Curcumin-based near-infrared fluorescent probes targeting Aβ aggregates, their synthesis methods, and applications

Abstract

This invention relates to the field of fluorescent probe technology, specifically to a curcumin-based near-infrared fluorescent probe targeting Aβ aggregates, its synthesis method, and its applications. This invention uses Aβ aggregates as the targeting group and modifies the aromatic groups at both ends of the curcumin compound with cyclic groups to obtain a probe compound. The compound has the general structural formula shown in (I). This probe can cross the blood-brain barrier and specifically bind to the Aβ protein, a biomarker of Alzheimer's disease. Furthermore, its near-infrared imaging characteristics reduce damage to brain cells and increase imaging resolution and sensitivity. This fluorescent probe is of great significance for the early diagnosis of Alzheimer's disease.

Description

Technical Field

[0001] This invention relates to the field of fluorescent probe technology, specifically to curcumin-based AIE near-infrared fluorescent probes targeting Aβ aggregates, their synthesis methods and applications, and particularly to the application of 4-diethylamino-2-methoxyphenyl modified curcumin-based AIE near-infrared fluorescent probes in the detection of Aβ aggregates. Background Technology

[0002] Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by memory impairment and decreased language skills. It is incurable, but early diagnosis and intervention can significantly reduce its impact on patients and their families, allowing for slower or even preventative disease progression. Therefore, early AD diagnosis is crucial. Currently, various techniques, including immunological analysis, probe imaging, and electrochemistry, are used for early AD diagnosis. Abnormal accumulation of β-amyloid protein (Aβ) is one of the most important causes of AD and is commonly used as a biomarker for its diagnosis.

[0003] Near-infrared fluorescence (NIRF) imaging (>630nm) technology is widely used in in vivo imaging, which greatly overcomes the problems of strong tissue absorption, scattering and autofluorescence interference faced by traditional fluorescence imaging (400-900nm). It has the characteristics of being non-invasive, fast, safe, having a relatively deep tissue penetration distance, and high sensitivity and resolution.

[0004] Curcumin is a natural phenolic compound extracted from the turmeric plant. It possesses various pharmacological effects, including anti-tumor, anti-inflammatory, and anti-fibrotic properties, and has significant application value in the prevention and treatment of cerebrovascular diseases. Furthermore, the highly delocalized π-electrons and symmetrical structure of curcumin and its derivatives endow them with excellent optical and electrical properties. Curcumin exhibits a high affinity for Aβ peptide aggregates, making it suitable as a fluorescent probe for Aβ peptide aggregates. However, it suffers from problems such as short emission wavelength and aggregation-induced quenching, preventing its use in NIRF imaging.

[0005] Aggregation-induced emission (AIE) occurs when molecules with AIE-related groups aggregate, restricting their intramolecular motion (rotation and vibration). This results in a decrease in the proportion of energy released through motional relaxation and an increase in the proportion of energy released through radiation, leading to enhanced fluorescence. Probes exhibiting the AIE effect show almost no fluorescence in solution but significantly enhanced fluorescence in the aggregated state, overcoming the quenching problem of traditional fluorescent probes. This unique optical property offers broad application prospects in fields such as bioimaging and therapy. Summary of the Invention

[0006] The purpose of this invention is to provide a curcumin-based near-infrared fluorescent probe for Aβ aggregation, its synthesis method, and its application. By modifying the traditional curcumin structure, fluorescence emission is achieved in the near-infrared range, and the fluorescence intensity increases significantly with the increase of the fluorescent probe concentration, exhibiting the AIE effect. This yields a near-infrared fluorescent probe that specifically binds to Aβ, enabling early diagnosis and monitoring of AD.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: a curcumin-based AIE near-infrared fluorescent probe targeting Aβ aggregates, using Aβ aggregates as the targeting group, and modifying the aromatic groups at both ends of the basic skeleton of the compound curcumin with cyclic groups to obtain the probe compound, wherein the compound has the general structural formula shown in (I):

[0008]

[0009] A curcumin-based AIE near-infrared fluorescent probe targeting Aβ aggregates was further modified by boron cyclization of the dicarbonyl sites to obtain a probe compound having the general structural formula shown in (II):

[0010]

[0011] Furthermore, for curcumin-based AIE near-infrared fluorescent probes targeting Aβ aggregates, when the probe compound is an asymmetric compound:

[0012] R1 is 4-diethylamino-2-methoxyphenyl or 3-indolyl;

[0013] R2 is 4-dimethylaminophenyl.

[0014] Furthermore, for curcumin-based AIE near-infrared fluorescent probes targeting Aβ aggregates, when the probe compound is a symmetrical compound:

[0015] R1 is 4-diethylamino-2-methoxyphenyl;

[0016] R2 is 4-diethylamino-2-methoxyphenyl.

[0017] Furthermore, for curcumin-based AIE near-infrared fluorescent probes targeting Aβ aggregates, when the probe compound is an asymmetric compound:

[0018] R3 is 4-diethylamino-2-methoxyphenyl or 3-indolyl;

[0019] R4 is 4-dimethylaminophenyl.

[0020] Furthermore, for curcumin-based AIE near-infrared fluorescent probes targeting Aβ aggregates, when the probe compound is an asymmetric compound:

[0021] R3 is 2-thienyl, 2-furanyl, 2-quinolinyl, 2-imidazolyl, or 2-thiazolyl.

[0022] R4 is 4-dimethylaminophenyl.

[0023] Furthermore, for curcumin-based AIE near-infrared fluorescent probes targeting Aβ aggregates, when the probe compound is a symmetrical compound:

[0024] R3 is 4-diethylamino-2-methoxyphenyl;

[0025] R4 is 4-diethylamino-2-methoxyphenyl.

[0026] Furthermore, the curcumin-based AIE near-infrared fluorescent probe targeting Aβ aggregates has the following structural formula:

[0027]

[0028] The application of the curcumin-based AIE near-infrared fluorescent probe targeting Aβ aggregates in the detection of Aβ aggregates.

[0029] In the aforementioned application, the Aβ aggregate is an Aβ dimer.

[0030] The beneficial effects of this invention are as follows:

[0031] 1. By modifying the aromatic groups at both ends of curcumin and boronizing the dicarbonyl structure, a series of fluorescent probes with AIE effect were synthesized, which solved the problem that current curcumin-based Aβ fluorescent probes are prone to aggregation and fluorescence quenching.

[0032] 2. Curcumin-like compounds were designed and synthesized as fluorescent probes for in vivo imaging of AD pathology. They exhibited fluorescence emission in the near-infrared range, providing conditions for the use of NIRF imaging technology.

[0033] 3. Curcumin-like compounds were designed and synthesized as fluorescent probes for in vivo imaging of AD pathology. They have high affinity for Aβ and their fluorescence intensity increases significantly after binding to Aβ, exhibiting high specificity and detection capability. They can be used for early diagnosis and monitoring of AD.

[0034] The following synthetic routes describe the preparation of derivatives of general formulas (I) and (II) of the present invention. All starting materials are prepared by methods well known to those skilled in the art of organic chemistry, or are commercially available, as described in these reaction formulas. All final derivatives of the present invention are prepared by methods described in the following reaction formulas or by similar methods well known to those skilled in the art of organic chemistry. All variable factors used in these reaction formulas are defined below or as defined in the claims.

[0035] (I) Route 1

[0036] First, the asymmetric derivative of general formula (Ⅰ) was synthesized according to the following synthetic route.

[0037]

[0038] (II) Route 2

[0039] Next, the symmetrical derivative of general formula (Ⅰ) was synthesized according to the following synthetic route.

[0040]

[0041] All derivatives of general formula (I) of the present invention can be prepared by condensation reaction from the corresponding intermediates according to the methods of routes 1 and 2.

[0042] (III) Route 3

[0043] First, the asymmetric derivative of general formula (II) was synthesized according to the following synthetic route.

[0044]

[0045] (IV) Route 4

[0046] Next, the symmetrical derivative of general formula (II) was synthesized according to the following synthetic route.

[0047]

[0048] All derivatives of general formula (II) of the present invention can be prepared from the corresponding intermediates by condensation reaction according to the methods of routes 3 and 4.

[0049] The substituents R in the intermediates of the above synthetic routes are all as defined above. Attached Figure Description

[0050] Figure 1 In diagram a, the ultraviolet absorption spectrum of fluorescent probe compound 1 is shown.

[0051] b is the UV absorption spectrum of the fluorescent probe compound 2.

[0052] c is the UV absorption spectrum of fluorescent probe compound 3.

[0053] d is the UV absorption spectrum of fluorescent probe compound 4.

[0054] e is the UV absorption spectrum of fluorescent probe compound 5.

[0055] f is the ultraviolet absorption spectrum of fluorescent probe compound 6.

[0056] Figure 2 In diagram 'a', the fluorescence spectra of fluorescent probe compounds 1 and 4 are shown.

[0057] b is the fluorescence spectrum of fluorescent probe compounds 2 and 5.

[0058] c is the fluorescence spectrum of fluorescent probe compounds 3 and 6.

[0059] d shows the fluorescence spectra of fluorescent probe compounds 1, 2, and 3.

[0060] e is the fluorescence spectrum of fluorescent probe compounds 4, 5, and 6.

[0061] Figure 3 In the middle, 'a' represents fluorescent probe compound 1 and Aβ. 1-40 Aβ after aggregate binding 1-40 aggregate fluorescence spectrum,

[0062] b is the fluorescent probe compound 4 and Aβ 1-40 Aβ after aggregate binding 1-40 aggregate fluorescence spectrum,

[0063] c represents fluorescent probe compound 2 and Aβ. 1-40 Aβ after aggregate binding 1-40 aggregate fluorescence spectrum,

[0064] d is the fluorescent probe compound 5 and Aβ 1-40 Aβ after aggregate binding 1-40 aggregate fluorescence spectrum,

[0065] e is the fluorescent probe compound 3 and Aβ 1-40 Aβ after aggregate binding 1-40 aggregate fluorescence spectrum,

[0066] f is the fluorescent probe compound 6 and Aβ 1-40Aβ after aggregate binding 1-40 Fluorescence spectrum of aggregates.

[0067] Figure 4 In the middle, 'a' represents fluorescent probe compound 2 and Aβ. 1-40 Fluorescence spectrum of compound 2 after aggregate binding.

[0068] b is the fluorescent probe compound 5 and Aβ 1-40 Fluorescence spectrum of compound 5 after aggregation.

[0069] Figure 5 In figure a, fluorescence imaging of fluorescent probe compound 2 in WT and APP / PS1 mice is shown.

[0070] b is the fluorescence intensity change curve of fluorescent probe compound 2 in WT and APP / PS1 mice.

[0071] Figure 6 In figure a, fluorescence imaging of fluorescent probe compound 4 in WT and APP / PS1 mice is shown.

[0072] b is the fluorescence intensity change curve of fluorescent probe compound 4 in WT and APP / PS1 mice.

[0073] Figure 7 In figure a, fluorescence imaging of fluorescent probe compound 5 in WT and APP / PS1 mice is shown.

[0074] Fluorescence intensity change curves of b fluorescent probe compound 5 in WT and APP / PS1 mice. Detailed Implementation

[0075] The present invention will be further described in detail below with reference to specific embodiments. The specific embodiments described below are not intended to limit the present invention, but only to explain the present invention.

[0076] Example 1 Synthesis of fluorescent probe compounds (I) Synthesis of intermediate 1: (E)-6-(4-(dimethylamino)phenyl)-5-ene-2,4-dione

[0077] Acetylacetone (60 mmol, 6.00 g) and boron trioxide (120 mmol, 8.35 g) were added to 30 mL of ethyl acetate, and the mixture was heated to 80 °C and reacted for 0.5 h. Then, p-dimethylaminobenzaldehyde (20 mmol, 2.98 g) and tri-n-butyl borate (66 mmol, 15.19 g) were added, and the mixture was reacted at 80 °C for 0.5 h. Next, n-butylamine (60 mmol, 4.39 g) was added dropwise, and the mixture was reacted at 80 °C for 12 h. The mixture was cooled to 50 °C, and 20 mL of 0.4 M hydrochloric acid was added, and the mixture was reacted for 1 h. The reaction was monitored by TLC until complete. After cooling to room temperature, the mixture was washed with water, and the aqueous phase was extracted with ethyl acetate (20 mL × 3). The organic phases were then combined, washed with saturated NaCl solution, and dried over anhydrous Na₂SO₄. After filtration and concentration under reduced pressure, intermediate 1 crude product was obtained. The obtained solid was purified by silica gel column chromatography [eluent: V (petroleum ether): V (ethyl acetate) = 3:1], and the corresponding components were collected to obtain intermediate 1.

[0078] (II) Synthesis of dicarbonyl asymmetric curcumin derivatives (compounds 1 and 2)

[0079] Intermediate 1 (6 mmol, 1.39 g) was added to 20 mL of ethyl acetate, and the mixture was heated to 80 °C and reacted for 0.5 h. Then, 3-indolecarboxaldehyde (6 mmol, 0.87 g) or 4-diethylamino-2-methoxybenzaldehyde (6 mmol, 1.24 g) and tri-n-butyl borate (19.8 mmol, 4.56 g) were added, and the mixture was reacted at 80 °C for 0.5 h. Next, n-butylamine (18 mmol, 1.32 g) was added dropwise, and the mixture was reacted at 80 °C for 12 h. The mixture was cooled to 50 °C, and 10 mL of 0.4 M hydrochloric acid was added, and the mixture was reacted for 1 h. The reaction was monitored by TLC until complete. After cooling to room temperature, the mixture was washed with water, and the aqueous phase was extracted with ethyl acetate (20 mL × 3). The organic phases were then combined, washed with saturated NaCl solution, and dried over anhydrous Na₂SO₄. After filtration and concentration under reduced pressure, crude products of compound 1 or 2 are obtained. The resulting solid is purified by silica gel column chromatography [eluent: V (petroleum ether): V (ethyl acetate) = 2:1], and the corresponding components are collected to obtain compound 1 or compound 2.

[0080] (III) Synthesis of dicarbonyl symmetrical curcumin derivatives (compound 3)

[0081] Acetylacetone (12 mmol, 1.2 g) and boron trioxide (24 mmol, 1.67 g) were added to 20 mL of ethyl acetate, and the mixture was heated to 80 °C and reacted for 0.5 h. 4-Diethylamino-2-methoxybenzaldehyde (6 mmol, 1.24 g) and tri-n-butyl borate (19.8 mmol, 4.56 g) were added, and the mixture was reacted at 80 °C for 0.5 h. n-Butylamine (18 mmol, 1.32 g) was added dropwise, and the mixture was reacted at 80 °C for 12 h after the addition was complete. The mixture was cooled to 50 °C, and 20 mL of 0.4 M hydrochloric acid was added, and the mixture was reacted for 1 h. The reaction was monitored by TLC until complete. After cooling to room temperature, the mixture was washed with water, and the aqueous phase was extracted with ethyl acetate (20 mL × 3). The organic phases were then combined, washed with saturated NaCl solution, and dried over anhydrous Na₂SO₄. After filtration and concentration under reduced pressure, the crude product of compound 3 was obtained. The obtained solid was purified by silica gel column chromatography [eluent: V (petroleum ether): V (ethyl acetate) = 2:1], and the corresponding components were collected to obtain compound 3.

[0082] (iv) Synthesis of boron-cyclized asymmetric curcumin derivatives (compounds 4 and 5)

[0083] Compound 1 (3 mmol, 1.07 g) and compound 2 (3 mmol, 1.26 g) were mixed with boron trifluoride diethyl ether (3 mmol, 0.43 g) in a 1:1 ratio and reacted at 60 °C for 2 h. After the reactants were cooled to room temperature, they were distilled under reduced pressure to obtain an oily solid. The obtained solid was purified by silica gel column chromatography [eluent: V (petroleum ether): V (ethyl acetate) = 1:3], and the target products of the corresponding fractions were collected.

[0084] (V) Synthesis of boron-cyclized symmetrical curcumin derivatives (Compound 6)

[0085] Compound 3 (3 mmol, 1.43 g) and boron trifluoride diethyl ether (3 mmol, 0.43 g) were mixed in a 1:1 ratio and reacted at 60 °C for 2 h. After the reactants were cooled to room temperature, they were distilled under reduced pressure to obtain an oily solid. The obtained solid was purified by silica gel column chromatography [eluent: V (petroleum ether): V (ethyl acetate) = 1:3], and the target products of the corresponding fractions were collected.

[0086] The compounds of Example 1 were prepared according to the general preparation method described above (see Table 1).

[0087] Table 1

[0088]

[0089]

[0090] Example 2: Determination of excitation and emission wavelengths of fluorescent probe compounds

[0091] Weigh out a quantitative amount of the dried probe compound, dissolve it in a small amount of methanol solution, and then bring the volume to 2.5 × 10⁻⁶ with PBS buffer. -5 mol / L, configured to a probe compound concentration of 2.5 × 10⁻⁶. -5 A mol / L solution, using a buffer solution as a reference, was subjected to a full scan by ultraviolet spectrophotometry within the scanning wavelength range of 200–800 nm. The spectrum is shown below. Figure 1 As shown, the excitation wavelengths of each compound were determined. Then, the emission wavelengths of the compounds were detected and compared using fluorescence spectrophotometry, and the spectra are shown below. Figure 2 As shown.

[0092] Figure 1 These are the UV absorption spectra of fluorescent probe compounds 1-6. Figure 2 These are the fluorescence spectra of the fluorescent probe compounds. The experimental results show that all compounds emit wavelengths above 600 nm, with compounds 2, 3, 4, 5, and 6 emitting wavelengths above 630 nm, falling within the near-infrared emission wavelength range.

[0093] from Figure 2 As shown in a, b, and c, the emission wavelength of the boron-cyclized compound is much longer than that of the non-boron-cyclized compound, and the fluorescence intensity is also relatively higher. This is because boron cyclization strengthens its planar structure and increases the π-π conjugation of the compound. On the other hand, boron cyclization promotes the formation of a D-π-A conjugated system, reducing the HOMO-LUMO band gap, resulting in a significant redshift effect on both the maximum excitation wavelength and the emission wavelength. Figure 2 As shown in d and e, the maximum emission wavelengths of compounds 2, 3, 5, and 6 are significantly greater than those of compounds 1 and 4. This is likely because 2-methoxy-4-diethylaminobenzyl has a stronger electron-donating effect, resulting in a greater conjugation and thus increasing the emission wavelength. Among these, compounds 2 and 5 exhibit significantly higher fluorescence intensity and relatively larger emission wavelengths than the other compounds, indicating that the co-substitution of 2-methoxy-4-diethylaminobenzyl and 4-dimethylaminobenzyl contributes more to the fluorescence intensity than other substituents.

[0094] Example 3 Compound and Aβ 1-40 Oligomer binding assay

[0095] (I) Solution preparation

[0096] (1) Preparation of PBS-HCl-NaCl (1mol / L, pH=7.4) buffer solution: Dissolve 1g of phosphate in a certain amount of distilled water and bring the volume to 1000ml; then measure 8.33ml of concentrated hydrochloric acid (12mol / L) and dilute it with distilled water to bring the volume to 1000ml; finally, dissolve 2.925g of NaCl solid in 250ml of PBS stock solution and 400ml of HCl stock solution, and dilute it with water to bring the volume to 1000ml.

[0097] (2) Aβ peptide solution (1.0×10) -5 Preparation of (mol / L): Dissolve Aβ peptide in PBS-HCl-NaCl buffer and bring the volume to 100 ml.

[0098] (3) Preparation of compound solutions: Accurately weigh compounds 1-6, dissolve them in a small amount of PBS-HCl-NaCl (1 mol / L, pH = 7.4) buffer solution, and dilute to 25 ml in a volumetric flask to obtain 2.5 × 10⁻⁶ compounds. -3 Stock solutions of compounds 1-6 in mol / L.

[0099] (II) Experimental Methods

[0100] To test the interaction between the compound and the Aβ aggregate, we used fluorescence spectroscopy: first, 2.5 mL of Aβ peptide stock solution (1.0 × 10⁻⁶) was added to a fluorescent cuvette. -5 Then, using a pipette, 2.5 μL of stock solutions of compounds 1-6 (2.5 × 10⁻⁶ mol / L) were added sequentially to the cuvette. -3 mol / L), with a concentration range of 0.0 × 10⁻⁶. -6 mol / L~5.0×10 -5 mol / L. After the solution was mixed and allowed to stand for 5 min, the excitation wavelength was set to 267.5 nm, the excitation wavelength of Aβ peptide, and the fluorescence emission spectrum from 200 to 800 nm was scanned at room temperature.

[0101] (III) Results and Discussion

[0102] Figure 3 The probe compounds are respectively with Aβ 1-40 Aβ after aggregate binding 1-40 aggregate fluorescence spectrum, from Figure 3 As can be seen from af, with an excitation wavelength of 267.5 nm, Aβ appears at around 525 nm. 1-40 The maximum emission wavelength of the aggregate was used for observation within this range to discover the relationship between the probe compound and Aβ. 1-40 After the aggregates bound, significant fluorescence enhancement was observed in all samples, and the fluorescence intensity increased with increasing compound concentration, indicating that the probe compound binds to Aβ.1-40 The aggregates exhibited good binding ability, and the fluorescence intensity was positively correlated with the compound concentration, which prepared the groundwork for further experiments.

[0103] Figure 4 It is probe compounds 2, 5 and Aβ 1-40 Fluorescence spectrum of the compound after aggregate binding. From Figure 4 As can be seen from a and b, the maximum emission wavelength of the compound appears around 600 nm. Observations within this range reveal that probes 2 and 5 are related to Aβ. 1-40 After aggregation, the emission wavelength exhibits a blue shift, approximately 30 nm and 80 nm, respectively. However, with increasing compound concentration, the fluorescence intensity gradually increases, and the emission wavelength gradually red-shifts, without any quenching effect. The increase in fluorescence intensity is positively correlated with concentration, indicating the presence of an emission emission interference (AIE) effect. These changes in fluorescence properties make the detection of amblycemic index (AD) visible. Boron-cyclized compounds show greater changes in fluorescence intensity and a larger red-shift in emission wavelength compared to non-boron-cyclized compounds, resulting in more pronounced changes in fluorescence phenomena. This provides a basis for further in vivo brain-targeted imaging in APP / PS1 mice.

[0104] Example 4: In vivo imaging

[0105] (I) Experimental Methods

[0106] Compounds 2, 4, and 5 were selected as in vivo imaging dyes by analyzing the emission wavelength and binding affinity of the probe compounds and compared. Their emission wavelengths are located in the near-infrared region, which have strong penetrability and visibility. They can efficiently penetrate cells and tissues and exhibit deep red fluorescence in in vivo imaging images.

[0107] Twelve female APP / PS1 mice and three WT mice were divided into three groups: A, B, and C. Each group contained three APP / PS1 mice and one WT mouse. Equal amounts of probe compounds 2, 4, and 5 were injected into each group, respectively. 100 μL of the drug was injected intravenously into each mouse, and the mice were anesthetized using an isoflurane gas anesthesia machine. The animals were kept under complete anesthesia for approximately 2-3 minutes.

[0108] Fluorescence imaging of mice in each group was recorded using an IVIS Lumina LT Series III in vivo imaging system at 0, 5, 10, 30, 60, 120, and 240 minutes after intravenous injection of the probe. After the animal experiment, the isoflurane gas anesthesia machine was turned off, and the mice were kept breathing in pure oxygen for about 5-10 minutes to facilitate their rapid recovery.

[0109] (II) Results and Discussion

[0110] Figure 5Figure a shows the fluorescence imaging of fluorescent probe compound 2 in mice. As shown, almost all the fluorescence signals are concentrated in the brain. After intravenous injection, the fluorescence intensity of the compound in the brain region of APP / PS1 mice is much higher than that of wild-type mice. These very clear visualization results indicate that these compounds can cross the blood-brain barrier and specifically capture and label Aβ aggregates in vivo, further confirming the feasibility of imaging in vivo after the probe compounds bind to Aβ aggregates.

[0111] Figure 5 Figure b shows the fluorescence intensity change curve of fluorescent probe compound 2 in mice. It can be seen that compound 2 exhibits strong fluorescence in the brain 5 minutes after intravenous injection, reaching its peak intensity. Subsequently, the fluorescence gradually weakens and disappears after metabolism. APP / PS1 mice and WT mice show corresponding fluorescence change trends, with the fluorescence intensity in APP / PS1 mice being significantly greater than that in WT mice, indicating that compound 2 can be used as a probe for detecting Aβ aggregates. However, this probe compound has certain drawbacks: its metabolic elimination rate is too rapid, and it still exhibits strong fluorescence in the brains of WT mice even when it has not bound to Aβ aggregates.

[0112] Figure 6 Figure a shows the fluorescence imaging of fluorescent probe compound 4 in mice, and figure b shows the fluorescence intensity change curve of fluorescent probe compound 4 in mice. As shown in Figure a, the Aβ aggregate sites in APP / PS1 mice were identifiable within 2 hours after injection of compound 4. Over time, the probe accumulated more and more at the protein site, and the fluorescence signal intensity was greater than that in WT mice at all time points. Figure b shows that the fluorescence intensity in APP / PS1 mice reached its peak approximately 1 hour after injection, and then began to decrease. In WT mice, the fluorescence intensity reached its peak approximately 30 minutes after intravenous injection, and then began to decrease. Furthermore, the fluorescence intensity in the brain of APP / PS1 mice was greater than that in WT mice at each time point. Compared to compound 2, compound 4 has a significantly lower residence time and metabolic rate, which is more conducive to improving its bioavailability and facilitating the detection of Aβ aggregates.

[0113] Figure 7Figure a shows the fluorescence imaging of fluorescent probe compound 5 in mice, and figure b shows the fluorescence intensity change curve of fluorescent probe compound 5 in mice. As can be seen from figures a and b, the fluorescence intensity in APP / PS1 mice reached its peak approximately 2 hours after intravenous injection of compound 5, and then gradually weakened after metabolism. This further delayed the metabolism time of the probe in the mouse brain, compensating for the shortcomings of the probe compound's rapid and early metabolism in the brain. In contrast, WT mice did not show significant fluorescence changes at any time point, indicating that compound 5 produces almost no fluorescence in the absence of Aβ aggregates, but specifically binds to Aβ aggregates in the presence of Aβ aggregates, producing changes in fluorescence intensity. This further demonstrates that compound 5 possesses AIE properties, facilitating subsequent observation and making it an ideal fluorescent probe compound.

[0114] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Any modifications, equivalent substitutions, or improvements made within the scope of the technical concept of the present invention are included within the protection scope of the present invention.

Claims

1. A curcumin-based near-infrared fluorescent probe targeting Aβ aggregates, characterized in that, It has the following structural formula: 。 2. The application of the curcumin-based near-infrared fluorescent probe targeting Aβ aggregates as described in claim 1 in the preparation of reagents for detecting Aβ aggregates.

3. The application according to claim 2, characterized in that, The Aβ aggregates are Aβ dimers.

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