CN109182327B - Application of magnetic nanoparticles in nucleic acid extraction and preparation method thereof - Google Patents
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Abstract
The invention discloses an application of magnetic nanoparticles in nucleic acid extraction, wherein the magnetic nanoparticles are magnetic Fe coated with a polydopamine coating on the surface 3 O 4 Nanoparticles. The magnetic nanoparticles provided by the invention have superparamagnetism, high environmental stability and monodispersity, the polydopamine coating coated on the surfaces of the nanoparticles is rich in amino and hydroxyl groups, the efficient adsorption of nucleic acid can be realized, the efficiency and the quality of nucleic acid adsorption of the existing magnetic nanoparticles are improved, the efficient and rapid extraction of nucleic acid can be realized, and when the magnetic nanoparticles are applied to the extraction of human whole blood, the blood treatment is not required, so that the magnetic nanoparticles are suitable for gene diagnosis and treatment of clinical diseases. The preparation method of the magnetic nanoparticles disclosed by the invention effectively simplifies the preparation process of the magnetic nanoparticles serving as a nucleic acid adsorption reagent, reduces the preparation cost, and is suitable for preparation and application of the magnetic nanoparticles.
Description
Technical Field
The invention belongs to the technical field of nano materials, and particularly relates to application of magnetic nanoparticles in nucleic acid extraction and a preparation method thereof.
Background
Nucleic acids are the material basis for the storage, replication and transmission of genetic information, and are key substances in a series of important vital activities, such as normal growth, development, reproduction, heredity and mutation of organisms. Therefore, the isolation and purification of nucleic acid is the first problem to be solved in genetic engineering or protein engineering research. At the same time, the isolation of DNA is a crucial process in molecular biology and is also an essential step in the initiation of other downstream activities such as sequencing, amplification, hybridization, ligation, cloning and biological detection.
At present, nucleic acid extraction techniques can be classified into two types, liquid phase extraction and solid phase extraction, depending on the nucleic acid extraction method. Compared with the liquid phase extraction method, the solid phase extraction can overcome the defect of incomplete separation of an organic phase and a water phase in the liquid phase extraction. The solid phase extraction method mainly utilizes the interaction (electrostatic interaction, affinity interaction, hydrogen bonding, ion exchange, etc.) between a solid phase adsorbent and nucleic acid to achieve the purpose of separating nucleic acid. Among them, magnetic Solid Phase Extraction (MSPE) technology using Magnetic Nanoparticles (MNPs) as a solid phase adsorbent is increasingly being applied to the extraction of genomic DNA from bacteria or cell lysates, since Magnetic Nanoparticles (MNPs) can be removed by an external magnetic field. In the magnetic solid phase extraction technology (MSPE), the selection of Magnetic Nanoparticles (MNPs) as solid phase adsorbents has a significant impact on the efficiency, quality, and cost of nucleic acid extraction.
Since magnetic nanoparticles are easily aggregated to change their magnetic properties, it is common in the prior art to coat the surface of the magnetic nanoparticles with a shell layer, for example, silicon dioxide (SiO) 2 ) The magnetic nano-particles are widely applied to coating the magnetic nano-particles due to good hydrophilicity, no toxicity and protection of the magnetic nano-particles. At present, most of them are adopted
The magnetic nano particles coated by the silicon dioxide are synthesized by the method, namely, silanization reagents (such as tetraethoxysilane) are hydrolyzed under the catalysis of alkali to synthesize magnetic particles with core-shell structures, the particles can be modified by the silanization reagents again, and the enrichment and extraction of nucleic acid molecules are realized through surface modification groups. The above-mentioned coated SiO 2 Although the magnetic nanoparticles can extract nucleic acid molecules, siO is used 2 The coating step of (2) increases the preparation cost of the magnetic nano particles and complicates the preparation process; and, the above-mentioned coating SiO 2 When the magnetic nanoparticles are used for nucleic acid extraction, there is a problem that the adsorption efficiency is low.
Disclosure of Invention
Therefore, the technical problem to be solved by the present invention is to overcome the defect of low adsorption efficiency of magnetic nanoparticles for extracting nucleic acid in the prior art.
Therefore, the invention provides the following technical scheme:
the invention provides an application of magnetic nanoparticles in nucleic acid extraction, wherein the magnetic nanoparticles are magnetic Fe coated with a polydopamine coating on the surface 3 O 4 Nanoparticles.
Optionally, in the above application, the magnetic nanoparticle has a saturation magnetization of 40.7emu/g, the magnetic nanoparticle has a particle size of 110-130nm, and the polydopamine coating has a thickness of 20nm.
The invention provides a preparation method of magnetic nanoparticles, which comprises the following steps:
(1) With FeCl 3 ·6H 2 Synthesizing magnetic Fe by hydrothermal method by using O as raw material 3 O 4 Nanoparticles;
(2) Mixing dopamine hydrochloride, tris-HCl buffer solution and water to form dopamine solution, and adding the magnetic Fe into the dopamine solution 3 O 4 Stirring the nano particles for 10 hours at room temperature to obtain black precipitates;
(3) Washing and drying the black precipitate to obtain the magnetic Fe coated with the polydopamine coating 3 O 4 Nanoparticles.
Alternatively, in the above preparation method, the concentration of the Tris-HCl buffer is 10mM, and the pH is 8.5; the Tris-HCl buffer solution: the dopamine hydrochloride salt: the magnetic Fe 3 O 4 Nanoparticle (g: g: g) is 3.
Alternatively, in the above preparation method, the step (1) comprises:
FeCl 3 ·6H 2 Dissolving O in ethylene glycol, and performing ultrasonic treatment to obtain a clear solution;
adding sodium acetate and polyethylene glycol 10000 into the clarified solution, and violently stirring to obtain a dark yellow solution;
heating the dark yellow solution at the temperature of 200 ℃ for 48 hours, and then washing and drying the solution to obtain magnetic Fe 3 O 4 Nanoparticles.
Further optionally, the abovePreparation method of the FeCl 3 ·6H 2 O: the weight ratio of the ethylene glycol: the sodium acetate: the polyethylene glycol 10000 (g: L: g) = 1.35.
Optionally, for the above-mentioned use, the magnetic nanoparticles are made by the method of any one of claims 3-6.
Optionally, in the above-mentioned application, the nucleic acid extraction comprises the following steps:
lysing nucleic acid in a biological sample, and adding a nucleic acid binding solution and magnetic nanoparticles to the lysed sample solution; the magnetic nano particles are magnetic Fe coated with polydopamine coating on the surface 3 O 4 A nanoparticle, the nucleic acid binding solution comprising polyethylene glycol and sodium chloride;
magnetic nanoparticles bind nucleic acids to form magnetic Fe 3 O 4 A complex of a nanoparticle and a nucleic acid, which complex is separated under the action of an external magnetic field;
washing and drying the complex, adding a nucleic acid elution solution into the complex, and separating the magnetic Fe under the action of an external magnetic field 3 O 4 And (3) the nano particles and the nucleic acid to obtain the nucleic acid.
Further optionally, for the above-described use, the nucleic acid binding solution comprises 20% (w/v) polyethylene glycol, 4mol/L sodium chloride, and the pH of the nucleic acid binding solution is 2.
Optionally, for the above-mentioned application, the biological sample is a human whole blood sample, and the lysing nucleic acids in the biological sample comprises:
adding an anticoagulant containing EDTA dipotassium into a human whole blood sample, then adding deionized water to destroy erythrocyte membranes, repeatedly mixing, centrifuging, and removing a supernatant to obtain a precipitate;
adding a solution containing proteinase K to the precipitate, dissolving the precipitate, standing at 65 ℃, and collecting supernatant, wherein the supernatant contains nucleic acid.
The technical scheme of the invention has the following advantages:
1. the magnetic nano-particles provided by the inventionThe magnetic nanoparticles are magnetic Fe coated with polydopamine coating on the surface 3 O 4 Nanoparticles.
Because the iron oxide nano particles are easy to aggregate to cause magnetic change, the adsorption and extraction capacity of the iron oxide nano particles as magnetic nano materials is limited, and the magnetic Fe provided by the invention 3 O 4 The surface of the nano particle is coated with a polydopamine coating. The dopamine coating not only has certain colloid and chemical stabilizing effects and prevents magnetic Fe 3 O 4 The nano particles are agglomerated, the superparamagnetism of the magnetic particles is kept, the remanence and the coercive force of the magnetic nano particles approach to zero, and the magnetic response is strong; on the other hand, the dopamine surface is rich in amino and hydroxyl groups, so that the adsorption of nucleic acid molecules can be realized through electrostatic action or hydrogen bonds with nucleic acid molecules, and the nucleic acid molecules are coated with SiO on the conventional surface 2 Magnetic Fe coated with dihydroxysuccinic acid, methylimidazolium bromide, etc 3 O 4 Nanoparticles or Fe 3 O 4 Compared with magnetic particles formed by a composite material of carbon nanotubes, the magnetic particle has higher DNA adsorption efficiency (the adsorption efficiency can reach more than 90 percent). The magnetic nanoparticles have good dispersibility in aqueous solution, can realize high-efficiency adsorption of nucleic acid molecules in the solution to obtain a nucleic acid-nanoparticle compound, and then utilize magnetic Fe under the action of an external magnetic field 3 O 4 The superparamagnetism and environmental stability of the nano particles can extract a nucleic acid-nano particle compound from a mixed solution, and the purified target nucleic acid molecule can be obtained by separating nucleic acid and magnetic nano particles. When the magnetic nanoparticles provided by the invention are applied to nucleic acid extraction, the rapid and efficient extraction of nucleic acid can be realized, the use of chemical reagents in the nucleic acid extraction process is reduced, the physical and chemical damages to the nucleic acid are reduced, the quality of separated nucleic acid molecules is improved, and the nucleic acid molecules are suitable for further biological research and analysis such as PCR amplification.
2. The saturation magnetization of the magnetic nanoparticles provided by the invention is 40.7emu/g, the particle size of the magnetic nanoparticles is 110-130nm, and the thickness of the polydopamine coating is 20nm. The magnetic nanoparticles have uniform particle size distribution, saturation magnetization intensity easy to be operated by an external magnetic field, large specific surface area and superparamagnetism, and the surface charge, steric hindrance and the like of the magnetic nanoparticles with the particle size, the saturation magnetization intensity and the polydopamine coating thickness within the above range can meet the requirements of colloid stability, so that the synergistic effect of the magnetic nanoparticles is fully exerted, and the magnetic nanoparticles have high adsorbability on nucleic acid molecules.
3. The preparation method of the magnetic nanoparticles provided by the invention is characterized in that a hydrothermal method is utilized to synthesize magnetic Fe 3 O 4 Nanoparticles, magnetic Fe produced 3 O 4 The nano particles have uniform particle size, good magnetic property and magnetic Fe 3 O 4 Stirring the nano particles and dopamine hydrochloride in the presence of Tris-HCl buffer solution at room temperature to prepare magnetic Fe coated with polydopamine coating on the surface 3 O 4 The preparation method of the nano particles is simple, and the conditions are easy to realize. In the preparation process of the magnetic nanoparticles, a coupling agent is not needed, and the nanoparticles are not needed to be subjected to surface modification, so that the magnetic nanoparticles capable of being used for nucleic acid adsorption are obtained, the preparation process of the magnetic nanoparticles serving as a nucleic acid adsorption reagent is effectively simplified, and the preparation cost is reduced.
4. The preparation method of the magnetic nanoparticles provided by the invention controls the concentration and pH of Tris-HCl buffer solution, as well as Tris-HCl buffer solution, dopamine hydrochloride and magnetic Fe 3 O 4 The using mass ratio of the nano particles can ensure that the polydopamine is firmly adhered to the magnetic Fe 3 O 4 A polydopamine coating with the thickness of 20nm is formed on the surface of the nano particles so as to improve the nucleic acid adsorption effect of the magnetic nano particles.
5. The hydrothermal method provided by the invention is used for synthesizing magnetic Fe 3 O 4 Method for preparing nanoparticles with FeCl 3 ·6H 2 O is used as raw material, glycol is used as high boiling point reducing agent, sodium acetate and polyethylene glycol 10000 are used for avoiding magnetic Fe 3 O 4 The nano particles are agglomerated in the preparation process, and the reaction conditions and the addition of substances are regulated and controlledAnd adding the solution to obtain the superparamagnetic particles with uniform particle size, and being suitable for the coating of the polydopamine coating in the next step.
6. The nucleic acid extraction method provided by the invention comprises the steps of adding a nucleic acid binding solution and magnetic nanoparticles into a sample solution after cracking; the magnetic nano particles are magnetic Fe with the surface coated with polydopamine coating 3 O 4 A nanoparticle, the nucleic acid binding solution comprising polyethylene glycol and sodium chloride.
The polyethylene glycol and sodium chloride can create a super-good salt solution environment for the combination of the magnetic nanoparticles and the nucleic acid, so that nucleic acid molecules such as DNA (deoxyribonucleic acid) form a super-polymerization state, hydrogen bonds between dopamine surface groups and the nucleic acid are promoted, and the electrostatic action between the dopamine surface groups and the nucleic acid can be promoted by regulating isoelectric points. The adsorption efficiency of the magnetic nanoparticles to nucleic acid molecules is improved, and the magnetic nanoparticles also have high adsorption efficiency particularly to small fragment DNA with the fragment length of less than 200 bp.
7. According to the nucleic acid extraction method provided by the invention, the nucleic acid binding solution is further optimized, when the concentration of polyethylene glycol is 20% (w/v), the concentration of sodium chloride is 4mol/L, and the pH value of the nucleic acid binding solution is 2, under the conditions of PEG and NaCl with certain concentrations, the collision and repulsion of magnetic nanoparticles at spatial positions are increased, and the magnetic nanoparticles are in a suspension state and are not easy to settle; meanwhile, the molecular conformation of the DNA is changed, the DNA is condensed, the hydrogen bond between the DNA molecule and the magnetic nano particle is increased, and the aggregation efficiency is increased. At a pH of 2 for the nucleic acid binding solution, the DNA is negatively charged due to deprotonation of the phosphate group. Thus, negatively charged DNA can be positively charged through electrostatic interaction with PDA @ Fe 3 O 4 Adsorbing; by setting the concentration of each component in the nucleic acid binding solution and the pH value of the solution, the adsorption efficiency of the magnetic nanoparticles on nucleic acid can be further improved, and effective nucleic acid extraction with the adsorption efficiency exceeding 90% can be realized.
8. When the nucleic acid extraction kit and the nucleic acid extraction method provided by the invention are applied to whole blood extraction, the whole blood sample does not need to be pretreated, the extraction step of the whole blood sample is simplified, the nucleic acid extraction speed is improved, and the nucleic acid extraction kit and the nucleic acid extraction method are suitable for realizing clinical rapid gene diagnosis and identification. Meanwhile, the nucleic acid extraction kit and the nucleic acid extraction method provided by the invention have high nucleic acid extraction capacity and high adsorption rate, can reduce the damage of an organic solvent to nucleic acid, are suitable for extracting low-content circulating free DNA or extracting target nucleic acid of tissues, saliva, bacteria and viruses, and provide effective nucleic acid extraction tools and methods for clinical diagnosis and individualized treatment of diseases.
Drawings
FIG. 1a shows magnetic nanoparticles (PDA @ Fe) of example 1 of the present invention 3 O 4 ) (0.2 μm scale) transmission electron microscopy characterization;
FIG. 1b shows magnetic nanoparticles (PDA @ Fe) of example 1 of the present invention 3 O 4 ) (0.2 μm scale) transmission electron microscopy characterization;
FIG. 1c shows magnetic nanoparticles (PDA @ Fe) provided by the present invention 3 O 4 ) (0.2 μm scale) transmission electron microscopy characterization;
FIG. 2 shows magnetic nanoparticles (PDA @ Fe) provided by the present invention 3 O 4 ) X-ray diffraction pattern of (a);
FIG. 3 is the magnetic nanoparticle (PDA @ Fe) provided by the present invention 3 O 4 ) With Fe 3 O 4 A graph of magnetization of;
FIG. 4 shows magnetic nanoparticles (PDA @ Fe) provided by the present invention 3 O 4 ) (ii) an infrared absorption spectrum of (a);
FIG. 5 shows magnetic nanoparticles (PDA @ Fe) provided by the present invention 3 O 4 ) With Fe 3 O 4 Zeta potential of (2) as a function of pH;
FIG. 6a is a graph of PEG concentration vs. PDA @ Fe in a nucleic acid binding solution provided by the present invention 3 O 4 A detection result graph of the influence of the efficiency of adsorbing the genomic DNA;
FIG. 6b is a graph of NaCl concentration vs. PDA @ Fe in the nucleic acid binding solution provided by the present invention 3 O 4 A detection result graph of the influence of the efficiency of adsorbing the genomic DNA;
FIG. 6c is the pH value of the nucleic acid binding solution of the present invention versus PDA @ Fe 3 O 4 A detection result graph of the influence of the efficiency of adsorbing the genomic DNA;
FIG. 7 is a graph showing the results of detecting the adsorption rate of a nucleic acid extraction kit to a fragment DNA in Experimental example 2 of the present invention;
FIG. 8 is a graph showing the results of examining the DNA extraction ability of the nucleic acid extraction kit according to Experimental example 3 of the present invention;
FIG. 9 is a graph showing the result of agarose gel electrophoresis detection of human whole blood genomic DNA extracted in example 3 of the present invention;
FIG. 10 is a graph showing the results of electrophoretic detection of PCR products using human whole blood genomic DNA extracted in example 3 of the present invention as a template.
Detailed Description
The technical solutions of the present invention will be described clearly and completely below, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention. In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
The materials and reagents involved in the following examples are as follows:
iron chloride hexahydrate (FeCl 3.6h2o), anhydrous sodium acetate (NaAc), ethanol, diethylene glycol (DEG), disodium Ethylenediaminetetraacetate (EDTA) was purchased from tianjin mao chemical agents factory (tianjin, china). Tris (hydroxymethyl), polyethylene glycol 10000, polyethylene glycol 6000, sodium hydroxide (NaOH) and sodium chloride (NaCl) were purchased from guangzhou chemical reagent works (guangzhou, china). Dopamine hydrochloride was purchased from alfa aesar (shanghai, china). Hydrochloric acid (HCl) and acetic acid (CH 3 COOH) were both from tianjin waste chemical company (tianjin, china). The water used in the experiments was obtained from the ELGA water purification system (ELGA, london, UK). Human EDTA-anticoagulated whole blood for isolation was collected at the university of langzhou secondary hospital (langzhou, china).
GeneRuler50bp-500bp DNA ladder was purchased from Biotechnology corporation (Shanghai, china) and consisted of 10 fragments ranging from 50 to 500bp with a total concentration of 0.5mg/ml. Ace Taq DNA polymerase (5U/. Mu.l), 25mM MgCl 2, 10 xpcr buffer (100 mM Tris-HCl [ ph8.3],500mM KCl) and deoxynucleoside triphosphate (dNTP) mixture (including dATP, dGTP, dCTP and dTTP, where the concentration of each dNTP is 2.5 mM) were purchased from nanjing nuozokenza biotechnology limited (tokyo, china). The primers used for the PCR reaction were synthesized by Nanjing Biotechnology Ltd (Nanjing, china). TIANAmp DNA kit, buffer FG, buffer CL were purchased from Tiangen Biotech Inc. (Beijing, china).
Example 1
This example provides a magnetic nanoparticle (PDA @ Fe) 3 O 4 ) The preparation method comprises the following steps:
(1) With FeCl 3 ·6H 2 Synthesizing magnetic Fe by hydrothermal method by using O as raw material 3 O 4 Nanoparticles
FeCl 3 ·6H 2 O (1.35 g) was dissolved in ethylene glycol (40 mL) and a clear solution was formed by sonication. Then, sodium acetate (3.6 g) and polyethylene glycol 10000 (1.0 g) were added to the solution, and the mixture was vigorously stirred until a uniform dark yellow solution was obtained. The solution was placed in a high pressure reactor of polytetrafluoroethylene and heated at 200 ℃ for 48 hours. Washing the product with ethanol and water for several times, and drying at 60 deg.C under nitrogen atmosphere for 10 hr to obtain carboxyl modified magnetic Fe 3 O 4 Nano particles for later use;
(2) Dopamine hydrochloride (200 mg) was mixed with 0.12g of Tris-HCl buffer (10 mM, pH 8.5) and 100ml of water to prepare a dopamine solution. Then modifying the carboxyl group with magnetic Fe 3 O 4 The nanoparticles (200 mg) were added to the solution and stirred at room temperature for 10 hours to give a black precipitate;
(3) Washing the black precipitate with water several times, and drying at 60 deg.C under nitrogen atmosphere to obtain magnetic nanoparticles (PDA @ Fe) 3 O 4 )。
Test method and results
Magnetic nanoparticles (PDA @ Fe) prepared in this example 3 O 4 ) Characterization was performed with the following results:
(1) Transmission Electron Microscopy (TEM) characterization
Magnetic nanoparticles (PDA @ Fe) were aligned using a FEI F30 transmission electron microscope (FEI, hillsboro, USA) 3 O 4 ) The particle size and morphology of (a) are observed, and the results are shown in fig. 1 a-1 c: PDA @ Fe 3 O 4 The particles are monodisperse, the shape is approximately spherical, the particle size in a TEM image is counted by Nano Measurer software to obtain PDA @ Fe 3 O 4 The size distribution of the particles is relatively concentrated, ranging from 110 to 130nm, with an average particle size of 120nm. PDA was coated homogeneously on Fe 3 O 4 The thickness of the PDA was about 20nm on the surface of the particles.
(2) Characterization by X-ray diffraction Spectroscopy (XRD)
Magnetic nanoparticles (PDA @ Fe) were paired with Rigaku X-ray diffractometer D/max-2400 (Rigaku, tokyo, japan) 3 O 4 ) The results of the analysis of the crystal form information are shown in fig. 2: the diffraction angle 2 theta of the characteristic peak is obtained by X-ray diffraction and appears at 17.8 degrees, 30.2 degrees, 35.4 degrees, 42.9 degrees, 53.4 degrees, 57.0 degrees and 62.7 degrees; the corresponding crystal plane indices are (110), (220), (311), (400), (422), (511), and (533), respectively. These peaks indicate that the magnetic particles produced were Fe3O4 and were of single phase cubic structure (JCPDS 88-0315). XRD results showed that the amorphous coated PDA layer did not affect Fe 3 O 4 A crystalline phase of (a).
(3) Characterization of magnetization curves
Magnetic Fe was measured at 300K using a vibrating sample magnetometer (PPMS-9, quantum design, san Diego, USA) 3 O 4 Nanoparticle and magnetic Fe coated with polydopamine coating on surface 3 O 4 Nanoparticle (PDA @ Fe) 3 O 4 ) Magnetization curve of (1), analysis of Fe at room temperature by VSM 3 O 4 And PDA @ Fe 3 O 4 The magnetic properties of (a). The results are shown in the magnetization curves in fig. 3: fe 3 O 4 And PDA @ Fe 3 O 4 The saturation magnetization values of (A) were 71.5 and 40.7emu/g, respectively (FIG. 3). The curve shows PDA @ Fe 3 O 4 There is no hysteresis and negligible remanence and coercivity are shown, indicating that the outlined nanomaterials have super-complianceAnd (4) magnetism. At the same time, with Fe 3 O 4 In contrast, PDA @ Fe 3 O 4 The decrease in saturation magnetization demonstrates that PDA is in Fe 3 O 4 And (3) modifying the particles.
(4) Infrared absorption Spectroscopy (FTIR) characterization
Magnetic Fe was analyzed using FTIR (Perkinelmer Spectrum GX, USA) 3 O 4 Nanoparticle (PDA @ Fe) 3 O 4 ) Surface functional group information of (1). The results are shown in FIG. 4: in this figure, located at about 579cm -1 The absorption peak is present in Fe 3 O 4 The characteristics of the Fe-O bonds in the nanoparticles. At 1619 and 3418cm -1 Peaks corresponding to surface adsorbed water and hydroxyl groups appeared. At 3418cm -1 ，2922cm -1 ，1466cm -1 And 876cm -1 The peaks shown in (b) represent OH stretch, CH stretch, C = C stretch and CH stretch, respectively, on the phenyl ring, which correspond to PDA @ Fe 3 O 4 the-OH and-C = C-functional group of the phenol. The results show that PDA successfully immobilized Fe by physical and chemical adsorption of its surface 3 O 4 Of the surface of (a).
(5) Zeta potential (Zeta potential) characterisation
The surface charge of the adsorbing material has an important effect on the adsorption capacity of the material, and the zeta potential was measured using a zetasizer nano ZS (Malvern, worcestershire, UK) and the results are shown in fig. 5: as the pH of the solution increases, the zeta potential of both materials decreases. Fe 3 O 4 Has an isoelectric Point (PI) of about 5.0. After further coating with PDA, the pI increased to 5.5.PDA @ Fe 3 O 4 The surface charge of (a) is positive at pH values below the pI and negative at pH values above the pI. Fe 3 O 4 And PDA @ Fe 3 O 4 The zeta potential of the particles reaches a maximum in the binding solution (pH 2.0). Fe 3 O 4 Zeta potential of 12.1mV versus PDA @ Fe 3 O 4 The zeta potential of (b) was 28.6mV. PDA @ Fe 3 O 4 The positive zeta potential of (2) is due to PDA @ Fe 3 O 4 Surface presence of PDA to produce, fe 3 O 4 And PDA @ Fe 3 O 4 The zeta potential difference between the particles again indicates that the PDA is at magnetic Fe 3 O 4 The nanoparticles are modified.
Example 2
The present embodiment provides a nucleic acid extraction kit, including a nucleic acid binding solution and magnetic nanoparticles:
the nucleic acid binding solution comprises 20% (w/v) of polyethylene glycol, 4mol/L of sodium chloride, and the pH of the nucleic acid binding solution is 2;
the magnetic nanoparticles were the magnetic nanoparticles prepared in example 1 (PDA @ Fe) 3 O 4 )。
Example 3
This example provides a nucleic acid extraction method using the nucleic acid extraction kit provided in example 2, the extraction method comprising the steps of:
(1) Cleaving DNA from human whole blood sample
(1) Mu.l of EDTA-K2 (dipotassium EDTA) anticoagulated blood was added to a 1.5ml centrifuge tube using a micropipette gun. Thereafter, 300. Mu.l of sterile deionized water was added to the tube to disrupt the erythrocyte membranes. Repeatedly mixing for several times, centrifuging the mixed solution at 12000rpm/min for 3 min, and removing the supernatant to obtain precipitate;
(2) buffer CL (300. Mu.l) was added to the pellet and the mixture was mixed several times as well. Centrifuging the mixture at 12000rpm/min for 1 min, and discarding the supernatant;
(3) proteinase K-buffer FG mix (1) (g/V) was prepared and added to the pellet. The solution was immediately inverted a few times until the precipitate was completely dissolved. Then, after the instantaneous centrifugation, the centrifuge tube was placed in a metal bath at 65 ℃ and left to stand for 10 minutes, and the supernatant containing the nucleic acid was collected. The supernatant (cell lysate) was transferred to a new 1.5mL Eppendorf tube and stored at 4 ℃ before use.
(2) Magnetic nanoparticles (PDA @ Fe) 3 O 4 ) Binding nucleic acids to form magnetic nanoparticles (PDA @ Fe) 3 O 4 ) A complex with a nucleic acid, which complex is separated under the action of an external magnetic field;
cell lysate (150. Mu.l) was added to 1.5mL Epp containing 300. Mu.L of nucleic acid binding solution (20% (w/v) PEG,4M sodium chloride, pH 2.0)endorf tube, followed by 40ngpda @ fe3o4. The mixture was left at room temperature for 10 minutes to form magnetic nanoparticles (PDA @ Fe) 3 O 4 ) A complex with a nucleic acid. Then, PDA @ Fe was separated on a magnetic separation stand 3 O 4 Complexes with nucleic acids and supernatant was discarded.
(3)PDA@Fe 3 O 4 The complex with the nucleic acid was washed twice with a 70% (v/v) ethanol solution and dried at room temperature. From DNA with PDA @ Fe by adding 50. Mu.L of elution solution (Fujifilm, japan, pH 8.0) 3 O 4 The adsorbed DNA was eluted and incubated at room temperature for 10 minutes. Thereafter, magnetic separation is performed using an external magnet. The DNA extracted from the eluate is then used as a template for subsequent PCR amplification. The capacity of the absorbed DNA was quantified by measuring the absorbance value measured at 260nm, and the purity of the DNA was evaluated using the ratio of the absorbances at 260nm and 280 nm.
Experimental example 1
This example analyzes the magnetic nanoparticles (PDA @ Fe) of nucleic acid binding solution in nucleic acid extraction kit under the conditions of different solution pH, different polyethylene glycol concentration and different sodium chloride concentration 3 O 4 ) The effect of the efficiency of DNA adsorption.
DNA capture and elution the following analytical methods were used:
to investigate the optimal extraction conditions for the subsequent isolation of DNA from human whole blood, genomic DNA was selected as the target extract for the measurement of PDA @ Fe 3 O 4 The extraction yield of nucleic acid. Genomic DNA was dissolved in sterile deionized water to prepare a DNA standard solution (50 ng/. Mu.l). DNA solution (20. Mu.L, DNA amount 1. Mu.g), 100. Mu.L binding buffer (equal volumes of PEG solution {0% -40% } and NaCl solution { 0-6 mol/L }) and 30. Mu.g PDA @ Fe 3 O 4 Mix into a 1.5mL EP tube and the total volume of the mixture is 0.1mL. The mixture was then stirred slowly at room temperature for 10 minutes. Thereafter, magnetic separation is performed using an external magnet. The supernatant was then carefully removed and collected and UV-determined at 260nm using a Nanodrop 2000 spectrophotometer (Thermal scientific, USA). The amount of DNA captured is based on the residual amount of DNA in the supernatant before magnetic separationAnd (4) calculating. The extraction rate (%) was calculated by the following formula:
C 0 (ng/. Mu.l) and C (ng/. Mu.l) represent the initial concentration of DNA in solution and the supernatant concentration, respectively. V 0 (. Mu.l) and V (. Mu.l) represent the volumes of the originally prepared DNA solution and the supernatant. Washing of DNA with 70% (v/v) ethanol and PDA @ Fe 3 O 4 The mixture was dried twice at room temperature. The adsorbed DNA molecules were then eluted from the conjugate by adding 50 μ l of elution buffer (Fujifilm, japan, pH = 8.0) and incubating at room temperature for 10 min. Carefully taking the supernatant, and measuring the absorbance value of the supernatant at 260nm to calculate the DNA amount adsorbed by the magnetic beads.
The experimental results are as follows:
first, the mass based on the original genomic DNA was 1. Mu.g, PDA @ Fe 3 O 4 30 μ g, naCl concentration 4M, pH of the binding solution 2.0, and total volume 120 μ l, to investigate PEG concentration vs PDA @ Fe 3 O 4 Influence on the capture efficiency of genomic DNA. As shown in FIG. 6a, the highest extraction efficiency was achieved at 20% (w/v) for PEG, and the capture rate of genomic DNA was up to 90.2%. Therefore, 20% PEG optimized conditions were chosen for subsequent experiments. The PEG with specific molecular weight and concentration mainly has the effects of interacting with salt ions, changing the molecular conformation of DNA with different lengths, increasing the viscosity degree of a system, enabling magnetic beads to be in a suspended state, being not easy to settle, and increasing the collision and repulsion of the magnetic beads at a spatial position, thereby enhancing the aggregation efficiency and effect of nucleic acid and the magnetic beads.
Next, the effect of different NaCl concentrations (0M-6M) on DNA isolation was investigated. As shown in FIG. 6b, the amount of desorbed DNA increases as the concentration increases from 1M to 4M. At pH8.0, the extraction rate peaked at 90.3%, so the optimum concentration of NaCl was about 4M.
Finally, the pH of the solution is also an important factor. It can regulate and control the electrostatic acting force between the surfaces of the adsorbed objects and can also absorb the self-body of the adsorbing material due to electricityThe electrostatic effect caused by the charge distribution has a certain influence. The present study investigated the effect of binding buffer (equal volume 20% PEG,4M NaCl) on the efficiency of genomic DNA enrichment at pH ranging from 2.0 to 8.0. As shown in FIG. 6c, the maximum extraction rate of the captured DNA corresponds to 90% of the extraction rate of DNA at pH 2.0. The result and electrostatic force were PDA @ Fe 3 O 4 The prediction of the main driving force for DNA adsorption is identical. PDA @ Fe 3 O 4 Zeta potential in solutions of different pH (FIG. 5) shows PDA @ Fe 3 O 4 Has an isoelectric point of 5.5. Thus, in the pH range of 2.0-5.0, a certain amount of DNA can be positively charged with PDA @ Fe 3 O 4 And (4) adsorbing. PDA @ Fe when pH is above 5.5 3 O 4 Is negatively charged with DNA, resulting in almost no adsorption of DNA at pH 6.0-10.0 on PDA @ Fe 3 O 4 The above. The phosphodiester in DNA is a strong acid with a pKa of less than 1. Above pH 1.0, the DNA is negatively charged due to deprotonation of the phosphate group. Thus, negatively charged DNA can be positively charged through electrostatic interaction PDA @ Fe 3 O 4 And (4) adsorbing.
Experimental example 2
This example examined the magnetic nanoparticles (PDA @ Fe) prepared in example 1 3 O 4 ) Adsorption rate to fragment DNA.
The experimental method comprises the following steps:
1. and (3) PCR amplifying fragments at SNP sites of four genes of APOC3, APOA5, SLC2A9 and ABCG2 by taking human genome DNA as a template. The PCR reaction system consists of the following parts: DNA template (0.5. Mu.L), 2 XPCR buffer, 1.5mM MgCl 2 0.4mM dNTP,0.1mM forward and reverse primers, 0.25U/ml Taq DNA polymerase and DEPC water. The total reaction volume was 10. Mu.L. The control solution (blank) contains all PCR reagents except the DNA template. The primers used for PCR and the amplification conditions for the different SNPs are listed in Table 1 and Table 2.
TABLE 1 PCR primers
TABLE 2 PCR amplification conditions
2. The DNA fragments in the PCR reaction solution were extracted using the nucleic acid extraction method provided in example 3, in which equal volumes of nucleic acid binding solution (20% PEG and 4M NaCl pH2.0; 120mL) and 0.04mg of magnetic nanoparticles (PDA @ Fe 3 O 4 ). The recovered DNA was analyzed by electrophoresis on a 4% agarose gel at 100V for 15 minutes, using a PCR reaction solution without nucleic acid extraction as a control.
The experimental results are as follows:
FIG. 7 shows the result of the adsorption detection of small fragment DNA by the nucleic acid extraction kit. As can be seen from FIG. 7, magnetic nanoparticles (PDA @ Fe) 3 O 4 ) Can adsorb small fragment DNA from 100bp to 200bp, and the adsorption rate can reach about 90%, so that the nucleic acid extraction kit provided by the invention can be applied to the recovery of amplification product DNA and the enrichment and extraction of free DNA (100 bp-200 bp).
Experimental example 3
This example examined the magnetic nanoparticles (PDA @ Fe) prepared in example 1 3 O 4 ) Extraction ability for DNA: different amounts of original genomic DNA (2-10. Mu.g), and PDA @ Fe were added to the nucleic acid binding solution (20% PEG and 4M NaCl, pH 2.0) 3 O 4 (0.06 mg). After mixing well, incubation was carried out for 10 minutes, followed by magnetic separation using an external magnet, absorbance of the supernatant at 260nm was measured and the amount of adsorbed DNA was calculated.
The results are shown in FIG. 8, PDA @ Fe 3 O 4 The amount of adsorbed DNA was linear in the range of 2. Mu.g to 8. Mu.g, and beyond this range, the amount of separation plateaued. PDA @ Fe 3 O 4 Ability to extract DNAIt was 116.7mg g-1.
Experimental example 4
This experimental example examined the applicability of the human whole blood genomic DNA extracted in example 3, and the human whole blood genomic DNA extracted in example 3 was examined by electrophoresis on 1% agarose gel (100v, 12min).
The results are shown in FIG. 9. After electrophoresis, the band shows a single bright band under an automated gel imager (Shanghai, china). Rs121918382 site of APROC3 gene (Table 1) was selected for amplification to verify the possibility of using the product template for PCR amplification. FIG. 10 shows the electropherograms of the standard GeneRuler50bp-500bp DNA ladder, PCR products and blank samples. In the electropherogram of the product DNA (FIG. 10), the electrophoresis result of the PCR product shows a single bright band with clear background and proper position, which indicates that the genomic DNA extracted in example 3 of the present invention can be directly used as a template for downstream PCR.
Comparative example 1
This comparative example compares the magnetic nanoparticles (PDA @ Fe) prepared in example 1 of the present invention 3 O 4 ) And the DNA extraction effect of the commercial magnetic beads and the DNA purification kit. Using magnetic nanoparticles (PDA @ Fe) 3 O 4 ) Method for extracting DNA the nucleic acid extraction method provided in example 3 was referred to.
The comparison results are shown in Table 3, magnetic nanoparticles (PDA @ Fe) 3 O 4 ) As magnetic nanoparticles, the magnetic nanoparticles have excellent adsorption capacity in Magnetic Solid Phase Extraction (MSPE), and the extracted DNA has high concentration. In addition, the magnetic nano particle (PDA @ Fe) provided by the invention is applied 3 O 4 ) The DNA is extracted, and the whole adsorption and elution processes are carried out at room temperature (25 ℃) without high-temperature incubation. In addition, PDA @ Fe is used 3 O 4 The nucleic acid method of (a) does not use any toxic solvents and frequent centrifugation, it also avoids the risk of relatively large number of steps in commercial kits increasing sample loss. Absorbance of eluted DNA was measured at 260 and 280nm, respectively, and as shown in Table 3, PDA @ Fe 3 O 4 The A260/A280 ratio of the extracted DNA was 1.82, indicating that the extracted DNA was pure enough to be used as a template for PCR amplification.
TABLE 3 PDA @ Fe 3 O 4 Extraction comparison with commercial magnetic beads and DNA purification kit
Comparative example 2
This comparative example compares PDA @ Fe prepared in inventive example 1 3 O 4 The difference between the magnetic nanomaterial and the existing magnetic nanomaterial in terms of DNA extraction capability and DNA adsorption efficiency is that the DNA extraction capability is tested by the method provided in Experimental example 3 of the present invention, and the DNA adsorption efficiency is tested by the method provided in Experimental example 1 of the present invention. The magnetic nano material is specifically as follows:
DMSA-MNP，Fe 3 O 4 the surface of Magnetic Nano Particles (MNP) is modified with dimercaptosuccinic acid, the particle size of the MNP is about 8.4nm, and the maximum zeta potential is 51.4 +/-7.2 mV;
Fe 3 O 4 @SiO 2 ，Fe 3 O 4 magnetic nano particle surface coated SiO 2 ，Fe 3 O 4 An average particle diameter of 14.1nm and SiO 2 Thickness of 1.2nm and saturation magnetization of 41.56emu g -1 ；
IL@Fe 3 O 4 ，Fe 3 O 4 The surface of the magnetic nano-particles is modified with 1-hexyl-3-methylimidazolium bromide, and the average particle size is 13nm;
PEI@Fe 3 O 4 ，Fe 3 O 4 the surface of the magnetic nano particle is coated with polyethyleneimine (PEI @) Fe 3 O 4 The average particle size is 100nm, and the maximum zeta potential is 45mV;
DES-Fe 3 O 4 MWCNTs from Fe 3 O 4 Forming magnetic nanoparticles with composite material of carbon nanotubes (MWCNTs), coating poly (ethylene glycol) -based eutectic solvent on the surface, wherein the average diameter of the MWCNTs is 10-15nm, and Fe 3 O 4 The average particle diameter of (1) is 10-20nm, and the maximum zeta potential is about 12mV;
MIm-MPs，Fe 3 O 4 the surface of the magnetic nano-particles is modified with N-methylimidazole, the average particle size of the MIm-MPs is 60nm,
Fe 3 O 4 @PANI，Fe 3 O 4 the surface of the magnetic nano particle is coated with polyaniline and Fe 3 O 4 The average particle diameter of the magnetic nanoparticles is about 300nm, the thickness of PANI (polyaniline) is about 30nm, and the saturation magnetization is 62.2 emu-g -1 ；
TABLE 4
| Magnetic nano material | Extraction Capacity (mg/g) | Adsorption Rate (%) |
| DMSA-MNP | 30.7 | 86 |
| Fe 3 O 4 @SiO 2 | 27.86 | 68 |
| IL@Fe 3 O 4 | 19.8 | 65 |
| PEI@Fe 3 O 4 | 61.8 | 85 |
| DES-Fe 3 O 4 /MWCNTs | 177.6 | 79 |
| MIm- |
25 | 61 |
| Fe 3 O 4 @PANI | 20.08 | 77 |
| PDA@Fe 3 O 4 | 116.7 | 90 |
The results are shown in Table 4, and compared with DMSA-MNP and Fe 3 O 4 @SiO 2 、IL@Fe 3 O 4 、PEI@Fe 3 O 4 、MIm-MPs、Fe 3 O 4 Comparison of @ PANI with PDA @ Fe prepared in example 1 of the present invention 3 O 4 The extraction capability and the adsorption rate of the DNA are obviously improved; and DES-Fe 3 O 4 Compared with MWCNTs, although PDA @ Fe 3 O 4 The DNA extraction ability of the DNA is weaker than that of DES-Fe 3 O 4 MWCNTs, but PDA @ Fe 3 O 4 The efficiency of DNA adsorption is higher. Based on this, PDA @ Fe 3 O 4 Can be considered as an ideal nucleic acid adsorbing material.
In conclusion, the magnetic nano particle PDA @ Fe provided by the invention 3 O 4 Verified as successfully functionalized by PDA, applying PDA @ Fe 3 O 4 Human genomic DNA can be isolated by a simple and efficient method. Transmission electron microscope observation shows that PDA @ Fe 3 O 4 Is monodisperse, highly crystalline, with a narrow size distribution, and the VSM results indicate its superparamagnetism, which is a desirable property for biological applications. The experimental results show that the adsorption process of nucleic acid, the concentrations of PEG and NaCl solution, the pH value of the binding solution and PDA @ Fe 3 O 4 The amount of (c) is relevant. Study ofIt was found that modified PDA @ Fe 3 O 4 Not only can genomic DNA be extracted, but also DNA with small fragments can be efficiently extracted. Compared with the method for extracting nucleic acid by commercialized magnetic beads and purification columns, PDA @ Fe 3 O 4 Has stronger adsorption capacity (P) to nucleic acid components in blood samples<0.05). Further, PDA @ Fe 3 O 4 Can be directly applied to the extraction and purification of human genome DNA without pretreatment, thereby being capable of more conveniently, quickly and efficiently serving diagnosis and treatment in the aspect of disease genes. Most importantly, PDA @ Fe 3 O 4 The application of the composite nano particles has great potential in the field of efficient separation of biomolecule samples.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. It is not necessary or necessary to exhaustively enumerate all embodiments herein, and obvious variations or modifications can be made without departing from the scope of the invention.
Claims (3)
1. The application of the magnetic nanoparticle adsorbent in nucleic acid extraction is characterized in that the magnetic adsorbent is magnetic Fe with a polydopamine coating coated on the surface 3 O 4 Nanoparticles, the nucleic acid extraction comprising the steps of:
cracking nucleic acid in a biological sample, and adding a nucleic acid binding solution and a magnetic adsorbent to the cracked sample solution; the nucleic acid binding solution consists of 20% polyethylene glycol and 4mol/L sodium chloride, and the pH of the nucleic acid binding solution is 2;
combining the magnetic adsorbent with the nucleic acid to form a complex of the magnetic adsorbent and the nucleic acid, and separating the complex under the action of an external magnetic field;
washing and drying the compound, adding a nucleic acid elution solution into the compound, and separating the magnetic adsorbent from the nucleic acid under the action of an external magnetic field to obtain the nucleic acid;
the preparation method of the magnetic adsorbent comprises the following steps:
(1) FeCl is added 3 ·6H 2 Dissolving O in ethylene glycol, and performing ultrasonic treatment to obtain a clear solution; adding sodium acetate and polyethylene glycol 10000 into the clarified solution, and stirring vigorously to obtain a dark yellow solution; heating the dark yellow solution at 200 ℃ for 48 hours, and then washing and drying the solution to obtain magnetic Fe 3 O 4 Nanoparticles;
(2) Mixing dopamine hydrochloride, tris-HCl buffer solution and water to form dopamine solution, and adding the magnetic Fe in the step (1) into the dopamine solution 3 O 4 Stirring the nano particles for 10 hours at room temperature to obtain black precipitates;
(3) Washing and drying the black precipitate in the step (2) to obtain a magnetic adsorbent;
the concentration of the Tris-HCl buffer solution is 10mM, and the pH value is 8.5; the Tris-HCl buffer solution: the dopamine hydrochloride salt: the magnetic Fe 3 O 4 Nanoparticles (g: g: g) is 3;
the FeCl 3 ·6H 2 O: the weight ratio of the ethylene glycol: the sodium acetate: the polyethylene glycol 10000 (g: L: g) = 1.35.
2. The use of claim 1, wherein the magnetic adsorbent has a saturation magnetization of 40.7emu/g, the magnetic adsorbent has a particle size of 110-130nm, and the polydopamine coating has a thickness of 20nm.
3. Use according to claim 1 or 2, wherein the biological sample is a human whole blood sample and the nucleic acids in the lysed biological sample comprise:
adding an anticoagulant containing EDTA dipotassium into a human whole blood sample, then adding deionized water to destroy erythrocyte membranes, repeatedly mixing, centrifuging, and removing a supernatant to obtain a precipitate;
adding a solution containing proteinase K to the precipitate, dissolving the precipitate, standing at 65 ℃, and collecting supernatant, wherein the supernatant contains nucleic acid.
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