Placenta targeting peptide plCSA-BP modified tetrahedral framework nucleic acid as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of biological medicines, and particularly relates to placenta targeting peptide plCSA-BP modified tetrahedral framework nucleic acid as well as a preparation method and application thereof. The placenta targeting peptide plCSA-BP is creatively combined with tFNAs to form a tFNAs / plCSA-BP compound, the compound has excellent placenta targeting property and can effectively improve the function of placenta trophoblasts, so that the treatment effect of preeclampsia is remarkably improved, a new treatment strategy is provided for the placenta diseases in the gestation period, and the placenta targeting peptide plCSA-BP has a good application prospect. The application prospect of the nano material in placental disease treatment is expanded.

Description

Technical Field

[0001] The present invention belongs to the field of biomedicine technology, and in particular relates to a tetrahedral framework nucleic acid modified with a placenta targeting peptide plCSA-BP, and a preparation method and application thereof. Background Art

[0002] Preeclampsia (PE) is a subtype of hypertensive disorders of pregnancy (HDP), a unique complication of pregnancy, and one of the main causes of maternal morbidity and mortality. Its clinical manifestations include new hypertension (systolic blood pressure ≥140 mmHg and / or diastolic blood pressure ≥90 mmHg) and proteinuria at or after 20 weeks of pregnancy. Severe symptoms may be accompanied by systemic multi-organ lesions, such as acute kidney injury, liver involvement, neurological symptoms (eclampsia, mental status changes, blindness, stroke, clonus, severe headache, persistent visual scotomas), or hematological complications (thrombocytopenia, disseminated intravascular coagulation or hemolysis), as well as uterine-placental dysfunction (such as abnormal umbilical artery Doppler waveforms on ultrasound, fetal growth restriction or stillbirth). Extensive studies have shown that placental dysfunction is one of the causes of major obstetric complications such as preeclampsia. The pathogenesis of preeclampsia is not fully understood, but it is generally believed to be a two-stage development process, including poor placental implantation and subsequent maternal systemic inflammatory response and vascular endothelial damage. Currently, there is no effective treatment for placental dysfunction in the perinatal period, and preventive measures are often ineffective. However, with the integration of nanoscience and medicine, fine experiments on the human placenta are expected to develop new and efficient nanotherapeutic strategies to address the challenges of managing placental dysfunction. Packaging multifunctional molecules into specific delivery systems with high targeting capabilities, combining diagnosis and treatment, has become a novel therapeutic diagnostic method. Nanomedicine provides a new therapeutic means to achieve targeted drug delivery through nanoparticles, which is expected to improve the treatment of placental dysfunction.

[0003] Tetrahedral framework nucleic acids (tFNAs) are self-assembled nucleic acid materials that can be easily synthesized and used. Due to the biological properties of nucleic acids, they have favorable safety. Self-assembled tFNAs are composed of four single-stranded DNAs (ssDNAs) based on complementary base pairing. Compared with conventional ssDNAs, which are difficult to enter cells, tFNAs can be absorbed by cells in large quantities through caveolin-mediated endocytosis without further delivery assistance. Studies have shown that tFNAs can promote the proliferation, migration, differentiation, and autophagy of various cells. It also has good anti-inflammatory, antioxidant, and anti-apoptotic effects, which can promote the repair and regeneration of epithelial tissues such as skin, mucosa, and cornea, and significantly reduce the formation of scars. Previous studies have developed placenta-targeted nanoparticles-placental-like chondroitin sulfate A binding polypeptide (plCSA-BP), which achieves specific drug delivery to the placental trophoblast and avoids the toxic side effects of drugs on the mother and fetus. So far, there has been no research on the use of tFNA for targeted placental treatment. Further research is needed to determine whether tFNA can successfully target the placenta and exert a better therapeutic effect. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a placenta targeting peptide plCSA-BP modified tetrahedral framework nucleic acid and its preparation method and application, so as to achieve targeted delivery of tetrahedral framework nucleic acid nanomaterials to the placenta area, thereby improving the placenta's uptake efficiency of nanomaterials and improving the therapeutic effect on preeclampsia.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: In the first aspect, the present invention provides a tetrahedral framework nucleic acid modified with a placenta targeting peptide plCSA-BP, comprising a tetrahedral framework nucleic acid, and a placenta targeting peptide plCSA-BP carried on the tetrahedral framework nucleic acid; the tetrahedral framework nucleic acid is self-assembled by four DNA single strands with nucleotide sequences such as those shown in SEQ ID NO.1-4 through the principle of complementary base pairing.

[0006] Preferably, the amino acid sequence of the placenta targeting peptide plCSA-BP is as shown in SEQ ID NO.5.

[0007] The present invention combines the targeting molecule plCSA-BP of placental trophoblast cells with tFNAs to form a tFNAs / plCSA-BP complex, thereby constructing a new nano drug delivery system. The complex can efficiently deliver drugs to the placental region, thereby improving the efficiency of the placenta's uptake of nanomaterials, and has significant therapeutic potential, especially in the intervention of placental diseases during pregnancy such as preeclampsia. The tetrahedral framework nucleic acid complex of the present invention can effectively improve the stability and targeting of drugs due to its unique nanostructure and biocompatibility, optimize the release mechanism of drugs in the placenta, thereby enhancing the therapeutic effect. Through this innovative strategy, the present invention not only provides new ideas and means for the treatment of placental diseases, but also broadens the application prospects of DNA nanomaterials in targeted placental treatment, and provides new possibilities for the clinical treatment of pregnancy-related diseases.

[0008] Preferably, the molar ratio of the tetrahedral framework nucleic acid to the placenta targeting peptide plCSA-BP is 1:1.

[0009] Preferably, the effective concentration of the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP is 125-250 nM.

[0010] Preferably, the effective concentration of the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP is 250 nM.

[0011] Experimental investigations revealed that the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP described in the present invention can effectively promote the growth of HTR8 / SVneo cells at a working concentration of 250 nM, and significantly enhance the migration and invasion abilities of the cells, and the anti-apoptosis effect of the cells is also significantly improved at this concentration.

[0012] In a second aspect, the present invention provides a method for preparing the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP, comprising the following steps: The placenta targeting peptide plCSA-BP is connected to a single DNA strand of the tetrahedral framework nucleic acid, and then the four DNA strands are dissolved in TM buffer, and then a PCR reaction is performed to obtain the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP.

[0013] Preferably, the four DNA single strands have the same final concentration in the TM buffer, which is 1 μM-100 μM.

[0014] Preferably, the reaction conditions of the PCR are: maintaining at 95°C for 10 min, then rapidly cooling to 4°C and maintaining for more than 20 min.

[0015] In a third aspect, the present invention provides the use of the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP in the preparation of a drug for treating placental dysfunction in preeclampsia.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention innovatively combines the placenta targeting peptide plCSA-BP with tFNAs to form a tFNAs / plCSA-BP complex. The complex has excellent placenta targeting and can effectively improve the function of placental trophoblasts, thereby significantly improving the therapeutic effect of preeclampsia. The present invention provides a new treatment strategy for placental diseases during pregnancy and expands the application prospects of nanomaterials in the treatment of placental diseases. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The characteristics and cellular uptake results of tFNAs; Figure 1 A in the figure is a schematic diagram of tFNAs synthesis; Figure 1 B in the figure is a transmission electron microscope (ATEM) image showing the morphology of tFNA; Figure 1 C in the figure is the PAGE test result, where I is S1, II is S2, III is S3, IV is S4, and V is tFNAs; Figure 1 D in the figure is the Zeta potential result of tFNAs; Figure 1 Panel E is the confocal laser scanning microscopy image of Cy5-ssDNAs and Cy5-tFNAs taken up by HTR8 / SVneo cells.

[0018] Figure 2 The results of tFNAs in vitro cell experiments are shown in Figure 2. Figure 2 A in the figure is the result of toxicity test; Figure 2 B is a schematic diagram of HTR8 / SVneo cell migration and invasion; Figure 2 C in the figure shows the migration and invasion results of HTR8 / SVneo cells; Figure 2 D in the figure is the result of flow cytometry apoptosis detection of HTR8 / SVneo cells.

[0019] Figure 3 The results of the in vivo treatment of preeclampsia are as follows: Figure 3 A in the figure is a schematic diagram of animal experiment; Figure 3 B in the figure is the Cy5 signal intensity results of in vivo imaging observation of mice in each group; Figure 3 C in the figure is the result of the changes in systolic blood pressure during pregnancy in each group of mice; Figure 3 D in the figure is the fetal weight results of mice in each group; Figure 3 E in the figure is the placenta weight results of mice in each group; Figure 3 F in the figure is the physical diagram of the fetal size of mice in each group; Figure 3 G in the figure is the comparison of H&E staining of the placenta of mice in each group.

[0020] Figure 4 The test results of the biosafety of the material in vivo, among which, Figure 4 A in the figure is a solid diagram of the size of a mouse fetus; Figure 4 B in the figure is the fetal weight results of mice in each group; Figure 4 C in the figure is the placenta weight results of mice in each group; Figure 4 D in the figure shows the H&E staining results of mouse placenta, liver and kidney. DETAILED DESCRIPTION

[0021] The above contents of the present invention are further described in detail below through specific implementation methods in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments.

[0022] Unless otherwise specified, the reagents used in the examples are conventional reagents in the art and can be purchased through commercial channels. The experimental operations not specifically described in the examples are conventional operations in the art or can be understood or known by those skilled in the art based on the existing technology or common knowledge they master.

[0023] Example 1. Preparation of placenta targeting peptide plCSA-BP modified tetrahedral framework nucleic acids (plCSA-BP / tFNAs) tFNAs were prepared using the four DNA single strands S1, S2, S3 and S4 in Table 1. The specific method was as follows: equimolar amounts of the four DNA single strands (S1, S2, S3 and S4 in Table 1) were added to TM buffer (50 Mm MgCl2 and 10 Mm TrisHCl, pH 8.0) so that the final concentrations of the four DNA single strands after dissolution were all 100 μM. After dissolution, they were fully mixed and placed in a PCR instrument. After a series of heating procedures (maintaining 95°C for 10 min, rapidly cooling to 4°C for more than 20 min), they were self-assembled through the principle of base complementary pairing to obtain DNA tetrahedrons (tFNAs).

[0024] Table 1 The placenta targeting peptide plCSA-BP (EDVKDINFDTKEKFLAGCLIVSFHEGKC) (SEQ ID NO.5) was synthesized by Shanghai Bioengineering, and the N-terminus of the peptide was modified with azide, which was connected to the 5'-end modified DBCO of the S2 single chain in Table 1. Then, the tetrahedral framework nucleic acid complex plCSA-BP / tFNAs (p-tFNAs) can be prepared using S1, plCSA-BP-S2, S3 and S4 in Table 1 according to the same method as above. The molar ratio of the tetrahedral framework nucleic acid to the placenta targeting peptide plCSA-BP is 1:1.

[0025] Polyacrylamide gel electrophoresis (PAGE) and atomic force microscopy (AFM) were used to verify the synthesis of tFNAs and to show their size and shape. Dynamic light scattering (DLS) (Nano ZS, Malvern, UK) was used to measure the zeta potential of tFNAs.

[0026] The results are as follows Figure 1 As shown, first, tFNAs are self-assembled from four equimolar amounts of ssDNA ( Figure 1 A in the figure), and the successful synthesis of tFNAs was detected by PAGE ( Figure 1 C in. Figure 1 The AFM image in Figure B shows that tFNAs have a triangular appearance, and the average size value was measured. In addition, the zeta potential ( Figure 1 The successful synthesis of tRNAs was also confirmed.

[0027] Experimental Example 1. Study on the Cellular Uptake and Toxicity of tFNAs (1) Cellular uptake: Test method: Cy5 fluorescent dye was attached to the 5' end of the S1 chain, and the same method as in Example 1 was used to synthesize tFNAs labeled with Cy5. HTR8 / SVneo cell suspension was inoculated in a confocal dish and pre-cultured in an incubator for 24 h. Cy5-labeled tFNAs (each drug concentration was 125 nM) were then added. After culturing in the incubator for 24 h, the medium was removed and the cells were washed three times with PBS for 5 min each. The cells were then fixed with 4% paraformaldehyde for 30 min, the paraformaldehyde was removed, and the cells were washed three times with PBS for 5 min each. The cells were then treated with phalloidin (FITC-labeled) and protected from light for 10-30 min. The phalloidin was removed and the cells were washed three times with PBS for 5 min each. The cells were then treated with DAPI and protected from light for 15 min. The DAPI was removed and the cells were washed three times with PBS for 5 min each. The cells were then sealed with 10% glycerol, protected from light, and stored at 4°C. A confocal microscope (LSM 880 with Airyscan, Germany) was used to observe the distribution of Cy5 fluorescence signals in cells.

[0028] The results show that: from the images of laser confocal microscopy ( Figure 1 In (E), it can be observed that Cy5-labeled tFNAs are widely distributed in the cytoplasm of cells. The results show that the tFNAs can be taken up by HTR8 / SVneo cells to exert subsequent biological effects after entry into the cell.

[0029] (2) Cytotoxic effect: Test method: The CCK-8 detection kit was used to detect the cell activity after tFNAs treatment. HTR8 / SVneo cells were inoculated in 96-well plates and pre-cultured in an incubator for 24 hours. Subsequently, tFNAs were added at concentrations of 62.5nM, 125nM, 250nM, 375nM, and 500nM. After 24 hours of treatment, the original culture medium was removed and CCK-8 detection solution was added. The absorbance was measured at 450nm by a microplate reader to calculate the cell activity.

[0030] The results show: Figure 2 In Figure A, the results of CCK-8 showed that tFNAs can effectively promote the growth of HTR8 / SVneo cells, and the 250nM concentration has a more obvious promoting effect on the activity of HTR8 / SVneo cells.

[0031] (3) Cell migration assay: Test method: The experiment was divided into 3 groups: I-blank group; II-hypoxia treatment group; III-hypoxia treatment + 250nMtFNAs group, and at least 3 cells were plated in each group. The old culture medium of HTR8 / SVneo cells was discarded, and the cells were digested with 0.25% trypsin, centrifuged at room temperature, 900rpm for 5min, and the supernatant was discarded. The cells were resuspended in PBS, washed once, centrifuged and the original culture medium supernatant was discarded, and an appropriate amount of culture medium was added. After the cells were suspended, the cell density was calculated using a counter to make the cell density reach 3×10 4 / ml. Take out the 24-well plate from the cell culture incubator and gently aspirate the liquid in the upper chamber of the chamber. Add 600μL of complete culture medium to the lower chamber of each well of the 24-well plate. Add 200μL of cell suspension to the upper chamber of the chamber to evenly distribute the cells in the upper chamber of the chamber. Place the cells in a cell culture incubator and continue to culture for 48 hours at 37°C and 5% CO2. Take out the Transwell chamber, discard the culture medium in the chamber, fix it in 4% paraformaldehyde for 30 minutes, then rinse it in PBS 3 times, 5 minutes each time, then stain it in 1% crystal violet for 15-20 minutes, and rinse it in PBS 6 times after staining, 5 minutes each time. Use a cotton swab to gently wipe off the residual cells in the upper chamber of the Transwell, rinse it clean and dry it, and then count the number of cells in the lower chamber under an inverted microscope.

[0032] The results show: Figure 2In Figure C, the results showed that compared with the control group cells, the migration ability of the HTR8 / SVneo cell line treated with hypoxia was significantly decreased, and the migration ability of the hypoxia treatment + 250nMtFNAs group was increased compared with the simple hypoxia treatment group.

[0033] (4) Cell invasion assay: Test method: Take out Matrigel from -20℃ and place it in a 4℃ refrigerator overnight to melt Matrigel into liquid. Precool EP tubes, pipette tips and 1640 culture medium in a 4℃ refrigerator. Take out the 8μm diameter Transwell chamber and gently place it in a 24-well plate. Dilute Matrigel with precooled 1640 culture medium, vertically drip Matrigel to the bottom of the upper chamber of the chamber, 100ul / well, avoid bubbles, and place the 24-well plate in a 37℃ incubator for 0.5-1h to allow Matrigel to coagulate.

[0034] The experiment was divided into 3 groups: I-blank group; II-hypoxia treatment group; III-hypoxia treatment + 250nM tFNAs group, and at least 3 cells were plated in each group. The old culture medium of HTR8 / SVneo cells was discarded, and the cells were digested with 0.25% trypsin, centrifuged at room temperature, 900rpm for 5min, and the supernatant was discarded. The cells were resuspended in PBS, washed once, centrifuged and the original culture medium supernatant was discarded, and an appropriate amount of culture medium was added. After the cells were suspended, the cell density was calculated using a counter to make the cell density reach 2×10 5 / ml. Take out the 24-well plate from the cell culture incubator and gently remove the liquid in the upper chamber of the chamber. Add 600μL of complete culture medium to the lower chamber of each well of the 24-well plate. Add 200μL of cell suspension to the upper chamber of the chamber to evenly distribute the cells in the upper chamber of the chamber. Place the cells in a cell culture incubator and continue to culture for 48 hours at 37°C and 5% CO2. Take out the Transwell chamber, discard the culture medium in the chamber, fix it in 4% paraformaldehyde for 30 minutes, then rinse it in PBS 3 times, 5 minutes each time, then stain it in 1% crystal violet for 15-20 minutes, and rinse it in PBS 6 times after staining, 5 minutes each time. Use a cotton swab to gently wipe off the residual cells and Matrigel in the upper chamber of the Transwell, rinse it clean and dry it, and then count the number of cells in the lower chamber under an inverted microscope.

[0035] The results show: Figure 2 In Figure C, the results showed that compared with the control group cells, the invasion ability of the HTR8 / SVneo cell line treated with hypoxia was significantly decreased, and the invasion ability of the hypoxia treatment + 250nMtFNAs group was higher than that of the simple hypoxia treatment group.

[0036] (5) Cell apoptosis experiment: The experiment was divided into 3 groups: I-blank group; II-hypoxia treatment group; III-hypoxia treatment + 250nM tFNAs group, and each group of cells was plated at least 3 duplicate wells; HTR8 / SVneo cells were cultured in 6-well plates for 24 hours, and then 250nM tFNAs were added for 24 hours. Subsequently, the cells were digested with EDTA-free trypsin, and the cell suspension was collected and centrifuged at 1000r / min for 5 minutes. After washing with PBS and centrifuging, FITC-PI apoptosis detection reagent was added, and cell apoptosis was detected by flow cytometry.

[0037] The results are as follows Figure 2 As shown in D, the results showed that compared with the control group cells, the HTR8 / SVneo cell line treated with hypoxia had obvious cell apoptosis, and the hypoxia treatment + 250nM tFNAs group had an anti-apoptotic effect.

[0038] Experimental Example 2. Detection of the in vivo therapeutic effect of plCSA-BP / tFNAs nanomaterials Methods: 8-10-week-old C57B / 6 mice were selected and divided into 4 groups (6 mice in each group), including saline group, L-NAME group, L-NAME+tFNAs group, and L-NAME+p-tFNAs group. The animals were housed under standard light-dark cycle conditions (12 h:12 h, temperature 25°C) with free access to food and water. After 1 week of adaptation, healthy male mice and female mice were mated at night in a ratio of 1:2. The female mice that were stuffed were identified as pregnant, and this day was defined as the gestational day (GD0.5). Starting from GD9.5, pregnant mice in groups 2-4 were subcutaneously injected with L-NAME (HY-18729A, MedChemExpress, MonmouthJunction, NJ, USA) (125 mg / kg / d). Pregnant mice in the control group were subcutaneously injected with saline (equal to L-NAME) starting from the 9th day of gestation for 9 days. The blood pressure of mice was monitored regularly, and mice were killed by exsanguination under anesthesia with 5% isoflurane inhalation in room air at GD17.5. Tissues and serum were collected for further analysis.

[0039] Results: Figure 3 As shown in B, compared with the non-placenta-targeted group, the placenta-targeted p-tFNAs reached the placenta in greater amounts within 24 hours, indicating that the nanomaterial p-tFNAs carrying the placenta-targeted peptide achieved specific drug delivery to the placental trophoblast. Compared with the saline group, the blood pressure in the L-NAME group increased significantly, and the blood pressure in the L-NAME+tFNAs group and the L-NAME+p-tFNAs group decreased compared with the PE group, with the L-NAME+p-tFNAs group having the most significant effect. The fetal weight in the L-NAME group decreased significantly, The L-NAME+p-tFNAs group could significantly increase the fetal weight. Figure 3 As shown in C, D, E, and F in Figure 3. To determine whether placenta-targeted p-tFNAs would improve the placental structure of preeclampsia mice, this study used H&E staining to analyze the structural changes of the placenta in each group. Figure 3 As shown in G, under low-power observation, it was found that compared with the normal saline group, the ratio of the labyrinth area to the connecting area of ​​the placenta in the L-NAME injection group was significantly increased. The increase in the ratio of the labyrinth area to the connecting area of ​​the placenta was mainly related to the decrease in the area of ​​the connecting area and the increase in the labyrinth area. The injection of placenta-targeted p-tFNAs can appropriately reverse the changes in placental structure induced by L-NAME.

[0040] Then, the tumors and vital organs of the mice were collected for histopathological examination and immunofluorescence staining. Figure 4 As shown in Figures AC, there was no significant decrease in fetal weight and placental weight after tFNAs injection in pregnant mice. Figure 4 As shown in D, the H&E staining results showed that there was no obvious inflammation and pathological damage in organs such as the placenta, liver and kidney, which indicates that tFNAs have good biocompatibility and biosafety in vivo.

[0041] In summary, the nanomaterial with placenta-targeted therapeutic effect provided by the present invention, i.e., tFNAs / plCSA-BP complex, is a nanomaterial with placenta-targeted properties and improved placental trophoblast function. At the same time, the tFNAs / plCSA-BP complex of the present invention has high safety while achieving placental treatment, and no side effects and hazards were found in in vitro and in vivo experiments. The present invention provides a new strategy for placenta-targeted treatment of pregnancy diseases in the future.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A tetrahedral framework nucleic acid modified with a placenta targeting peptide plCSA-BP, characterized in that: It includes a tetrahedral framework nucleic acid, and a placenta targeting peptide plCSA-BP carried on the tetrahedral framework nucleic acid; The tetrahedral framework nucleic acid is self-assembled by four DNA single strands with nucleotide sequences such as SEQ ID NO.1-4 through the principle of complementary base pairing.

2. The placenta targeting peptide plCSA-BP modified tetrahedral framework nucleic acid according to claim 1, characterized in that: The amino acid sequence of the placenta targeting peptide plCSA-BP is shown in SEQ ID NO.

5.

3. The placenta targeting peptide plCSA-BP modified tetrahedral framework nucleic acid according to claim 1, characterized in that: The molar ratio of the tetrahedral framework nucleic acid to the placenta targeting peptide plCSA-BP is 1:

1.

4. The method for preparing the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP according to any one of claims 1 to 3, characterized in that: The following steps are involved: The placenta targeting peptide plCSA-BP is connected to a single DNA strand of the tetrahedral framework nucleic acid, and then the four DNA strands are dissolved in TM buffer, and then a PCR reaction is performed to obtain the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP.

5. The preparation method according to claim 4, characterized in that: The final concentrations of the four DNA single strands in TM buffer were the same, and the final concentrations were all 1 μM-100 μM.

6. The preparation method according to claim 5, characterized in that: The reaction conditions of the PCR are: maintaining at 95° C. for 10 min, then rapidly cooling to 4° C. and maintaining for more than 20 min.

7. Use of the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP as claimed in any one of claims 1 to 3 in the preparation of a drug for treating placental dysfunction in preeclampsia.

8. The use according to claim 7, characterized in that The effective concentration of the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP is 125-250 nM.

9. The use according to claim 8, characterized in that The effective concentration of the tetrahedral framework nucleic acid modified with the placenta targeting peptide plCSA-BP is 250 nM.

Images