MAGNETIC FERROFERRIC OXIDE NANOPARTICLE, AND PREPARATION METHOD THEREFOR AND USE THEREOF

Abstract

The present invention discloses a magnetic ferroferric oxide nanoparticle, and a preparation method therefor and the use thereof. The magnetic ferroferric oxide nanoparticle contains ferroferric oxide and a hydrophilic macromolecule, wherein the ferroferric oxide and the hydrophilic macromolecule are in at least one of the following relationships (1) and (2): (1) the hydrophilic macromolecule is adsorbed on the surface of the ferroferric oxide; and (2) the ferroferric oxide and the hydrophilic macromolecule are in the state of mutual embedding or occlusion. In the present invention, the hydrophilic macromolecule is used as a stabilizer, and ferrous ions and ferric ions form the magnetic ferroferric oxide nanoparticle by means of coprecipitation; and the magnetic ferroferric oxide nanoparticle has a relatively high longitudinal magnetic relaxation rate r.sub.1, a relatively low transverse/longitudinal magnetic relaxation rate ratio (r.sub.2/r.sub.1), good water solubility, high stability, and good biocompatibility, and can be used as a contrast agent for T1-weighted magnetic resonance imaging (MRI) to improve the contrast and sensitivity of MRI.

Claims

1. A magnetic ferroferric oxide nanoparticle, comprising ferroferric oxide and a hydrophilic macromolecule, wherein the ferroferric oxide and the hydrophilic macromolecule are in at least one of the following relationships (1) and (2): (1) the hydrophilic macromolecule is adsorbed on a surface of the ferroferric oxide; and (2) the ferroferric oxide and the hydrophilic macromolecule are mutually embedded or occluded; and the magnetic ferroferric oxide nanoparticle simultaneously has the following properties 1) to 4): 1) an average particle size is greater than 2 nm and less than 5 nm; 2) an electrokinetic potential is less than or equal to 10 mV; 3) a hydrodynamic diameter is less than or equal to 20 nm; and 4) a longitudinal magnetic relaxation rate r.sub.1 value under a magnetic field intensity of 3.0 T is greater than 5 mM.sup.1 s.sup.1; and a longitudinal magnetic relaxation rate r.sub.1 value under a magnetic field intensity of 1.0 T is greater than 10 mM.sup.1 s.sup.1.

2. The magnetic ferroferric oxide nanoparticle according to claim 1, wherein the hydrophilic macromolecule comprises any one or a copolymer or mixture of several of a carboxylic acid-containing macromolecule, an amino-containing macromolecule, a hydroxyl-containing macromolecule, an amide-containing macromolecule and a polysaccharide.

3. The magnetic ferroferric oxide nanoparticle according to claim 2, wherein the carboxylic acid-containing macromolecule comprises any one or more of polyglutamic acid, polyaspartic acid, polymaleic acid, poly(2-ethylacrylic acid) and polyepoxysuccinic acid.

4. The magnetic ferroferric oxide nanoparticle according to claim 2, wherein the amino-containing macromolecule comprises any one or more of polylysine, polyhistidine, poly-L-arginine and polydimethyl diallyl ammonium chloride.

5. The magnetic ferroferric oxide nanoparticle according to claim 2, wherein the hydroxyl-containing macromolecule comprises any one or more of polyserine, polythreonine, polytyrosine and tannic acid.

6. The magnetic ferroferric oxide nanoparticle according to claim 2, wherein the amide-containing macromolecule comprises any one or more of polyglutamine, polyasparamide, polyacrylamide and polymethacrylamide.

7. The magnetic ferroferric oxide nanoparticle according to claim 2, wherein the polysaccharide comprises one or two of hyaluronic acid and sodium alginate.

8. A preparation method for the magnetic ferroferric oxide nanoparticle according to claim 1, comprising a step of: coprecipitating ferrous ions and ferric ions to form the magnetic ferroferric oxide nanoparticle by using the hydrophilic macromolecule as a stabilizer.

9. The preparation method according to claim 8, wherein the preparation method for the magnetic ferroferric oxide nanoparticle comprises the following steps of: heating a hydrophilic macromolecule solution, then mixing the hydrophilic macromolecule solution after being subjected to heating with an iron ion mixed solution comprising ferrous ions and ferric ions for a coordination reaction, and then adding an alkali liquor for a coprecipitation reaction to obtain the magnetic ferroferric oxide nanoparticle.

10. A magnetic resonance imaging contrast agent comprising the magnetic ferroferric oxide nanoparticle according to claim 1.

11. The magnetic ferroferric oxide nanoparticle according to claim 1, wherein a Zeta potential of the magnetic ferroferric oxide nanoparticle is less than or equal to 30 mV.

12. The magnetic ferroferric oxide nanoparticle according to claim 1, wherein a hydrodynamic diameter of the magnetic ferroferric oxide nanoparticle is less than or equal to 20 nm.

13. The magnetic ferroferric oxide nanoparticle according to claim 1, wherein a molecular weight of the hydrophilic macromolecules is 1,000 to 10,000.

14. The preparation method according to claim 9, wherein in the iron ion mixed solution, a concentration of ferrous ions is 30 mM to 500 mM, and a concentration of ferric ions is 60 mM to 1,000 mM.

15. The preparation method according to claim 9, wherein a concentration of the hydrophilic macromolecule solution is 0.1 mg/mL to 20 mg/mL.

16. The preparation method according to claim 9, wherein the ferrous ions are obtained by hydrolysis of water-soluble ferrous salt, and the water-soluble ferrous salt comprises any one or more of ferrous chloride, ferrous nitrate, ferrous bromide and ferrous sulfate.

17. The preparation method according to claim 9, wherein the ferric ions are obtained by hydrolysis of water-soluble ferric salt, and the water-soluble ferric salt comprises any one or more of ferric chloride, ferric nitrate, ferric bromide and ferric sulfate.

18. The preparation method according to claim 9, wherein after the alkali liquor is added into a mixed solution of the iron ion mixed solution and the hydrophilic macromolecule solution, a pH value of a reaction system is 8 to 10.

19. The preparation method according to claim 9, wherein the alkali liquor comprises at least one of sodium hydroxide and an aqueous solution thereof, potassium hydroxide and an aqueous solution thereof, and ammonia water.

20. The preparation method according to claim 9, wherein the hydrophilic macromolecule solution is heated at a temperature of 25 C. to 100 C., the coprecipitation reaction is conducted at a temperature of 25 C. to 100 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 A shows a transmission electron micrograph of -PGA-ES-MION6 in Example 1, and FIG. 1 B shows a particle size distribution diagram of -PGA-ES-MION6 in Example 1;

[0046] FIG. 2A shows a hydraulic diameter of -PGA-ES-MION6 in Example 1, and FIG. 2B shows a Zeta potential diagram of -PGA-ES-MION6 in Example 1;

[0047] FIG. 3A shows a longitudinal MRI relaxation rate of -PGA-ES-MION6 in Example 1, and FIG. 3B shows a transverse MRI relaxation rate of -PGA-ES-MION6 in Example 1;

[0048] FIG. 4 shows a saturation magnetization diagram of -PGA-ES-MION6 in Example 1;

[0049] FIG. 5A shows an X-ray photoelectron spectrogram of -PGA-ES-MION6 in Example 1, and FIG. 5B shows an X-ray diffraction diagram of -PGA-ES-MION6 in Example 1;

[0050] FIG. 6 shows an infrared absorption spectrogram of -PGA-ES-MION6 in Example 1;

[0051] FIG. 7A shows T.sub.1-weighted MRI images of -PGA-ES-MION6 aqueous solutions at different concentrations in Example 1 and pure water, FIG. 7B shows corresponding MRI signal intensities of -PGA-ES-MION6 aqueous solutions at different concentrations in Example 1;

[0052] FIG. 8 is a MRI image showing a tumor-bearing mouse after being injected with -PGA-ES-MION6 in Example 1;

[0053] FIG. 9A shows a transmission electron micrograph of PASP-ES-MION9 in Example 2, and FIG. 9B shows a particle size distribution diagram of PASP-ES-MION9 in Example 2;

[0054] FIG. 10A shows a hydraulic diameter of PASP-ES-MION9 in Example 2; and FIG. 10B shows a Zeta potential diagram of PASP-ES-MION9 in Example 2;

[0055] FIG. 11A shows a longitudinal MRI relaxation rate of PASP-ES-MION9 in Example 2, and FIG. 11B shows a transverse MRI relaxation rate of PASP-ES-MION9 in Example 2;

[0056] FIG. 12A shows an X-ray photoelectron spectrogram of PASP-ES-MION9 in Example 2, and FIG. 12B shows an X-ray diffraction diagram of PASP-ES-MION9 in Example 2;

[0057] FIG. 13 shows an infrared absorption spectrogram of PASP-ES-MION9 in Example 2;

[0058] FIG. 14A shows T.sub.1-weighted MRI images of PASP-ES-MION9 aqueous solutions at different concentrations in Example 2, and FIG. 14B shows corresponding MRI signal intensities of PASP-ES-MION9 aqueous solutions at different concentrations in Example 2;

[0059] FIG. 15 a MRI image showing a tumor-bearing mouse after being injected with PASP-ES-MION9 in Example 2;

[0060] FIG. 16A shows a longitudinal MRI relaxation rate of HPMA-ES-MION in Example 3, and FIG. 16B shows a transverse MRI relaxation rate of HPMA-ES-MION in Example 3;

[0061] FIG. 17A shows a longitudinal MRI relaxation rate of PEAA-ES-MION in Example 4, and FIG. 17B shows a transverse MRI relaxation rate of PEAA-ES-MION in Example 4;

[0062] FIG. 18A shows a longitudinal MRI relaxation rate of PESA-ES-MION in Example 5, and FIG. 18B shows a transverse MRI relaxation rate of PESA-ES-MION in Example 5;

[0063] FIG. 19A shows a longitudinal MRI relaxation rate of -PL-ES-MION in Example 6, and FIG. 19B shows a transverse MRI relaxation rate of -PL-ES-MION in Example 6;

[0064] FIG. 20 A shows a longitudinal MRI relaxation rate of PLH-ES-MION in Example 7, and FIG. 20B shows a transverse MRI relaxation rate of PLH-ES-MION in Example 7;

[0065] FIG. 21A shows a longitudinal MRI relaxation rate of PLR-ES-MION in Example 8, and FIG. 21B shows a transverse MRI relaxation rate of PLR-ES-MION in Example 8;

[0066] FIG. 22A shows a longitudinal MRI relaxation rate of PDDA-ES-MION in Example 9, and FIG. 22B shows a transverse MRI relaxation rate of PDDA-ES-MION in Example 9;

[0067] FIG. 23A shows a longitudinal MRI relaxation rate of PSer-ES-MION in Example 10, and FIG. 23B shows a transverse MRI relaxation rate of PSer-ES-MION in Example 10;

[0068] FIG. 24A shows a longitudinal MRI relaxation rate of PThr-ES-MION in Example 11, and FIG. 24B shows a transverse MRI relaxation rate of PThr-ES-MION in Example 11;

[0069] FIG. 25A shows a longitudinal MRI relaxation rate of PTyr-ES-MION in Example 12, and FIG. 25B shows a transverse MRI relaxation rate of PTyr-ES-MION in Example 12;

[0070] FIG. 26A shows a longitudinal MRI relaxation rate of TA-ES-MION in Example 13, and FIG. 26B shows a transverse MRI relaxation rate of TA-ES-MION in Example 13;

[0071] FIG. 27A shows a longitudinal MRI relaxation rate of PolyQ-ES-MION in Example 14, and FIG. 27B shows a transverse MRI relaxation rate of PolyQ-ES-MION in Example 14;

[0072] FIG. 28A shows a longitudinal MRI relaxation rate of PHEA-ES-MION in Example 15, and FIG. 28B shows a transverse MRI relaxation rate of PHEA-ES-MION in Example 15;

[0073] FIG. 29A shows a longitudinal MRI relaxation rate of PAM-ES-MION in Example 16, and FIG. 29B shows a transverse MRI relaxation rate of PAM-ES-MION in Example 16;

[0074] FIG. 30A shows a longitudinal MRI relaxation rate of PMAM-ES-MION in Example 17, and FIG. 30B shows a transverse MRI relaxation rate of PMAM-ES-MION in Example 17;

[0075] FIG. 31A shows a longitudinal MRI relaxation rate of HA-ES-MION in Example 18, and FIG. 31B shows a transverse MRI relaxation rate of HA-ES-MION in Example 18;

[0076] FIG. 32A shows a longitudinal MRI relaxation rate of SA-ES-MION in Example 19, and FIG. 32B shows a transverse MRI relaxation rate of SA-ES-MION in Example 19;

[0077] FIG. 33A shows a longitudinal MRI relaxation rate of -PGA/PASP-ES-MION in Example 20, and FIG. 33B shows a transverse MRI relaxation rate of -PGA/PASP-ES-MION in Example 20; and FIG. 34A shows a longitudinal MRI relaxation rate of HPMA/PASP-ES-MION in Example 21, and FIG. 34A shows a transverse MRI relaxation rate of HPMA/PASP-ES-MION in Example 21.

DETAILED DESCRIPTION

[0078] Technical solutions of the present disclosure are further described in detail hereinafter with reference to specific examples. Raw materials used in the following examples may be commercially available conventionally, unless otherwise specified; and the processes are all conventional processes in the art, unless otherwise specified.

Example 1

Preparation of Magnetic Ferroferric Oxide Nanoparticle (v-PGA-ES-MION):

[0079] 20 mL of polyglutamic acid -PGA (Mw=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing FeSO.sub.4 and FeCl.sub.3 was added into the flask, and then added with 6 mL of ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as -PGA-ES-MION. Concentrations of the polyglutamic acid aqueous solution, the mixed aqueous solution and the ammonia water and corresponding samples were shown in Table 1.

[0080] Physical properties of the sample in Example 1 were characterized. A recovery rate of iron of the sample in Example 1 was calculated to be 96%, which indicated that a utilization rate of a raw material was high, so that a cost could be effectively reduced. The sample in Example 1 and commercially available products Gadavist and Magnevist were respectively prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by 1.0 T, clinical 3.0 T and 7.0 T MRI systems to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2. A longitudinal magnetic relaxation rate r.sub.1 and a transverse magnetic relaxation rate r.sub.2 were calculated by the following formula (c is a concentration of a magnetic substance in a contrast agent, and T.sub.1 is relaxation time, wherein i=1 or 2), and results were shown in Table 1.

[00001]$r_i=\frac{\left(1/T_i\right)}{c}$

TABLE-US-00001 TABLE 1 Synthesis of -PGA-ES-MION and MRI characterization results Recovery Name of C.sub.-PGA C.sub.FeCl3 C.sub.FeSO4 C.sub.NH3H2O rate of iron H.sub.0 r.sub.1 r.sub.2 sample (mg/mL).sup.a (mM).sup.a (mM).sup.a (%).sup.a (%).sup.b (T) (mM.sup.1s.sup.1) (mM.sup.1s.sup.1) r.sub.2/r.sub.1 -PGA-ES- 2.0 500 250 28 98.0 3.0 8.59 268.9 31.3 MION1 -PGA-ES- 1.0 500 250 28 93.8 3.0 8.41 285.9 34.0 MION2 -PGA-ES- 0.5 500 250 28 78.0 3.0 7.04 221.7 31.5 MION3 -PGA-ES- 0.25 500 250 28 25.4 3.0 7.26 247.9 34.2 MION4 -PGA-ES- 2.0 500 250 0.5 92.1 3.0 2.79 0.06 47.5 0.2 17.0 0.3 MION5 -PGA-ES- 2.0 500 250 1 96.1 3.0 5.70 0.04 70.2 1.5 12.3 0.2 MION6 1.0 10.11 0.69 103.6 4.5 10.3 1.1 -PGA-ES- 2.0 500 250 2 95.3 3.0 6.42 0.03 104.3 0.4 16.3 0.1 MION7 -PGA-ES- 2.0 500 250 4 98.7 3.0 6.94 0.04 119.4 2.8 17.2 0.4 MION8 Gadavist 3.0 4.64 4.81 1.04 Magnevist 3.0 4.58 4.98 1.09 .sup.ais a concentration of a reactant added before the reaction; and .sup.bis a molar percentage of an iron content of the ferroferric oxide in the raw material iron added.

[0081] Specifically, FIG. 1A shows a transmission electron micrograph (TEM) of the sample -PGA-ES-MION6 in Example 1, and FIG. 1B shows a particle size distribution diagram of the sample -PGA-ES-MION6 in Example 1. It can be seen from the transmission electron micrograph of FIG. 1A that the nanoparticles are uniform in size and evenly dispersed, and particle size distributions of 100 nanoparticles randomly selected from FIG. 1A are counted to obtain the distribution diagram of FIG. 1B. It can be seen from the distribution diagram that the particle size of the sample is mainly about 3.5 nm. An average particle size of the sample -PGA-ES-MION6 is less than 5 nm, and the sample has the potential to be the T.sub.1 contrast agent from the view of particle size. FIG. 2A shows a hydraulic diameter of the sample -PGA-ES-MION6 in Example 1, and FIG. 2B shows a Zeta potential diagram of the sample -PGA-ES-MION6 in Example 1. A hydraulic diameter of the sample is 8.7 nm, and a polymer dispersity index (PDI) of the sample is 0.265, which indicates good dispersity. A Zeta potential of the sample is 37.3 mV, and water phase dispersity of the sample can be improved by charge repulsion, which is beneficial for blood circulation of the sample.

[0082] The concentrations of the polyglutamic acid aqueous solution, the mixed aqueous solution and the ammonia water have a great influence on the MRI performance of the sample. Under different synthetic conditions, the sample -PGA-ES-MION6 has the best comprehensive MRI performance. FIG. 3A and FIG. 3B show MRI relaxation rates of the sample -PGA-ES-MION6 in Example 1 (three samples -PGA-ES-MION6-1, -PGA-ES-MION6-2 and -PGA-ES-MION6-3 were tested in parallel for three times). A slope of a fitted line is a corresponding magnetic relaxation rate. It can be seen from FIG. 3A or FIG. 3B that goodness of linear fitting is 0.999 or more, which proves that the sample has an excellent linear relationship, thus indicating that the relaxation time may be changed linearly with a change of a concentration of the sample.

[0083] Table 1 shows the r.sub.1 value and the r.sub.2/r.sub.1 ratio of the sample -PGA-ES-MION1-8 in Example 1 under different magnetic field intensities (7.0 T, 3.0 T or 1.0 T), and simultaneously shows the r.sub.1 values and the r.sub.2/r.sub.1 ratios of the commercially available products Gadavist and Magnevist under the magnetic field intensity of 3.0 T. The r.sub.1 value of the sample -PGA-ES-MION6 in Example 1 under the magnetic field intensity of 3.0 T is 5.7 mM.sup.1 s.sup.1, which is higher than the r.sub.1 value of 4.6 mM.sup.1 s.sup.1 of the commercially available products, thus indicating an excellent magnetic resonance imaging capability. FIG. 4 shows a saturation magnetization diagram of -PGA-ES-MION6 in Example 1. It can be seen from the figure that the sample in Example 1 is paramagnetic, which accords with the property of the magnetic ferroferric oxide nanoparticle. A magnitude of the saturation magnetization is positively correlated with the particle size. It can be seen from the figure that the saturation magnetization of the sample in Example 1 is 16 emu/g, which corresponds to the particle size less than 5 nm shown in the electron micrograph in FIG. 1A. The r.sub.2 value of the contrast agent is positively correlated with the saturation magnetization, and small saturation magnetization corresponds to a small r.sub.2 value, which corresponds to the small r.sub.2 value shown in Table 1.

[0084] FIG. 5A shows an X-ray photoelectron spectrogram (XPS) of -PGA-ES-MION6 in Example 1, and FIG. 5B shows an X-ray diffraction diagram (XRD) of -PGA-ES-MION6 in Example 1. Peaks centered at 711.6 eV and 725.1 eV in the XPS of FIG. 5A correspond to binding energies of Fe.sup.2+2p and Fe.sup.3+2p respectively, which indicates that trivalent iron and divalent iron exist at the same time, and proves that the sample in Example 1 is the ferroferric oxide. Two characteristic peaks (235.6 and 262.9) in the XRD of FIG. 5B correspond to crystal layers [(311) and (440)] of the ferroferric oxide, which proves that the sample in Example 1 is the ferroferric oxide in a crystal structure. The XRD and the XPS jointly prove the successful preparation of the ferroferric oxide in Example 1, and then prove the successful preparation of the magnetic ferroferric oxide nanoparticle in Example 1 in combination with the electron micrograph in FIG. 1B.

[0085] FIG. 6 shows an infrared absorption spectrogram of -PGA-ES-MION6 prepared in Example 1. An infrared absorption curve of -PGA and an infrared absorption curve of -PGA-ES-MION6 both show an absorption peak a (1,404 cm.sup.1), which is a bending vibration peak of CH.sub.2, thus indicating the existence of the -PGA in the sample. In addition, the infrared absorption curve of the -PGA-ES-MION6 shows absorption peaks b and c, which are stretching vibration peaks of FeO, while the infrared absorption curve of the -PGA does not show the absorption peaks b and c, which further proves the successful preparation of the magnetic ferroferric oxide nanoparticle -PGA-ES-MION6.

[0086] FIG. 7A shows T.sub.1-weighted MRI images of -PGA-ES-MION6 aqueous solutions at different concentrations in Example 1, and FIG. 7B shows corresponding MRI signal intensities of -PGA-ES-MION6 aqueous solutions at different concentrations in Example 1. The magnetic field intensity is 3.0 T, and scanning parameters are: TE=8.6 ms and TR=500 ms. It can be seen from the MRI image of FIG. 7(a) that an MRI signal of the aqueous solution containing the sample -PGA-ES-MION6 is obviously enhanced compared with pure water (a concentration of iron is 0), and shows a gradient enhancement with the increase of the concentration of the sample. It can be seen from FIG. 7(b) that, when the concentration of iron in the -PGA-ES-MION6 solution is 200 M, a signal-to-noise ratio (SNR) of the MRI is 240%, which indicates that the sample -PGA-ES-MION6 can effectively improve the contrast and sensitivity of the MRI, thus showing the good magnetic resonance imaging performance of the -PGA-ES-MION6 in Example 1.

[0087] FIG. 8 is a MRI image showing a tumor-bearing mouse after being injected with -PGA-ES-MION6 in Example 1, with an injection dosage of 5 mg/kg. 7.0 T magnetic resonance imaging (MRI) is carried out on the mouse at 0 hour, 1 hour, 2 hours, 3 hours, 4 hours and 8 hours before and after tail vein injection of the sample into the mouse. It can be seen from the figure that, with the increase of injection time of the sample, an MRI signal of a tumor shows a trend of increasing first and then decreasing, and the MRI signal is the highest at 3 hours after injection. In-vivo imaging results show that the sample -PGA-ES-MION6 in Example 1 has a good magnetic resonance imaging effect on the tumor of the mouse.

Example 2

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PASP-ES-MION):

[0088] 20 mL of polyaspartic acid PASP (M.sub.w=7,000 to 8,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing FeSO.sub.4 and FeCl.sub.3 was added into the flask, and then added with 6 mL of ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PASP-ES-MION. Concentrations of the polyaspartic acid aqueous solution, the mixed aqueous solution and the ammonia water and corresponding samples were shown in Table 2.

[0089] Physical properties of the sample in Example 2 were characterized. A recovery rate of iron of the sample in Example 2 was calculated to be 89.6%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 2 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2. A longitudinal magnetic relaxation rate r.sub.1 and a transverse magnetic relaxation rate r.sub.2 were calculated, and results were shown in Table 2.

TABLE-US-00002 TABLE 2 Synthesis of PASP-ES-MION and MRI characterization results Recovery Name of C.sub.PASP C.sub.FeCl3 C.sub.FeSO4 C.sub.NH3H2O rate of iron H.sub.0 r.sub.1 r.sub.2 sample (mg/mL).sup.a (mM).sup.a (mM).sup.a (%).sup.a (%).sup.b (T) (mM.sup.1 s.sup.1) (mM.sup.1 s.sup.1) r.sub.2/r.sub.1 PASP-ES- 4.0 500 250 1 92.7 3.0 0.99 3.71 3.76 MION1 PASP-ES- 2.0 500 250 1 96.6 3.0 2.01 14.04 6.98 MION2 PASP-ES- 1 500 250 1 89.3 3.0 4.66 88.50 19.00 MION3 PASP-ES- 0.5 500 250 1 90.3 3.0 5.41 153.09 28.31 MION4 PASP-ES- 2 500 250 8 99.2 3.0 5.53 0.04 31.0 0.05 5.62 0.1 MION5 PASP-ES- 2 500 250 4 98.4 3.0 5.22 0.03 27.3 0.56 5.22 0.1 MION6 PASP-ES- 2 500 250 2 98.8 3.0 3.83 0.02 25.1 0.51 6.54 0.2 MION7 PASP-ES- 2 500 250 0.5 97.5 3.0 0.32 0.01 5.8 0.08 18.2 0.4 MION8 PASP-ES- 1.5 375 187.5 4 89.6 3.0 7.3 35.8 4.9 MION9 PASP-ES- 1 250 125 4 87.7 3.0 6.2 33.0 5.3 MION10 PASP-ES- 0.5 125 62.5 4 97.7 3.0 6.0 38.8 6.5 MION11 .sup.ais a concentration of a reactant added before the reaction; and .sup.bis a molar percentage of an iron content of the ferroferric oxide in the raw material iron added.

[0090] FIG. 9A shows a transmission electron micrograph of the sample PASP-ES-MION9 in Example 2, and FIG. 9B shows a particle size distribution diagram of the sample PASP-ES-MION9 in Example 2. It can be seen from the transmission electron micrograph of FIG. 9A that the nanoparticles are uniform in size and evenly dispersed, and particle size distributions of 100 nanoparticles randomly selected from FIG. 9A are counted to obtain the distribution diagram of FIG. 9 B. It can be seen from the distribution diagram that the particle size of the sample mainly ranges from 2.6 nm to 5.0 nm, and an average particle size of the sample is 3.7 nm, thus meeting the requirement that the particle size of the ferroferric oxide as the T.sub.1 contrast agent is less than 5 nm. FIG. 10A shows a hydraulic diameter of the sample PASP-ES-MION9 in Example 2, and FIG. 10B shows a Zeta potential diagram of the sample PASP-ES-MION9 in Example 2. It is measured that an average value of hydraulic diameters of three samples (PASP-ES-MION9-1, PASP-ES-MION9-2 and PASP-ES-MION9-3) is 14.7 nm, and a PDI of the sample is 0.224, which indicates good dispersity. A Zeta potential of the sample is 50.7 mV, and water phase dispersity of the sample can be improved by charge repulsion, which is beneficial for blood circulation of the sample.

[0091] The concentrations of the polyaspartic acid aqueous solution, the mixed aqueous solution and the ammonia water have a great influence on the MRI performance of the sample. Under different synthetic conditions, the sample PASP-ES-MION9-10 has a better comprehensive MRI performance. Taking the PASP-ES-MION9 as an example, FIG. 11A and FIG. 11B show MRI relaxation rates of the sample PASP-ES-MION9 in Example 2. It can be seen from FIG. 11A or FIG. 11B that goodness of linear fitting of a fitted line is 0.99 or more, which proves that the sample has a good linear relationship. Table 2 shows the r.sub.1 value and the r.sub.2/r.sub.1 ratio of the sample PASP-ES-MION9 in Example 2 under the magnetic field intensity of 3.0 T. The r.sub.1 value of the sample PASP-ES-MION9 in Example 2 under the magnetic field intensity of 3.0 T is 7.3 mM.sup.1 s.sup.1, which is higher than the r.sub.1 value of 4.64 mM.sup.1 s.sup.1 of the commercially available products. In addition, the r.sub.2/r.sub.1 ratio of the sample PASP-ES-MION9 under the magnetic field intensity of 3.0 T is only 4.9. The results show that the sample PASP-ES-MION9 in Example 2 under the magnetic field intensity of 3.0 T has an extremely high r.sub.1 value and an extremely low r.sub.2/r.sub.1 ratio.

[0092] FIG. 12A shows an X-ray photoelectron spectrogram of the PASP-ES-MION9 in Example 2, and FIG. 12B shows an X-ray diffraction diagram of the PASP-ES-MION9 in Example 2. Peaks centered at 710.3 eV and 723.8 eV in the XPS of FIG. 12A correspond to binding energies of Fe.sup.2+2p and Fe.sup.3+2p respectively, which indicates that trivalent iron and divalent iron exist at the same time, and proves that the sample in Example 2 is the ferroferric oxide. Two characteristic peaks (235.3 and 262.4) in the XRD of FIG. 12B correspond to crystal layers [(311) and (440)] of the ferroferric oxide, which proves that the sample in Example 2 is the ferroferric oxide in a crystal structure. The XRD and the XPS jointly prove the successful preparation of the ferroferric oxide in Example 2, and then prove the successful preparation of the magnetic ferroferric oxide nanoparticle in Example 2 in combination with the electron micrograph in FIG. 9A.

[0093] FIG. 13 shows an infrared absorption spectrogram of PASP-ES-MION9 prepared in Example 2. An infrared absorption curve of PASP and an infrared absorption curve of PASP-ES-MION9 both show an absorption peak a (1,400 cm.sup.1), which is a stretching vibration peak of COO, thus indicating the existence of the PASP in the sample. In addition, the infrared absorption curve of PASP-ES-MION9 shows an absorption peak b, which is a stretching vibration peak of FeO, while the infrared absorption curve of the PASP does not show the absorption peak b, which further proves the successful preparation of the magnetic ferroferric oxide nanoparticle PASP-ES-MION9.

[0094] FIG. 14A shows T.sub.1-weighted MRI images of PASP-ES-MION9 aqueous solutions at different concentrations in Example 2, and FIG. 14B shows corresponding MRI signal intensities of PASP-ES-MION9 aqueous solutions at different concentrations in Example 2. The magnetic field intensity is 3.0 T, and scanning parameters are: TE=8.4 ms and TR=200 ms. It can be seen from the MRI image of FIG. 14 (a) that an MRI signal of the aqueous solution containing the sample PASP-ES-MION9 is obviously enhanced compared with pure water (a concentration of iron is 0), and shows a gradient enhancement with the increase of the concentration of the sample. It can be seen from FIG. 14 (b) that, when the concentration of iron in the sample PASP-ES-MION9 aqueous solution is 1,000 M, SNR of the MRI is 1,025%, which proves that the PASP-ES-MION9 can effectively improve the contrast and sensitivity of the MRI, thus showing the excellent magnetic resonance imaging performance of the PASP-ES-MION9 in Example 2.

[0095] FIG. 15 shows a MRI image showing a tumor-bearing mouse after being injected with PASP-ES-MION9 in Example 2, with an injection dosage of 5 mg/kg. 7.0 T magnetic resonance imaging (MRI) is carried out on the mouse at 0 hour, 1 hour, 2 hours, 3 hours, 4 hours and 8 hours before and after tail vein injection of the sample into the mouse. It can be seen from the figure that, with the increase of injection time of the sample, an MRI signal of a tumor is increased first and then decreased, and the MRI signal is the highest at 3 hours after injection. In-vivo imaging results show that the PASP-ES-MION9 in Example 2 has a good magnetic resonance imaging effect on the tumor of the mouse.

Example 3

Preparation of Magnetic Ferroferric Oxide Nanoparticle (HPMA-ES-MION):

[0096] 20 mL of 2 mg/mL polymaleic acid HPMA (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as HPMA-ES-MION.

[0097] A performance test was carried out on the sample in Example 3. A recovery rate of iron of the sample in Example 3 was calculated to be 87.2%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 3 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples HPMA-ES-MION-1, HPMA-ES-MION-2 and HPMA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 16A and FIG. 16B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.90.3 mM.sup.1 s.sup.1, an r.sub.2 value was 32.31.9 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 4.70.4 in Example 3. It was proved that the magnetic ferroferric oxide nanoparticle (HPMA-ES-MION) in Example 3 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 4

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PEAA-ES-MION):

[0098] 20 mL of 2 mg/mL poly(2-ethylacrylic acid) PEAA (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PEAA-ES-MION.

[0099] A performance test was carried out on the sample in Example 4. A recovery rate of iron of the sample in Example 4 was calculated to be 89.1%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 4 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PEAA-ES-MION-1, PEAA-ES-MION-2 and PEAA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 17 A and FIG. 17B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 7.80.2 mM.sup.1 s.sup.1, an r.sub.2 value was 19.81.7 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 2.50.3 in Example 4. The results proved that the magnetic ferroferric oxide nanoparticle (PEAA-ES-MION) in Example 4 had an extremely high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 5

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PESA-ES-MION):

[0100] 20 mL of 2 mg/mL polyepoxysuccinic acid PESA (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PESA-ES-MION.

[0101] A performance test was carried out on the sample in Example 5. A recovery rate of iron of the sample in Example 5 was calculated to be 93.2%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 5 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PESA-ES-MION-1, PESA-ES-MION-2 and PESA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 18A and FIG. 18B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 7.20.2 mM.sup.1 s.sup.1, an r.sub.2 value was 26.12.1 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 3.60.3 in Example 5. The results proved that the ferroferric oxide nanoparticle (PESA-ES-MION) in Example 5 had an extremely high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 6

Preparation of Magnetic Ferroferric Oxide Nanoparticle (-PL-ES-MION):

[0102] 20 mL of 2 mg/mL polylysine -PL (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as -PL-ES-MION.

[0103] A performance test was carried out on the sample in Example 6. A recovery rate of iron of the sample in Example 6 was calculated to be 82.6%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 6 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples -PL-ES-MION-1, -PL-ES-MION-2 and -PL-ES-MION-3 were tested in parallel for three times). As shown in FIG. 19A and FIG. 19B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.20.3 mM.sup.1 s.sup.1, an r.sub.2 value was 32.53.8 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 5.30.9 in Example 6. The results proved that the magnetic ferroferric oxide nanoparticle (-PL-ES-MION) in Example 6 had an extremely high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 7

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PLH-ES-MION):

[0104] 20 mL of 2 mg/mL polyhistidine PLH (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PLH-ES-MION.

[0105] A performance test was carried out on the sample in Example 6. A recovery rate of iron of the sample in Example 7 was calculated to be 85.7%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 7 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PLH-ES-MION-1, PLH-ES-MION-2 and PLH-ES-MION-3 were tested in parallel for three times). As shown in FIG. 20 A and FIG. 20B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 5.70.4 mM.sup.1 s.sup.1, an r.sub.2 value was 46.67.0 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 8.31.5 in Example 7. The results proved that the magnetic ferroferric oxide nanoparticle (PLH-ES-MION) in Example 7 had an extremely high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 8

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PLR-ES-MION):

[0106] 20 mL of 2 mg/mL poly-L-arginine PLR (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PLR-ES-MION.

[0107] A performance test was carried out on the sample in Example 8. A recovery rate of iron of the sample in Example 8 was calculated to be 83.9%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 8 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PLR-ES-MION-1, PLR-ES-MION-2 and PLR-ES-MION-3 were tested in parallel for three times). As shown in FIG. 21 A and FIG. 21B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 5.20.2 mM.sup.1 s.sup.1, an r.sub.2 value was 55.09.1 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 10.61.8 in Example 8. The results proved that the magnetic ferroferric oxide nanoparticle (PLR-ES-MION) in Example 8 had an extremely high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 9

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PDDA-ES-MION):

[0108] 20 mL of 2 mg/mL polydimethyl diallyl ammonium chloride PDDA (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PDDA-ES-MION.

[0109] A performance test was carried out on the sample in Example 9. A recovery rate of iron of the sample in Example 9 was calculated to be 90.4%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 9 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PDDA-ES-MION-1, PDDA-ES-MION-2 and PDDA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 22 A and FIG. 22B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 7.10.5 mM.sup.1 s.sup.1, an r.sub.2 value was 70.09.1 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 9.91.8 in Example 9. The results proved that the magnetic ferroferric oxide nanoparticle (PDDA-ES-MION) in Example 9 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 10

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PSer-ES-MION):

[0110] 20 mL of 2 mg/mL polyserine PSer (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PSer-ES-MION.

[0111] A performance test was carried out on the sample in Example 10. A recovery rate of iron of the sample in Example 10 was calculated to be 88.2%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 10 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PSer-ES-MION-1, PSer-ES-MION-2 and PSer-ES-MION-3 were tested in parallel for three times). As shown in FIG. 23 A and FIG. 23B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 5.80.25 mM.sup.1 s.sup.1, an r.sub.2 value was 63.48.7 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 11.01.3 in Example 10. The results proved that the magnetic ferroferric oxide nanoparticle (PSer-ES-MION) in Example 10 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 11

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PThr-ES-MION):

[0112] 20 mL of 2 mg/mL polythreonine PThr (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PThr-ES-MION.

[0113] A performance test was carried out on the sample in Example 11. A recovery rate of iron of the sample in Example 11 was calculated to be 85.7%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 11 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PThr-ES-MION-1, PThr-ES-MION-2 and PThr-ES-MION-3 were tested in parallel for three times). As shown in FIG. 24A and FIG. 24B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.60.4 mM.sup.1 s.sup.1, an r.sub.2 value was 57.22.5 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 8.70.8 in Example 11. The results proved that the magnetic ferroferric oxide nanoparticle (PThr-ES-MION) in Example 11 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 12

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PTyr-ES-MION):

[0114] 20 mL of 2 mg/mL polytyrosine PTyr (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PTyr-ES-MION.

[0115] A performance test was carried out on the sample in Example 12. A recovery rate of iron of the sample in Example 12 was calculated to be 83.2%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 12 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PTyr-ES-MION-1, PTyr-ES-MION-2 and PTyr-ES-MION-3 were tested in parallel for three times). As shown in FIG. 25A and FIG. 25B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.40.2 mM.sup.1 s.sup.1, an r.sub.2 value was 59.75.8 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 9.41.2 in Example 12. The results proved that the magnetic ferroferric oxide nanoparticle (Pyr-ES-MION) in Example 12 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 13

Preparation of Magnetic Ferroferric Oxide Nanoparticle (TA-ES-MION):

[0116] 20 mL of 2 mg/mL tannic acid TA (M.sub.w=1,700) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as TA-ES-MION.

[0117] A performance test was carried out on the sample in Example 13. A recovery rate of iron of the sample in Example 13 was calculated to be 92.7%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 13 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples TA-ES-MION-1, TA-ES-MION-2 and TA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 26A and FIG. 26B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 7.30.4 mM.sup.1 s.sup.1, an r.sub.2 value was 58.93.2 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 8.10.8 in Example 13. The results proved that the magnetic ferroferric oxide nanoparticle (TA-ES-MION) in Example 13 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 14

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PolyQ-ES-MION):

[0118] 20 mL of 2 mg/mL polyglutamine PolyQ (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PolyQ-ES-MION.

[0119] A performance test was carried out on the sample in Example 14. A recovery rate of iron of the sample in Example 14 was calculated to be 87.5%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 14 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PolyQ-ES-MION-1, PolyQ-ES-MION-2 and PolyQ-ES-MION-3 were tested in parallel for three times). As shown in FIG. 27 A and FIG. 27B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 7.00.2 mM.sup.1 s.sup.1, an r.sub.2 value was 56.80.8 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 8.10.3 in Example 14. The results proved that the magnetic ferroferric oxide nanoparticle (PolyQ-ES-MION) in Example 14 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 15

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PHEA-ES-MION):

[0120] 20 mL of 2 mg/mL polyasparamide PHEA (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PHEA-ES-MION.

[0121] A performance test was carried out on the sample in Example 15. A recovery rate of iron of the sample in Example 15 was calculated to be 85.4%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 15 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PHEA-ES-MION-1, PHEA-ES-MION-2 and PHEA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 28A and FIG. 28B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.90.4 mM.sup.1 s.sup.1, an r.sub.2 value was 49.27.2 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 7.20.8 in Example 15. The results proved that the magnetic ferroferric oxide nanoparticle (PHEA-ES-MION) in Example 15 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 16

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PAM-ES-MION):

[0122] 20 mL of 2 mg/mL polyacrylamide PAM (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PAM-ES-MION.

[0123] A performance test was carried out on the sample in Example 16. A recovery rate of iron of the sample in Example 16 was calculated to be 84.3%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 16 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PAM-ES-MION-1, PAM-ES-MION-2 and PAM-ES-MION-3 were tested in parallel for three times). As shown in FIG. 29A and FIG. 29B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 7.20.2 mM.sup.1 s.sup.1, an r.sub.2 value was 50.26.8 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 6.90.9 in Example 16. The results proved that the magnetic ferroferric oxide nanoparticle (PAM-ES-MION) in Example 16 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 17

Preparation of Magnetic Ferroferric Oxide Nanoparticle (PMAM-ES-MION):

[0124] 20 mL of 2 mg/mL polymethacrylamide PMAM (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as PMAM-ES-MION.

[0125] A performance test was carried out on the sample in Example 17. A recovery rate of iron of the sample in Example 17 was calculated to be 90.7%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 17 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples PMAM-ES-MION-1, PMAM-ES-MION-2 and PMAM-ES-MION-3 were tested in parallel for three times). As shown in FIG. 30A and FIG. 30B, a change relationship between 1/T; and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.50.3 mM.sup.1 s.sup.1, an r.sub.2 value was 55.84.8 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 8.50.5 in Example 17. The results proved that the magnetic ferroferric oxide nanoparticle (PMAM-ES-MION) in Example 17 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 18

Preparation of Magnetic Ferroferric Oxide Nanoparticle (HA-ES-MION):

[0126] 20 mL of 2 mg/mL hyaluronic acid HA (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as HA-ES-MION.

[0127] A performance test was carried out on the sample in Example 18. A recovery rate of iron of the sample in Example 18 was calculated to be 89.5%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 18 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples HA-ES-MION-1, HA-ES-MION-2 and HA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 31A and FIG. 31B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.50.2 mM.sup.1 s.sup.1, an r.sub.2 value was 71.85.1 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 11.00.6 in Example 18. The results proved that the magnetic ferroferric oxide nanoparticle (HA-ES-MION) in Example 18 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 19

Preparation of Magnetic Ferroferric Oxide Nanoparticle (SA-ES-MION)

[0128] 20 mL of 2 mg/mL sodium alginate SA (M.sub.w=2,000) aqueous solution was subjected to bubble deoxygenation with nitrogen in a three-necked flask for 1 hour, and then heated at 100 C. to reflux. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as SA-ES-MION.

[0129] A performance test was carried out on the sample in Example 19. A recovery rate of iron of the sample in Example 19 was calculated to be 89.5%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 19 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples SA-ES-MION-1, SA-ES-MION-2 and SA-ES-MION-3 were tested in parallel for three times). As shown in FIG. 32A and FIG. 32B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 7.00.4 mM.sup.1 s.sup.1, an r.sub.2 value was 57.210.7 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 8.21.7 in Example 19. The results proved that the magnetic ferroferric oxide nanoparticle (SA-ES-MION) in Example 19 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 20

Preparation of Magnetic Ferroferric Oxide Nanoparticle (-PGA/PASP-ES-MION):

[0130] 20 mL of 2 mg/mL polyglutamic acid -PGA/polyaspartic acid PASP (polyglutamic acid has a M.sub.w of 2,000, and polyaspartic acid has a M.sub.w of 7,000 to 8,000) mixture (in a mass ratio of 1:1) solution was heated to reflux in a three-necked flask, and subjected to bubble deoxygenation with nitrogen for 1 hour. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as -PGA/PASP-ES-MION.

[0131] A performance test was carried out on the sample in Example 20. A recovery rate of iron of the sample in Example 20 was calculated to be 93.7%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 20 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples -PGA/PASP-ES-MION-1, -PGA/PASP-ES-MION-2 and -PGA/PASP-ES-MION-3 were tested in parallel for three times). As shown in FIG. 33A and FIG. 33B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.70.4 mM.sup.1 s.sup.1, an r.sub.2 value was 63.48.7 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 9.50.7 in Example 20. The results proved that the magnetic ferroferric oxide nanoparticle (-PGA/PASP-ES-MION) in Example 20 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

Example 21

Preparation of Magnetic Ferroferric Oxide Nanoparticle (HPMA/PASP-ES-MION):

[0132] 20 mL of 2 mg/mL polymaleic acid HPMA/polyaspartic acid PASP (polymaleic acid has a M.sub.w of 2,000, and polyaspartic acid has a M.sub.w of 7,000 to 8,000) mixture (in a mass ratio of 1:1) solution was heated to reflux in a three-necked flask, and subjected to bubble deoxygenation with nitrogen for 1 hour. 0.4 mL of a mixed aqueous solution containing 0.25 M FeSO.sub.4 and 0.5 M FeCl.sub.3 was added into the flask, and then added with 6 mL of 1% ammonia water. The mixture reacted for 1 hour under magnetic stirring at 100 C., and was allowed to stand and cooled. The sample after the reaction was dialyzed and purified, and the final sample was marked as HPMA/PASP-ES-MION.

[0133] A performance test was carried out on the sample in Example 21. A recovery rate of iron of the sample in Example 21 was calculated to be 90.1%, which indicated that a utilization rate of a raw material was high, so that cost saving was realized. The sample in Example 21 was prepared into 6 aqueous solutions with different concentrations, and in-vitro imaging tests were carried out by a clinical 3.0 T MRI system (Philips, Ingenia) to obtain longitudinal relaxation time T.sub.1 and transverse relaxation time T.sub.2 (three samples HPMA/PASP-ES-MION-1, HPMA/PASP-ES-MION-2 and HPMA/PASP-ES-MION-3 were tested in parallel for three times). As shown in FIG. 34A and FIG. 34B, a change relationship between 1/T.sub.i and a concentration of iron was drawn, and a slope of a fitted line was a magnetic relaxation rate of T.sub.i (i=1 or 2). Thus, it could be seen that, under the 3.0 T MRI system, an r.sub.1 value was 6.40.1 mM.sup.1 s.sup.1, an r.sub.2 value was 26.12.8 mM.sup.1 s.sup.1, and an r.sub.2/r.sub.1 ratio was 4.10.4 in Example 21. The results proved that the magnetic ferroferric oxide nanoparticle (HPMA/PASP-ES-MION) in Example 21 had a high r.sub.1 value and a low r.sub.2/r.sub.1 ratio, and could be used as a T.sub.1-weighted MRI contrast agent with good biocompatibility.

[0134] The above examples are the preferred implementations of the present disclosure, but the implementations of the present disclosure are not limited by the above examples. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present disclosure should be equivalent substitute modes, and should be included in the scope of protection of the present disclosure.