UiO-66-(OH) 2 / Au heterogeneous composite nanomaterial, preparation method and application of UiO-66-(OH) 2 / Au heterogeneous composite nanomaterial as SALDI-MS matrix in small molecule substance detection

Abstract

The invention discloses a UiO-66-(OH) 2 / Au heterogeneous composite nano-material, a preparation method and application of the UiO-66-(OH) 2 / Au heterogeneous composite nano-material as an SALDI-MS matrix in small molecule substance detection. According to the method, 2, 5-dihydroxy terephthalic acid and ZrCl4 are used as raw materials, UiO-66-(OH) 2 is rapidly synthesized through solvothermal reaction, and in-situ reduction of gold nanoparticles is achieved based on the reducibility of UiO-66-(OH) 2. When the UiO-66-(OH) 2 / Au heterogeneous composite nanomaterial is used as a substrate for detecting an analyte, the UiO-66-(OH) 2 / Au heterogeneous composite nanomaterial shows excellent salt tolerance and has good universal detection capability on metabolic molecules such as amino acids and saccharides. Compared with a traditional organic substrate, the background peak is clean and simple, and interference is greatly reduced. The material is expected to be used as an excellent matrix of SALDI-MS.

Description

Technical Field

[0001] The present invention relates to the technical field of mass spectrometry detection, and in particular to a UiO-66-(OH)2 / Au heterogeneous composite nanomaterial, a preparation method and an application of the material as a SALDI matrix in the detection of small molecule substances. Background Art

[0002] Matrix-assisted laser desorption ionization (MALDI) is a well-known soft ionization technique that is very popular for analyzing proteins, peptides, and other large biomolecules in biological samples. MALDI's advantages, such as high ionization efficiency, high sensitivity, simple sample preparation, and high tolerance to salts and common chemical buffer components, have led to its wide application in biology, genetics, food chemistry, medical research, and clinical diagnostics.

[0003] While MALDI-TOF MS offers numerous advantages, organic matrices can strongly interfere with detection results in the molecular weight range (m / z <700 Da), and heterogeneous crystallization between the matrix and the analyte can affect reproducibility and quantification. Consequently, a new technique, surface-assisted laser desorption ionization (SALDI), has been developed. The high porosity and large surface area of ​​MOFs facilitate the formation of uniform co-crystallization systems with the analyte. Their strong absorption in the ultraviolet region meets the laser energy absorption and transfer requirements of SALDI. Furthermore, their ease of functionalization greatly expands their application in the detection of small molecule analytes. Precious metal nanomaterials, such as Au NPs, are widely used in SALDI due to their unique optical and electronic properties. The formation of heterogeneous composite nanomaterials not only retains the original properties of MOFs but also significantly enhances their optical absorption, resulting in excellent photothermal and photoelectric conversion capabilities and improved laser desorption ionization efficiency. However, MOFs typically require lengthy synthesis times, and the formation of heterogeneous composite nanomaterials often requires prolonged adsorption of HAuCl₄ and the addition of reducing agents.

[0004] Therefore, a green in situ method was used to synthesize UiO-66-(OH)2 / Au heterogeneous composite nanomaterials, which reduced the synthesis time of MOFs and did not require a reducing agent, thereby reducing the reaction time, improving its desorption ionization efficiency and heat transfer efficiency, and fully combining the advantages of MOFs and Au NPs on the matrix. Summary of the Invention

[0005] To address the technical challenges faced by metal-organic frameworks (MOFs) in laser desorption ionization (SALDI) mass spectrometry (LSI-MS), this paper proposes an innovative heterogeneous composite nanomaterial solution: a UiO-66-(OH)2 / Au heterogeneous composite nanomaterial. This novel material aims to address the challenges of MOFs, such as the single peak formation of analytes, low heat transfer, and low desorption and ionization efficiency. The present invention also provides a method for preparing the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial and its potential application as a SALDI matrix for small molecule detection.

[0006] To achieve the above-mentioned and other related purposes, the present invention provides the following technical solutions: The first aspect of the present invention provides a method for preparing a UiO-66-(OH)2 / Au heterogeneous composite nanomaterial, comprising the following steps: (1) 2,5-Dihydroxyterephthalic acid (DHTA), triethylamine (TEA), glacial acetic acid and polyvinylpyrrolidone (PVP) were dissolved in dimethylformamide (DMF) solvent and stirred at room temperature to obtain a mixed solution; the obtained mixed solution was heated to 120-125 °C in an oil bath, and zirconium tetrachloride (ZrCl4) in DMF solvent was added and the solvent thermal reaction was carried out for 20-25 min; after the solution was cooled to room temperature, the product was washed and centrifuged to obtain pure UiO-66-(OH)2.

[0007] (2) At room temperature, UiO-66-(OH)2 and PVP were dissolved / dispersed in an aqueous solution and stirred evenly to obtain a mixed solution; HAuCl4 was added to the mixed solution and stirred to react to obtain UiO-66-(OH)2 / Au heterogeneous composite nanomaterials.

[0008] Wherein, in step (1), the molar ratio of DHTA to ZrCl4 is 14:1.

[0009] PVP is added during the synthesis process. PVP acts as a steric stabilizer or end-capping agent, primarily protecting the product from aggregation. Because hydroxyl groups are highly polar and can aggregate during crystal formation during the reaction, the addition of PVP further reduces the aggregation of UiO-66-(OH)2. The ratio of PVP to ZrCl4 is 25-125 g:1 mmol, preferably 25-100 g:1 mmol, more preferably 75-100 g:1 mmol, and most preferably 87.5 g:1 mmol.

[0010] During the synthesis of UiO-66-(OH)2, triethylamine was added. Due to its ability to proton-removal from the ligand, the reaction time was significantly reduced. Since the hydroxyl groups in the ligand also coordinate with the metal ion center, acetic acid was added to adjust the morphology. The molar ratio of DHTA, TEA, and glacial acetic acid was 1:1.5:625.

[0011] Preferably, the solvent thermal reaction time in step (1) is 20 minutes.

[0012] Wherein, in step (2), the mass ratio of UiO-66-(OH)2 to PVP is 1:(10-50); preferably, the mass ratio of UiO-66-(OH)2 to PVP is 1:50.

[0013] Wherein, in step (2), gold nanoparticles are prepared by the reducing property of UiO-66-(OH)2 itself, thereby realizing green in-situ reduction preparation of Au NPs on UiO-66-(OH)2, and finally forming UiO-66-(OH)2 / Au heterogeneous composite nanomaterials. The mass of HAuCl4 is 0.2% to 0.5% of the mass of UiO-66-(OH)2; preferably, the mass of HAuCl4 is 0.3% to 0.5% of the mass of UiO-66-(OH)2; more preferably, the mass of HAuCl4 is 0.4% to 0.5% of the mass of UiO-66-(OH)2; most preferably, the mass of HAuCl4 is 0.4% to 0.5% of the mass of UiO-66-(OH)2.

[0014] The stirring reaction in step (2) is carried out at room temperature with a stirring speed of 600 rpm for 30 min.

[0015] The average molecular weight of the PVP in step (1) or step (2) is between 30,000 and 50,000; preferably, the average molecular weight of the PVP is 40,000.

[0016] The second aspect of the present invention provides a UiO-66-(OH)2 / Au heterogeneous composite nanomaterial prepared by the above method.

[0017] The third aspect of the present invention provides an application of the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial prepared by the aforementioned method as a matrix in the fields of mass spectrometry imaging, metabolomics, etc., especially as a SALDI-MS matrix in the detection of small molecule metabolites.

[0018] Furthermore, the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial can be used to detect at least one of alanine, glycine, proline, valine, fructose, glucose, maltose, sucrose, serine, aspartic acid, threonine, lysine, glutamic acid, tryptophan, cysteine, isoleucine, leucine, phenylalanine, glutamine, aspartic acid, histidine, and free fatty acids.

[0019] As described above, the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial, its preparation method, and its use as a SALDI matrix in the detection of small molecules of the present invention have at least the following beneficial effects: 1. The present invention adds triethylamine during the synthesis of UiO-66-(OH)2, significantly reducing the synthesis reaction time. Acetic acid is added to adjust the morphology, and PVP is added during the synthesis process to reduce the agglomeration of UiO-66-(OH)2. Green in-situ preparation of gold nanoparticles is achieved on UiO-66-(OH)2, ultimately forming a UiO-66-(OH)2 / Au heterogeneous composite nanomaterial. This heterogeneous composite nanomaterial also has significantly increased optical absorption and excellent photothermal and photoelectric conversion capabilities, significantly improving its desorption and ionization efficiency. It is very helpful for detecting small molecule analytes in the low mass range and increasing the types of analytes that can be detected.

[0020] 2. The synthesis time period of the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial in the present invention is short, the preparation method is simple, and the prepared UiO-66-(OH)2 / Au heterogeneous composite nanomaterial has a small particle size, excellent salt resistance and reproducibility, and has broad application value in the field of analysis and detection.

[0021] 3. Compared with UiO-66-(OH)2 materials without the addition of Au NPs, the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial has better heat transfer performance and higher desorption and ionization performance than the SALDI-MS matrix, significantly improving the accuracy, repeatability and detection efficiency of SALDI-MS analysis, while simplifying the operation process and reducing costs, opening up new paths for the development of mass spectrometry analysis technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 SEM (A) and TEM images (B) of the UiO-66-(OH)2 / Au-4 heterogeneous composite nanomaterials prepared in the present invention, as well as SEM (C) of UiO-66-(OH)2 prepared without adding PVP and SEM (D) of UiO-66-(OH)2 prepared with a reaction time of 9 hours.

[0023] Figure 2These are the Uv-Vis diagrams of the UiO-66-(OH)2 prepared in Example 1 of the present invention and the UiO-66-(OH)2 / Au heterogeneous composite nanomaterials prepared in Examples 4-7.

[0024] Figure 3 These are the XRD patterns of the UiO-66-(OH)2 prepared in Example 1 of the present invention and the UiO-66-(OH)2 / Au heterogeneous composite nanomaterials prepared in Examples 4-7.

[0025] Figure 4 SY value diagram of 4-C-BP detected using UiO-66-(OH)2 prepared in Example 1 of the present invention and UiO-66-(OH)2 / Au prepared in Examples 4-7 as matrices.

[0026] Figure 5 Mass spectra of sodium tetraphenylborate detected using UiO-66-(OH)2 prepared in Example 1 of the present invention and UiO-66-(OH)2 / Au prepared in Examples 4-7 as matrices.

[0027] Figure 6 Mass spectra of free fatty acids detected using UiO-66-(OH)2 prepared in Example 1 of the present invention and UiO-66-(OH)2 / Au prepared in Examples 4-7 as matrices.

[0028] Figure 7 The UiO-66-(OH)2 / Au prepared in Example 6 of the present invention was used as a matrix to detect the mass spectra of lactose, galactose, raffinose, fructose, glucose, maltose, and sucrose, respectively; wherein M is the corresponding analyte, and the analyte concentration is 0.01 mol / L.

[0029] Figure 8 The UiO-66-(OH)2 / Au prepared in Example 6 of the present invention detects 19 kinds of amino acids, namely alanine, glycine, proline, valine, serine, aspartic acid, threonine, lysine, glutamic acid, tryptophan, cysteine, isoleucine, leucine, phenylalanine, glutamine, asparagine, and histidine; wherein the amino acid concentration is 0.01 mol / L.

[0030] Figure 9 Mass spectra of histidine and glucose detected at high salt concentrations using UiO-66-(OH)2 / Au prepared in Example 6 of the present invention as a matrix; the salt concentrations were 10 mM, 100 mM, and 1000 mM; and the histidine and glucose concentrations were 0.001 mol / L.

[0031] Figure 10The mass spectrum of a mixture of 19 amino acids detected using 2,5-dihydroxybenzoic acid (DHB), a traditional matrix.

[0032] Figure 11 Mass spectrum of a mixture of 19 amino acids detected using α-cyano-4-hydroxycinnamic acid (CHCA) as the matrix.

[0033] Figure 12 This is the mass spectrum of a mixture of 19 amino acids detected using UiO-66-(OH)2 / Au prepared in Example 6 of the present invention as a matrix. DETAILED DESCRIPTION

[0034] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Example 1

[0035] A UiO-66-(OH)2 nanomaterial is prepared by the following method: (1) Dissolve 4 mM DHTA, 6 mM TEA, and 3.5 g of PVP (40000) in a round-bottom flask containing 140 mL of DMF solution.

[0036] (2) Add 20 mL of glacial acetic acid (0.35 mol) and 10 mL of DMF solution containing ZrCl4 (4 mM) at 120°C and let the reaction stand for 20 min.

[0037] (3) After the solution was cooled to room temperature, the product was washed with DMF, acetone, methanol, ethanol, and water in sequence, and then centrifuged and vacuumed to obtain 100 mg of pure UiO-66-(OH)2. Example 2

[0038] The preparation method of UiO-66-(OH)2 is the same as that in Example 1, except that PVP is not added. Example 3

[0039] The preparation method of UiO-66-(OH)2 is the same as that in Example 1, except that the reaction time is 8 h. Example 4

[0040] A UiO-66-(OH)2 / Au heterogeneous composite nanomaterial is prepared by the following method: (1) The preparation method of UiO-66-(OH)2 is the same as that in Example 1; (2) UiO-66-(OH)2 (100 mg) and 5 g PVP (40000) were dissolved in 250 mL of water, and 2 mL of HAuCl4 aqueous solution (1% w / v) was added and stirred for 30 min; (3) Centrifuge at 9000 rpm and then wash with water and methanol to obtain a purple powder named UiO-66-(OH)2 / Au-2. Example 5

[0041] The difference between this example and Example 4 is that the amount of HAuCl4 aqueous solution (1%) used is 3 mL, and the product is named UiO-66-(OH)2 / Au-3. Example 6

[0042] The difference between this example and Example 4 is that the amount of HAuCl4 aqueous solution (1%) used is 4 mL, and the product is named UiO-66-(OH)2 / Au-4. Example 7

[0043] The difference between this example and Example 4 is that the amount of HAuCl4 aqueous solution (1%) used is 5 mL, and the product is named UiO-66-(OH)2 / Au-5.

[0044] Performance Characterization

[0045] 1. Take SEM and TEM images of the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial prepared in Example 6. Figure 1 As shown in (A, B), different Au NPs are distributed on the UiO-66-(OH )2 Failure to add PVP or excessively long reaction times will result in severe aggregation of UiO-66-(OH)2 ( Figure 1 C, D).

[0046] 2. The UiO-66-(OH)2 and UiO-66-(OH)2 / Au heterogeneous composite nanomaterials prepared in the process of Examples 4-7 were subjected to ultraviolet absorption spectrum analysis. Figure 2 As shown in Figure 3, the addition of Au NPs increased the absorption peaks at 320 nm and 540 nm.

[0047] 3. The UiO-66-(OH)2 prepared in the process of Example 4-7 was mixed with UiO-66-(OH )2 / Au heterogeneous composite nanomaterials XRD analysis Figure 3As shown in the figure, the existence state and distribution of Au NPs at different loading levels can be seen. The XRD spectrum of the original UiO-66-(OH)2 is consistent with the simulated UiO-66 data, indicating that it has good crystallinity and structural integrity. The characteristic peaks are located at about 7.5°, 14.0°, and 28.5°, corresponding to the (111), (200), and (600) crystal planes. With the loading of Au NPs, new diffraction peaks appear in the XRD spectrum. These peaks are attributed to the face-centered cubic structure of gold, specifically the characteristic peaks of the (111), (200), (220), and (311) crystal planes appearing at about 38.2°, 44.4°, 64.6°, and 77.5°.

[0048] 4. 4-Chlorobenzyl-pyridine (4-(4-Chlorobenzyl)pyridine), 4-C-BP, can undergo specific fragmentation in positive ion mode, thereby generating a stable ion signal. Under the same laser energy conditions, it produces a characteristic ion fragment peak F⁺ (m / z 125) and a parent ion peak M⁺ (m / z 204). The parent ion fragmentation degree SY value (defined as the ratio of the fragment ion intensity to the parent ion intensity, i.e., SY = I((fragment) / I(parent ion)) is related to the heat transfer performance of the matrix. The prepared UiO-66-(OH)2 was mixed with UiO-66-(OH )2 / Au heterogeneous composite nanomaterials, 4-C-BP was detected using MALDI-MS instrument, and the SY value was calculated as Figure 4 As shown in the figure, the addition of Au NPs significantly improved the heat transfer efficiency of the matrix, among which UiO-66-(OH)2 / Au-4 had the best heat transfer efficiency.

[0049] 5. Sodium tetraphenylborate is an organic salt with negative charge. In the negative ion mode, the signal can be detected only after the desorption process. Therefore, it is often used to measure the desorption efficiency of the substrate. )2 The desorption efficiency of the Au / Au heterogeneous composite nanomaterials was evaluated by detecting sodium tetraphenylborate in negative ion mode. Figure 5 As shown in Figure 2, Au NPs greatly improved the desorption efficiency of the matrix, among which the best desorption efficiency was achieved by UiO-66-(OH)2 / Au-4 heterogeneous composite nanomaterial, with an average ion signal intensity of 2.38×10 5 , than UiO-66-(OH)2(1.2×10 3 ) increased by about 200 times.

[0050] 6. Free fatty acids are highly volatile, and their charge-deficient atoms can effectively capture electrons from the substrate and generate negatively charged ions. They are a good analyte for evaluating the ionization efficiency of the LDI process. )2 / Au heterogeneous composite nanomaterials were used to detect free fatty acids to evaluate the ionization efficiency of the matrix. Figure 6 As shown in Figure 2, the addition of Au NPs greatly improved the ionization efficiency, among which UiO-66-(OH)2 / Au-4 had the best ionization efficiency (1.05×10 5 ), compared with UiO-66-(OH)2 without Au NPS (2×10 3 ) increased by 50 times.

[0051] 7. Figure 7 Using UiO-66-(OH)2 / Au as the matrix, the mass spectra of lactose, galactose, raffinose, fructose, glucose, maltose, and sucrose were analyzed respectively; where M is the corresponding analyte, and the concentration of the analyte is 0.01 mol / L.

[0052] 8. Figure 8 UiO-66-(OH)2 / Au NPs were used as the matrix to analyze 19 amino acids, including alanine, glycine, methionine, proline, valine, serine, arginine, aspartic acid, threonine, lysine, glutamic acid, tryptophan, cysteine, isoleucine, leucine, phenylalanine, glutamine, asparagine, and histidine. The concentration of the amino acids was 0.01 mol / L.

[0053] 9. Figure 9 UiO-66-(OH)2 / Au NPs were used as the matrix to detect histidine and glucose at high salt concentrations of 10 mM, 100 mM, and 1000 mM, respectively. The concentrations of histidine and glucose were 0.001 mol / L. 10. The SALDI-MS spectra of DHB, CHCA and UiO-66-(OH)2 / Au for the detection of 19 amino acid mixtures are as follows: Figure 10 、 Figure 11 and Figure 12 , UiO-66-(OH)2 / Au-4 matrix can detect all amino acids in the mixed solution; while DHB and CHCA can only detect 7 and 11 amino acids, respectively.

[0054] according to Figure 10-12The test results show that the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial prepared by the present invention expands the types of detected analytes. Compared with traditional organic matrices, the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial detects more amino acids and can play a good role in fields such as metabolomics.

[0055] In summary, the present invention uses DHTA and ZrCl4 as raw materials, regulates the reaction through triethylamine, acetic acid and PVP to obtain UiO-66-(OH)2, and then obtains UiO-66-(OH)2 / Au heterogeneous composite nanomaterials through in-situ green reduction. Triethylamine accelerates the reaction rate, acetic acid regulates the morphology, and PVP reduces its aggregation. In-situ green reduction does not require an additional reducing agent. This composite material has good heat transfer and desorption ionization efficiency in the field of small molecule analysis, has extremely high salt tolerance and reproducibility, and has good universal detection capabilities for metabolic molecules such as amino acids and sugars. Therefore, the present invention effectively overcomes the various shortcomings of the existing technology and has high industrial utilization value.

[0056] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A method for preparing UiO-66-(OH)2 / Au heterogeneous composite nanomaterial, characterized in that: The following steps are involved: (1) 2,5-Dihydroxyterephthalic acid, triethylamine, glacial acetic acid and polyvinylpyrrolidone were dissolved in dimethylformamide to obtain a mixed solution; the mixed solution was heated to 120-125 °C in an oil bath, and a dimethylformamide solution of ZrCl4 was added, and the mixture was subjected to solvent thermal reaction for 20-25 min; after the solution was cooled to room temperature, the product was washed and centrifuged to obtain UiO-66-(OH)2; (2) At room temperature, UiO-66-(OH)2 and polyvinyl pyrrolidone were dispersed or dissolved in water and stirred to obtain a mixed solution; HAuCl4 solution was added to the mixed solution and stirred to react to obtain UiO-66-(OH)2 / Au heterogeneous composite nanomaterials.

2. The method for preparing the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial according to claim 1, characterized in that: In step (1), the molar ratio of 2,5-dihydroxyterephthalic acid to ZrCl4 is 14:1; and / or the molar ratio of 2,5-dihydroxyterephthalic acid, triethylamine and glacial acetic acid is 1:1.5:

625.

3. The method for preparing the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial according to claim 1, characterized in that: In step (1), the ratio of polyvinyl pyrrolidone to ZrCl4 is 25~125g:1mmol.

4. The method for preparing the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial according to claim 1, characterized in that: In step (2), the mass ratio of UiO-66-(OH)2 to polyvinyl pyrrolidone is 1:10~50.

5. The method for preparing the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial according to claim 1, characterized in that: In step (2), the mass of HAuCl4 is 0.2% to 0.5% of the mass of UiO-66-(OH)2.

6. The method for preparing the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial according to claim 1, characterized in that: The stirring reaction in step (2) is carried out at room temperature, at a stirring speed of 600 rpm, and for 30 min.

7. The method for preparing the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial according to claim 1, characterized in that: The average molecular weight of the polyvinyl pyrrolidone in step (1) or step (2) is 30,000-50,000.

8. The UiO-66-(OH)2 / Au heterogeneous composite nanomaterial prepared by the method according to any one of claims 1 to 7.

9. Use of the UiO-66-(OH)2 / Au heterogeneous composite nanomaterial according to claim 8 as a matrix in the fields of mass spectrometry imaging, metabolomics, etc.

10. The use according to claim 9, characterized in that The UiO-66-(OH)2 / Au heterogeneous composite nanomaterial is used as a SALDI-MS matrix in the detection of small molecule metabolites.

Images