CN109568609B - Chemical exchange saturation transfer contrast agent and preparation method and application thereof - Google Patents
Chemical exchange saturation transfer contrast agent and preparation method and application thereof Download PDFInfo
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- A61K49/00—Preparations for testing in vivo
- A61K49/06—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations
- A61K49/18—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by a special physical form, e.g. emulsions, microcapsules, liposomes
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- A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
- A61K49/00—Preparations for testing in vivo
- A61K49/06—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations
- A61K49/08—Nuclear magnetic resonance [NMR] contrast preparations; Magnetic resonance imaging [MRI] contrast preparations characterised by the carrier
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Abstract
The disclosure provides a chemical exchange saturation transfer contrast agent, and a preparation method and application thereof, and belongs to the technical field of nuclear magnetic resonance imaging. The contrast agent is a novel lipoCEST contrast agent, and on the basis of keeping the advantages of high sensitivity and the like of the original iodine CEST contrast agent, the contrast agent also has high biocompatibility and safety, solves the defects that the drainage of the traditional CEST contrast agent such as iohexol and the like in a tumor region is fast, the retention rate is low and the like, and improves the EPR effect of the tumor region. The contrast agent is prepared by wrapping an iodine contrast agent with a surfactant, wherein the surfactant is selected from one or a mixture of more of phosphatidylcholine liposome, phosphatidylethanolamine liposome, phosphatidylserine, lecithin or cholesterol. The contrast agent is used for magnetic resonance imaging.
Description
Technical Field
The invention relates to the technical field of magnetic resonance imaging, in particular to a chemical exchange saturation transfer contrast agent and a preparation method and application thereof.
Background
Magnetic Resonance Imaging (MRI) is an advanced medical image diagnostic technique, which utilizes different tissues of a living body to generate different resonance signals under an external magnetic field image to image, the strength of the magnetic resonance signals depends on the content of water in the tissues and the relaxation time of protons in water molecules, and tissue necrosis, ischemia, respective malignant lesions and the like can be effectively detected.
In clinical MRI, a contrast agent (contrast agent) is an image enhancing contrast agent used to shorten the imaging time and improve the contrast and definition of the image, and can change the relaxation rate of water protons in local tissues in vivo and improve the contrast of the image between normal and diseased sites.
Many biological macromolecules such as protein, glycosaminoglycan, glycogen, etc. contain hydrogen protons, so that the hydrogen protons are saturated by applying a pre-Saturation pulse to the biological macromolecules during magnetic resonance scanning, the saturated hydrogen protons are chemically exchanged with the hydrogen protons in the surrounding water, the content of the biological macromolecules in a human body can be indirectly reflected by measuring the signal change of water molecules, and the Chemical Exchange Saturation Transfer (CEST) technology is developed on the basis of the principle.
The chemical exchange saturation transfer contrast agent (CEST contrast agent) at present comprises diamagnetic CEST (DIACEST) contrast agent and paramagnetic CEST (PARACEST) contrast agent, the diamagnetic CEST contrast agent is mainly small molecules, such as carbohydrate, amino acid, ammonium ion, heterocyclic compound and other synthesized CEST contrast agents, and because the chemical shift is small, the generated CEST signal intensity is poor, and the generated CEST signal intensity is difficult to be clearly distinguished from weak CEST signals caused by other tissue metabolites with exchangeable protons in vivo, and the confusion signal influence is large. (Chemical Exchange Transfer (CEST) Imaging: Description of technical and technical Clinical applications. Current radio Reports,2013,1(2): 102-. Paramagnetic CEST contrast agents are mainly synthesized from metal complexes gadolinium, manganese, lanthanide, whose chemical shifts are large and can effectively improve CEST contrast, but their sensitivity is affected by signal broadening and T1, T2 shortening, and require stronger pulse power (paramagnet lathanide complexes as space information for medical imaging, chemistry, 2006,35(6): 500-.
In addition, liposome CEST contrast agents (lipoCEST), nanoparticles, hyperpolarized gas CEST contrast agents (hyper CEST), and the like have been recently proposed. The liposome CEST contrast agent uses liposome to wrap paramagnetic CEST molecules, when presaturation pulse is applied, the speed of free water molecules inside the compartment passing through the lipid bilayer is slowed down, and meanwhile, the Shift agent (SR) and the free water molecules inside the compartment carry out rapid chemical exchange, so that the sensitivity of CEST signals is greatly improved, and the sensitivity can reach the nano level.
For example patent application CN200680014240 discloses a MRI contrast agent comprising CEST-active paramagnetic complexes.
Patent application CN201010210639 discloses an active targeting polymer nanoparticle magnetic resonance contrast agent.
Patent application CN201410255442 discloses an MRI contrast agent prepared from integrin-targeted manganese-gadolinium hybrid bimetallic paramagnetic nano-colloid.
Patent application CN201510319595 discloses an IL-13 modified gadolinium chelate containing liposome targeted magnetic resonance imaging contrast agent.
However, due to the complex in vivo components, the magnetic field is subject to more interference factors, such as direct water saturation (DS) Effect, conventional MT (MTC) Effect of a semisolid pool, and the like, and NOE (NOE) Effect, the synthesis and discovery of CEST contrast agents with high efficiency, high sensitivity, high biocompatibility, and high safety still bring certain technical challenges and difficulties.
Disclosure of Invention
The invention provides a chemical exchange saturation transfer contrast agent (CEST contrast agent), and provides a novel liposome CEST contrast agent which has high biocompatibility and safety on the basis of retaining the advantages of high sensitivity and the like of an original iodine CEST contrast agent.
The invention provides a CEST contrast agent, which is prepared by wrapping an iodine contrast agent with a surfactant.
Further, the molar ratio of the surfactant to the iodine contrast agent is 0.8-1.2: 1.
Further, the surfactant is selected from one or more of phosphatidylcholine liposome, phosphatidylethanolamine liposome, phosphatidylserine, lecithin or cholesterol.
Further, the iodine contrast agent is one or a mixture of more of iohexol, iopamidol, iodofluoroalcohol, iotrolan and iododicinol.
Further, the surfactant is a mixture of phosphatidylcholine-like liposome, phosphatidylethanolamine-like liposome, phosphatidylserine or lecithin and cholesterol in a molar ratio of 8: 1.
Further, the phosphatidylcholine liposome comprises: dimyristoylphosphatidylcholine (DMPC), Dilauroylphosphatidylcholine (DLPC), Dipalmitoylphosphatidylcholine (DPPC), Dioleoylphosphatidylcholine (DOPC), Distearoylphosphatidylcholine (DSPC), diarachioyl phosphatidylcholine (DAPC) and palmitoyloleoylphosphatidylcholine (POPC);
the phosphatidylethanolamine lipidosome comprises: dipalmitoyl phosphatidylethanolamine (DPPE), dilauroyl phosphatidylethanolamine (DLPE), dimyristoyl phosphatidylethanolamine (DMPE), dioleoyl phosphatidylethanolamine (DOPE), 1, 3-dipalmitoyl phosphatidylethanolamine (1,3-DPPE), diphytanoyl phosphatidylethanolamine (DPPE), and distearoyl phosphatidylethanolamine (DSPE).
Further, the preparation method of any one of the chemical exchange saturation transfer contrast agents comprises the following steps: uniformly mixing an iodine contrast agent with ultrapure water or PBS buffer solution to obtain an iodine contrast agent mixed solution;
dissolving surfactant in chloroform or ether solvent;
and adding the mixed solution of the iodine contrast agent into the dissolved surfactant, performing ultrasonic treatment for 10min under the ice bath condition, removing an organic phase at room temperature, and performing dialysis to obtain the chemical exchange saturated transfer contrast agent formed by wrapping the iodine contrast agent by the surfactant.
Further, the organic phase (chloroform or ether) was removed by rotary evaporation at room temperature.
Further, the hydrated particle size of the prepared contrast agent under dynamic light scattering is about 100 nm.
Further, any of the above chemical exchange saturation transfer contrast agents is used for chemical exchange saturation transfer magnetic resonance imaging.
Compared with the prior art, the invention has the following advantages:
1) the invention provides a CEST contrast agent, belongs to a novel liposome CEST contrast agent, and has high biocompatibility and safety on the basis of retaining the advantages of high sensitivity and the like of the original iodine CEST contrast agent.
2) Iodine contrast agents such as iohexol are commonly used as clinical X-ray contrast agents and recently also as CEST contrast agents, but have disadvantages of rapid excretion and low retention in tumor regions. The current concept of all iodine contrast agents is essentially to improve from mono-iodine, di-iodine to tri-iodine or from ionic, low ionic to non-ionic. The inventor of the invention realizes the coating of the iodine contrast agent by the liposome by coating the iodine contrast agent with the surfactant and modifying the size of the iodine contrast agent, thereby not only obtaining a novel liposome CEST contrast agent (lipoCEST contrast agent), but also solving the defects of quick excretion of the iodine contrast agent and low retention rate of a tumor region.
3) The CEST contrast agent provided by the invention is prepared by coating an iodine contrast agent with a surfactant, is synthesized by a nanotechnology, has an effective EPR support size, improves the EPR effect of a tumor region, and thus obtains a stable and accurate CEST signal.
4) The CEST contrast agent provided by the invention brings technical support for further researching tumor acidic microenvironment.
5) The CEST contrast agent provided by the invention is coated with the surfactant, can take lipid as a modification layer, can be further coupled with targeting molecules such as disease surface specificity markers, polypeptide, antibody, ligand and the like through functional groups on the surface of the modification layer, realizes a targeting delivery function, and lays a research foundation for further synthesizing novel lipoCEST with targeting and carrying therapeutic drugs.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic flow chart of a preparation method of LipoCEST nanoparticles according to an embodiment of the present invention.
FIG. 2 is a DLS diagram of LipoCEST nanoparticles as described in example 1 of the present invention.
FIG. 3 is a TEM image of LipoCEST nanoparticles of example 1 of the present invention.
FIG. 4 shows the result of MRI imaging of LipoCEST nanoparticles according to example 1 of the present invention.
Fig. 5 is a scanning image of LipoCEST nanoparticles injected into rat tail according to the experimental group of example 1 of the present invention.
Fig. 6 is a scanning image of iohexol injection injected into rat tail in the control group of example 1 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Iodine contrast agents are commonly used in clinical X-ray contrast agents, and can also be used as CEST contrast agents because they contain exchangeable hydrogen protons in their chemical structure, which can chemically exchange with hydrogen protons of surrounding free water molecules after saturation by applying a pre-saturation pulse, and cause a decrease in the water signal in the Z-magnetization direction. However, they have disadvantages such as rapid excretion and low retention rate in tumor regions. And is now limited to CEST imaging of the kidney when used as a CEST contrast agent.
The embodiment of the invention provides a CEST contrast agent which is prepared by wrapping an iodine contrast agent with a surfactant.
Wherein the surfactant is selected from one or more of phosphatidylcholine liposome, phosphatidylethanolamine liposome, phosphatidylserine, lecithin or cholesterol. The molar ratio of the surfactant to the iodine contrast agent is 0.8-1.2: 1.
The inventor finds that the iodine contrast agent is coated by the surfactant, the size of the iodine contrast agent is modified, the iodine contrast agent is coated by the liposome, the defects that the iodine contrast agent is fast in excretion and low in retention rate of a tumor region are overcome, and the novel liposome CEST contrast agent (lipoCEST contrast agent) is obtained and has high sensitivity and high efficiency.
The existing liposome contrast agent is a liposome-coated paramagnetic CEST molecule, and has high sensitivity and high efficiency because the speed of water passing through a lipid bilayer is much slower. However, the research and development of CEST contrast agents with high biocompatibility and high safety still bring certain technical challenges and difficulties on the basis of high efficiency and high sensitivity because of the need of stronger pulse power, complex in-vivo components and more interference factors on a magnetic field. The CEST contrast agent provided by the embodiment of the invention belongs to a novel liposome CEST contrast agent, retains the advantages of high sensitivity and the like of the liposome CEST contrast agent, most of iodine contrast agents are discharged through the kidney in an original shape after being injected, no obvious metabolism exists in the body, all the iodine contrast agents are discharged from the body in an original shape, and the biocompatibility and the safety of the CEST contrast agent are improved.
In one embodiment of the present invention, the surfactant is selected from one or more of phosphatidylcholine liposome, phosphatidylethanolamine liposome, phosphatidylserine and lecithin, and cholesterol.
Wherein, the phosphatidylcholine liposome comprises: dimyristoylphosphatidylcholine (DMPC), Dilauroylphosphatidylcholine (DLPC), Dipalmitoylphosphatidylcholine (DPPC), Dioleoylphosphatidylcholine (DOPC), Distearoylphosphatidylcholine (DSPC), diarachioyl phosphatidylcholine (DAPC) and palmitoyloleoylphosphatidylcholine (POPC).
The phosphatidylethanolamine lipidosome comprises: dipalmitoylphosphatidylethanolamine (DPPE), Dilauroylphosphatidylethanolamine (DLPE), Dimyristoylphosphatidylethanolamine (DMPE), Dioleoylphosphatidylethanolamine (DOPE), 1, 3-dipalmitoylphosphatidylethanolamine (1,3-DPPE), Diphytanoylphosphatidylethanolamine (DPPE), and Distearoylphosphatidylethanolamine (DSPE).
In the embodiment of the invention, the liposome is a double-layer membrane closed particle consisting of phosphatidylcholine liposome, phosphatidylethanolamine liposome, phosphatidylserine, lecithin and an additive (cholesterol), and can coat the iodine contrast agent to modify the size of the iodine contrast agent, so that the iodine contrast agent is coated by the liposome. The liposome provided by the embodiment of the invention is easy to degrade, and has the advantages of low drug toxicity, high stability, no immunogenicity, slow release effect and the like.
In a further embodiment of the invention, the surfactant is a mixture of phosphatidylcholine-like liposomes and cholesterol. Phosphatidylcholine-like liposomes, such as Dipalmitoylphosphatidylcholine (DPPC), whose close and loose extent is influenced by the power of the presaturation pulse, i.e. the phospholipid layers will be closely arranged when the presaturation pulse is applied, which is advantageous for controlling the exchange rate; when the presaturation pulse disappears (in the pulse interval period), the phospholipid layer is arranged to be in a loose state, so that certain permeability is kept between the phospholipid layer and the outside, chemical exchange is realized between iodine and surrounding water molecules, and the novel liposome contrast agent obtained after the iodine contrast agent is coated still has CEST signals.
In yet another embodiment of the invention, the molar ratio of phosphatidylcholine niosomes, phosphatidylethanolamine niosomes, phosphatidylserine or lecithin to cholesterol is 8: 1.
The sensitivity of CEST signals of the lipoCEST contrast agent is influenced by the permeability of a phospholipid membrane, the larger the permeability is, the faster the chemical exchange rate is, if the chemical exchange rate is greater than the chemical shift of the lipoCEST contrast agent, the synthesized nanoparticles cannot meet the conditions of the lipoCEST contrast agent, and CEST signals disappear from a Z-spectrum and cannot be used as CEST contrast agents. If the exchange rate is too slow, the sensitivity of the CEST signal is greatly reduced. The surfactant obtained by mixing the components according to the proportion can play a role in adjusting membrane fluidity, can be filled in part of phospholipid membrane gaps to adjust the permeability of the phospholipid membrane gaps, and is beneficial to obtaining a better CEST signal.
In another embodiment of the present invention, the molar ratio of the surfactant to the iodine contrast agent is 0.8 to 1.2: 1. For example, the molar ratio of surfactant to iodine contrast agent may be 0.8:1, 1:1, 1.2:1, and the like. The reasonable proportion design of the surfactant and the iodine contrast agent influences whether the surfactant reasonably coats the iodine contrast agent or not, and whether the coated iodine contrast agent can be used for CEST imaging or not, so that a better CEST signal is obtained. This value is too large, resulting in a waste of material; if the value is too small, the coating effect is affected.
In another embodiment of the present invention, the iodine contrast agent is one or a mixture of more of iohexol, iopamidol, iodofluoroalcohol, iotrolan and iododicinol.
Iodine compounds such as iohexol, iopamidol and iodofluoroalcohol are clinically used X-ray contrast agents (iodine contrast agents). The iodine compounds can be used as X-ray contrast agent, and can be used for enhanced scanning in neuroradiology, angiography, urology, CT examination, arthroscopy, fistula tract angiography, digital subtraction angiography, etc., and has wide application. Recently, the compound is also used as a pH-sensitive CEST contrast agent, but factors such as small size and fast excretion bring certain challenges to the acquisition of CEST signals in a tumor region. The existing iodine contrast agents are generally improved from the concept of mono-, di-or triiodine (triiodocyclobenzene). The embodiment of the invention provides a novel liposome contrast agent, and the defects of quick excretion and low retention rate of a tumor region of the iodine contrast agent are overcome by coating the iodine contrast agent with a surfactant.
In still another embodiment of the present invention, the hydrated particle size (hydrodynamic diameter) of the provided novel LipoCEST contrast agent under Dynamic Light Scattering (DLS) is about 70-240 nm, for example, 100 nm.
The novel LipoCEST contrast agent provided by the embodiment of the invention has the size conforming to the effective EPR support size, and can improve the EPR effect of a tumor region, so that a stable and accurate CEST signal is obtained, and technical support is brought for further researching a tumor acid microenvironment.
As shown in FIG. 1, another embodiment of the present invention provides a method for preparing a chemical exchange saturation transfer contrast agent. The method specifically comprises the following steps:
and (3) uniformly mixing the iodine contrast agent with ultrapure water or PBS buffer solution to obtain an iodine contrast agent mixed solution. Wherein the molar ratio of the iodine contrast agent to the ultrapure water is 8: 1.
The surfactant is dissolved with chloroform or ether solvent.
And adding the mixed solution of the iodine contrast agent into the dissolved surfactant, performing ultrasonic treatment for 10min under the ice bath condition, removing an organic phase at room temperature, and performing dialysis to obtain the chemical exchange saturated transfer contrast agent formed by coating the iodine contrast agent with the surfactant.
Further, the definition of the surfactant and the iodine contrast agent is as described above. For example, the surfactant is one or more of phosphatidylcholine liposome, phosphatidylethanolamine liposome, phosphatidylserine, lecithin or cholesterol. The molar ratio of the surfactant to the iodine contrast agent is 0.8-1.2: 1.
For another example, the hydrated particle size of the obtained contrast agent under dynamic light scattering is about 70 to 240nm, for example, may be 100 nm.
Further, the organic phase (chloroform or ether used to dissolve the surfactant) was removed by rotary evaporation at room temperature.
The embodiment of the invention provides a preparation method of a CEST contrast agent, which combines a nano synthesis technology to realize the coating of a surfactant on an iodine contrast agent, and prepares a novel liposome CEST contrast agent, thereby solving the defects of quick excretion of the iodine contrast agent, low retention rate of a tumor region and the like. Meanwhile, on the basis of high efficiency and high sensitivity, the biological compatibility and the safety are further high.
The existing iodine compounds have low retention rate in a tumor region due to small size, quick excretion and the like, and the acquisition of CEST signals in the tumor region has certain challenges. Therefore, in order to overcome the defect, the invention synthesizes effective EPR supporting size by using a nanotechnology, improves the EPR effect of a tumor region, thereby obtaining a stable and accurate CEST signal and bringing technical support for further researching a tumor acid microenvironment.
In yet another aspect, an embodiment of the present invention provides a use of any one of the above contrast agents in magnetic resonance imaging.
The contrast agent is used for MR CEST pH-map imaging of solid tumors, wherein the pH-map is a spatial distribution map for evaluating acidity coefficient values of tumor cell acidity microenvironment. The solid tumors include malignant solid tumors and benign solid tumors, and the solid tumors in the invention mainly refer to malignant solid tumors. The malignant solid tumor mainly comprises clinically common malignant tumors including lung cancer, liver cancer, breast cancer, prostatic cancer, kidney cancer, brain malignant glioma and the like. The existing iodine contrast agent has the defects of quick excretion, low retention rate in a tumor area and the like. The current use as CEST contrast agent is also limited to CEST imaging of the kidney. The invention provides a novel lipoCEST contrast agent by coating the iodine contrast agent with the surfactant and modifying the size of the iodine contrast agent, and solves the limitations.
The following further describes the novel lipoCEST contrast agent provided by the embodiment of the invention, and the preparation method and application thereof in detail with reference to the specific embodiment.
Example 1
Preparation of lipoCEST contrast agent
1) Uniformly mixing iohexol and ultrapure water to obtain iohexol mixed solution;
2) dissolving lecithin and cholesterol in chloroform to obtain a dissolved surfactant, wherein the molar ratio of the lecithin to the cholesterol is 8: 1;
3) the iohexol mixture was added to the dissolved surfactant (iohexol: surfactant 1:1 (molar ratio)), performing ultrasonic treatment for 10min under a probe type ultrasonic ice bath condition, removing an organic phase at room temperature by using a rotary evaporator, and dialyzing to obtain lipoCEST nanoparticles, namely the lipoCEST contrast agent.
FIG. 2 shows a DLS diagram of the obtained lipoCEST nanoparticles, as shown in FIG. 1, the particle sizes (hydrated particle sizes) of the lipoCEST nanoparticles are substantially distributed in the range of 70-240 nm (the particle size 116nm accounts for about 97.4%), and are mainly concentrated near 100nm, and the sizes accord with EPR effect support sizes.
Fig. 3 shows a TEM (transmission electron microscope) image of the resulting LipoCEST nanoparticles.
Figure 4 shows the results of MRI CEST imaging of LipoCEST nanoparticles with CEST signal at 4.3ppm chemical shift. The percentage of its CEST signal is shown in table 1.
The instrument comprises the following steps: bruker 9.4T Biospec MRI with Bruker magnetic resonance imager
Sample preparation: 100 microliters of the synthesized LipoCEST nanoparticles were added to 1.5ml Ep tubes, and each of the Ep tubes containing the sample was sealed with a sealing film to prevent the sample from flowing out. The Ep tube containing the sample was then placed in a 40ml ultra pure water centrifuge tube. The sealing film is also used to seal the water.
Imaging conditions are as follows: the coil used is1The H body part double-resonance radio frequency coil can be used as a transmitter and a receiver at the same time; the imaging ambient temperature was room temperature, 26 ℃. The Imaging sequence used is Echo Planar Imaging (EPI).
An imaging process: the sample is placed on the scanning bed in the middle of the magnet and inserted1The H-body part double-resonance radio frequency coil is tuned by using an adapter, and enters a bed after infrared positioning. Sweeping a Localizer sequence to complete spatial positioning, sweeping a T2Turbo to perform main magnetic field B0-map and 3mm slice shimming, and then sweeping EPI sequences with different parameters including EPI-OUT, EPI-conservation power, duration time and EPI-pass (water conservation shift reference); the EPI-out is a control sequence, the saturation power and duration time can be set according to the pre-saturation pulse and saturation time that need to be applied, and the EPI-wassr sequence is used to correct the inhomogeneity of the main magnetic field.
Parameters are as follows:
TE (echo time): 20ms, TR (repetition time): 15ms, Averages:1, repetition: 203, Scan time:30m50s, Badwidth:300000, Image size:64x64, FOV (field of view, imaging field): 35x35, RF amplitude: 1.2. mu.T, Number-offset-Experiment:203, Min-process-offset: 4000Hz, Max-process-offset: 4000Hz, offset-step:39Hz, Length:5000 ms.
Fig. 5 and 6 show the scanning imaging of LipoCEST nanoparticles at time 11 after injecting into the rat tail and the scanning imaging of iohexol injection at time 1 after injecting into the rat tail according to the embodiment of the invention. Wherein lipoCEST nanoparticles are used as an experimental group for carrying out rat tail intravenous injection, and iohexol injection is used as a control group for carrying out rat tail intravenous injection.
Table 2 specifically shows CEST signals of the control group and the experimental group corresponding to time points 0 to 12. Each time point represents the time taken for each scan of the CEST sequence (11m40s), i.e. time point 1 is the imaging at 11m40s after the rat tail injection of contrast agent, time point 2 is the imaging at 23m20s, and so on. Time point 0 is the contrast imaging before the contrast agent rat tail vein injection. The control group at time points 9-12 did not continue imaging because the transrenal excretion phase of the iodine-based contrast agent was acquired, i.e., the control group at time point 1(11m40s) was transrenal (excretion was fast). Whereas the experimental group was excreted via the kidney at time point 11(128m20 s). Compared with the traditional iodine contrast agent, the method reserves enough time (about 12 times of relaxation time) for acquiring the CEST signals of the tumor region, and solves the problem of fast excretion.
Example 2
Preparation of lipoCEST contrast agent
1) Uniformly mixing iopamidol with ultrapure water to obtain an iopamidol mixed solution;
2) dissolving lecithin and cholesterol in chloroform to obtain a dissolved surfactant, wherein the molar ratio of the lecithin to the cholesterol is 8: 1;
3) the iopamidol mixed solution was added to the dissolved surfactant (iopamidol: and (3) surfactant is 1:0.8 (molar ratio)), performing ultrasonic treatment for 10min under a probe type ultrasonic ice bath condition, removing an organic phase at room temperature by using a rotary evaporator, and dialyzing to obtain lipoCEST nanoparticles, namely the lipoCEST contrast agent.
CEST signal intensity is shown in table 1.
Example 3
Preparation of lipoCEST contrast agent
1) Uniformly mixing iopamidol with ultrapure water to obtain an iopamidol mixed solution;
2) dissolving lecithin and cholesterol in chloroform to obtain a dissolved surfactant, wherein the molar ratio of the lecithin to the cholesterol is 8: 1;
3) the iopamidol mixed solution was added to the dissolved surfactant (iopamidol: surfactant 1:1 (molar ratio)), performing ultrasonic treatment for 10min under a probe type ultrasonic ice bath condition, removing an organic phase at room temperature by using a rotary evaporator, and dialyzing to obtain lipoCEST nanoparticles, namely the lipoCEST contrast agent.
The percentage of CEST signal is shown in table 1.
Example 4
Preparation of lipoCEST contrast agent
1) Uniformly mixing iopamidol with ultrapure water to obtain an iopamidol mixed solution;
2) dissolving lecithin and cholesterol in chloroform to obtain a dissolved surfactant, wherein the molar ratio of the lecithin to the cholesterol is 8: 1;
3) the iopamidol mixed solution was added to the dissolved surfactant (iopamidol: and (3) surfactant is 1:1.2 (molar ratio)), performing ultrasonic treatment for 10min under a probe type ultrasonic ice bath condition, removing an organic phase at room temperature by using a rotary evaporator, and dialyzing to obtain lipoCEST nanoparticles, namely the lipoCEST contrast agent.
The percentage of CEST signal is shown in table 1.
Example 5
Preparation of lipoCEST contrast agent
1) Uniformly mixing iohexol and ultrapure water to obtain iohexol mixed solution;
2) dissolving DDPC and cholesterol in chloroform to obtain a dissolved surfactant, wherein the molar ratio of DDPC to cholesterol is 8: 1;
3) the iohexol mixture was added to the dissolved surfactant (iohexol: surfactant 1:1 (molar ratio)), performing ultrasonic treatment for 10min under a probe type ultrasonic ice bath condition, removing an organic phase at room temperature by using a rotary evaporator, and dialyzing to obtain lipoCEST nanoparticles, namely the lipoCEST contrast agent.
The percentage of CEST signal is shown in table 1.
Comparative example 1
Preparation of lipoCEST contrast agent control group
1) Uniformly mixing iohexol and ultrapure water to obtain iohexol mixed solution;
2) dissolving soybean phospholipid and cholesterol in chloroform to obtain a dissolved surfactant, wherein the molar ratio of the soybean phospholipid to the cholesterol is 8: 1;
3) PBS buffer was added to the dissolved surfactant (PBS: surfactant 1:1 (molar ratio)), sonicated with a probe-type ultrasound ice bath for 10min, the organic phase was removed using a rotary evaporator at room temperature, and dialyzed to obtain control nanoparticles.
The percentage of CEST signal is shown in table 1.
TABLE 1
Remarking: all CEST signal intensity calculations of the above tables are obtained by the formula S1-S2/S0, wherein S0 is the signal value of free water molecules when the pre-saturation pulse is not applied; s2 is the free water signal value in the Z-axis direction with the decline of CEST signal chemical shift position after the presaturation pulse is applied; s1 is the corresponding symmetric chemical shift point on the Z-spectrum of S2, which is free of CEST signal.
As can be seen from the comparison of examples 1-5 with comparative example 1, the coating of the iodine contrast agent is realized, and the coated iodine contrast agent still has a good CEST signal.
TABLE 2
Compared with the experimental group and the control group in the embodiment 1, the embodiment of the invention provides the novel lipoCEST contrast agent, the coating of the surfactant on iopamidol and iohexol is realized by combining nano synthesis, the size of the lipoCEST contrast agent is modified, the defects that the excretion of iodine contrast agents such as the CEST contrast agent iohexol mainly exchanging common protons is fast in a tumor region, the retention rate is low and the like are overcome, the EPR effect of the tumor region is improved, and an effective basis is provided for capturing CEST signals of an interested region. Compared with the traditional iodine contrast agent, the method reserves enough time for acquiring the CEST signals of the tumor region, the relaxation time is about 12 times, and the problem of fast excretion is solved. And the EPR effect of the nano modification of the size in the tumor region has enough advantages compared with the prior iodine contrast agent, and the liposome material has good biocompatibility and provides enough guarantee in the aspect of safety.
In the description herein, references to the description of "one embodiment," "another embodiment," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention. The scope of the invention is defined by the appended claims and equivalents thereof.
Claims (2)
1. A chemical exchange saturation transfer contrast agent is characterized in that the contrast agent is formed by wrapping an iodine contrast agent by a surfactant;
wherein the molar ratio of the surfactant to the iodine contrast agent is 1: 1; the iodine contrast agent is iohexol; the surfactant is a mixture of lecithin and cholesterol in a molar ratio of 8: 1;
wherein the contrast agent is prepared by the following method:
uniformly mixing an iodine contrast agent with ultrapure water to obtain an iodine contrast agent mixed solution;
dissolving the surfactant with chloroform;
and adding the mixed solution of the iodine contrast agent into the dissolved surfactant, performing ultrasonic treatment for 10min under an ice bath condition, removing an organic phase by rotary evaporation at room temperature, and dialyzing to obtain the chemical exchange saturated transfer contrast agent formed by wrapping the iodine contrast agent by the surfactant.
2. A method for preparing a chemical exchange saturation transfer contrast agent according to claim 1, comprising the steps of:
uniformly mixing an iodine contrast agent with ultrapure water to obtain an iodine contrast agent mixed solution;
dissolving the surfactant with chloroform;
and adding the mixed solution of the iodine contrast agent into the dissolved surfactant, performing ultrasonic treatment for 10min under an ice bath condition, removing an organic phase by rotary evaporation at room temperature, and dialyzing to obtain the chemical exchange saturated transfer contrast agent formed by wrapping the iodine contrast agent by the surfactant.
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| 《碘海醇脂质体的研制》;祝侠丽 等;《中国药学杂志》;20050622;第40卷(第12期);第916-918页 * |
| 《碘造影剂脂质体的研究进展》;于洋 等;《中国医学影像技术》;20080602;第2 4卷(第6期);第968-972 * |
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