Small molecule compound used as biocatalyst, and delivery system and application thereof

Abstract

The invention belongs to the field of biological medicine, and particularly relates to a small molecule compound used as a biocatalyst, and a delivery system and application thereof. According to the present invention, the excellent SOD and CAT enzyme activity of the small molecule compound having the molecular structure represented by the formula (I) is found for the first time, and the radiation-induced lung injury caused by radiotherapy can be further prevented. In addition, the invention also develops an erythrocyte-based delivery system for delivering the small molecule compound, so as to enhance the targeting and bioavailability of the small molecule compound at the radiation-induced lung injury part. # imgabs0 # (I)

Description

Technical Field

[0001] The present invention belongs to the field of biomedicine, and particularly relates to a small molecule compound used as a biocatalyst, its delivery system and its application. Background Art

[0002] The mortality rate of malignant tumors ranks second globally, second only to cardiovascular diseases, and has become the most important health threat worldwide. Facing the challenge of the high incidence of tumors, radiotherapy occupies an important position in tumor treatment, with a cure rate of 40 - 45%. Although radiotherapy performs well in eliminating cancer cells, its damage to normal tissues, especially problems such as radiation pneumonitis and radiation-induced heart disease, which are radiation-induced tissue damage problems, remains a difficult problem in radiotherapy. Reducing damage to healthy tissues and improving the accuracy and safety of treatment are key goals that need to be considered in radiotherapy. Radiotherapy has an obvious dose-effect relationship in the radiotherapy of chest tumors led by lung cancer. As the irradiation dose increases, the risk of local recurrence decreases accordingly. However, the increase in the radiotherapy dose for chest tumors is limited by the toxicity of normal tissues. Among them, radiation-induced lung injury (RILI) is one of the most important dose-limiting toxicities, with an incidence rate of 16.7% - 50.3%. Although currently, with the improvement of precise planning, positioning technology, respiratory gating management, image-guided technology, etc., and through the use of intensity-modulated radiotherapy (IMRT), stereotactic body radiotherapy (SBRT), and the research and development of new radioprotective agents, the risk of radiation pneumonitis has been significantly reduced clinically, but the probability of symptomatic pneumonia still accounts for 9.4% - 28%. The occurrence of RILI in clinical diagnosis and treatment will lead to the interruption of the radiotherapy, chemotherapy, immunotherapy or targeted therapy courses of tumor patients, thus affecting the tumor control rate, prolonging the hospital stay, causing a large economic burden of the disease, and becoming a difficult problem for clinicians to treat RILI.

[0003] The occurrence of RILI is mainly due to the impaired barrier functions of vascular endothelial cells and alveolar epithelial cells. In response to its complex and crosstalking pathogenesis, numerous related prevention and treatment studies have emerged, including glucocorticoids, traditional Chinese medicine extracts, antioxidant therapies such as sulfhydryl compounds, antioxidant enzymes and analogs, plant antioxidants, etc. However, in fact, except for glucocorticoids, there is still a lack of specific and effective drugs. Corticosteroids can reduce the inflammatory response and also inhibit the TNF-induced nitric oxide-mediated toxicity of endothelial cells and lymphocytes. However, considering the many side effects of glucocorticoids, such as secondary pulmonary infection, elevated blood sugar, peptic ulcer, Cushing's syndrome, obesity, osteoporosis, etc., corticosteroids are not suitable for preventing RP or long-term use. Therefore, there is an urgent need to develop methods for effectively preventing and treating RILI with few side effects. Summary of the Invention

[0004] To solve the above problems, the present invention for the first time discovers that small molecule compounds having a molecular structure as shown in formula (I) have excellent SOD and CAT enzyme activities, and further discovers that they can protect against radiation-induced lung injury. In addition, the present invention also develops an erythrocyte-based delivery system for delivering the small molecule compound to enhance the targeting and bioavailability of the small molecule compound at the RILI site.

[0005] The molecular structure shown in formula (I) is as follows:

[0006]

[0007] (I).

[0008] Specifically, in a first aspect, the present invention provides an application of a small molecule compound as a biocatalyst, wherein the molecular structure of the small molecule compound is as shown in formula (I).

[0009] Furthermore, the biocatalyst has SOD and CAT enzyme activities.

[0010] In a second aspect, the present invention provides an application of a small molecule compound in the preparation of a drug for protecting against radiation-induced lung injury, wherein the molecular structure of the small molecule compound is as shown in formula (I).

[0011] As used herein, the preparation method of the small molecule compound having a molecular structure as shown in formula (I) can be prepared by a suitable method known in the art. For example, it can be prepared by the synthetic route shown in the present invention Figure 1 shown.

[0012] As used herein, SOD enzyme activity refers to the activity of superoxide dismutase (SOD), and CAT enzyme activity refers to the activity of catalase (CAT).

[0013] In a third aspect, the present invention provides an application of a delivery system for delivering the small molecule compound as described herein in the preparation of a drug for protecting against radiation-induced lung injury.

[0014] Furthermore, the delivery system includes erythrocytes loaded with the small molecule compound.

[0015] In a fourth aspect, the present invention provides a delivery system, which includes erythrocytes loaded with the small molecule compound as described herein.

[0016] In a fifth aspect, the present invention provides a preparation method of a delivery system as described herein, which includes the following steps:

[0017] (1) Disperse the small molecule compound as described herein in a phosphate buffer solution;

[0018] (2) Mix the suspension of the small molecule compound with the erythrocyte suspension resuspended in the erythrocyte preservation solution, and then let it stand for reaction, so that the small molecule compound is adsorbed on the surface of the erythrocytes through electrostatic interaction, and the erythrocytes loaded with the small molecule compound are obtained.

[0019] Further, the concentration of the suspension of the small molecule compound is 500 ug / mL.

[0020] Further, the erythrocytes are derived from C57BL / 6 mice.

[0021] Further, the volume ratio of erythrocytes to erythrocyte preservation solution in the erythrocyte suspension is 1:2.

[0022] Further, the mixing volume ratio of the suspension of the small molecule compound to the erythrocyte suspension is 20:1.

[0023] Further, the standing time is 30 - 60 min, and the standing temperature is 25 - 37 °C.

[0024] Advantageous Effects of the Invention

[0025] The present invention firstly discovers that a small molecule compound with a molecular structure shown in formula (I) (referred to as Ru(bda)[Me-bpy]2[PF6]2 or simply Ru in this specification and the accompanying drawings) has excellent SOD and CAT enzyme activities, and further discovers that it can protect against radiation-induced lung injury. The structure of this small molecule compound has a highly distorted octahedral configuration, where the O-Ru-O angle is 123°, which is greater than the ideal octahedral configuration. Substrates such as reactive oxygen species (ROS) can easily bind to its active sites, showing efficient electron / proton transfer effects and excellent SOD and CAT mimetic enzyme activities. Due to its unique physical and chemical properties, good biocompatibility, and ability to effectively resist oxidative stress damage and regulate the body's immune system, this small molecule compound is expected to become a non-hormonal anti-inflammatory candidate drug for the treatment of RILI.

[0026] Further, in order to ensure the effective delivery of this small molecule compound in vivo, controlled release in the lungs, and reduction of systemic toxicity, the present invention has developed an erythrocyte carrier system loaded with this small molecule compound (referred to as RBC@Ru(bda)[Me-bpy]2[PF6]2 or simply RBC@Ru in this specification and the accompanying drawings), so as to enhance the targeting and bioavailability of this small molecule compound at the RILI site and achieve the precise release of the drug under specific conditions (such as enzyme activity, charge, pH, osmotic pressure, etc.). Description of the Drawings

[0027] Figure 1Shows the molecular structure and synthesis process schematic diagram of the small molecule compound Ru(bda)[Me-bpy]2[PF6]2.

[0028] Figure 2 Shows the performance and characterization results of Ru(bda)[Me-bpy]2[PF6]2 and RBC@Ru(bda)[Me-bpy]2[PF6]2: (a) 1H NMR spectrum; (b) 13C NMR spectrum; (c) CAT enzyme activity assay; (d) SOD enzyme activity assay; (e) Transmission electron microscopy (TEM) scan and elemental mapping distribution (Mapping); (f) Zeta potential detection.

[0029] Figure 3 Shows the preparation and action schematic diagram of Ru loaded on RBC.

[0030] Figure 4 Shows the in vitro experimental results of lung radiation protection: Representative ROS images (a) and quantitative statistics (b) of BEAS-2B cells treated differently; Representative Live / Dead fluorescence staining (c) and quantitative statistics (d); Representative aggregates / monomers fluorescence staining (e) and quantitative statistics (f); Representative γ-H2AX fluorescence staining (g) and quantitative statistics (h); Representative flow cytometry detection of cell apoptosis images (i) and quantitative statistics (j); Schematic diagram of Ru scavenging intracellular ROS and protecting cells (k). The differences were all statistically significant.

[0031] Figure 5 Shows the in vivo experimental results of lung radiation protection: (a) Chest hair removal of mice treated differently; (b) Body weight and survival rate of mice; (c) Lung tissue photos and wet weights; (d) Results of HE, masson, immunohistochemistry (IHC) and immunofluorescence staining (IF) staining of mouse lung tissue sections.

[0032] Figure 6 Shows the biodistribution of Ru and RBC@Ru: Fluorescence imaging (a) and quantitative statistics (b) of the lungs of mice after intravenous injection of cy5.5-labeled Ru and RBC@Ru; And ex vivo organ imaging (c) and quantitative statistics (d). Specific embodiments

[0033] The following specific examples are used to further illustrate the present invention, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

[0034] Example 1: Synthesis of the small molecule compound Ru

[0035] The synthesis route is asFigure 1 as shown

[0036] 1. Weigh 1 g of RuCl3-xH2O and place it in a 50 mL flask. Then add 15 mL of dimethyl sulfoxide (DMSO), reflux for 5 minutes, cool to room temperature, and distill under reduced pressure. After leaving a small amount of solvent, filter, wash with excess acetone, dry in vacuo, collect the yellow powder to obtain Ru(DMSO)4Cl2.

[0037] 2. Weigh 484 mg of Ru(DMSO)4Cl2 and 244 mg of H2BDA, place them in a 100 mL two-necked flask, add 40 mL of methanol and 0.8 mL of triethylamine, reflux for 12 hours, wash with excess methanol, acetone, and ether, dry in vacuo, collect the red-brown powder Ru(bda)(DMSO)2.

[0038] 3. Weigh 206.67 mg (0.1 mol) of [Me-Bpy]Cl, dissolve it in a certain amount of deionized water to form a saturated solution A. Weigh 736.24 mg of KPF6 and dissolve it in a certain amount of deionized water to form a saturated solution B. Rapidly add solution B to solution A to produce a precipitate. Filter, wash with 10 mL of water, dry in vacuo, collect the off-white solid [Me-bpy][PF6].

[0039] 4. Weigh 85 mg of pyridine-4-sulfonic acid and 100 mg of [Me-bpy][PF6], place them in a 50 mL flask, add 15 mL of methanol and reflux for 12 h. Filter, collect the filtrate, wash with excess methanol and ether to obtain a red-black solid. Dissolve the red-black solid in 80 mL of a methanol / acetone mixed solution (1:1), rotary evaporate to 10 mL, then add 40 mL of methanol and evaporate until a precipitate forms. Filter, wash with 10 mL of methanol, and then wash with excess ether. Dry in vacuo, collect the red-black solid Ru(bda)[Me-bpy]2[PF6]2.

[0040] Example 2: Structural and mimetic enzyme activity characterization of Ru(bda)[Me-bpy]2[PF6]2 (Ru)

[0041] The structure and composition of Ru(bda)[Me-bpy]2[PF6]2 (Ru) were characterized in detail by nuclear magnetic resonance (NMR) technology. The 1H NMR and 13C NMR spectra are shown in Figures Figure 2 a and 2b respectively, which confirm the synthesis of Ru.

[0042] The guaiacol method was used to detect the catalase (CAT) activity of the materials; the xanthine oxidase method was used to determine the superoxide dismutase (SOD) activity. The results are as Figure 2 shown in Figures 2c and 2d. Ru has an extremely high scavenging rate and a very fast scavenging rate, indicating that Ru is a highly efficient biocatalyst, which is the first discovery of the present invention.

[0043] Example 3: Preparation of RBC@Ru

[0044] The preparation method of RBC loaded with Ru(bda)[Me-bpy]2[PF6]2 is as follows (refer to Figure 3 ):

[0045] (1) Collect whole blood from healthy male C57BL / 6 mice (20 - 22 g; 6 - 8 weeks old). Over-anesthetize and sacrifice the mice with isoflurane, take the blood from the eye socket, and store it in an EDTA anticoagulant tube. Gently invert to prevent blood clotting. The whole blood sample is centrifuged at 2000 rpm for 5 min at 4°C, and the supernatant containing plasma and white blood cells is discarded. The precipitated red blood cells are centrifuged and washed three times with 1× pre-cooled phosphate buffer saline (PBS) to separate and purify the free red blood cells. The purified red blood cells are resuspended in Alsever's solution at a ratio of 1:2 (v / v). Store at 4°C for no more than 7 days before the experiment.

[0046] (2) Accurately weigh the Ru powder and transfer it to a 1.5 mL microcentrifuge tube. Vortex mix in isotonic PBS to obtain a uniform reddish-brown suspension (500 μg / mL), and mix it with the red blood cell suspension obtained in step 1 at a volume ratio of 20:1. Use a pipette to gently blow and disperse evenly for 3 - 5 minutes, and incubate at 37°C for 30 minutes to promote the interaction of the drug carriers. After incubation, centrifuge the suspension at 2000 rpm (4°C, 5 minutes), and discard the supernatant. Repeat washing three times with ice-cold PBS to remove any unbound complexes, and obtain the purified RBC@Ru structure. Resuspend the RBC@Ru in an equal volume of PBS and store it at 4°C for later use.

[0047] (3) Verify that the RBC has successfully loaded the small molecule drug Ru through Zeta potential detection, transmission electron microscopy (TEM) scanning, and elemental mapping distribution (Mapping) ( Figure 2 Figures 2e and Figure 2 2f).

[0048] Example 4: Application of Ru(bda)[Me-bpy]2[PF6]2 in the protection against radiation-induced lung injury

[0049] Experimental materials and methods

[0050] 1. Cell lines: Human lung bronchial epithelial cells (BEAS-2B) and human embryonic lung fibroblasts (HELF) were cultured using a medium containing high-glucose DMEM (VivaCell), 0.5 mg / mL penicillin-streptomycin (Gibco), and 10% certified fetal bovine serum (VivaCell, Shanghai, China, C3840-0500).

[0051] 2. In vitro cell function protection experiments

[0052] 2.1. Detection of ROS scavenging in cells after X-ray irradiation: BEAS-2B and HELF cells in the growth phase were collected, counted using a cell counting chamber, and then seeded in 6-well plates (15×10 4 / well) and cultured overnight. A cell culture medium containing Ru (80 ug / mL) was prepared and divided into the following groups: control group, Ru(bda)[Me-bpy]2[PF6]2 (abbreviated as Ru) group, RT (X-ray treatment) group, and RT+Ru(bda)[Me-bpy]2[PF6]2 (abbreviated as RT+Ru) group. The original cell culture medium of each group of cells was removed, and the drug-containing medium was added and incubated for 2 h. Subsequently, the drug-containing medium was aspirated, and fresh medium was added. The RT and RT+Ru groups were irradiated with 20 Gy of X-ray. 2 h after the irradiation ended, the original medium was aspirated, and serum-free medium containing DCFH-DA prepared according to the ROS detection kit instructions (1 mL / well) was added, and the cells were incubated in the incubator in the dark for 20 min. After washing the cells 3 times with serum-free medium, the green fluorescence of ROS in each group of cells was observed under a fluorescence microscope.

[0053] 2.2. Live / dead staining with calcein-AM / PI staining: BEAS-2B and HELF cells in the growth phase were collected and seeded in 6-well plates (8×10 4 / well) and cultured overnight. The steps of cell drug administration and irradiation treatment were the same as above. 48 h after the irradiation ended and the culture, 1 µl of AM solution was used to stain live cells in the detection buffer, and 1 µl of PI solution was used to stain dead cells. Then, the cells in each group were observed under a fluorescence microscope to capture the cells and count them.

[0054] 2.3. Mitochondrial membrane potential (JC-1) detection: BEAS-2B and HELF cells in the growth phase were collected and seeded in 6-well plates (8×10 4Cultivate overnight in (the well of the 96-well plate). The steps of cell administration and irradiation treatment are the same as above. Add 1 ml of JC-1 staining working solution and mix well. After 24 h of incubation after the irradiation is completed, incubate at 37 ºC in the cell culture incubator for 20 minutes, then aspirate the supernatant, and wash twice with JC-1 staining buffer (1X). Then add 2 ml of cell culture medium, which can contain serum and phenol red. Finally, observe under a fluorescence microscope or a laser confocal microscope.

[0055] 2.4. DNA damage: Collect BEAS-2B and HELF cells in the growth phase and seed them in a 96-well plate (1×10 4 / well) and cultivate overnight. The steps of cell administration and irradiation treatment are the same as above. Within 6 h after the irradiation is completed, fix with 4% paraformaldehyde and wash 3 times with the washing solution, 5 min each time. Add the immunostaining blocking solution and block at room temperature for 20 min. After blocking, add rabbit anti-γ-H2AX monoclonal antibody, incubate overnight at 4 ºC, and then wash 3 times with the washing solution, 5 min each time. Add anti-rabbit 488, incubate in the dark at room temperature for 1 h, and then counterstain the cell nuclei with DAPI staining solution at room temperature. Wash the cells with the washing solution and then place them under a fluorescence microscope for detection.

[0056] 2.5. Flow cytometry for apoptotic cells (Annexin V-FITC): Collect BEAS-2B and HELF cells in the growth phase and seed them in a 6-well plate (8×10 4 / well) and cultivate overnight. The steps of cell administration and irradiation treatment are the same as above. After 48 h of incubation after the irradiation is completed, collect the cell supernatant into a centrifuge tube, add an appropriate amount of trypsin cell digestive solution, terminate the digestion with the collected cell culture medium, centrifuge at 1200 rpm for 5 minutes, discard the supernatant, collect the cells, wash with PBS and centrifuge, and then add the apoptosis detection reagent respectively. Then incubate in the dark at room temperature (10 - 20 ºC) for 10 - 20 minutes. Finally, detect with a flow cytometer. Annexin V-FITC shows green fluorescence and propidium iodide (PI) shows red fluorescence.

[0057] 3. In vivo experiment on protecting against radiation-induced lung injury

[0058] Animal model: Male C57 mice (6 - 8 weeks old, 20 - 25 g) were purchased from GemPharmatech Co., Nanjing, China. All animal experimental procedures were carried out in accordance with the "Regulations on the Administration of Laboratory Animals" approved by the State Council of the People's Republic of China. All mice were housed under specific pathogen-free (SPF) conditions (temperature ~22 °C, humidity ~50%), with a 12 / 12 h dark / light cycle. One week after feeding, start to establish a mouse model of radiation-induced lung injury (single thoracic irradiation of 17 Gy). The specific grouping and detection content are as follows:

[0059] The mice were randomly divided into 5 groups: a control group (Control), a Ru group, an RT group, an RT+Ru group, and an RT+RBC@Ru group. Mice in the Ru group and the RT+Ru group were given an intravenous injection of Ru via the tail vein 1 h before radiotherapy, and mice in the RT+RBC@Ru group were given an intravenous injection of RBC@Ru via the tail vein 1 h before radiotherapy. The injection concentration for the above three groups of mice was 500 μg / mL (100 uL) / mouse, and the drug was administered twice a week. The diet, activity, chest hair loss, body weight, and survival of the mice were observed every 3 days. On the 30th day, the mice were euthanized, and lung tissues were taken for detection. The collected lung tissues were fixed with 4% paraformaldehyde, paraffin sections were prepared, and staining, section scanning, and image analysis were performed. HE and Masson staining were performed on the sections to observe the differences in inflammatory structures and collagen deposition between the drug-treated group and the control group. IHC staining and multi-color immunofluorescence staining were used to detect the expression of HIF-α and TUNEL. Through the above in vivo related research, the feasibility, safety, and effectiveness of the small molecule drug Ru in the treatment of radiation-induced lung injury were explored.

[0060] 4. In vivo biodistribution of RBC@Ru

[0061] To quantitatively evaluate the biodistribution of RBC@Ru, cy5.5-labeled Ru and RBC@Ru were intravenously injected into mice after irradiation, and in vivo imaging analysis of mice and ex vivo imaging analysis of tissues and organs were performed at different time points.

[0062] Experimental results

[0063] 1. In vitro cell function protection experiment: After verifying the multi-enzyme-like antioxidant activity of Ru, human lung bronchial epithelial cells (BEAS-2B) and human embryonic lung fibroblasts (HELF) were cultured in vitro in the present invention, and cells were stimulated to produce reactive oxygen species (ROS) under an X-ray system. After intervention with the synthesized RU drug, the intracellular ROS content was quantified using a reactive oxygen fluorescence probe (DCFH-DA) through a fluorescence microscope and a flow cytometer. Further, a series of experiments such as live-dead fluorescence detection, DNA damage, cell cycle, flow cytometry apoptosis, cell senescence, and mitochondrial membrane potential were used to verify the SOD and CAT enzyme activities of RU, which confirmed at multiple levels that it has the ability to scavenge ROS, reduce intracellular DNA damage, inhibit apoptosis of lung endothelial cells, and promote the growth and repair of lung endothelial cells.

[0064] The results showed that compared with the RT group, the RT+Ru group significantly reduced the generation of ROS and effectively alleviated the cellular oxidative stress state ( Figure 4 a, b). Live-dead AM / PI fluorescence staining showed that the red fluorescence signal in the RT+Ru group decreased, and the ratio of dead / live cells was significantly reduced compared with the RT group ( Figure 4c, d). Mitochondrial membrane potential detection showed that the RT + Ru group significantly alleviated mitochondrial damage compared with the RT group ( Figure 4 e, f). The expression level of the DNA damage marker γ-H2AX also decreased significantly ( Figure 4 g, h). Flow cytometry was used to detect the apoptosis rate of cells. It was found that the apoptosis rate of the RT group increased significantly, while that of the RT + Ru group decreased significantly ( Figure 4 i, j). The above data indicated that Ru could significantly alleviate radiation-induced oxidative stress, apoptosis and DNA damage ( Figure 4 k).

[0065] 2. In vivo lung radioprotection experiment: The results showed that hair loss on the chest of mice in the RT + RBC@Ru and RT + Ru groups was significantly alleviated compared with the RT group ( Figure 5 a), and the survival rate of mice in the RT + RBC@Ru and RT + Ru groups was significantly better than that of the RT group, and the body weight of mice increased compared with the RT group, but was lower than that of the non-irradiated group ( Figure 5 b). After dissection, it was observed that the congestion and edema of the lung tissue in the drug treatment group were alleviated, the wet weight of the lung tissue decreased, and the lung coefficient decreased. Moreover, all the observed indexes of the RT + RBC@Ru group were significantly better than those of the RT + Ru group, fully demonstrating the targeted delivery effect of avoiding hepatic "first-pass elimination" after intravenous injection of Ru loaded on red blood cells, increasing the utilization rate and the duration of action of the drug, and exerting a better radioprotective effect in vivo ( Figure 5 c). The results of HE pathological staining showed that the infiltration of inflammatory cells in the RT + RBC@Ru and RT + Ru groups was less than that in the simple RT group, with slight widening of the alveolar septum and a little alveolar fusion, and the pulmonary inflammatory reaction was significantly lighter than that in the RT group; Masson staining showed that the deposition of collagen fibers was significantly reduced in the RT + RBC@Ru and RT + Ru groups; immunohistochemistry (IHC) and immunofluorescence (IF) staining showed that the expression of HIF-α and TUNEL decreased ( Figure 5 d). The above results all confirmed that the RT + Ru group alleviated the lung tissue damage after radiotherapy compared with the RT group, and the effect of the RT + RBC@Ru group was more obvious, indicating that the red blood cell-based delivery system could achieve the effective delivery of Ru in vivo, and could enhance the targeting and bioavailability of the drug at the site of radioactive lung injury.

[0066] 3. Biodistribution of RBC@Ru: The results showed that cy5.5-labeled RBC@Ru concentrated in the lungs immediately within 1 hour after intravenous injection and maintained a significant fluorescence signal for up to 48 hours. Although the fluorescence intensity in the lungs showed time-dependent clearance, the elimination of RBC@Ru was still slow ( Figure 6a, b), which fully demonstrated the targeted accumulation of RBC@Ru in the lung. Ex vivo organ imaging showed that a small amount of Ru was also distributed in the liver, kidney, or other tissues, which might be related to systemic clearance metabolism or the uptake of the drug by the mononuclear phagocyte system. At 48 h after injection, the fluorescence intensity of the RT+RBC@Ru group in the lung was significantly stronger than that of the RT+Ru group, which might be related to the sustained release of the drug ( Figure 6 c, d). RBC-mediated delivery fundamentally altered the biodistribution of the drug, redirected its tissue tropism by hitchhiking through the circulation, and provided important support for its effective pulmonary radioprotection.

[0067] It should be noted that the description and drawings of the present invention give preferred embodiments of the present invention. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. These embodiments do not serve as additional limitations to the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosed content of the present invention more thorough and comprehensive. Moreover, the above technical features continue to be combined with each other to form various embodiments not listed above, all of which are regarded as within the scope described in the description of the present invention; further, for those of ordinary skill in the art, improvements or changes can be made according to the above description, and all such improvements and changes should fall within the protection scope of the appended claims of the present invention.

Claims

1. Use of a small molecule compound as a biocatalyst, characterized in that, The molecular structure of the small molecule compound is shown in formula (I): (I) The biocatalyst has SOD and CAT enzyme activities.

2. Use of a small molecule compound or its delivery system in the preparation of a drug for protecting against radiation-induced lung injury, characterized in that, The molecular structure of the small molecule compound is shown in formula (I).

3. The application according to claim 2, wherein The delivery system includes red blood cells loaded with the small molecule compound.

4. A delivery system, characterized in that, The delivery system includes red blood cells loaded with the small molecule compound defined in claim 1.

5. A method for preparing a delivery system as described in claim 4, characterized in that, Comprising the following steps: (1) Disperse the small molecule compound defined in claim 1 in phosphate buffer; (2) Mix the suspension of the small molecule compound with the red blood cell suspension resuspended in the red blood cell preservation solution and then let it stand for reaction, so that the small molecule compound is adsorbed on the surface of the red blood cells by electrostatic interaction to obtain red blood cells loaded with the small molecule compound.

6. The preparation method according to claim 5, characterized in that, The concentration of the suspension of the small molecule compound is 500 ug / mL.

7. The preparation method according to claim 5, characterized in that, The red blood cells are derived from C57BL / 6 mice.

8. The preparation method according to claim 5, characterized in that, The volume ratio of red blood cells to red blood cell preservation solution in the red blood cell suspension is 1:

2.

9. The preparation method according to claim 5, characterized in that, The mixing volume ratio of the suspension of the small molecule compound to the red blood cell suspension is 20:

1.

10. The preparation method according to claim 5, characterized in that, The standing time is 30 - 60 min, and the standing temperature is 25 - 37 °C.

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