hydrogen peroxide; and the alkali is ammonia.

5. The method for preparing COPT nanoparticles for treating AKI conversion to CKD as described in claim 3, characterized in that: Step S1 includes one or more of the following features: (1) The mass ratio of the divalent cobalt salt to polyethylene glycol is 3.75:1; (2) The divalent cobalt salt is added in two parts. The mass ratio of the amount of divalent cobalt salt added in the first part to the amount of divalent cobalt salt added in the second part is 2:

1. The reaction time in the first part is 10 min and the temperature is 80°C. The second reaction lasted 12 hours and was carried out at a temperature of 60°C.

6. The method for preparing COPT nanoparticles for treating AKI conversion to CKD as described in claim 3, characterized in that: Step S2 includes one or more of the following features: (1) The mass ratio of activator to polyethylene glycol is 2:5; (2) The activators are EDC and Sulfo-NHS, and the mass ratio of EDC to Sulfo-NHS is 1:1; (3) The activation time is 12 hours and the temperature is room temperature.

7. The method for preparing COPT nanoparticles for treating AKI conversion to CKD as described in claim 3, characterized in that: In step S3, the mass ratio of TPP to polyethylene glycol is 119:1, the reaction time is 12 hours, and the reaction temperature is room temperature.

8. The use of the COPT nanoparticles for treating AKI-to-CKD conversion as described in claim 1 or 2 in the preparation of a medicament for treating acute kidney injury and its conversion to chronic kidney disease.

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