DNA tetrahedral nano device with PEG molecule space accurate arrangement and preparation method and application thereof

Abstract

The invention provides a DNA tetrahedral nano device with PEG molecule space accurate arrangement and a preparation method and application thereof. Specifically, the invention provides a nucleic acid tetrahedral nanostructure which comprises a tetrahedral composite structure formed by assembling a plurality of nucleic acid monomers, and the tetrahedral composite structure is coupled with PEG molecules. By utilizing addressability and programmability of the DNA nanotechnology, the conformation with the highest space coverage rate can be realized by accurately controlling the spatial position of the PEG molecule in the DNA nanostructure, and the biological stability can be greatly improved.

Description

Technical Field

[0001] The present invention belongs to the field of materials and biomedicine technology, and in particular relates to a DNA tetrahedron nanodevice with precise spatial arrangement of PEG molecules and a preparation method and application thereof. Background Art

[0002] Polyethylene glycol (PEG) is an inert, non-carcinogenic polymer and is currently one of the preferred polymers for modifying the surface of bioactive molecules and nanoparticles. Polyethylene glycol modification is also called PEGylation of molecules, which can enhance the solubility of hydrophobic drugs, proteins, liposomes, and nucleic acids, improve their stability, and prolong their half-life. Many chemical drugs, proteins, peptides, etc. have their own defects while producing efficacy, and PEG modification can just make up for these problems, including: increasing the water solubility of the modified substance, reducing the immunogenicity of the modified substance, improving the pharmacokinetic and pharmacodynamic properties of the modified substance, and increasing the clinical application range of the modified substance.

[0003] However, current PEGylation modifications are often irregular or random, making it difficult to obtain PEG-modified products with precise spatial arrangement of PEG molecules.

[0004] Therefore, there is an urgent need in the art to develop PEG modification methods and products with precise spatial arrangement of PEG molecules. Summary of the invention

[0005] The purpose of the present invention is to provide a PEG-modified product with precise spatial arrangement of PEG molecules.

[0006] Another object of the present invention is to provide a method for preparing and applying a PEG-modified product having precise spatial arrangement of PEG molecules.

[0007] In a first aspect of the present invention, a nucleic acid tetrahedron nanostructure is provided, wherein the nucleic acid tetrahedron nanostructure comprises a tetrahedron composite structure formed by assembling a plurality of nucleic acid monomers, and the tetrahedron composite structure is coupled with a PEG molecule.

[0008] In another preferred embodiment, the nucleic acid monomer is selected from the following group: DNA, RNA, locked nucleic acid, peptide nucleic acid, or a combination thereof.

[0009] In another preferred embodiment, the nucleic acid tetrahedron nanostructure is a DNA nucleic acid tetrahedron nanostructure.

[0010] In another preferred embodiment, the multiple nucleic acid monomers constituting the nucleic acid tetrahedral nanostructure are independent of each other, but can interact with each other through base pairing and the like to form a tetrahedral composite structure.

[0011] In another preferred embodiment, each nucleic acid monomer is independently modified by a PEG molecule or is not modified by a PEG molecule.

[0012] In another preferred embodiment, among the single nucleic acid chains (or nucleic acid monomers) constituting the nucleic acid tetrahedral nanostructure, 2, 3, or 4 nucleic acid monomers are modified by PEG.

[0013] In another preferred embodiment, all nucleic acid monomers are modified with PEG.

[0014] In another preferred embodiment, for each nucleic acid monomer modified by PEG, the modified site may be one or more.

[0015] In another preferred embodiment, the number of sites modified by PEG on a nucleic acid monomer is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more, preferably 2-5.

[0016] In another preferred embodiment, the PEG is generally a PEG molecule formed by 2-20 (preferably 2-10, more preferably 3-6) ethylene glycol monomers.

[0017] In the present invention, the length of each nucleic acid monomer is generally 21-63 nt, preferably 57-63 nt.

[0018] In another preferred embodiment, in the nucleic acid tetrahedral nanostructure, the length of each nucleic acid monomer is the same or substantially the same (eg, the length difference is ≤10%, or ≤5 nt).

[0019] In another preferred embodiment, the size of the nucleic acid tetrahedral nanostructure is about 5-30 nanometers, preferably 7-20 nanometers.

[0020] In another preferred embodiment, the nucleic acid tetrahedral nanostructure has a structure of formula A:

[0021] Z-PEG(A)

[0022] In the formula,

[0023] Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers;

[0024] PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure.

[0025] In another preferred embodiment, the nucleic acid tetrahedral nanostructure has a structure of formula B:

[0026] Z-PEGn(B)

[0027] In the formula,

[0028] Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers;

[0029] PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure;

[0030] n is the number of PEG molecules coupled to a nucleic acid tetrahedral nanostructure, which is 1-100, preferably 2-50, and more preferably 3-30.

[0031] In another preferred embodiment, the nucleic acid tetrahedron nanostructure is a drug-loaded nucleic acid tetrahedron nanostructure.

[0032] In another preferred embodiment, the nucleic acid tetrahedral nanostructure is a complex of formula I:

[0033] Z-PEG-D(I)

[0034] In the formula,

[0035] Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers;

[0036] PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure;

[0037] D stands for drug.

[0038] In another preferred embodiment, the drug-carrying nucleic acid tetrahedral nanostructure has a structure of Formula II:

[0039] Z-PEGn-Dm(II)

[0040] In the formula,

[0041] Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers;

[0042] PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure;

[0043] n is the number of PEG molecules coupled to a nucleic acid tetrahedral nanostructure, which is 1-100, preferably 2-50, and more preferably 3-30;

[0044] D stands for drug;

[0045] m is the number of drugs covalently coupled to one nucleic acid tetrahedral nanostructure via a PEG molecule, m is ≥1, and preferably m≤n.

[0046] In another preferred embodiment, m is 1-100, preferably 2-50, more preferably 3-30.

[0047] In another preferred embodiment, the ratio of m / n is 10-100%, preferably 20-90%, and more preferably 50-80%.

[0048] In a second aspect of the present invention, a method for preparing the nucleic acid tetrahedral nanostructure according to the first aspect of the present invention is provided, comprising the steps of:

[0049] (a) providing nucleic acid monomers, wherein at least one nucleic acid monomer is coupled to a PEG molecule;

[0050] (b) mixing and annealing the nucleic acid monomers to assemble and form the nucleic acid tetrahedral nanostructure according to the first aspect of the present invention.

[0051] In another preferred embodiment, a PEG molecule is coupled to the nucleic acid monomer at a predetermined position.

[0052] In another preferred embodiment, the method further comprises the steps of:

[0053] (c) covalently coupling the nucleic acid tetrahedral nanostructure obtained in step (b) with a drug to obtain a drug-loaded nucleic acid tetrahedral nanostructure.

[0054] In another preferred embodiment, the drug is selected from the following group: small molecule drugs, peptide drugs, protein drugs or a combination thereof.

[0055] In another preferred embodiment, the drug is deferoxamine.

[0056] In the third aspect of the present invention, there is provided a use of the nucleic acid tetrahedral nanostructure according to the first aspect of the present invention, which is used to prepare PEGylated drugs.

[0057] It should be understood that within the scope of the present invention, the above-mentioned technical features of the present invention and the technical features specifically described below (such as embodiments) can be combined with each other to form a new or preferred technical solution. Due to space limitations, they will not be described one by one here. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The schematic diagram shows the structure of the assembly of DNA tetrahedron with PEG molecular spatial conformation. The purple area is the DNA base modified with PEG, and the yellow area is the DNA base not modified with PEG.

[0059] Figure 2 Atomic force microscopy characterization of DNA tetrahedron with spatial conformation of PEG molecules is shown.

[0060] Figure 3 The size and electrical characterization results of DNA tetrahedron with PEG molecular spatial conformation are shown.

[0061] Figure 4The structure characterization results of the DNA nanomachine synthesized by the present invention are shown. The lanes are as follows: Lane 1 is a band of a PEGylated tetrahedral DNA nanomachine; Lane 2 is a DNA nanomachine that is not PEGylated; Lane 3 is a 20 bp DNA standard, and the DNA fragments from top to bottom are 500 bp, 400 bp, 300 bp, 200 bp, 180 bp, 160 bp, 140 bp, 120 bp, 100 bp, 80 bp, 60 bp, 40 bp, and 20 bp, respectively. DETAILED DESCRIPTION

[0062] The inventors have, after extensive and in-depth research, provided a unique nucleic acid tetrahedron nanostructure with precise spatial arrangement of PEG molecules for the first time. The inventors have designed and prepared nucleic acid tetrahedron nanostructures (such as DNA tetrahedron nanostructures) of different conformations, thereby achieving precise control of the spatial position of PEG molecules in the DNA nanostructure. The nucleic acid tetrahedron nanostructure of the present invention can be a nanomachine that can carry drugs, thereby greatly improving the biological stability, half-life and safety of the loaded drugs. The present invention has been completed on this basis.

[0063] Nucleic acid tetrahedral nanostructure of the present invention

[0064] As used herein, the terms "the nucleic acid tetrahedral nanostructure of the present invention", "the nanostructure of the present invention", "the DNA molecular machine of the present invention", "the nanodevice of the present invention", "the tetrahedral nanostructure of the present invention" and "the nucleic acid tetrahedral nanostructure with precise spatial arrangement of PEG molecules" are used interchangeably to refer to the nucleic acid tetrahedral nanostructure described in the first aspect of the present invention, which has a tetrahedral structure formed by the assembly of nucleic acid single strands, and the nucleic acid tetrahedral nanostructure is also coupled to the PEG molecule in the predetermined space of the nucleic acid tetrahedral nanostructure (or the predetermined position of the nucleic acid monomer). It should be understood that the nucleic acid tetrahedral nanostructure of the present invention can be

[0065] It should be understood that the nucleic acid monomers in the nucleic acid tetrahedral nanostructure of the present invention may include (but are not limited to): DNA, RNA, locked nucleic acid, peptide nucleic acid, or a combination thereof.

[0066] In a preferred embodiment, the nucleic acid tetrahedral nanostructure of the present invention is a DNA nucleic acid tetrahedral nanostructure.

[0067] In the present invention, the schematic diagram of the nucleic acid tetrahedron nanostructure is as follows Figure 1 As shown, the purple area is the DNA base modified by PEG, and the yellow area is the DNA base not modified by PEG. In the present invention, the multiple nucleic acid monomers constituting the nucleic acid tetrahedral nanostructure are independent of each other, but can interact with each other through base pairing and the like to form a tetrahedral composite structure.

[0068] In the present invention, although the nucleic acid tetrahedral nanostructure is modified by at least one or more PEG molecules, each nucleic acid monomer can be independently modified by a PEG molecule or not. In other words, in the present invention, at least one nucleic acid monomer is coupled to a PEG molecule or modified by a PEG molecule.

[0069] Preferably, in the present invention, among the nucleic acid single strands (or nucleic acid monomers) constituting the nucleic acid tetrahedral nanostructure, 2, 3, or 4 nucleic acid monomers are modified by PEG. More preferably, all nucleic acid monomers are modified by PEG.

[0070] For each nucleic acid monomer modified by PEG, the modified site can be one or more. Typically, on a nucleic acid monomer, the number of sites modified by PEG is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more, preferably 2-5.

[0071] In the present invention, the PEG is generally a PEG molecule formed by 2-20 (preferably 2-10, more preferably 3-6) ethylene glycol monomers.

[0072] In another preferred embodiment, the nucleic acid tetrahedral nanostructure of the present invention may also be coupled with one or more PEG molecules with a higher molecular weight, that is, PEG molecules formed by 20-10000 ethylene glycol monomers.

[0073] In the present invention, the length of each nucleic acid monomer is generally 21-63 nt, preferably 57-63 nt.

[0074] Preferably, in the nucleic acid tetrahedral nanostructure of the present invention, the length of each nucleic acid monomer is the same or substantially the same (eg, the length difference is ≤10%, or ≤5 nt).

[0075] In a preferred embodiment, the size of the nucleic acid tetrahedral nanostructure of the present invention can be controlled to be between 5 and 30 nanometers, preferably between 7 and 20 nanometers, by setting the length of the nucleic acid monomer sequence.

[0076] application

[0077] The present invention also provides applications of the nucleic acid tetrahedron nanostructure in various occasions.

[0078] Typically, the nucleic acid tetrahedral nanostructure of the present invention can be used as a carrier for loading drugs. It should be understood that the loaded drugs are small molecule drugs, peptide drugs, or protein drugs.

[0079] The DNA tetrahedral nanostructure of the present invention has a nanometer-scale size, and the spatial position of the coupled PEG molecules can be precisely controlled. Therefore, a highly uniform nanomachine (or nanocarrier) for drug delivery can be prepared, thereby greatly improving the biological stability, half-life and safety of the drug.

[0080] In another preferred embodiment, a drug formed by covalently coupling the nucleic acid tetrahedral nanostructure of the present invention with the small molecule compound deferoxamine is constructed. The drug has an improved renal clearance rate and can be applied to blood purification, especially the efficient treatment of iron overload, and thus used for the treatment of related diseases such as hemosiderosis.

[0081] It should be understood that in the art, any active pharmaceutical ingredient that can be PEGylated can be covalently coupled to the PEG on the nucleic acid tetrahedral nanostructure of the present invention to obtain a complex of formula I:

[0082] Z-PEG-D(I)

[0083] In the formula,

[0084] Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers;

[0085] PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure;

[0086] D stands for drug.

[0087] Preferably, the drug-carrying nucleic acid tetrahedral nanostructure has a structure of Formula II:

[0088] Z-PEGn-Dm(II)

[0089] In the formula,

[0090] Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers;

[0091] PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure;

[0092] n is the number of PEG molecules coupled to a nucleic acid tetrahedral nanostructure, which is 1-100, preferably 2-50, and more preferably 3-30;

[0093] D stands for drug;

[0094] m is the number of drugs covalently coupled to one nucleic acid tetrahedral nanostructure via a PEG molecule, m is ≥1, and m≤n.

[0095] In another preferred embodiment, m is 1-100, preferably 2-50, more preferably 3-30.

[0096] In another preferred embodiment, the ratio of m / n is 10-100%, preferably 20-90%, and more preferably 50-80%.

[0097] Preparation method

[0098] The present invention also provides a method for preparing the nucleic acid tetrahedron nanostructure of the present invention, comprising the steps of:

[0099] (a) providing nucleic acid monomers, wherein at least one nucleic acid monomer is coupled to a PEG molecule;

[0100] (b) mixing and annealing the nucleic acid monomers to assemble and form the nucleic acid tetrahedral nanostructure of the present invention.

[0101] Typically, in the present invention, a predetermined number of PEG molecules are first synthesized into the phosphate backbone of DNA nucleotides by covalent linkage, thereby obtaining a conjugate of DNA nucleotide monomers and PEG molecules; then, these conjugates of nucleotide monomers and PEG are used to add and react one by one on a solid phase to synthesize a long DNA chain, thereby achieving the coupling of a predetermined number (e.g., 2-15) of PEG molecules to a single DNA chain; thirdly, through complementary base pairing of DNA, the assembly of DNA chains is achieved to form a three-dimensional nucleic acid tetrahedral nanostructure, thereby accurately spatially arranging and regulating the PEG molecules according to the requirements of three-dimensional distribution.

[0102] When it is necessary to prepare a drug-loaded nucleic acid tetrahedron nanostructure, the method of the present invention further comprises step (c): covalently coupling the nucleic acid tetrahedron nanostructure obtained in step (b) with the drug to obtain the drug-loaded nucleic acid tetrahedron nanostructure.

[0103] The main advantages of the present invention include:

[0104] (a) The drug platform of the present invention is based on DNA nanotechnology, has a simple preparation process, and has uniform structure and properties.

[0105] (b) The DNA nanostructure of the present invention is highly designable and its morphological characteristics can be precisely controlled.

[0106] (c) The yield of the DNA nanostructure prepared by the present invention is high, which can reach more than 90%.

[0107] (d) The present invention utilizes the addressability of DNA nanotechnology and can achieve the highest spatial coverage conformation by precisely controlling the spatial position of PEG molecules in the DNA nanostructure, thereby greatly improving its biological stability.

[0108] (f) The present invention uses the programmability of DNA nanotechnology to construct a DNA molecular machine with precisely controllable size, which can quickly pass through the glomerular filtration membrane of the kidney (less than 6 nanometers) in the body, thereby controlling its biological distribution in the body, achieving rapid clearance and excretion of the drug, and increasing its circulation time while greatly improving its biosafety.

[0109] (g) The DNA molecular machine provided by the present invention can be used as a universal drug delivery platform to target ions, small molecules, nucleic acid macromolecules, proteins and peptides in the body to achieve the function of targeted and directional removal in the body. It has very good promotion and universality.

[0110] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the present invention. The experimental methods in the following examples where specific conditions are not specified are usually performed under conventional conditions, such as those described in Sambrook et al., Molecular Cloning: A Laboratory Manual (New York: Cold Spring Harbor Laboratory Press, 1989), or under conditions recommended by the manufacturer. Unless otherwise indicated, percentages and parts are weight percentages and weight parts.

[0111] Example 1

[0112] Preparation of Tetrahedral Nucleic Acid Monomers

[0113] The sequences of a set of nucleic acid monomers used to construct nucleic acid tetrahedral nanostructures are shown in Tables 1 and 2.

[0114] The nucleic acid monomers shown in Table 1 and Table 2 were synthesized using conventional artificial synthesis methods.

[0115] Table 1 Sequences of nucleic acid monomers in normal unPEGylated tetrahedrons

[0116]

[0117] Table 2 Monomer sequences of PEGylated tetrahedrons, where the underlined bases are PEGylated bases

[0118]

[0119] Note: The PEG in Table 2 is PEG containing 3 ethylene glycol monomers.

[0120] For the nucleic acid monomers shown in Table 2, a predetermined number of PEG molecules are first synthesized into the backbone of DNA nucleotides by covalent linkage, and a predetermined number (here 12) of PEG molecules are coupled to each edge of the tetrahedron using DNA solid phase synthesis.

[0121] Example 2

[0122] Assembly of DNA nanomachines

[0123] In the example, nucleic acid monomers shown in Table 2 prepared in Example 1 were used to prepare nucleic acid tetrahedral nanostructures.

[0124] The method is as follows: 4 oligonucleotides (nucleic acid monomer chains) of 63 bases are annealed to assemble, wherein each chain extends along the three sides of one face of a tetrahedron, and each single strand of DNA is structurally split into three edge regions, each edge being composed of two complementary DNA double strands. Therefore, each position of the tetrahedron is formed by double-stranded complementary hybridization with base sequence specificity. The sequences of the 4 nucleic acid monomer chains are described in Tables 1 and 2.

[0125] All single-stranded DNA oligonucleotides were in 1×TAE-Mg 2 + (12.5 mM magnesium acetate, 2 mM EDTA, 20 mM acetic acid and 40 mM Tris base, pH 8.0). The four oligonucleotides were then mixed and the mixture was annealed from 90°C to 4°C using the temperature gradient shown in Table 3 below.

[0126] Table 3

[0127]

[0128] During the annealing process, the DNA chains are assembled through complementary base pairing to form a three-dimensional DNA nanostructure, thereby precisely arranging and regulating the PEG molecules according to the three-dimensional distribution requirements. The schematic diagram of the nucleic acid tetrahedral nanostructure is shown in Figure 1 shown.

[0129] The prepared nucleic acid tetrahedral nanostructures were characterized by atomic force microscopy and polyacrylamide electrophoresis using conventional instruments and methods.

[0130] result

[0131] The results are as follows Figure 2 , Figure 3 and Figure 4 shown.

[0132] Figure 2 Atomic force microscopy characterization of DNA tetrahedron with PEG molecule spatial conformation is shown, indicating that the assembly forms a tetrahedral structure.

[0133] Figure 3 The size and electrical characterization results of the DNA tetrahedron with the spatial conformation of the PEG molecule are shown, indicating that its size is 5-10 nm.

[0134] Figure 4 The results of structural characterization of the DNA nanomachine synthesized by the present invention are shown, wherein the molecular weight of the PEGylated nucleic acid tetrahedron nanostructure is larger, which is consistent with the expected value.

[0135] Example 3

[0136] Preparation of drug-loaded nucleic acid tetrahedral nanostructures

[0137] In this example, the nucleic acid tetrahedron nanostructure prepared in Example 2 is covalently coupled with a chelating agent molecule (drug molecule) to obtain a drug-loaded nucleic acid tetrahedron nanostructure. The method is as follows:

[0138] Deferoxamine is a very specific Fe ion (Fe 3 +) chelators have a very strong affinity for iron ions. By click chemistry, deferoxamine molecules can be coupled to the ends of DNA chains to form stable DNA modifications. By assembling different numbers (4-20) of deferoxamine nanochelators on tetrahedral DNA nanomachines, Fe ions can be chelated in the blood. 3 +Effective removal.

[0139] The tetrahedral structure of the PEG nucleic acid loaded with deferoxamine is identical to the tetrahedral conformation characterized by the original design, and the structure is consistent. Because the size of the small molecule deferoxamine is small, the size of the tetrahedral structure has not changed significantly, and its edge length is also 5-10nm.

[0140] discuss

[0141] PEG modification has three main advantages:

[0142] 1. Improved pharmacokinetic and pharmacodynamic properties: Studies have shown that after PEG modification, the pharmacokinetic properties in vivo will change significantly, including: prolonged plasma half-life, increased in vivo drug release, reduced renal clearance, etc.;

[0143] 2. Enhanced stability: After PEGylation of proteins and peptides, a thicker hydration film will be formed on their surface to prevent the occurrence of agglutination and precipitation. Modification of the connecting bond (acyl, ether, disulfide bond, etc.) between PEG and lipid derivatives can also increase the stability of liposomes. In addition, the flexible chain of PEG can produce a steric hindrance effect, protecting the modified substance from protease attack and increasing the stability of the modified substance.

[0144] 3. Improve the distribution of drugs in the body: After the drug is modified by PEG, the molecular weight increases, which greatly reduces its glomerular filtration during systemic administration, thereby reducing its excretion through urine. In addition, the stability of the drug modified by PEG in the systemic circulation is improved, and the retention time is prolonged, which is beneficial to improve the distribution of the drug in the body, especially the accumulation of macromolecular drugs in tumors and inflammatory sites with enhanced retention effects, thereby prolonging the drug's in vivo treatment time.

[0145] In the present invention, by utilizing the addressability and programmability of DNA nanotechnology, the spatial position of the PEG molecule in the DNA nanostructure can be precisely controlled to achieve the conformation with the highest spatial coverage, which can greatly improve its biological stability. The drug adjuvant design scheme of the present invention provides a new idea for effective and safe drug therapy.

[0146] All documents mentioned in the present invention are cited as references in this application, just as each document is cited as reference individually. In addition, it should be understood that after reading the above teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A nucleic acid tetrahedral nanostructure, characterized in that: The nucleic acid tetrahedron nanostructure comprises a tetrahedron composite structure formed by assembling a plurality of nucleic acid monomers, and the tetrahedron composite structure is coupled with a PEG molecule.

2. The nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: The nucleic acid monomer is selected from the group consisting of DNA, RNA, locked nucleic acid, peptide nucleic acid, or a combination thereof.

3. The nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: The nucleic acid tetrahedron nanostructure is a DNA nucleic acid tetrahedron nanostructure.

4. The nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: In the nucleic acid single chains (or nucleic acid monomers) constituting the nucleic acid tetrahedral nanostructure, 2, 3, or 4 nucleic acid monomers are modified by PEG.

5. The nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: On a nucleic acid monomer, the number of sites modified by PEG is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more, preferably 2-5.

6. The nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: The size of the nucleic acid tetrahedral nanostructure is about 5-30 nanometers, preferably 7-20 nanometers.

7. The nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: The nucleic acid tetrahedral nanostructure has a structure of formula A: Z-PEG(A) In the formula, Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers; PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure.

8. The nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: The nucleic acid tetrahedral nanostructure is a complex of formula I: Z-PEG-D(I) In the formula, Z is a nucleic acid tetrahedral nanostructure formed by the assembly of nucleic acid monomers; PEG represents a PEG molecule coupled to the nucleic acid tetrahedral nanostructure; D stands for drug.

9. The method for preparing nucleic acid tetrahedral nanostructures according to claim 1, characterized in that: Includes steps: (a) providing nucleic acid monomers, wherein at least one nucleic acid monomer is coupled to a PEG molecule; (b) mixing and annealing the nucleic acid monomers to assemble and form the nucleic acid tetrahedral nanostructure according to claim 1.

10. The use of the nucleic acid tetrahedral nanostructure according to claim 1, characterized in that: Used to prepare PEGylated drugs.

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