WO2022032871A1

WO2022032871A1 - Infrared ii region fluorogold nanocluster, preparation and application thereof

Info

Publication number: WO2022032871A1
Application number: PCT/CN2020/123606
Authority: WO
Inventors: 李瑞宾; 王威力
Original assignee: 苏州大学
Priority date: 2020-08-11
Filing date: 2020-10-26
Publication date: 2022-02-17
Also published as: CN111849467A; CN111849467B

Abstract

Provided are preparation and application of an infrared II region fluorogold nanocluster. An aqueous phase synthesis method is adopted, the preparation method comprises: dissolving chloroauric acid HAuCl ₄ into a strong alkaline aqueous solution, reducing trivalent gold ions Au ³⁺ into gold atoms Au ⁰ by using a reducing agent, selecting protein ligand template molecules containing sulfydryl (cysteine) and conjugated functional groups, and changing conditions like temperature and reaction time by using a microwave-assisted synthesis device, such that the gold atoms grow and gather in the corresponding ligand template to form the gold nanocluster. The gold nanocluster can emit infrared II region fluorescence, and has relatively high fluorescence quantum yield and good biological safety.

Description

Infrared II region fluorescent gold nanoclusters and their preparation and application

technical field

The invention relates to the technical field of infrared II region fluorescent materials, in particular to an infrared II region fluorescent gold nanocluster and its preparation and application.

Background technique

Infrared II region fluorescence imaging technology refers to the imaging research technology that uses infrared laser (>808nm) to excite materials to emit near-infrared II region fluorescence (1000nm-1700nm), and conduct real-time and dynamic detection at the level of living organisms. This technology originated from an important scientific hypothesis in the research of fluorescence quantum dot bioimaging by Carroll et al. in 2006: the near-infrared II region (1000nm-1700nm) fluorescence bioimaging effect is better than the visible light region and infrared I region (400-1000nm). This hypothesis has been recognized by many scholars as soon as it was put forward. Compared with traditional optical imaging technology, infrared region II imaging has high sensitivity (detection limit: 10 ^-15 mol/L), high time (<50ms) and spatial resolution ( <25μm), deep tissue penetration ability (>2cm), low cost, no radiation, low biological tissue self-luminescence interference and other advantages, and become a hot field of bioimaging research in recent years. In 2018, top engineering materials journals such as Nature Nanotechnology and Nature Materials have successively reported the synthesis and preparation of new infrared II materials and their imaging applications in vivo (such as the brain, liver, and intestine). It is a very exploratory and challenging hot research field in biological imaging technology.

At present, it has been found that nanomaterials with infrared II fluorescence imaging properties mainly include the following two categories: doped rare earth element fluorescent materials and heavy metal quantum dots. These two nanomaterials have different emission mechanisms.

Rare earth element-doped nano-fluorescent materials are usually composed of a matrix and an activator. The matrix is a compound (such as: Y ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ ) as the host of the material, and the activator is a small amount of dopant as the luminescent center. Impurity ions (especially positive trivalent rare earth element ions, such as: Sm ³⁺ , Eu ³⁺ , Tb ³⁺ , Dy ³⁺ , Nd ³⁺ , Ho ³⁺ , Er ³⁺ , Tm ³⁺ , Yb ³⁺ ), For IR II rare earth doped nanoparticles, the emission wavelength depends on the elemental species of the doped activator. For example, Ho, Pr, Tm and Er are capable of emitting fluorescence at 1185, 1310, 1475 and 1525 nm, respectively. This material has excellent optical properties such as: long fluorescence lifetime, narrow spectral line, wide coverage of fluorescence emission wavelength, etc., but the quantum yield is low (0.1%-3%). Moreover, the biological stability of rare earth-doped nano-fluorescent materials is poor, and rare earth elements are easily combined with phosphoric acid and converted into rare earth phosphate compounds, resulting in fluorescence quenching, triggering the activation of cellular NLRP3 inflammasomes and the release of inflammatory factors. Therefore, the biosafety of IR II rare earth materials is a major obstacle to clinical application.

Heavy metal quantum dots are mainly composed of IV, II-VI, IV-VI or III-V group elements, containing a limited number of atoms to form a lattice, and the three dimensions are in the order of nanometers, and the excitons are placed in three spaces. Directionally bound semiconductor nanostructures. The light-emitting mechanism of heavy metal quantum dots lies in the action of excitons. The light-emitting process is that the negative electrons in the valence band are excited to transition to the conduction band, leaving a positive hole to form an electron-hole combination, which will appear when the excitons are deactivated. At the same time, with the change of the lattice size of quantum dots, the energy band gap between the valence band and the conduction band will change, which affects the change of the emission wavelength from visible light to infrared light. As a novel semiconductor nanomaterial, quantum dots have many unique optical properties, especially in the range of infrared II fluorescence (1000-1700nm). Compared with other fluorescent materials, quantum dots have a large absorption coefficient and a quantum yield. High (QY>15%) and other characteristics, it has extremely high research value in infrared Ⅱ fluorescence imaging. However, infrared II fluorescent quantum dots are mostly composed of active heavy metals, such as: PbS, Ag ₂ Se, CdTe/HgTe, which are easily released in biological media and cause cytotoxicity. At present, some scholars have proved that the heavy metal ions released by intravenous injection of quantum dots containing heavy metal ions have significant toxic and side effects on nerve cells.

The significant cytotoxic side effects of the above two types of infrared II materials are the shortcomings and deficiencies of the existing technology. Therefore, how to synthesize and prepare nano-imaging materials in the infrared II region with good biocompatibility is an important aspect of the current nano-bioimaging research field. Scientific question.

Although gold nanomaterials have microwave absorption properties, high surface activity, optical properties, photocatalytic properties, photoelectrochemical properties and photothermal properties, and optical conversion properties (absorption, emission, scattering, plasmon resonance), although gold nanomaterials have unique properties due to their unique The physicochemical properties of gold nanomaterials have potential applications in a variety of biomedical imaging, but there is no research on the preparation and imaging applications of gold nanomaterials in the infrared II region. This is because gold nanomaterials have fluorescent properties that depend on particle size, and their emission spectra can be tuned in different wavelength bands (visible light region to infrared region) through size control, but the near-infrared region (especially the 800- 1000nm) luminescent gold nanomaterials do not obey the quantum size effect theory, and it is difficult to achieve their emission spectrum in the near-infrared II region through size regulation.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the purpose of the present invention is to provide an infrared II region fluorescent gold nanocluster and its preparation and application. The gold nanocluster of the present invention can emit infrared II region fluorescence and has good biological safety.

The first object of the present invention is to provide a preparation method of fluorescent gold nanoclusters in the infrared II region, comprising the following steps:

(1) adding the alkaline aqueous solution to the tetrachloroauric acid aqueous solution to react until the tetrachloroauric acid aqueous solution becomes colorless and transparent, then adding the aqueous solution of the ligand template molecule to the colorless and transparent solution to obtain a mixed solution, the mixed solution The pH value is 10-11 (preferably pH10); wherein, the ligand template molecule includes polypeptides, macromolecular compounds, amino acids or proteins; and the ligand template molecules include thiol-containing and conjugated molecular structure-containing functional groups;

(2) Using sodium borohydride (NaBH ₄ ) aqueous solution to reduce Au ³⁺ in the mixed solution to gold atom Au ⁰ , and then continue the reaction to make gold atoms grow and aggregate in the ligand template molecule to form gold nanoclusters, gold nanoclusters. The number of gold atoms in the cluster is 10-25.

Further, in step (1), the molar ratio of the thiol-containing functional group and the conjugated molecular structure-containing functional group in the ligand template molecule is 1/18-18/1.

Further, the conjugated molecule includes one or more of imidazole ring, benzene ring and phenol.

Further, in step (1), the functional group containing a thiol group is derived from cysteine (Cys); the functional group containing a conjugated molecular structure is derived from histidine (His), tyrosine (Tyr) and tryptophan (Trp) one or more.

Further, in step (1), the molar ratio of the thiol-containing functional group and the conjugated molecule-containing functional group is 8:10.

Preferably, in step (1), the ligand template molecule includes cysteine, histidine and tyrosine. The molar ratio of cysteine, histidine and tyrosine was 5-8:6-8:6-7.

Further, in step (1), the protein is selected from one or more of ribonuclease (RNase-A), bovine serum albumin (BSA) and β-lactoglobulin (β-lactoglobulin). Preferably, the protein is RNase-A.

Further, when the ligand template molecule includes a polypeptide or protein, the molar ratio of tetrachloroauric acid and the ligand template molecule is 20-25:1; when the ligand template molecule includes a polymer compound or an amino acid, the tetrachloroauric acid and the ligand template molecule are included. The molar ratio of bulk template molecules was 20-25:14-18.

Further, in step (1), the alkaline aqueous solution is an aqueous sodium hydroxide (NaOH) solution. Preferably, the concentration of the aqueous sodium hydroxide solution is 1M. In step (1), the function of the alkaline condition is to deprotonate the thiol group of the ligand template molecule and the functional group of the conjugated molecular structure, which is more conducive to the combination of the ligand molecule and the gold ions on the surface of the gold cluster to form a stable structure. If the mixed solution of the ligand template molecule and tetrachloroauric acid is flocculated, add some more sodium hydroxide to make the pH of the mixed solution greater than or less than the isoelectric point of the protein.

Preferably, in step (1), the concentration of the aqueous solution of tetrachloroauric acid is 15 mM; the aqueous solution of the ligand template molecule is 10 mg/mL-25 mg/mL. As the concentration of the ligand-template molecule increases, the fluorescence intensity of the gold clusters increases, but the emission spectrum has a blue-shift of 50-200 nm.

In step (1), after adding the ligand template molecule, Au ³⁺ ions in the solution are freely distributed in the ligand template molecule, providing space for the subsequent aggregation of gold atoms to form gold nanoclusters.

Further, the molar ratio of sodium borohydride in step (2) to tetrachloroauric acid in step (1) is 0.02-0.1:1.

Further, in step (2), the aqueous solution of sodium borohydride is added dropwise to the mixed solution so that Au ³⁺ ions are reduced to Au ⁰ . Due to the high surface energy of Au ⁰ , it will rapidly aggregate to form clusters in a microwave heating environment, and the surface of The gold ions of Au 0 combine with the ligand to form a stable structure, or the Au ⁰ can slowly grow into gold clusters by reacting at 4 °C for 24-72 h.

Further, in step (2), the reduced solution is reacted at 4°C for 24-72h or under 100W, 50-100°C (preferably 70°C) microwave for 30-90s (preferably 60s), The gold atoms grow and aggregate in the ligand template molecules to form gold nanoclusters, and the reaction solution is finally a brown-black transparent and clear solution.

In step (2), sodium borohydride plays the role of reducing agent, and the addition amount of reducing agent should be controlled within a suitable range, and its consumption is too much, and the reduction reaction is too violent, which will cause black precipitation in the mixed solution or change immediately. It is black, indicating that a large number of gold atoms aggregate to form gold nanoparticles rather than clusters, so it is difficult to form gold nanoclusters with infrared II region fluorescence effect.

Further, in step (2), after the gold nanoclusters are formed, a dialysis bag with a molecular weight cut-off of 20000 Da is used to remove unreacted ions (eg Au ³⁺ , Na ⁺ , Cl ^- ) by dialysis.

The second object of the present invention is to claim a fluorescent gold nanocluster in the infrared II region prepared by the above preparation method, which comprises gold nanoclusters and ligand template molecules attached to the surface of the gold nanoclusters, gold nanoclusters The number of gold atoms in the cluster is 10-25, and the ligand template molecules include polypeptides, polymer compounds, amino acids or proteins; and the ligand template molecules include functional groups containing sulfhydryl groups and conjugated molecular structures.

Further, the functional group containing a thiol group is derived from cysteine (Cys); the functional group containing a conjugated molecular structure is derived from one of histidine (His), tyrosine (Tyr) and tryptophan (Trp). or several.

Preferably, the ligand template molecule comprises a polypeptide, amino acid or protein. Polypeptides, amino acids or proteins include amino acids containing sulfhydryl groups and amino acids containing conjugated molecular structures.

Preferably, cysteine, histidine and tyrosine are included in both amino acids and proteins. Among them, cysteine contains sulfhydryl group, histidine contains conjugated imidazole, and tyrosine contains conjugated benzene ring.

Preferably, the molar ratio of cysteine, histidine and tyrosine in the amino acid or protein is 8:4:6.

Further, the protein is selected from one or more of ribonuclease (RNase-A), bovine serum albumin (BSA) and β-lactoglobulin.

Preferably, the ligand template molecule is selected from ribonuclease, β-lactoglobulin, dihydrothio-sulfobetaine or polypeptide (CYKPCHCYKPCHYCKPYCHCKPYCHY- _NH2 ).

Further, in each gold nanocluster, the total number of cysteine, histidine and tyrosine in the ligand template molecule is 14-18.

Further, in step (1), the molar ratio of tetrachloroauric acid and ligand template molecule is 20-25:1.

The third object of the present invention is to claim the application of the above-mentioned infrared II region fluorescent gold nanoclusters in the preparation of near-infrared II region fluorescent imaging preparations.

Further, the formulation is an oral formulation. The fluorescent gold nano-cluster in the infrared II region of the invention has good biocompatibility and safety, and can be administered into the organism by oral administration.

Further, imaging preparations are used to detect intestinal diseases such as mechanical bowel obstruction and obstructive bowel cancer. Using the infrared II region fluorescent gold nanoclusters of the present invention can effectively study the biological safety structure-activity relationship of gold nanoclusters, provide guidance for the safety design of gold-based nano biological products, and accelerate the application of gold nanometer products to clinical imaging. promotion.

In the present invention, the fluorescent gold nanocluster in the infrared II region refers to that its fluorescence emission peak is in the near-infrared II region, and the emission wavelength corresponding to the emission peak is 1000-1400 nm.

The infrared II region fluorescent gold nanocluster of the present invention can emit infrared II region fluorescence, and its luminescence mechanism is caused by the joint action of two theories, namely quantum size effect and ligand-to-metal charge transfer theory. The electron-donating characteristics of the ligand affect the transition energy level of the gold ion (Au ¹⁺ ) on the metal surface and then to the electron excitation of the internal gold atom (Au ⁰ ), and the orbit from the cluster to the ligand energy level affects the relaxation phenomenon of the electron returning to the ground state, thereby changing the luminescence wavelength. The invention affects the charge transfer process from the ligand in the gold cluster to the metal by introducing a functional group structure containing a conjugated system and a sulfhydryl group. The introduction of the aromatic conjugated system provides a wider transition for the electrons inside the gold cluster after being excited. The band gap from the ligand to the gold cluster is further narrowed, and then the luminescence of the gold nanocluster is red-shifted to the infrared II region. Specifically, the principle is as follows:

When the number of gold atoms in the gold nanocluster is N<30, the luminescence principle basically conforms to the quantum size effect, the position of the emission peak is positively related to the number of gold atoms, and the emission wavelength E _ev =E _Fermi /N ^1/3 ; where E _Fermi is Fermi energy of gold; N is the number of core atoms of the cluster. This conclusion suggests that the electronic structure of the clusters depends on the free electron density of the metal as well as the cluster size. However, it is difficult to obtain fluorescent gold nanoclusters in the infrared II region only by relying on quantum size theory, and the properties of the ligands must be considered.

At the same time, according to the theory of charge transfer transition from metal to ligand, fluorescence is mainly generated by the charge transfer from the atoms in the ligand to the central gold atom. The essence of this process is the redox process of the metal, and the transition process needs to absorb specific energy. To exhibit a specific emission, the charge transition will only occur if the orbital energy levels of the ligand match the empty orbital energy levels of the metal. This requires the lone electron energy of the ligand to be relatively high. Therefore, the ligand template molecule of the present invention includes amino acids containing sulfhydryl groups and amino acids containing conjugated molecules, which can bind to Au ions on the surface of gold clusters to a large extent. affects the electronic structure on gold clusters, leading to the creation of complex molecular orbitals. The luminescence intensity and wavelength can be adjusted by changing the electron-donating properties of the ligand without changing the core ligand. The conjugated molecular structure contained in the ligand, such as: imidazole ring, benzene ring, phenol structure can increase the electronic transition range, extend the π bond, enhance the electron delocalization range, and make the fluorescence red shift. The key lies in the degree of aggregation on the surface of the ligand. and electron cloud density changes. Figure 1 is a schematic diagram of the effect of different ligands on the electronic transition energy level of Au; Figure 1a1, a2, and a3 are schematic diagrams of the molecular structure of cysteine, histidine and tyrosine combined with Au; Figure 1b1, b2 and b3 are the molecular orbital energy level diagrams after the combination of cysteine, histidine and tyrosine, respectively.

By the above scheme, the present invention has the following advantages:

The invention adopts an aqueous phase synthesis method, dissolves tetrachloroauric acid HAuCl ₄ in a strong alkaline solution, uses a reducing agent to reduce trivalent gold ion Au ³⁺ to gold atom Au ⁰ , selects a specific ligand template, It includes amino acids containing sulfhydryl groups and functional groups containing conjugated molecules, and then by changing conditions such as temperature and reaction time, gold atoms are grown and aggregated in the corresponding ligand templates to form gold nanoclusters. The invention adopts the biologically inert element Au to synthesize and prepare the infrared II nanometer material, which can effectively improve the biocompatibility of the gold nanocluster, and provides a safe and biologically friendly new nanomaterial for the field of infrared II region imaging. The number and ratio of amino acids containing sulfhydryl groups and conjugated molecules can control the infrared emission wavelength of gold nanoclusters in II region.

The above description is only an overview of the technical solution of the present invention. In order to understand the technical means of the present invention more clearly and implement it according to the content of the description, the following description is given with the preferred embodiments of the present invention and the detailed drawings.

Description of drawings

Figure 1 is a schematic diagram of the effect of different ligands on the electronic transition energy level of Au;

Figure 2 is a schematic diagram of the synthesis process of fluorescent gold nanoclusters in the infrared II region;

Fig. 3 is the emission spectrum of the gold nanocluster prepared in Example 1;

4 is the high-resolution transmission electron microscope and particle size distribution test results of the gold nanoclusters prepared in Example 1;

Fig. 5 is the atomic force microscope characterization result of the gold nanocluster prepared in Example 1;

Fig. 6 is the quantum yield of gold clusters calculated in comparison with IR-26 molecules;

Fig. 7 is the MTS toxicity test result of different infrared II region nanomaterials to different cells;

Fig. 8 is the live and dead staining results of different cells in different infrared region II nanomaterials;

Fig. 9 is the real-time imaging monitoring result of the mouse intestinal in vivo of the gold nanoclusters prepared in Example 1 orally administered in Example 1;

Description of reference numbers:

1-HAuCl4; ₂ -NaBH4; 3-RNase-A; ₄ -Au.

detailed description

The specific embodiments of the present invention will be further described in detail below with reference to the examples. The following examples are intended to illustrate the present invention, but not to limit the scope of the present invention.

In the following examples of the present invention, the materials used are as follows:

Deionized water (resistivity 18.2mΩcm), tetrachloroauric acid (HAuCl ₄ ·3H ₂ O, ≥49.0% Au basis), sodium hydroxide (NaOH), sodium borohydride (NaBH ₄ , ≥98.0%), RNase- A (MW: 13.7 kDa, >70 U/mg), BSA (98% pure).

Example 1

(1) Dissolve the ligand template molecule RNase-A in water to prepare a ligand template solution with a concentration of 10 mg/mL. Furthermore, tetrachloroauric acid was dissolved in water to obtain a chloroauric acid solution with a concentration of 15 mM. Both solutions were prepared in 500 μL.

(2) 50 μL of 1M sodium hydroxide aqueous solution was added dropwise to the chloroauric acid solution, the golden yellow chloroauric acid solution was observed to fade, and then the ligand template solution was added to form a mixed solution. The pH of the mixed solution is about 11.

(3) After mixing well for 5 minutes, 10 μL of a reducing agent NaBH ₄ aqueous solution (concentration 15 mM) was added dropwise to the above mixed solution. The mixed solution was placed in a refrigerator at 4 °C overnight to obtain a dark brown transparent and clear mixed solution, indicating that the reaction was complete, and the solution contained a large number of gold nanoclusters RNase-A@AuNCs. Dissolve the product obtained in step (3) in water, use a dialysis bag with a molecular weight cut-off of 20,000 Da to remove unreacted ions by dialysis, and store in a refrigerator at 4°C.

The method of microwave-assisted synthesis can also be used to add the mixed solution of the reducing agent added in step (3) into the microwave synthesizer, the reaction energy is 100W, and the reaction is performed at 70 ° C for 60 seconds, and gold nanoclusters can also be prepared, so there is no need to wait. The finished product is ready in 1 minute overnight.

Example 2

Gold nanoclusters were prepared according to the method of Example 1, except that RNase-A was replaced with equimolar amounts of β-lactoglobulin, bovine blood serum albumin (BSA), dihydrolipoic acid, dihydrosulfide-sulfonic acid betaine, glutathione, mercaptoethanol or bioengineered custom polypeptide (the amino acid sequence structure of which is shown in Table 1).

The infrared II region fluorescence properties of several gold _nanoclusters prepared in the above examples _were tested. It can be seen from the table that all eight ligand molecules can emit fluorescence in the infrared II region, and ribonuclease, β-lactoglobulin, dihydrothio-sulfobetaine, and bioengineered customized polypeptides (containing sulfhydryl and The fluorescence emission peaks of gold nanoclusters prepared by conjugated molecules) are in the near-infrared II region (NIR-II), while the fluorescence peaks of the infrared II region of bovine serum albumin (BSA), glutathione, and mercaptoethanol are slightly Blue shift, because bovine serum albumin (BSA), glutathione, and mercaptoethanol contain more sulfhydryl groups, and sulfhydryl groups will preferentially bind to Au. In the case of a low proportion of sulfhydryl ligands, conjugated molecules will tend to bind to gold. Cluster binding, so a higher ratio of sulfhydryl groups will cause a blue-shift of fluorescence, while a higher ratio of conjugated molecules will cause a red-shift of fluorescence.

Table 1 Test results of infrared II region fluorescence performance of gold nanoclusters prepared by different ligand-templated molecules

In the polypeptide sequences in Table 1, H represents histidine, Y represents tyrosine, and C represents cysteine.

Fig. 3 is the emission spectrum of the gold nanocluster prepared in Example 1, the emission peak is at 1050 nm, with a half-peak width of 205 nm, which is in the range of infrared II region.

Figure 4 is the high-resolution transmission electron microscope and particle size distribution test results of the gold nanoclusters prepared in Example 1. It can be seen from the figure that the gold nanoclusters are spherical, with an average particle size of 2.2±0.1 nm. The grid spacing is 0.25nm. In addition, atomic force microscopy showed that the particle size of gold nanoclusters was 3.5±0.5 nm, indicating that the thickness of protein ligands on the surface of gold nanoclusters was 0.65 nm (Fig. 5). It can be seen from Figure 6 that the quantum yield of the gold nanocluster RNase-A@AuNCs is 1.9%, and IR26 in the figure is the standard control.

In addition, the gold nanoclusters prepared in Example 1 were tested for biosafety. As a control, NaYF ₄ :Er/Yb RENPs doped with rare earth element nano fluorescent materials and heavy metal quantum dots Ag ₂ S QDs were selected for the same test.

MTS was used to test the toxicity of three different concentrations of infrared region II nanomaterials to HCT-116 human intestinal cancer cells, HepG-2 human liver cancer cells, THP-1 human monocytes, and BEAS-2B human lung normal epithelial cells. The results show that compared with heavy metal quantum dots and rare earth nanomaterials, gold nanoclusters prepared in Example 1 have basically no toxicity (Figures 7-8).

The gold nanoclusters prepared in Example 1 were administered to normal mice by oral administration. The abdomen of the mice needed to be depilated without anesthesia. The oral dose of each mouse was 2 mg/kg, which was injected by oral administration. in mice. The mouse intestine was monitored by in vivo real-time imaging, and the results are shown in Figure 9. Figures 9a2, b2, c2, d2, e2, and f2 correspond to the enlarged images of the dotted boxes in Figures 9a1, b1, c1, d1, e1, and f1. , Figures 9a3, b3, c3, d3, e3, and f3 correspond to the physical images of the isolated intestine in Figures 9a1, b1, c1, d1, e1, and f1. It can be seen from the figure that the gold nanoclusters of the present invention have stable infrared two-fluorescence luminescence ability, and can be used to detect intestinal diseases.

Example 3

Gold nanomaterials were prepared according to the method of Example 1, except that RNase-A was replaced with small molecular amino acids: cysteine, histidine and tyrosine, and the molar ratio of the three amino acids was changed to prepare different Gold nanomaterials.

Table 2 shows the effects of different amino acid ratios on the emission peak and morphology of gold nanomaterials. In Table 2, NA represents no fluorescence emission. It can be seen that only a specific ratio of amino acids can red-shift the emission peak of the gold nanoclusters to the infrared II region.

Table 2 Effects of different amino acid ratios on the emission peaks and morphology of gold nanoclusters

The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications can be made without departing from the technical principles of the present invention. , these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

A preparation method of infrared II region fluorescent gold nanoclusters, characterized in that it comprises the following steps:

(1) adding the alkaline aqueous solution to the tetrachloroauric acid aqueous solution to react until the tetrachloroauric acid aqueous solution becomes colorless and transparent, then adding the ligand template molecule to the colorless and transparent solution to obtain a mixed solution, the mixed solution The pH value is 10-11; wherein, the ligand template molecule includes polypeptide, polymer compound, amino acid or protein; and the ligand template molecule includes thiol-containing and conjugated molecular structure-containing functional groups;

(2) using sodium borohydride aqueous solution to reduce the Au 3+ in the mixed solution to gold atoms, and then continue the reaction to make the gold atoms grow and aggregate in the ligand template molecules to form gold nanoclusters, the gold nanoclusters The number of gold atoms is 10-25.
The preparation method according to claim 1, wherein in step (1), the molar ratio of the thiol-containing functional group and the conjugated molecular structure-containing functional group in the ligand template molecule is 1-18:1- 18.
The preparation method according to claim 1, wherein in step (1), the amino acids include cysteine, histidine and tyrosine, and the cysteine, histidine and tyrosine The molar ratio of amino acids is 5-8:6-8:6-7.
The preparation method according to claim 1, wherein in step (1), the protein is selected from one or more of ribonuclease, bovine serum albumin and β-lactoglobulin.
preparation method according to claim 1, is characterized in that: in step (1), when described ligand template molecule comprises polypeptide or protein, the molar ratio of tetrachloroauric acid and ligand template molecule is 20-25: 1. When the ligand template molecule includes a polymer compound or an amino acid, the molar ratio of tetrachloroauric acid and the ligand template molecule is 20-25:14-18.
The preparation method according to claim 1, wherein the molar ratio of sodium borohydride in step (2) to tetrachloroauric acid in step (1) is 0.02-0.1:1.
The preparation method according to claim 1, characterized in that: in step (2), the reduced solution is reacted at 4°C for 24-72h or at 100W, under microwave irradiation at 50-100°C for 30-90s , so that the gold atoms grow and aggregate in the ligand template molecules to form gold nanoclusters.
A fluorescent gold nanocluster in the infrared II region prepared by the preparation method according to any one of claims 1 to 7, characterized in that it comprises gold nanoclusters and ligands attached to the surface of the gold nanoclusters Template molecules, the number of gold atoms in the gold nanoclusters is 10-25, the ligand template molecules include polypeptides, polymer compounds, amino acids or proteins; and the ligand template molecules include thiol and Functional groups containing conjugated molecular structures.
Application of the infrared II region fluorescent gold nanoclusters of claim 8 in the preparation of near-infrared II region fluorescent imaging preparations.
The use according to claim 9, wherein the imaging preparation is used to detect intestinal diseases.