Chitosan-DFO conjugate, preparation method and application

Abstract

The invention relates to a chitosan-DFO conjugate as well as a preparation method and application thereof.The preparation method comprises the following steps: step 1, Boc-L-valine and N, N '-dicyclohexylcarbodiimide 4-dimethylaminopyridine are added into a solvent A, after a reaction, chitosan is added, the reaction continues, and a chitosan-Val-Boc conjugate is obtained; step 2, the chitosan-Val-Boc conjugate and trifluoroacetic acid are subjected to a reaction, and a chitosan-Val conjugate is obtained; 3, the chitosan-Val conjugate and p-SCN-Bn-DFO are subjected to a reaction, and the chitosan-DFO conjugate is obtained. The chitosan-DFO conjugate is used for replacing traditional DFO to serve as a chelating agent to mark 89Zr < 4 + >, and the formed product is stable in performance, long in residence time at the focus position, free of diffusion to other target organs and capable of being used in PET imaging and positioning imaging of the interventional focus position.

Description

Technical Field

[0001] The invention belongs to the technical field of nuclear medicine, and specifically relates to a chitosan-DFO conjugate, a preparation method and an application thereof. Background Art

[0002] 18 F is a commonly used radionuclide with good molecular imaging performance, but its half-life is short (t 1 / 2 =109min), which cannot meet the long-term imaging needs; 89 Zr is a new type of positron nuclide with a half-life of 78.4h and an average positron energy of 0.389MeV. It has better PET imaging quality and quantitative conditions, and is an ideal nuclide for PET imaging. Its labeled drug carriers with a longer biological half-life can be used in imaging that requires long-term observation.

[0003] 89 The labeling of Zr is mainly indirect labeling, that is, 89 Zr forms a complex with a bifunctional chelating group pre-attached to the carrier to complete the labeling. The commonly used chelating agent is deferoxamine (DFO), which is a hexacoordinate iron chelator. The three hydroxamic acid groups it contains can 89 Zr 4+ Chelation reaction occurs to form a stable complex. Studies have shown 89 Zr-DFO has good stability. After incubation in serum for 24 hours, 89 Zr 4+ The release was less than 0.2%, and the free amount in serum after 7 days 89 Zr 4+ Still less than 2%. 89 Zr-DFO has a short retention time at the lesion site and can easily diffuse to other target organs. It cannot stay at the lesion site for a long time and cannot locate the lesion site for imaging intervention. Therefore, its performance needs to be further improved. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a chitosan-DFO conjugate, a preparation method and an application thereof. The conjugate has stable performance, a long retention time at the lesion site, will not spread to other target organs, and can be used in PET imaging to locate and image the lesion site.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing a chitosan-DFO conjugate comprises the following steps:

[0007] Step 1, preparation of chitosan-Val-Boc conjugate: add Boc-L-valine and N,N'-dicyclohexylcarbodiimide 4-dimethylaminopyridine to solvent A, react for T1 time (0.3-0.7h, preferably 0.5h) at 20-30°C under a protective atmosphere, add chitosan, and continue to react for T2 time (1-3 days, preferably 3 days) to obtain chitosan-Val-Boc conjugate.

[0008] Step 2, removal of the protective group of chitosan-Val-Boc: reacting the chitosan-Val-Boc conjugate with trifluoroacetic acid to remove the protective group Boc of the chitosan-Val-Boc to obtain a chitosan-Val conjugate;

[0009] Step 3, preparation of chitosan-DFO conjugate: react chitosan-Val conjugate with p-SCN-Bn-DFO to obtain chitosan-DFO conjugate. In this step, the p-thiocyanatobenzyl group of p-SCN-Bn-DFO undergoes a coupling reaction with the amino group in the chitosan-Val conjugate to form a stable covalent bond.

[0010] As a further technical solution, in step 1, the solvent A is dichloromethane; T1 is 0.3 to 0.7 h, and T2 is 1 to 3 days;

[0011] As a further technical solution, in step 1, the molar ratio of Boc-L-valine, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 0.8-1.2:1.8-2.2:1.8-2.2, preferably 1:2:2;

[0012] As a further technical solution, in step 1, the mass ratio of Boc-L-valine to chitosan is 0.9-1.1:5.90-6.10;

[0013] As a further technical solution, in step 1, after continuing the reaction for 1 to 3 days, the reaction is terminated, and then the reaction solution is concentrated by rotary evaporation to remove part of the solvent A, and then ether is added for precipitation, and the chitosan-Val-Boc conjugate precipitate is filtered and collected, and then the chitosan-Val-Boc conjugate precipitate is redissolved with solvent A, and ether is added again for precipitation, and the redissolution and precipitation are repeated 1 to 5 (preferably 3 times) times to obtain a crude chitosan-Val-Boc conjugate; then, the crude chitosan-Val-Boc conjugate is redissolved with water to a solution concentration of 1 to 1.5 mg / mL, dialyzed for 1 to 5 days (preferably 3 days), and then freeze-dried to obtain a chitosan-Val-Boc conjugate.

[0014] As a further technical solution, the ether is glacial ether.

[0015] As a further technical solution, diethyl ether is added at a volume ratio of solvent A to diethyl ether of 0.8-1.2:4.8-5.2 (preferably 1.1-0.9:4.9-5.1, more preferably 1:5).

[0016] As a further technical solution, in step 1, the protective atmosphere is Ar2 atmosphere;

[0017] As a further technical solution, in step 2, chitosan-Val-Boc conjugate is reacted with trifluoroacetic acid to remove the protective group of chitosan-Val-Boc to obtain chitosan-Val conjugate, including: dissolving chitosan-Val-Boc conjugate in solvent B under protective atmosphere, then adding trifluoroacetic acid under ice-water bath conditions, stirring and reacting at 0-4°C for 1-3h to generate chitosan-Val conjugate; after the reaction is completed, the reaction solution is concentrated by rotary evaporation to remove solvent B, and chloroform is added to redissolve, and then ether (ice ether) is added for precipitation, and filtered to obtain a crude chitosan-Val conjugate; finally, the crude chitosan-Val conjugate is dissolved in water, dialyzed for 1-5 days, and freeze-dried to obtain a chitosan-Val conjugate;

[0018] As a further technical solution, the solvent B is dichloromethane.

[0019] As a further technical solution, the mass volume ratio of chitosan-Val-Boc conjugate, solvent B and trifluoroacetic acid is 2-6 g:18-22 mL:48-52 mL (preferably 4 g:20 mL:50 mL).

[0020] As a further technical solution, in step 2, the protective atmosphere is Ar2 atmosphere.

[0021] As a further technical solution, in step 3, the molar ratio of the chitosan-Val conjugate to p-SCN-Bn-DFO is 0.8-1.2:1.8-2.2 (preferably 1:2);

[0022] As a further technical solution, in step 3, the chitosan-Val conjugate is reacted with p-SCN-Bn-DFO to generate a chitosan-DFO conjugate, comprising:

[0023] First, chitosan-Val is dissolved in a sodium bicarbonate solution, and then a DMSO solution containing p-SCN-Bn-DFO is added, and the reaction is carried out at 20-30° C. for 0.5-1.5 h (preferably 1 h) to generate a chitosan-DFO conjugate. After the reaction is completed, the chitosan-DFO conjugate is ultrafiltered with hot water at 40-60° C., rotary concentrated to dryness, and then dissolved in hot water at 40-60° C. and dialyzed for 1-5 days (preferably 3 days) to obtain a chitosan-DFO conjugate.

[0024] As a further technical solution, the sodium bicarbonate solution is an aqueous solution of sodium bicarbonate, and the concentration of the sodium bicarbonate is 0.08 to 0.12 M, preferably 0.09 to 0.11 M, and more preferably 0.1 M;

[0025] As a further technical solution, the concentration of the p-SCN-Bn-DFO DMSO solution is 8 to 12 mg / mL, preferably 9 to 11 mg / mL, and more preferably 10 mg / mL.

[0026] The chitosan-DFO conjugate is prepared by the preparation method.

[0027] The chitosan-DFO conjugate is based on chitosan as the skeleton and is conjugated with deferoxamine.

[0028] The chitosan-DFO conjugate is used as a chelating agent in chelating radionuclides.

[0029] The chitosan-DFO conjugate is used as a chelating agent to prepare 89 The method of Zr-chitosan-DFO comprises the following steps:

[0030] Step 1: 89 After the ZrC2O4 solution and the Na2CO3 solution are mixed, react at 20-30°C for 1-5 minutes (preferably 3 minutes) to obtain a precursor solution;

[0031] Step 2: Add N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, chitosan-DFO conjugate solution and HEPES buffer to the precursor solution, adjust the pH value to 6.8-7.2, and react at 20-30°C for 0.5-1.5h to obtain 89 Zr-chitosan-DFO.

[0032] As a further technical solution, in step 1, the activity of the 89ZrC2O4 solution is 37-111MBq (preferably 74MBq); the concentration of the Na2CO3 solution is 1.5-2.5M (preferably 2M);

[0033] As a further technical solution, 89 The volume ratio of ZrC2O4 solution to Na2CO3 solution is 18-22:7-11 (20:9);

[0034] As a further technical solution, in step 2, the concentration of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer is 0.48-0.52M (preferably 0.5M) and the pH value is 7.1-7.3 (preferably 7.2);

[0035] As a further technical solution, in step 2, the concentration of chitosan-DFO conjugate in the chitosan-DFO conjugate solution is 0.8-1.2 mg / mL (1 mg / mL);

[0036] As a further technical solution, the chitosan-DFO conjugate solution adopts a borate buffer solution with a concentration of 8 to 12 mM and a pH of 8.2 to 8.6 (preferably a borate buffer solution with a concentration of 10 mM and a pH of 8.4);

[0037] As a further technical solution, in step 2, the concentration of HEPES buffer is 0.5 M and the pH value is 7.2.

[0038] As a further technical solution, when preparing the HEPES buffer, the pH is adjusted by a 0.8-1.2M (preferably 1M) NaOH solution or a 0.8-1.2M (preferably 1M) H2SO4 solution;

[0039] As a further technical solution, in step 2, the pH value is adjusted to 6.8-7.2 by 1.8-2.2M (preferably 2M) Na2CO3 solution;

[0040] As a further technical solution, in step 2, the volume ratio of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, chitosan-DFO conjugate solution and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer is 2.8-3.2:5.8-6.2:6.8-7.2.

[0041] As a further technical solution, in step 2, after reacting at 20-30°C for 0.5-1.5h, elution is performed using 300-700 μL of 8-12mM borate buffer solution (preferably 500 μL of 10mM borate buffer solution), and then centrifuged using a 3000MWCO ultrafiltration tube at 4000-6000 rpm (preferably 5000 rpm), and repeated 1-3 times (preferably 2 times) to obtain 89Zr-chitosan-DFO.

[0042] The method prepared 89 Zr-chitosan-DFO.

[0043] The 89 Application of Zr-chitosan-DFO in the preparation of molecular probes.

[0044] In the present invention, the reaction process of chitosan-DFO is as follows:

[0045] Reaction 1:

[0046] Reaction 2:

[0047] Reaction 3:

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The present invention uses chitosan as a skeleton, couples valine, and then reacts the amino group of the chitosan-Val conjugate with the p-thiocyanatobenzyl group of p-SCN-Bn-DFO to couple deferoxamine to chitosan to obtain a chitosan-DFO conjugate, which is used to replace the traditional DFO as a chelating agent for 89 Zr 4+ The mark formed by this method 89 Zr-chitosan-DFO has stable performance, a long retention time in the lesion site, and will not spread to other target organs. It can be used in PET imaging to locate and intervene in the lesion site. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Prepared in Example 1 89 Thin layer scanning of Zr-chitosan-DFO;

[0051] exist Figure 1 In, (a) TLC scanning spectrum, (b) peak analysis;

[0052] Figure 2 Prepared in Example 1 89 Axial image of preliminary imaging of Zr-chitosan-DFO in the hepatic artery of Beagle dogs;

[0053] Figure 3 Prepared in Example 1 89 Preliminary sagittal images of Zr-chitosan-DFO in the hepatic artery of Beagle dogs. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] In the present invention, room temperature refers to a temperature of 20 to 30°C.

[0056] Unless otherwise specified, the raw materials used in the present invention are commercially available.

[0057] Example 1

[0058] The preparation of 89Zr-chitosan-DFO comprises the following steps:

[0059] Step 1: Preparation of chitosan-DFO conjugate

[0060] Step 1-1, take 125mM Boc-L-valine (Boc-Val-OH), 250mM N,N'-dicyclohexylcarbodiimide (DCC), 250mM 4-Dimethylaminopyridine (DMAP) was dissolved in 40 mL of anhydrous dichloromethane (DCM), reacted at room temperature for 0.5 h under argon protection, 5.75 g of chitosan was added, and the reaction was continued at room temperature for 2 days to terminate the reaction, and then the reaction solution was concentrated by rotary evaporation, and after removing part of DCM, glacial ether was added for precipitation, and the chitosan-Val-Boc conjugate precipitate was filtered and collected, and then the chitosan-Val-Boc conjugate precipitate was redissolved with 40 mL of anhydrous DCM, and glacial ether was added again for precipitation, and the redissolution and precipitation were repeated 3 times to obtain a crude chitosan-Val-Boc conjugate; then the crude chitosan-Val-Boc conjugate was redissolved with ultrapure water to a solution concentration of 1-1.5 mg / mL, and then dialyzed for 3 days (MW 3.5Kda), and lyophilized to obtain 4.13 g of chitosan-Val-Boc conjugate;

[0061] Step 1-2, weigh 4g of chitosan-Val-Boc conjugate and dissolve it in 20mL DCM. In an ice-water bath at 0°C, add 50mL of trifluoroacetic acid under argon protection, stir and react for 2 hours, evaporate the solvent DCM, redissolve the product in chloroform, then add ice ether for precipitation, filter to obtain a crude chitosan-Val conjugate; then dissolve the crude chitosan-Val conjugate in 50°C hot water, dialyze for 3 days (MW 3.5Kda), and lyophilize to obtain 3.2g of chitosan-Val conjugate.

[0062] Step 1-3, according to the molar ratio of chitosan-Val conjugate to p-SCN-Bn-DFO being 1:2, 15.3 mg of chitosan-Val conjugate was weighed and dissolved in 4 mL of 0.1 M NaHCO3 solution, and p-SCN-Bn-DFO (p-SCN-Bn-deferoxamine) DMSO solution was slowly added dropwise. After reacting at room temperature for 1 hour, ultrafiltration was performed with 50 ° C hot water, spin-dried, and the spin-dried product was dissolved in 50 ° C hot water and dialyzed for 3 days to obtain 10.2 mg of chitosan-DFO conjugate with a purity of 99.3% and a yield of 66.6%.

[0063] Step 2: Preparation 89 Zr-Chitosan-DFO:

[0064] Use a pipette to accurately draw 84 μL of zirconium oxalate with an activity of 74 MBq [ 89Zr] solution into a glass reaction bottle, add 1M oxalic acid solution into the glass reaction bottle to make the total volume in the reaction bottle 200μL, use a pipette to accurately draw 90μL 2MNa2CO3 solution into the reaction bottle, incubate at room temperature for 3min, then gently shake the reaction bottle, and at the same time, add 0.3mL of 0.5M pH 7.2 HEPES solution, 0.6mL chitosan-DFO conjugate (1mg / mL, solvent is 10mM concentration, pH 8.4 borate buffer solution) solution and 0.7mL of 0.5M pH 7.2 HEPES solution into the reaction bottle in sequence, and incubate at room temperature for 1h; after the reaction is completed, use 500μL 10mM borate buffer solution to elute, and then use 3000MWCO ultrafiltration tube centrifugation at 5000 rpm, repeat twice to remove free 89 Zr, get 89 Zr-chitosan-DFO; the specific activity of the final solution is controlled to be 3mCi / mL.

[0065] Effect verification

[0066] 1. Experimental Methods

[0067] 1. 89 Radiochemical Purity Analysis of Zr-Chitosan-DFO

[0068] Using a thin layer scanner, Radio-iTLC method, with fast thin layer chromatography paper as the carrier, after spotting, use 20mM citric acid solution to develop the system, then dry the chromatography paper and use a thin layer scanner to collect data, after data collection is completed, obtain images for data analysis. Test results are as follows Figure 1 shown.

[0069] 2. PET imaging

[0070] 1) 89 Dosage and method of Zr-chitosan-DFO: Beagle dogs were generally anesthetized (1.5% sodium pentobarbital, 20 mg / kg), the femoral artery was bluntly separated, the femoral artery was punctured under direct vision, a 5F arterial sheath was inserted, and the femoral artery and arterial sheath were fixed with medical absorbable sutures. Under the guidance of a digital subtraction angiography machine (DSA), a 4F angiography catheter was inserted from the femoral artery to the abdominal aorta, a Y valve was connected to the end of the 4F angiography catheter, and a 2.4F microcatheter was selectively inserted into the common hepatic artery from the positive port of the Y valve, and 0.3mCi 89Zr-chitosan-DFO was injected through the microcatheter to avoid reflux as much as possible. After completion, the catheter and arterial sheath were pulled out, the femoral artery puncture site was ligated above, and the muscles and skin were sutured layer by layer.

[0071] 2) PET imaging study: using PET / CT tomography acquisition 89Distribution of Zr-chitosan-DFO in the liver of Beagle dogs 5 hours after injection. The animals were placed on the Discovery VCT bed board after general anesthesia. A whole-body CT scan was performed first to assist in tissue and organ identification and attenuation correction, and then a whole-body nuclear medicine signal scan from the head to the bottom of the lower limbs was performed. After the acquisition, the sagittal and axial images of the PET / CT imaging results were saved, and the CT images and nuclear medicine images of the two positions were observed with the naked eye. The test results are as follows: Figure 2-3 shown.

[0072] 2. Experimental Results and Analysis

[0073] 1. From Figure 1 It can be seen that 89 Zr-chitosan-DFO has a radioactive main peak at Rf0~0.1 ( Figure 1 The results showed that the radiochemical purity of the product was 98.68%.

[0074] 2. From Figure 2-3 It can be seen that: 89 Zr-chitosan-DFO was injected into the common hepatic artery via the femoral artery and remained in the liver without obvious diffusion, indicating that 89 Zr-chitosan-DFO can stay in the intervention site for a long time, and the lesion site can be accurately located through PET imaging.

[0075] In summary, the chitosan-DFO conjugate prepared by the present invention can be used as a chelating agent to couple zirconium oxalate [ 89 Zr], marking it as 89 Zr-chitosan-DFO is used in PET imaging to prolong 89 When Zr is retained in the lesion site, it is prevented from spreading to other target organs.

[0076] The above-described embodiments are only preferred embodiments of the present invention, and are not exhaustive of the feasible implementations of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a chitosan-DFO conjugate, characterized in that: The steps include: Step 1, preparation of chitosan-Val-Boc conjugate: add Boc-L-valine and N,N'-dicyclohexylcarbodiimide 4-dimethylaminopyridine into solvent A, react for T1 time at 20-30° C. under protective atmosphere, add chitosan, and continue to react for T2 time to obtain chitosan-Val-Boc conjugate; Step 2, removal of the protective group of chitosan-Val-Boc: reacting the chitosan-Val-Boc conjugate with trifluoroacetic acid to remove the protective group Boc of the chitosan-Val-Boc to obtain a chitosan-Val conjugate; Step 3, preparation of chitosan-DFO conjugate: react chitosan-Val conjugate with p-SCN-Bn-DFO to obtain chitosan-DFO conjugate.

2. The preparation method according to claim 1, characterized in that: In step 1, the solvent A is dichloromethane; T1 is 0.3 to 0.7 h, and T2 is 1 to 3 days; In step 1, the molar ratio of Boc-L-valine, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 0.8-1.2:1.8-2.2:1.8-2.2; In step 1, the mass ratio of Boc-L-valine to chitosan is 0.9-1.1:5.90-6.10; In step 1, after continuing the reaction for T2 time, the reaction is terminated, and then the reaction solution is concentrated by rotary evaporation to remove part of the solvent A, and then ether is added for precipitation, and the chitosan-Val-Boc conjugate precipitate is filtered and collected, and then the chitosan-Val-Boc conjugate precipitate is redissolved with solvent A, and ether is added again for precipitation, and the redissolution and precipitation are repeated 1 to 5 times to obtain a crude chitosan-Val-Boc conjugate; then, the crude chitosan-Val-Boc conjugate is redissolved with water in a ratio of 1 to 1.5 mg / mL, dialyzed for 1 to 5 days, and freeze-dried to obtain a chitosan-Val-Boc conjugate.

3. The preparation method according to claim 1, characterized in that: In step 2, chitosan-Val-Boc conjugate is reacted with trifluoroacetic acid to remove the protective group of chitosan-Val-Boc to obtain chitosan-Val conjugate, including: dissolving chitosan-Val-Boc conjugate in solvent B under a protective atmosphere, then adding trifluoroacetic acid, stirring and reacting at 0-4° C. for 1-3 hours to generate chitosan-Val conjugate; after the reaction is completed, concentrating the reaction solution by rotary evaporation, removing solvent B, adding chloroform to redissolve, then adding ether to precipitate, filtering, and obtaining a crude chitosan-Val conjugate; finally, dissolving the crude chitosan-Val conjugate in water, dialyzing for 1-5 days, and freeze-drying to obtain a chitosan-Val conjugate; The solvent B is dichloromethane.

4. The preparation method according to claim 1, characterized in that: In step 3, the molar ratio of the chitosan-Val conjugate to p-SCN-Bn-DFO is 0.8-1.2:1.8-2.2; In step 3, chitosan-Val conjugate is reacted with p-SCN-Bn-DFO to generate chitosan-DFO conjugate, comprising: First, chitosan-Val is dissolved in a sodium bicarbonate solution, and then a DMSO solution containing p-SCN-Bn-DFO is added and reacted at 20-30°C for 0.5-1.5h to generate a chitosan-DFO conjugate. After the reaction is completed, ultrafiltration is performed using hot water at 40-60°C, and the mixture is concentrated to dryness by rotation. Then, the solid is dissolved in hot water at 40-60°C and dialyzed for 1-5 days to obtain a chitosan-DFO conjugate.

5. The chitosan-DFO conjugate obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the chitosan-DFO conjugate as claimed in claim 5 as a chelating agent in chelating radionuclides.

7. Using the chitosan-DFO conjugate according to claim 5 as a chelating agent for preparation 89 The method of Zr-chitosan-DFO is characterized in that The steps include: Step 1: 89 After the ZrC2O4 solution and the Na2CO3 solution are mixed, the mixture is reacted at 20-30°C for 1-5 minutes to obtain a precursor solution; Step 2: Add N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, chitosan-DFO conjugate solution and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer to the precursor solution, adjust the pH value to 6.8-7.2, and react at 20-30° C. for 0.5-1.5 h to obtain 89 Zr-chitosan-DFO.

8. The method according to claim 7, characterized in that In step 1, 89 The activity of ZrC2O4 solution is 37-111MBq; the concentration of Na2CO3 solution is 1.5-2.5M; 89 The volume ratio of ZrC2O4 solution to Na2CO3 solution is 18-22:7-11; In step 2, the concentration of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer is 0.48-0.52 M and the pH value is 7.1-7.3; In the chitosan-DFO conjugate solution, the concentration of the chitosan-DFO conjugate is 0.8 to 1.2 mg / mL; The volume ratio of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer, chitosan-DFO conjugate solution and N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid buffer is 2.8-3.2:5.8-6.2:6.8-7.

2.

9. The method as claimed in claim 8 prepared 89 Zr-chitosan-DFO.

10. The method according to claim 9 89 Application of Zr-chitosan-DFO in the preparation of molecular probes.

Images