CN112834411B

CN112834411B - Metal nanoprobe applied to mass flow technology, preparation method and application

Info

Publication number: CN112834411B
Application number: CN202110016553.6A
Authority: CN
Inventors: 丁显廷; 党婧琪
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2021-01-07
Filing date: 2021-01-07
Publication date: 2022-05-27
Anticipated expiration: 2041-01-07
Also published as: CN112834411A

Abstract

The invention discloses a metal nanoprobe applied to a mass flow technology, which relates to the technical field of nanoprobes, wherein a metal organic framework material is taken as a label, a metal element of the metal organic framework is a metal element with the mass number of 75-209, and the metal nanoprobe can be used for the mass flow technology and the mass imaging technology; the invention also provides a preparation method of the metal nano probe based on the metal organic framework. The metal organic framework-based metal nano probe provided by the invention has the advantages that the metal content of a single probe is extremely high, the detection sensitivity is high when the probe is used for a mass flow technology, the signal-to-noise ratio is high, the detection channel is widened, the chemical synthesis is simple, the stability is high, and the technical effect is good.

Description

Metal nanoprobe applied to mass flow technology, preparation method and application

Technical Field

The invention relates to the technical field of nanoprobes, in particular to a metal nanoprobe applied to a mass flow technology, a preparation method and application thereof.

Background

Single cell, multiparameter detection technology is the hot spot of biological research, and it is significant to reveal complex cellular systems, such as disease principle, signal path, immune regulation mechanism. Among the well-established techniques for cell analysis, flow cytometry is widely used for its high-throughput, multi-target analysis platform. The detection principle of flow cytometry is based on fluorescence, and in the past forty years, the introduction of organic fluorescent dyes and inorganic fluorescent dyes has led to the increase of the synchronous detection parameters to 18. However, due to the overlap between spectra and the number of resolvable fluorescein, the highest detection channel is saturated.

To further broaden the detection channel, flow cytometry was combined with inductively coupled plasma mass spectrometry (ICP-MS) to develop single cell mass spectrometry flow technology (cytef). The main principle of the single-cell mass spectrometry flow technology is that metal elements are adopted to mark or identify signal molecules on the cell surface and inside as a report factor of target expression level; and then atomizing the single cell, removing common biological elements through a quadrupole rod, observing the atomic mass spectrum of the single cell by using an inductively coupled plasma mass spectrometry, converting the data of the atomic mass spectrum into the data of antigen molecules on the surface and inside of the cell, and analyzing the obtained data through professional bioinformatics, thereby realizing the fine observation of cell phenotype and signal network.

Currently, probes of the mass spectrometry flow technology are commercially available using a bifunctional chelating agent as a Metal Chelate (MCP) to label metal elements on antibodies for signal molecule recognition on the cell surface and inside. The metal chelating agent generally adopted internationally at present is based on a Maxpar X8 polymer system developed by European and American scholars, and the system takes 1,4,7, 10-tetraazacyclododecane-1, 4,7, 10-tetracarboxylic acid (DOTA) or diethyltriaminepentaacetic acid (DTPA) as a chelating monomer, can only be effectively combined with trivalent metal ions, and greatly limits the further development of a detection channel. Fluidigm has recently introduced a new metal labeling kit for cadmium isotopes, but currently less than half of the metal isotopes are still being developed for mass spectrometry flow technology. In addition, the metal supporting capacity of the Maxpar X8 polymer system is limited, and a single antibody can be only connected with 50-150 metal atoms, so that the detection sensitivity of the mass spectrometry flow type technology is reduced, the detection of cell surface trace antigen is difficult to realize, and the application of the CyTOF technology in basic biology is limited. Due to the low metal loading and limited binding capacity with metal ions of the Maxpar X8 polymer system, the mass flow technology urgently needs to develop a novel metal-loaded metal probe with a novel structure and high metal density. Furthermore, although the academia has designed various nanoparticle-based metal tags to improve sensitivity of CyTOF, it is still a global technical challenge to improve sensitivity while avoiding non-specific adsorption.

Therefore, the technical personnel in the field are dedicated to develop a metal nano probe capable of widening a CyTOF detection channel and reducing the detection lower limit, and the problems of the detection channel limitation and the sensitivity in the prior art are solved.

Disclosure of Invention

In view of the defects in the prior art, the technical problem to be solved by the invention is how to provide a metal nanoprobe which can widen a CyTOF detection channel and reduce the lower limit of detection, and improve the detection sensitivity and the detection efficiency of a mass flow technology.

In order to achieve the purpose, the invention provides a metal nanoprobe applied to a mass flow technology, wherein the metal nanoprobe takes a metal organic framework material as a metal label.

Further, the metal element of the metal organic framework is a metal element with a mass number of 75-209.

Further, the metal-organic framework is a zirconium-based metal-organic framework (Zr-MOF).

Further, the size of the metal organic framework is 20-50 nm.

A preparation method of a metal nanoprobe applied to a mass spectrometry flow technology comprises the following steps:

step 5.1: dissolving zirconium chloride in N, N-Dimethylformamide (DMF), and ultrasonically dispersing until the zirconium chloride is completely dissolved to prepare a storage solution 1; dissolving terephthalic acid (H2BDC) in DMF, and ultrasonically dispersing until the terephthalic acid is completely dissolved to prepare a storage solution 2; placing the

storage solutions

1 and 2 in an oven at 90 ℃ for preheating;

step 5.2: respectively adding the storage solution 1 and the storage solution 2 into a glass bottle, and fully and uniformly mixing by vortex; respectively taking two bottles of mixed liquor, dropwise adding Formic Acid (FA) with different amounts, vortexing, fully mixing uniformly, placing in a 90 ℃ oven, and reacting for 6 hours;

step 5.3: after the product is naturally cooled, centrifuging for 1h, and removing the precipitate; centrifuging the supernatant for 40min, collecting precipitate, washing with DMF five times and three times, and dispersing in deionized water to obtain UIO-66 crystal.

A preparation method of a metal nanoprobe applied to mass spectrometry flow technology is provided, wherein the coupling of a zirconium metal organic framework and an antibody comprises the following steps:

step 6.1: dissolving 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) in water to prepare an EDC aqueous solution; dissolving sulfo N-hydroxysuccinimide (sulfo-NHS) in water to prepare a sulfo-NHS aqueous solution;

step 6.2: dissolving the zirconium metal organic framework crystal in water, and adjusting the pH value by using a sensitive pH meter;

step 6.3: adding EDC solution, and mixing uniformly; then adding a sulfo-NHS solution, and mixing uniformly;

step 6.4: activating at room temperature for 30 min; centrifuging for 40min, discarding supernatant, and dissolving in deionized water;

step 6.5: adding deionized water into the ultrafiltration tube, adding antibody, and centrifuging at room temperature for 8 min; adding deionized water, centrifugally washing once, and dissolving the trapped substance in the tube in the deionized water;

step 6.6: and (3) adding the antibody aqueous solution obtained in the step 6.5 into the Zr-MOF solution obtained in the step 6.4, and reacting for 5 hours at normal temperature.

Further, the pH in step 6.2 ranges from 4.7 to 6.0.

Further, 2- (N-morpholine) ethanesulfonic acid (MES) buffer and phosphate buffer are used to adjust the pH in step 6.2.

The application of the metal nanoprobe in mass spectrometry flow technology (CyTOF).

The application of the metal nanoprobe in mass spectrometry imaging technology (IMC).

The invention has at least the following beneficial technical effects:

1. the metal nanoprobe applied to the mass flow technology provided by the invention has extremely high metal content of a single probe, and the metal label of Zr-MOF with the size of 32nm contains 10⁵And a zirconium atom.

2. The metal nano probe applied to the mass flow technology provided by the invention has higher detection sensitivity than commercial MCP, higher signal-to-noise ratio than the reported CyTOF metal nano probe, and widened detection channels, and the positive quadrivalent zirconium metal has four stable isotopes, and four CyTOF synchronous detection channels are added.

3. The metal nano probe applied to the mass flow technology provided by the invention is simple in chemical synthesis, UIO-66 can be synthesized in one step by a solvothermal method, and is rich in a large amount of metals without extra loading; the UIO-66 surface contains a large number of carboxyl groups, and functional group modification is not needed when the antibody is coupled.

4. The metal nano probe applied to the mass flow technology provided by the invention has good dispersibility of Zr-MOF in a water system and high stability, and can be stored in water for more than one year without changing chemical properties.

The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.

Drawings

FIG. 1 is a schematic diagram of a solvothermal synthesis of Zr-MOF according to a preferred embodiment of the present invention;

FIG. 2 is a schematic diagram showing the variation of the particle size of Zr-MOF under the control of formic acid according to a preferred embodiment of the present invention;

FIG. 3 is a schematic diagram showing the variation of particle size of Zr-MOF under the control of dichloroacetic acid according to a preferred embodiment of the present invention;

FIG. 4 is a schematic diagram showing the variation of the particle size of Zr-MOF under the control of formic acid and dichloroacetic acid according to a preferred embodiment of the present invention;

FIG. 5 is a schematic representation of the EDC/sulfo-NHS system for coupling antibodies to Zr-MOF surfaces in accordance with a preferred embodiment of the present invention;

FIG. 6 is a schematic representation of the Zr-MOF and EQbeads mixing for CyTOF mass spectrometry detection in accordance with a preferred embodiment of the present invention;

FIG. 7 is a schematic illustration of the signal intensity of four channels of Zr-MOF in relation to the concentration of Zr-MOF according to a preferred embodiment of the present invention;

FIG. 8 is a graph of detection sensitivity versus signal-to-noise ratio for a preferred embodiment of the present invention.

Detailed Description

The technical contents of the preferred embodiments of the present invention will be more clearly and easily understood by referring to the drawings attached to the specification. The present invention may be embodied in many different forms of embodiments and the scope of the invention is not limited to the embodiments set forth herein.

The invention provides a novel-structure ultra-small nano probe based on a mass flow technology of a metal organic framework material, which can widen a detection channel of the mass flow technology; in a preferred embodiment of the invention, the metal element of the metal-organic framework is a metal element having a mass number between 75 and 209, in particular a zirconium-based metal-organic framework Zr-MOF. In a preferred embodiment of the invention, the size of the Zr-MOF metal organic framework is 20-50 nm.

Example 1

In order to obtain Zr-MOF with uniform size and high solvent dispersibility, Zr-MOF is synthesized by a solvothermal method, the influence of the types (formic acid, acetic acid and dichloroacetic acid) of monocarboxylic acid regulators in a solvothermal reaction system and the reaction time on the particle size and the stability of a Zr-MOF material is systematically researched by changing various reaction conditions, the optimal reaction conditions are determined by condition optimization, and finally a small-size UIO-66 crystal structure which is stably dispersed in an aqueous solution is synthesized.

As shown in figure 1, Zr-MOF with different particle sizes is obtained through the concentration regulation and control of monocarboxylate regulators such as dichloroacetic acid and formic acid and through the time regulation and control. As shown in FIGS. 2 to 4, the change processes of Zr-MOF particle size under the regulation of formic acid and dichloroacetic acid are disclosed.

Example 2

The embodiment discloses a preparation method of 30nm Zr-MOF, which specifically comprises the following steps:

step 1: preparing a storage solution, specifically: dissolving 210mg of zirconium chloride in 30mL of N, N-dimethyl amide (DMF), and performing ultrasonic dispersion until the zirconium chloride is completely dissolved to prepare a dissolved solution 1; dissolving 500mg of terephthalic acid (H2BDC) in 10mL of DMF, and ultrasonically dispersing until the terephthalic acid is completely dissolved to prepare a storage solution 2; the

stock solutions

1 and 2 were placed in an oven at 90 ℃ for preheating.

Step 2: respectively adding 3mL of stock solution 1 and 1mL of stock solution 2 into a 10mL glass bottle, vortexing and fully mixing the bottles (stock solution 1+2 system), respectively dropwise adding 393 mu L and 141 mu L of formic acid into the two bottles, vortexing and fully mixing the bottles, placing the bottles in an oven at 90 ℃ and reacting for 6 hours. A small number of parallel experiments were performed simultaneously in this step.

And step 3: after the product is naturally cooled, centrifuging for 1h at 3000G, and discarding the precipitate; the supernatant 18000G was centrifuged for 40min, and the precipitate was collected, washed five times with DMF and three times with water, and finally dispersed in deionized water.

Example 3

As shown in FIG. 5, this example couples Zr-MOF material to antibodies via the EDC/NHS system.

1- (3-methylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) is a zero-length crosslinking agent used for coupling carboxyl groups with primary amines. EDC first reacts with the carboxyl group and forms an amine-reactive O-acylisourea intermediate which rapidly reacts with the amino group to form an amide bond and liberate the isourea by-product. The intermediate is unstable in aqueous solution, therefore, the two-step coupling method requires N-hydroxysuccinimide (NHS) for stabilization; failure to react with the amine will result in intermediate hydrolysis, carboxyl regeneration and release of the N-substituted urea.

When two-step coupled proteins of EDC and NHS or sulfo-NHS are used, EDC activation is most efficient at pH 4.5-7.2, and EDC reaction is usually carried out in MES buffer at pH 4.7-6.0. The reaction of sulfo-NHS activated molecules with primary amines is most efficient at pH 7.0-8.0, and sulfo-NHS ester reactions are typically carried out in Phosphate Buffered Saline (PBS) at pH 7.2-7.5. For best results in a two step reaction, the first reaction was performed in 2- (N-morpholine) ethanesulfonic acid (MES) buffer (or other non-amine, non-carboxylate buffer) at pH 5.0-6.0, and then the pH was raised to 7.2-7.5 with phosphate buffer. The amine buffering is performed immediately prior to reaction with the amine-containing molecule. The EDC reaction can be quenched with 2-mercaptoethanol (2-ME) or excess reagents (and pH adjusted) can be simply removed by buffer exchange with a desalting column.

The procedure for coupling the Zr-MOF material to the antibody by the EDC/NHS system in this example is as follows.

Step 1: solution preparation: 3.834mg of EDC was weighed and dissolved in 10mL of water, and 1.1mg of sulfo-NHS was weighed and dissolved in 1mL of water;

step 2: dissolving 50. mu.g UIO-66 in 300. mu.L ddH₂O, fine-tuning to pH 5.5 using a sensitive pH meter;

and step 3: adding 10 mu L of EDC solution, mixing uniformly, adding 10 mu L of NHS, and mixing uniformly;

and 4, step 4: activating at room temperature for 30 min; 14000G for 40min, discarding the supernatant, and dissolving in 300 μ L deionized water;

and 5: adding 300 mu L of deionized water into a 50kDa ultrafiltration tube, adding 5 mu G of antibody, and centrifuging at the normal temperature of 1000G for 8 min; adding 300 mul deionized water, centrifugally washing once, and dissolving the intercepted substance in 100 mul deionized water;

step 6: and (4) adding the antibody aqueous solution obtained in the step (5) into the Zr-MOF solution obtained in the step (4), and reacting for 5 hours at normal temperature.

Example 4

This example discloses Zr-MOF metal probes stained for cell surface markers and CyTOF detection. And mixing the positive cells combined with the Zr-MOF metal probes in a targeted manner and the non-targeted negative cells according to a certain proportion, and carrying out label dyeing by using the Zr-MOF metal probes so as to verify the specific binding capacity, the non-specific adsorption and the like of the Zr-MOF metal probes. The specific process is as follows:

(1) cisplatin staining and cell fixing are carried out on cells to be detected;

(2) counting cells, taking 3X 10⁵Adding the blob solution into each cell, standing at normal temperature for 10min, adding Zr-MOF metal probes with different concentrations, uniformly mixing, incubating at normal temperature for 30min, and centrifuging and washing for 2 times;

(3) adding 125nM Ir or 500nM Rh, 1h at room temperature or overnight at 4 deg.C, performing cell nucleus labeling, centrifuging, washing, and suspending in deionized water;

(4) resuspend with 10% Element Calibration (EQ) beads, place sample on ice and perform CyTOF detection.

FIG. 6 shows the signal intensities of four channels when Zr-MOF is mixed with EQbeads for CyTOF mass spectrometry detection; FIG. 7 shows that the signal intensity of four Zr-MOF channels is proportional to the Zr-MOF concentration under CyTOF mass spectrometry detection; the upper graph and the lower graph of FIG. 8 respectively show the sensitivity and the signal-to-noise ratio of Zr-MOF used for CyTOF mass spectrometry detection, and compared with the traditional nano probe, the result shows that the detection sensitivity of the Zr-MOF metal probe is higher than that of a commercial probe, and the signal-to-noise ratio is higher than that of the reported CyTOF nano probe.

In addition to the above examples, the metal probe based on metal organic framework of the present invention, when used in mass cytometry, includes but is not limited to labeling of cell markers; besides the detection of cell suspension, the method can also be used for the detection of cells fixed on a glass substrate and tissue sections; can be used for other detection means after cell incubation, such as mass spectrometry imaging technology; can be used for detecting single cell solution or multi-cell solution.

The metal organic framework-based nanoprobe comprises but is not limited to an antibody when functionalized on the surface of the nanoprobe, and can obtain targeting property by connecting an aptamer, a nanobody and the like.

The metal nano probe applied to the mass flow technology forms the metal label through the metal organic framework, the metal content of a single probe is extremely high, the detection sensitivity is improved, the detection channel is widened, the chemical synthesis of the nano probe is simple, and the stability is high. Therefore, the present invention has advantageous technical effects.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.

Claims

1. A metal nanoprobe for application in mass spectrometry flow technology, wherein the metal nanoprobe is metal-tagged with a zirconium-based metal organic framework (Zr-MOF), the zirconium-based metal organic framework specifically using UIO-66 crystals, and the coupling of the zirconium-based metal organic framework to an antibody comprises the following steps:

step 1.1: dissolving 1- (3-dimethylaminopropyl) -3-ethylcarbodiimide hydrochloride (EDC) in water to prepare an EDC aqueous solution; dissolving sulfo N-hydroxysuccinimide (sulfo-NHS) in water to prepare a sulfo-NHS aqueous solution;

step 1.2: dissolving crystals of UIO-66 of a zirconium-based metal organic framework in water, adjusting the pH value using a sensitive pH meter;

step 1.3: adding the EDC aqueous solution prepared in the step 1.1, and uniformly mixing; then adding the sulfo-NHS aqueous solution prepared in the step 1.1, and uniformly mixing;

step 1.4: activating at room temperature for 30 min; centrifuging for 40min, removing supernatant, and dissolving in deionized water to obtain Zr-MOF solution;

step 1.5: adding deionized water into the ultrafiltration tube, adding antibody, and centrifuging at room temperature for 8 min; adding deionized water, centrifugally washing once, and dissolving the trapped substance in the tube into the deionized water to prepare an antibody aqueous solution;

step 1.6: and (3) adding the aqueous antibody solution obtained in the step (1.5) into the Zr-MOF solution obtained in the step (1.4), and reacting for 5 hours at normal temperature.

2. The metal nanoprobe for application in mass spectrometry flow techniques of claim 1, wherein the size of the zirconium based metal organic framework is 20-50 nm.

3. The metal nanoprobe for application in mass spectrometry flow techniques of claim 1, wherein the zirconium-based metal organic framework is prepared by the following method,

step 3.1: dissolving zirconium chloride in N, N-Dimethylformamide (DMF), and ultrasonically dispersing until the zirconium chloride is completely dissolved to prepare a storage solution 1; dissolving terephthalic acid (H2BDC) in DMF, and ultrasonically dispersing until the terephthalic acid is completely dissolved to prepare a storage solution 2; placing the storage solutions 1 and 2 in an oven at 90 ℃ for preheating;

step 3.2: respectively adding the storage solution 1 and the storage solution 2 into a glass bottle, and fully and uniformly mixing by vortex; respectively taking two bottles of mixed liquor, dropwise adding Formic Acid (FA) with different amounts, vortexing, fully mixing uniformly, placing in a 90 ℃ oven, and reacting for 6 hours;

step 3.3: after the product is naturally cooled, centrifuging for 1h, and discarding the precipitate; centrifuging the supernatant for 40min, collecting precipitate, washing with DMF five times and three times, and dispersing in deionized water to obtain UIO-66 crystal.

4. The metal nanoprobe for use in mass spectrometry flow techniques of claim 1, wherein the pH in step 1.2 is in the range of 4.7-6.0.

5. The metal nanoprobe for use in mass spectrometry flow techniques of claim 1, wherein in step 1.2 2- (N-morpholine) ethanesulfonic acid (MES) buffer and phosphate buffer are used for pH adjustment.

6. Use of a metal nanoprobe according to any of claims 1 to 5 in mass spectrometry flow technology (CyTOF).

7. Use of a metal nanoprobe according to any of claims 1 to 5 in mass spectrometry imaging techniques (IMC).