A small molecule compound used as a biocatalyst, its delivery system and its applications

Abstract

The present invention belongs to the field of biomedicine and specifically relates to a small molecule compound used as a biocatalyst, its delivery system, and its application. The present invention first discovered that a small molecule compound having a molecular structure as shown in Formula (I) exhibits excellent SOD and CAT enzyme activities and further discovered that it can protect against radiation-induced lung injury. Furthermore, the present invention also developed an erythrocyte-based delivery system for delivering this small molecule compound to enhance its targeting and bioavailability at sites of radiation-induced lung injury. #imgabs0#(I).

Description

Technical Field

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

[0002] Malignant tumors have the second highest mortality rate globally, second only to cardiovascular disease, and have become a major global health threat. Faced with this high incidence of cancer, radiotherapy plays a crucial role in cancer treatment, with cure rates reaching 40-45%. Despite its remarkable effectiveness in eliminating cancer cells, radiotherapy's damage to normal tissues, particularly radiation-induced lung injury (RILI), remains a major challenge. Minimizing damage to healthy tissues and improving treatment precision and safety are key goals of radiotherapy. Radiotherapy for thoracic tumors, particularly lung cancer, demonstrates a distinct dose-response relationship, with increasing irradiation doses associated with a decreasing risk of locoregional recurrence. However, increasing the dose of thoracic tumor radiotherapy is limited by normal tissue toxicity, with radiation-induced lung injury (RILI) being one of the most significant dose-limiting toxicities, occurring in 16.7% to 50.3%. Although improvements in precise planning, positioning technology, respiratory gating management, and image-guided techniques, along with the use of intensity-modulated radiotherapy (IMRT), stereotactic body radiotherapy (SBRT), and the development of new radioprotectants, have significantly reduced the risk of radiation pneumonitis, the incidence of symptomatic pneumonia remains at 9.4% to 28%. The occurrence of RILI during clinical diagnosis and treatment can interrupt chemotherapy, radiotherapy, immunotherapy, or targeted therapy for cancer patients, thereby impacting tumor control rates, prolonging hospital stays, and imposing a significant economic burden, making it a challenging issue for clinicians treating RILI.

[0003] The occurrence of RILI is primarily due to impaired barrier function between vascular endothelial cells and alveolar epithelial cells. In response to its complex and intertwined pathogenesis, relevant prevention and treatment research has emerged in an endless stream, including glucocorticoids, traditional Chinese medicine extracts, antioxidant therapies such as sulfhydryl compounds, antioxidant enzymes and analogs, and plant antioxidants. However, in reality, there is still a lack of specific and effective drugs other than glucocorticoids. Corticosteroids can reduce inflammatory responses and inhibit TNF-induced nitric oxide-mediated endothelial cell and lymphocyte toxicity. However, given the numerous side effects of glucocorticoids, such as secondary lung infections, increased blood sugar, peptic ulcers, Cushing's syndrome, obesity, and osteoporosis, corticosteroids are not suitable for the prevention of RP or long-term use. Therefore, there is an urgent need to develop effective methods for the prevention and treatment of RILI with minimal side effects. Summary of the Invention

[0004] To address these issues, the present invention discovered for the first time that a small molecule compound having a molecular structure as represented by formula (I) exhibits excellent SOD and CAT enzyme activities and further demonstrates its ability to protect against radiation-induced lung injury. Furthermore, the present invention developed an erythrocyte-based delivery system for this small molecule compound to enhance its targeting and bioavailability at the site of RILI.

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

[0006]

[0007] (I).

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

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

[0010] In a second aspect, the present invention provides a use 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 shown in formula (I).

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

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

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

[0014] Furthermore, the delivery system includes red blood cells loaded with the small molecule compound.

[0015] In a fourth aspect, the present invention provides a delivery system comprising red blood cells loaded with a small molecule compound as described herein.

[0016] In a fifth aspect, the present invention provides a method for preparing the delivery system as described herein, comprising the following steps:

[0017] (1) dispersing the small molecule compound described herein in phosphate buffer;

[0018] (2) The suspension of the small molecule compound is mixed with the suspension of red blood cells resuspended in red blood cell preservation fluid and then allowed to stand for reaction, so that the small molecule compound is adsorbed on the surface of the red blood cells by electrostatic action, thereby obtaining red blood cells loaded with the small molecule compound.

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

[0020] Furthermore, the red blood cells are derived from C57BL / 6 mice.

[0021] Furthermore, the volume ratio of red blood cells to red blood cell preservation solution in the red blood cell suspension is 1:2.

[0022] Furthermore, the mixing volume ratio of the suspension of the small molecule compound to the red blood cell suspension is 20:1.

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

[0024] Advantageous Effects of the Invention

[0025] This invention, for the first time, discovered a small molecule compound with the molecular structure represented by Formula (I) (referred to as Ru(bda)[Me-bpy]2[PF6]2 or simply Ru in this specification and accompanying figures) that exhibits excellent SOD and CAT enzyme activities and further demonstrated its ability to protect against radiation-induced lung injury. This small molecule compound exhibits a highly distorted octahedral structure, with the O-Ru-O angle being 123°, larger than that of an ideal octahedral structure. Substrates such as reactive oxygen species (ROS) readily bind to its active site, exhibiting efficient electron / proton transfer and excellent SOD and CAT enzyme-mimetic activity. Due to its unique physical and chemical properties, excellent biocompatibility, and ability to effectively protect against oxidative stress and modulate the immune system, this small molecule compound holds promise as a non-hormonal anti-inflammatory drug candidate for the treatment of RILI.

[0026] Furthermore, to ensure the effective delivery of the small molecule compound in vivo, controlled release in the lungs, and reduced systemic toxicity, the present invention has developed a red blood cell carrier system loaded with the 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) to enhance the targeting and bioavailability of the small molecule compound at the RILI site and achieve precise release of the drug under specific conditions (such as enzyme activity, charge, pH, osmotic pressure, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

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

[0028] Figure 2 The performance and characterization results of Ru(bda)[Me-bpy]2[PF6]2 and RBC@Ru(bda)[Me-bpy]2[PF6]2 are shown: (a) H NMR spectrum; (b) C NMR spectrum; (c) CAT enzyme activity determination; (d) SOD enzyme activity determination; (e) transmission electron microscopy (TEM) scanning and elemental mapping distribution (Mapping); (f) Zeta potential detection.

[0029] Figure 3 Shown is a schematic diagram of the preparation and function of RBC loaded Ru.

[0030] Figure 4 The results of in vitro experiments on lung radioprotection are shown: representative ROS images (a) and quantitative statistics (b) of BEAS-2B cells treated with different methods; 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 images of cell apoptosis (i) and quantitative statistics (j); and schematic diagram of Ru scavenging intracellular ROS and protecting cells (k). The differences were statistically significant.

[0031] Figure 5 The in vivo experimental results of lung radioprotection are shown: (a) chest hair loss of mice receiving different treatments; (b) mouse body weight and survival rate; (c) lung tissue photos and wet weight; (d) HE, Masson, immunohistochemistry (IHC), and immunofluorescence (IF) staining results of mouse lung tissue sections.

[0032] Figure 6 The biodistribution of Ru and RBC@Ru is shown: fluorescence imaging (a) and quantitative statistics (b) in the mouse lungs after intravenous injection of Cy5.5-labeled Ru and RBC@Ru; as well as ex vivo organ imaging (c) and quantitative statistics (d). DETAILED DESCRIPTION

[0033] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

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

[0035] Synthesis route such as Figure 1 shown.

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

[0037] 2. Weigh 484 mg of Ru(DMSO)4Cl2 and 244 mg of H2BDA into 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. Vacuum dry to collect the reddish-brown powder Ru(bda)(DMSO)2.

[0038] 3. Weigh 206.67 mg (0.1 mol) of [Me-Bpy]Cl and 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, and vacuum dry to 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] into a 50 mL flask. Add 15 mL of methanol and reflux for 12 h. Filter, collect the filtrate, and wash with excess methanol and ether to obtain a reddish-black solid. Dissolve the reddish-black solid in 80 mL of a 1:1 methanol / acetone mixture and rotary evaporation to 10 mL. Then, add 40 mL of methanol and evaporate until a precipitate forms. Filter, wash with 10 mL of methanol, and then with excess ether. Vacuum dry, and collect the reddish-black solid, Ru(bda)[Me-bpy]2[PF6]2.

[0040] Example 2: Characterization of the structure and enzymatic activity 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 hydrogen and carbon NMR spectra are shown in Figure 2. Figure 2 a and 2b, 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. Figure 2 As shown in Figures 2c and 2d, Ru has an extremely high clearance rate and a very fast clearance rate, indicating that Ru is an extremely 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). Mice were anesthetized with isoflurane and killed by overdose. Blood was collected from the eyeballs and stored in EDTA-anticoagulant tubes. Gently invert to prevent coagulation. The whole blood sample was centrifuged at 2000 rpm for 5 min at 4°C, and the supernatant containing plasma and white blood cells was discarded. The precipitated red blood cells were washed three times with 1× pre-cooled phosphate-buffered saline (PBS) by centrifugation to separate and purify the free red blood cells. The purified red blood cells were resuspended in 1:2 (v / v) Alsever solution. 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), which is mixed with the red blood cell suspension obtained in step 1 at a volume ratio of 20:1. Pipette and blow gently to disperse evenly for 3-5 minutes, and incubate at 37°C for 30 minutes to promote drug-carrier interaction. 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 to obtain the purified RBC@Ru structure. Resuspend the RBC@Ru in an equal volume of PBS and store at 4°C for later use.

[0047] (3) Zeta potential detection, transmission electron microscopy (TEM) scanning and element mapping distribution (Mapping) verified that RBC was successfully loaded with small molecule drug Ru ( Figure 2 e and Figure 2 f).

[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 bronchial epithelial cells (BEAS-2B) and human embryonic lung fibroblasts (HELF) were cultured in DMEM (VivaCell) containing high-glucose, 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 experiment

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

[0053] 2.2. Live / dead staining: Calcein (AM) / Propidium iodide (PI) staining: BEAS-2B and HELF cells were collected during the growth phase and seeded in 6-well plates (8 × 10 4 Cells were cultured overnight in 4 wells (1 µl / well). Cell dosing and irradiation procedures were the same as above. 48 hours after irradiation, live cells were stained with 1 µl of AM solution in detection buffer, and dead cells were stained with 1 µl of PI solution. The captured cells in each cell group were then observed and counted using a fluorescence microscope.

[0054] 2.3. Mitochondrial membrane potential (JC-1) detection: BEAS-2B and HELF cells were collected during the growth phase and seeded in 6-well plates (8 × 10 4Culture overnight in 100 mL / well (1 mL / well). Follow the same procedures for cell dosing and irradiation as above. Add 1 mL of JC-1 staining working solution and mix thoroughly. 24 hours after irradiation, incubate in a cell culture incubator at 37°C for 20 minutes. Aspirate the supernatant and wash twice with JC-1 staining buffer (1X). Then, add 2 mL of cell culture medium, which may contain serum and phenol red. Observe under a fluorescence microscope or confocal laser scanning microscopy.

[0055] 2.4. DNA damage: BEAS-2B and HELF cells were collected during the growth phase and seeded in 96-well plates (1×10 4 Cells were cultured overnight in 4% paraformaldehyde ( / well). Cell dosing and irradiation procedures were the same as above. Within 6 hours after irradiation, cells were fixed with 4% paraformaldehyde and washed three times with washing buffer (5 minutes each). Immunostaining blocking buffer was added and blocked at room temperature for 20 minutes. After blocking, rabbit monoclonal antibody against γ-H2AX was added and incubated overnight at 4°C. Cells were then washed three times with washing buffer (5 minutes each). Anti-rabbit 488 was added and incubated at room temperature in the dark for 1 hour. Cell nuclei were counterstained with DAPI at room temperature. Cells were washed with washing buffer and examined under a fluorescence microscope.

[0056] 2.5. Flow cytometry of apoptosis (Annexin V-FITC): BEAS-2B and HELF cells were collected during the growth phase and seeded in 6-well plates (8 × 10 4 Cells were cultured overnight in 40% paraformaldehyde (400 μl / well) for 24 h. Cell dosing and irradiation procedures were the same as above. 48 h after irradiation, the cell supernatant was collected into a centrifuge tube and an appropriate amount of trypsin was added to the cell culture medium to terminate digestion. The tube was centrifuged at 1200 rpm for 5 minutes, the supernatant discarded, and the cells were collected. After washing with PBS and centrifugation, apoptosis detection reagents were added. The cells were then incubated at room temperature (10-20°C) in the dark for 10-20 minutes. Finally, flow cytometry was used to detect green fluorescence using Annexin V-FITC and red fluorescence using propidium iodide (PI).

[0057] 3. In vivo radiation-induced lung injury protection experiment

[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 performed 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. After one week of housing, a reflex lung injury model was established in mice (single intrathoracic irradiation of 17 Gy). The specific grouping and testing procedures are as follows:

[0059] Mice were randomly divided into five groups: control, Ru, RT, RT+Ru, and RT+RBC@Ru. Mice in the Ru and RT+Ru groups received Ru via the tail vein 1 hour before radiotherapy, while mice in the RT+RBC@Ru group received RBC@Ru via the tail vein 1 hour before radiotherapy. Each of the three groups received Ru at a concentration of 500 μg / mL (100 μL) twice weekly. Every three days, the mice were observed for dietary activity, chest hair removal, body weight, and survival. On day 30, the mice were euthanized, and lung tissue was obtained for examination. The collected lung tissue was fixed in 4% paraformaldehyde, paraffin-embedded sections were prepared, and staining, scanning, and image analysis were performed. Sections were stained with hematoxylin and eosin (HE) and Masson's staining to assess differences in inflammatory structures and collagen deposition between the drug-treated and control groups. Intracellular chromatin (IHC) staining and multicolor immunofluorescence staining were used to determine HIF-α and TUNEL expression. These in vivo studies demonstrated the feasibility, safety, and efficacy of the small molecule Ru in the treatment of radiation-induced lung injury.

[0060] 4. Biodistribution of RBC@Ru in vivo

[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 and ex vivo imaging of tissues and organs were performed at different time points.

[0062] Experimental results

[0063] 1. In vitro cell function protection experiment: After verifying Ru's multi-enzyme antioxidant activity, the present invention cultured human bronchial epithelial cells (BEAS-2B) and human embryonic lung fibroblasts (HELF) in vitro and stimulated the cells to produce reactive oxygen species (ROS) under an X-ray system. After intervention with a synthetic RU drug, intracellular ROS levels were quantified using a reactive oxygen species fluorescent probe (DCFH-DA) using fluorescence microscopy and flow cytometry. Ru's SOD and CAT enzyme activities were further verified through a series of experiments, including dead-alive fluorescence detection, DNA damage, cell cycle, flow cytometry, cell senescence, and mitochondrial membrane potential. These results confirmed its ability to scavenge ROS, reduce intracellular DNA damage, inhibit lung endothelial cell apoptosis, and promote lung endothelial cell growth and repair.

[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 of the RT+Ru group was reduced, and the dead / live cell ratio 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 of DNA damage marker γ-H2AX also decreased significantly ( Figure 4 g, h). Flow cytometry analysis of cell apoptosis showed that the cell apoptosis rate in the RT group was significantly increased, while that in the RT+Ru group was significantly decreased ( Figure 4 i, j). The above data indicate that Ru can significantly reduce radiation-induced oxidative stress, cell apoptosis and DNA damage ( Figure 4 k).

[0065] 2. In vivo lung radioprotection experiment: The results showed that the chest hair loss of mice in the RT+RBC@Ru and RT+Ru groups was significantly reduced 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 in the RT group, and the weight of mice increased compared with the RT group, but was lower than that of the non-irradiated group ( Figure 5 b). Post-mortem observations showed that the lung tissue congestion and edema of the mice in the drug treatment group were alleviated, the lung tissue wet weight decreased, and the lung coefficient decreased. In addition, all the observed indicators of the RT+RBC@Ru group were significantly better than those of the RT+Ru group. This fully demonstrated that the intravenous injection of red blood cell-loaded Ru avoided the targeted delivery of the liver "first-pass elimination", increased the utilization rate and duration of the drug, and exerted a better radiation protection effect in vivo ( Figure 5 c). HE pathological staining results showed that the inflammatory cell infiltration in the RT+RBC@Ru and RT+Ru groups was less than that in the RT group alone, with slight widening of the alveolar septa and a few alveolar fusions, and the pulmonary inflammatory response was significantly milder than that in the RT group. Masson staining showed that collagen fiber deposition 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 was decreased ( Figure 5 d). The above results all confirmed that the RT+Ru group alleviated lung tissue damage after radiotherapy compared with the RT group, and the effect of the RT+RBC@Ru group was more significant, indicating that the red blood cell-based delivery system can achieve effective delivery of Ru in vivo and enhance the targeting and bioavailability of drugs at the site of radiation-induced lung injury.

[0066] 3. Biodistribution of RBC@Ru: The results showed that Cy5.5-labeled RBC@Ru immediately concentrated in the lungs 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 a time-dependent clearance, the elimination of RBC@Ru was still slow ( Figure 6a, b), fully demonstrating the targeted accumulation of RBC@Ru in the lungs. In vitro organ imaging showed that a small amount of Ru was also distributed in the liver, kidney, or other tissues, which may be related to systemic clearance metabolism or drug uptake by the mononuclear phagocyte system. 48 hours after injection, the fluorescence intensity in the lungs of the RT+RBC@Ru group was significantly stronger than that of the RT+Ru group, which may be related to the sustained release of the drug ( Figure 6 c, d). Erythrocyte-mediated delivery fundamentally alters the drug's biodistribution, redirecting its tissue preference through circulatory hitchhiking and providing crucial support for its potent lung radioprotection.

[0067] It should be noted that the preferred embodiments of the present invention are given in the specification and drawings 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 are not intended to be additional limitations on the content of the present invention. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive. In addition, the above-mentioned technical features can be combined with each other to form various embodiments not listed above, which are all considered to be within the scope of the description of the present invention. Furthermore, it is obvious to those skilled in the art that improvements or changes can be made based on the above description, and all such improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A use of a small molecule compound as a biocatalyst not for diagnostic or therapeutic purposes, 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 use according to claim 2, characterized in that The delivery system includes red blood cells loaded with the small molecule compound.

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

5. A method for preparing the delivery system according to claim 4, characterized in that: The following steps are involved: (1) dispersing the small molecule compound as defined in claim 1 in a phosphate buffer; (2) The suspension of the small molecule compound is mixed with the suspension of red blood cells resuspended in red blood cell preservation fluid and then allowed to stand for reaction, so that the small molecule compound is adsorbed on the surface of the red blood cells by electrostatic action, thereby obtaining 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 were 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 minutes, and the standing temperature is 25-37°C.

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