A ppy@ceo2 np nanoparticle, a preparation method and application thereof

Abstract

The application discloses PPy@CeO2 NPs nanoparticles and a preparation method and application thereof, CeO2 nanoparticles are loaded on the surface of polypyrrole nanoparticles, and the preparation method comprises the following steps: S1, polypyrrole nanoparticles are synthesized by using a chemical oxidation polymerization method; S2, Ce 3+ is oxidized into CeO2 nanoparticles in an alkaline environment provided by hexamethylenetetramine, is mixed with polypyrrole nanoparticles, is coated on the surface of the polypyrrole nanoparticles, and PPy@CeO2 NPs nanoparticles are obtained. The PPy@CeO2 NPs nanoparticles can be applied to preparation of photothermal conversion agents and CDT reagents.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nanomaterials, and particularly to PPy@CeO2 NPs nanoparticles, a preparation method and application thereof. BACKGROUND

[0002] Cancer has become a global problem affecting people's health. Traditional cancer treatment options include surgery, chemotherapy, radiotherapy and combinations of the above treatments. However, these treatment methods have problems such as postoperative tumor recurrence, side effects on healthy tissues, and high clinical mortality. In recent years, new strategies such as photothermal therapy (PTT), chemical dynamic therapy (CDT) and photodynamic therapy (PDT) have been reported. These methods not only effectively kill tumor cells, but also have obvious advantages such as low toxicity and few side effects. However, it is difficult to completely eradicate solid tumors by using a single treatment method. At present, combined therapy has also been used in clinical treatment. Combined therapy combines the advantages of single therapy to better improve the efficiency of tumor treatment. The emergence of combined therapy provides a new solution for cancer treatment.

[0003] In recent years, nanotechnology has been widely used in clinical applications. Due to the excellent physical, chemical and optical properties of nanomaterials, many types of nanoparticles have been designed to overcome the limitations of single therapy. It is worth noting that the combined therapy of different therapies can produce better therapeutic effects than single therapy. Some nanoparticles can carry special molecules, including antibodies, anticancer drugs, polypeptides, proteins, DNA fragments and immunoadjuvants into tumor areas. In addition to serving as drug carriers, nanoparticles can also be used as photothermal conversion agents and CDT reagents for photothermal therapy (PTT) and chemical dynamic therapy (CDT), respectively, thereby realizing the combination of different therapies. Photothermal therapy is a new type of light-controllable, non-invasive and effective tumor treatment method, which is a promising alternative tumor treatment method. It uses near-infrared (NIR) laser irradiation combined with light-absorbing agents to specifically burn tumor tissue to avoid collateral damage to normal tissue. The synergistic effect between CDT and PTT has been widely studied and verified. A study found that when PTT and CDT are combined with chemotherapy, this multi-modal approach not only overcomes the limitations of PTT penetration depth, avoids drug resistance, but also improves the sensitivity of tumor tissue to ROS, achieving significant combined therapy.

[0004] According to research reports, CeO2 NPs is a nano-enzyme with multi-enzyme mimetic activity and has peroxidase activity, so it can achieve CDT treatment. Poly-pyridine nanoparticles have high photothermal conversion efficiency, light stability and low cytotoxicity, and as photothermal agents have received widespread attention from researchers. However, there is currently no related report on the combination of the two. SUMMARY

[0005] The application discloses PPy@CeO2 NPs nanoparticles and a preparation method and application thereof, CeO2 nanoparticles are loaded on the surface of polypyrrole nanoparticles, and a new idea is provided for preparation of a photothermal conversion agent and a CDT reagent.

[0006] To achieve the above object, the technical scheme of the application is:

[0007] The PPy@CeO2 NPs nanoparticles are obtained by loading CeO2 nanoparticles on the surface of polypyrrole nanoparticles.

[0008] The preparation method of the PPy@CeO2 NPs nanoparticles comprises the following steps:

[0009] S1. Synthesizing polypyrrole nanoparticles by using a chemical oxidation polymerization method;

[0010] S2. Making Ce 3+ oxidized into CeO2 nanoparticles in an alkaline environment provided by hexamethylenetetramine, mixing the CeO2 nanoparticles with the polypyrrole nanoparticles, coating the polypyrrole nanoparticles with the CeO2 nanoparticles, and obtaining the PPy@CeO2 NPs nanoparticles.

[0011] Further, the specific process of the step S1 is as follows: polyvinyl alcohol and water are mixed according to a mass ratio of 1:80-100, high-temperature stirring is performed until the polyvinyl alcohol is dissolved, after cooling, FeCl3 is added, the molar ratio of the polyvinyl alcohol to the FeCl3 is 1:0.9-2, stirring is performed, after the stirring is completed, pyrrole is added, the molar ratio of the polyvinyl alcohol to the pyrrole is 1-2:1, the mixture after the pyrrole is added is transferred to an ice bath, reaction is performed for 3.5-5 hours, after the reaction is completed, centrifugation is performed, the precipitate is collected, and the polypyrrole nanoparticles are obtained. In this step, the PPy NPs are formed by polymerization of pyrrole monomers in the presence of FeCl3 and PVA, and the FeCl3 and the PVA are used as an oxidant and a stabilizer respectively.

[0012] Further, based on the preferred scheme of the step S1, the mass ratio of the polyvinyl alcohol to water is 1:83.33, and the molar ratio of the polyvinyl alcohol to the FeCl3 is 1:1.28.

[0013] Further, based on the preferred scheme of the step S1, the molar ratio of the polyvinyl alcohol to the pyrrole is 1:1.69.

[0014] Further, the specific process of step S2 is as follows: 0.05-0.2 mol / L Ce(NO3)3·6H2O solution and 0.05-0.2 mol / L hexamethylenetetramine solution are mixed in a volume ratio of 1:0.5-8, polypyrrole nanoparticles are added in a solid-liquid ratio of 10:1-3 mg / mL, 4-10 times the volume of water and 4-10 times the volume of anhydrous ethanol are added, and the mixture is reacted at 55-70°C for 1.5-3h. The obtained mixed solution is washed and centrifuged to obtain PPy@CeO2NPs nanoparticles. In this step, the alkaline environment provided by the HTM makes Ce 3+ oxidized to CeO2nanoparticles, which are coated on the surface of PPy NPs to form PPy@CeO2NPs.

[0015] Further, based on the preferred scheme of step S2, after the reaction is completed, the mixed solution is washed with water and anhydrous ethanol for 2-3 times, respectively.

[0016] Further, based on the preferred scheme of step S2, the Ce(NO3)3·6H2O solution is 0.01 mol / L, the hexamethylenetetramine solution is 0.01 mol / L, and the Ce(NO3)3·6H2O solution and the hexamethylenetetramine solution are mixed in a volume ratio of 1:2.

[0017] Further, based on the preferred scheme of step S2, after the Ce(NO3)3·6H2O solution and the hexamethylenetetramine solution are mixed, polypyrrole nanoparticles are added in a solid-liquid ratio of 10:1.5 mg / mL.

[0018] The PPy@CeO2NPs nanoparticles described above or the PPy@CeO2NPs nanoparticles prepared by the preparation method described above are used in the preparation of photothermal conversion agents and CDT reagents.

[0019] The PPy@CeO2NPs nanoparticles described above, in which CeO2nanoparticles are loaded on the surface of polypyrrole nanoparticles to obtain PPy@CeO2NPs nanoparticles, have a significantly improved absorbance in the near-infrared waveband compared with CeO2NPs, and have good absorbance in the NIR I region, and can be used in the preparation of photothermal conversion agents, providing more choices for photothermal therapy.

[0020] Through in vitro anti-tumor activity tests, PPy@CeO2NPs nanoparticles can effectively kill Hela cells, indicating that PPy@CeO2NPs can be used in the preparation of photothermal conversion agents and CDT reagents, providing a new choice for PTT-CDT combined therapy. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 a is the SEM image of PPy NPs, Figure 1 b is the SEM image of PPy@CeO2 nanocomposites, Figure 1 c- Figure 1 d is the EDS spectrum of PPy NPs, Figure 1 e is the distribution map of C element in the EDS spectrum of PPy@CeO2 NPs, Figure 1 f is the distribution map of N element in the EDS spectrum of PPy@CeO2 NPs, Figure 1 g is the distribution map of Ce element in the EDS spectrum of PPy@CeO2 NPs.

[0022] Figure 2 a is the XRD spectrum of PPy@CeO2 NPs, Figure 2 b is the FTIR spectrum of PPy@CeO2 NPs, Figure 2 c is the UV-vis spectrum of PPy NPs, CeO2 NPs, PPy@CeO2 NPs.

[0023] Figure 3 a is the temperature rising curve of PPy@CeO2 NPs solution with different concentrations under 808 nm laser irradiation, Figure 3 b is the thermal imaging map of PPy@CeO2 NPs solution with different concentrations under 808 nm laser irradiation; Figure 3 c is the temperature rising curve of PPy@CeO2 NPs solution (100 μg / mL) under different power (0.5 W / cm 2 , 0.75 W / cm 2 、 1.0 W / cm 2 ) 808 nm laser irradiation; Figure 3 d is the temperature change map of PPy@CeO2 NPs solution (100 μg / mL) under four on / off cycles of 808 nm laser (1.0 W / cm 2 ) irradiation.

[0024] Figure 4 is the survival rate of HeLa cells treated by PPy@CeO2 NPs with different concentrations under the irradiation of 808 nm laser (1.0 W / cm 2 , 10 min) or not.

[0025] Figure 5 a, Figure 5 b are the DCF fluorescence imaging maps of HeLa cells treated by pbs buffer and PPy@CeO2 NPs solution respectively, Figure 5 c, Figure 5d are the DCF fluorescence imaging figures of HeLa cells treated by pbs buffer, PPy@CeO2 NPs solution under the irradiation of 808 nm laser, respectively.

[0026] Figure 6 a、 Figure 6 b are the Calcein-AM fluorescence imaging figures of HeLa cells treated by pbs buffer without and with the irradiation of 808 nm laser, respectively, Figure 6 c、 Figure 6 d are the Calcein-AM fluorescence imaging figures of HeLa cells treated by PPy@CeO2 NPs solution without and with the irradiation of 808 nm laser, respectively, Figure 6 e、 Figure 6 f are the PI fluorescence imaging figures of HeLa cells treated by pbs buffer without and with the irradiation of 808 nm laser, respectively, Figure 6 g、 Figure 6 h are the PI fluorescence imaging figures of HeLa cells treated by PPy@CeO2 NPs solution without and with the irradiation of 808 nm laser, respectively, Figure 6 i、 Figure 6 j are the Merge fluorescence imaging figures of HeLa cells treated by pbs buffer without and with the irradiation of 808 nm laser, respectively, Figure 6 k、 Figure 1 l are the Merge fluorescence imaging figures of HeLa cells treated by PPy@CeO2 NPs solution without and with the irradiation of 808 nm laser, respectively. DETAILED DESCRIPTION

[0027] The present application is further described in conjunction with the specific embodiments. However, the scope of the present application is not limited to the following embodiments.

[0028] Example 1 Preparation of PPy@CeO2 NPs nanoparticles

[0029] S1. Preparation of PPy NPs: 0.156 g of polyvinyl alcohol was mixed with 13 mL of deionized water, stirred at 80℃ for 1 h to fully dissolve, and after cooling to room temperature, 0.7345 g of FeCl3 was added, and stirred at room temperature for 1 h. After completion of stirring, 135.8 μL of pyrrole was added, and then the mixture after adding pyrrole was transferred to an ice bath, and reacted for 4 h. After completion of the reaction, centrifugal purification was performed, and the precipitate was collected to obtain polypyrrole nanoparticles.

[0030] S2. Preparation of PPy@CeO2NPs: 0.5 mL of 0.1 mol / L Ce(NO3)3·6H2O solution and 1 mL of 0.1 mol / L hexamethylenetetramine solution (HMT) were mixed, 10 mg of polypyrrole nanoparticles were added, 10 mL of deionized water and 10 mL of anhydrous ethanol were added, and the mixture was reacted at 60°C for 2 h. The obtained mixed solution was washed and centrifuged to obtain PPy@CeO2NPs nanoparticles.

[0031] Example 2 Preparation of PPy@CeO2NPs nanoparticles

[0032] S1. Preparation of PPy NPs: 0.156 g of polyvinyl alcohol was mixed with 15 mL of deionized water and stirred at 80°C for 0.9 h until completely dissolved. After cooling to room temperature, 1.0926 g of FeCl3 was added and stirred at room temperature for 1 h. After stirring was completed, 241.9 μL of pyrrole was added, and then the mixture after adding pyrrole was transferred to an ice bath and reacted for 4 h. After the reaction was completed, the precipitate was collected by centrifugal purification to obtain polypyrrole nanoparticles.

[0033] S2. Preparation of PPy@CeO2NPs: 0.5 mL of 0.1 mol / L Ce(NO3)3·6H2O solution and 1 mL of 0.1 mol / L hexamethylenetetramine solution (HMT) were mixed, 10 mg of polypyrrole nanoparticles were added, 10 mL of deionized water and 10 mL of anhydrous ethanol were added, and the mixture was reacted at 60°C for 2 h. The obtained mixed solution was washed and centrifuged to obtain PPy@CeO2NPs nanoparticles.

[0034] Example 3 Material characterization

[0035] The following tests of Examples 3-5 were carried out using the PPy@CeO2NPs nanoparticles of Example 1. The morphology of PPy NPs and PPy@CeO2NPs was characterized by SEM tests. From Figure 1 It was observed from a that PPy NPs were spherical in shape and uniform in size, about 100-200 nm; Figure 1 c- Figure 1 d is the EDS spectrum of PPy NPs. From the spectrum, it can be found that PPy NPs contain C and N elements. Figure 1 b shows that the surface of PPy NPs is coated with CeO2NPs, and the overall particle size of PPy@CeO2NPs does not change much compared with pure PPy NPs; Figure 1 e、 Figure 1 f shows that PPy@CeO2NPs contain C and N elements; in the EDS spectrum of PPy@CeO2NPs Figure 2In g, the presence of Ce element is detected, and it is uniformly distributed.

[0036] Figure 2 a is the XRD pattern of PPy@CeO2NPs, the four diffraction peaks of PPy@CeO2NPs at 28.5°, 33.0°, 47.5°, 56.3° respectively correspond to the (111), (200), (220) and (311) crystal faces of CeO2NPs (PDF NO. 43-1002). According to the literature, the diffraction peak at 18° is the characteristic peak of PPy NPs. It is proved that PPy@CeO2NPs is successfully synthesized. Further analysis of the chemical bonds of PPy@CeO2NPs by FTIR spectrum, as shown in Figure 2 b. In PPy@CeO2NPs, the wide band at 3432 cm -1 is the N-H vibration peak, the vibration peaks near 1558 cm -1 and 1481 cm -1 represent the anti-symmetric and symmetric stretching modes of polypyrrole, and the vibration peaks of C-N and C-H are respectively at 1315 cm -1 and 1049 cm -1 . The absorption peak at 917 cm -1 is the Ce-O stretching vibration absorption peak, which further proves that PPy NPs and PPy@CeO2NPs are successfully synthesized.

[0037] This example further analyzes the UV-vis spectrum of PPy NPs, CeO2NPs and PPy@CeO2NPs, as shown in Figure 3 c, the absorbance of CeO2NPs in the near-infrared region is low, in contrast, PPy NPs have good absorbance in the near-infrared region, and the overall absorbance of PPy@CeO2NPs in the near-infrared region is greatly improved after compounding, which is beneficial to the progress of photothermal therapy.

[0038] Example 4 Photothermal performance test of PPy@CeO2NPs

[0039] This test uses an 808 nm laser as a laser source to study the photothermal performance of PPy@CeO2NPs.

[0040] As shown in Figure 3 a, it is the solution of PPy@CeO2NPs with different concentrations (0, 50, 75, 100 μg / mL) under 808 nm laser (1.0 W / cm 2The temperature rising curve under irradiation. It can be observed from the figure that when the concentration of PPy@CeO2NPs is 0 μg / mL, the temperature of the solution does not change much, indicating that the 808 nm laser alone has no significant effect on the temperature of the aqueous solution without PPy@CeO2NPs. With the increase of the concentration of PPy@CeO2NPs, the temperature of the PPy@CeO2NPs solution also rises, and the temperature change of the PPy@CeO2NPs solution shows a dependence on the concentration of the solution. When the concentration of PPy@CeO2NPs is 100 μg / mL, the temperature reaches as high as 58 ℃, reaching the temperature of photothermal ablation. Figure 3 b is Figure 3 a corresponding thermal imaging diagram, the conclusion drawn is consistent with Figure 3 a.

[0041] The relationship between the temperature of PPy@CeO2NPs solution and the laser power density is explored as follows. Figure 3 c, the change of the temperature of PPy@CeO2NPs solution is proportional to the increase of the laser power density. With the increase of the laser power density, the temperature of PPy@CeO2NPs solution also rises. When the laser power density is 1.0 W / cm 2 , the temperature reaches as high as 58 ℃.

[0042] Figure 4 d is the temperature change diagram of PPy@CeO2NPs solution under four on / off cycles of 808 nm laser (1.0 W / cm 2 ) irradiation. It can be observed that the temperature of PPy@CeO2NPs remains stable under four on / off cycles, and the overall temperature under four cycles does not change much, indicating that PPy@CeO2NPs has good photothermal stability.

[0043] Example 5 In vitro anti-tumor activity of PPy@CeO2NPs

[0044] The MTT method was used to test the effect of PPy@CeO2NPs on the survival rate of Hela cells. The standard 3-(4,5-dimethylthiazol-2)-2,5-diphenyltetrazolium bromide (MTT) test was used to evaluate the in vitro cytotoxicity of the composite nanomaterials and the combined effect of PTT and CDT. First, Hela cells were seeded into a 96-well plate and incubated at 37°C for 12 h. Then, different concentrations of composite nanomaterial solution (0, 50, 75, and 100 μg / ml) were added and incubated for 24 h. After incubation, the experimental group was irradiated with an 808 nm laser at a certain power for a certain time, and the control group was not irradiated, and was incubated for another 24 h. Subsequently, the old culture medium was removed and washed twice with PBS, and 20 μL of MTT and 100 μL of culture medium were added. After incubation for 4 h, the MTT was removed and 100 μL of dimethyl sulfoxide (DMSO) was added for 15 min. Finally, the absorbance at 540 nm and 630 nm was measured using a microplate reader.

[0045] As shown in Figure 5 , it was observed from the graph that the concentration of PPy@CeO2NPs was inversely proportional to the survival rate of Hela cells, and the higher the concentration of PPy@CeO2NPs, the lower the cell survival rate. When PPy@CeO2NPs were used alone to co-incubate with Hela cells (left column), PPy@CeO2NPs caused some damage to the cells, but when laser irradiation was used in combination with PPy@CeO2NPs (right column), the combined treatment was significantly better than PPy@CeO2NPs alone. This result shows that laser irradiation successfully excited PPy@CeO2NPs to convert light energy into heat energy, improving the catalytic reaction of CeO2 and promoting the CDT process. When the concentration of PPy@CeO2NPs was 100 μg / mL, the survival rate of tumor cells was 24.3% under the irradiation of a 1.0 W / cm 2 laser. The above results demonstrate that PPy@CeO2NPs achieved effective killing of tumor cells.

[0046] The 2',7'-dichlorofluorescin diacetate (DCFH-DA) was used to detect the generation of ROS (·OH) in cells. Under the oxidation of ROS, non-fluorescent DCFH can be converted to green-fluorescent DCF. The ability of drugs to generate ROS in cells was detected by detecting the fluorescence of DCF. This work used an 808 nm laser to investigate the generation of ·OH in Hela cells with PPy@CeO2NPs, as shown in Figure 5 a, the PBS group without the addition of PPy@CeO2NPs did not produce green fluorescence, as shown in Figure 5As shown in b, HeLa cells treated with only PPy@CeO2NPs exhibited a small amount of green fluorescence, indicating that PPy@CeO2NPs have the ability to generate ROS. This is because CeO2 reacts with endogenous H2O2 in the weakly acidic tumor microenvironment to generate ·OH, which causes DCFH-DA to undergo a series of changes and ultimately be oxidized by ·OH to fluorescent DCF. Additionally, as... Figure 5 As shown in Figure c, no fluorescence signal was generated in the PBS+NIR group, indicating that laser irradiation alone cannot stimulate the production of intracellular ROS. However, combined with... Figure 6 As shown in Figure d, the PPy@CeO2NPs+NIR group subjected to laser irradiation produced more ROS, fully demonstrating that laser irradiation excites the photothermal properties of PPy@CeO2NPs, accelerating the Fenton-like reaction and generating more ·OH. Therefore, PPy@CeO2NPs has a good ability to generate ROS and can be used for PTT-CDT combination therapy.

[0047] This embodiment further uses Calcein-AM / PI co-staining to further evaluate the effect of PPy@CeO2NPs on HeLa cell survival, such as... Figure 6 As shown in a, 6b, 6i, and 6j, the PBS and PBS+NIR groups produced a large amount of green fluorescence, indicating that single laser irradiation does not affect cell viability. Figure 6 As shown in g, 6c, 6k, and 6l, HeLa cells treated with only PPy@CeO2NPs produced a small amount of red fluorescence, but still exhibited significant green fluorescence, indicating that PPy@CeO2NPs alone have some cell-killing ability, but the effect is not therapeutic. ​ As shown in d and 6h, after co-incubation of PPy@CeO2NPs with HeLa cells and subsequent laser irradiation, a large amount of red fluorescence was produced within the cells, while green fluorescence was almost completely eliminated, indicating that the 808 nm laser significantly enhanced the therapeutic effect of CDT. This result is consistent with the above MTT experiment results, further demonstrating that PPy@CeO2NPs can achieve PTT-CDT combined therapy.

[0048] The antitumor properties of PPy@CeO2NPs were tested for use in PTT-CDT combination therapy. The conclusions are as follows:

[0049] (1) SEM characterization of PPy@CeO2NPs showed that PPy was spherical and CeO2NPs were loaded on the surface of PPy to form PPy@CeO2NPs; EDS spectrum showed that C, N, Ce and O elements were uniformly distributed.

[0050] (2) The characterization methods such as XRD and FTIR were used to prove the successful synthesis of PPy@CeO2NPs; the diffraction peaks of CeO2NPs and PPy NPs were successfully tested in the XRD pattern of PPy@CeO2NPs, and the vibration peaks of N-H, C-N, C-H, etc. were tested in FTIR, which were the infrared characteristic peaks of PPy, and the Ce-O vibration peak was the infrared characteristic peak of CeO2NPs. The above data showed that PPy@CeO2NPs was successfully synthesized.

[0051] (3) The photothermal performance of PPy@CeO2NPs was tested by a thermal imager. The results showed that the temperature of PPy@CeO2NPs solution reached 58 ℃ when the concentration was 100 μg / mL and the laser power density was 1.0 W / cm 2 After four cycles of 10 min On and 5 min Off laser irradiation, the temperature of PPy@CeO2NPs solution remained basically unchanged, and the material had good photothermal stability.

[0052] (4) PPy@CeO2NPs was co-incubated with Hela cells, and the in vitro anti-tumor activity of PPy@CeO2NPs was analyzed by testing the survival rate of Hela cells under different concentrations and conditions, the amount of ROS produced in cells, and the staining of live / dead cells. Under the irradiation of 808 nm laser (1.0 W / cm 2 ), when the concentration of PPy@CeO2NPs was 100 μg / mL, the cell survival rate was 24.3%. The conclusion obtained from the live / dead cell staining picture of PPy@CeO2NPs was consistent with the MTT test results, which showed that PPy@CeO2NPs could be used for PTT-CDT combined therapy.

Claims

1. A method for preparing PPy@CeO2 NPs nanoparticles, characterized in that: CeO2 nanoparticles are loaded on the surface of polypyrrole nanoparticles; and the method specifically comprises the following steps: S1. synthesizing polypyrrole nanoparticles by chemical oxidation polymerization; the specific process of the step S1 is as follows: polyvinyl alcohol and water are mixed according to a mass ratio of 1: 80-100, high-temperature stirring is performed until the polyvinyl alcohol is dissolved, FeCl3 is added after the mixture is cooled, the molar ratio of polyvinyl alcohol to FeCl3 is 1: 0.9-2, pyrrole is added after stirring is completed, the molar ratio of polyvinyl alcohol to pyrrole is 1-2: 1, the mixture after the pyrrole is added is transferred to an ice bath, reaction is performed for 3.5-5 hours, and the precipitate is collected after centrifugation to obtain polypyrrole nanoparticles; and the specific process of the step S2 is as follows: 0.05-0.2 mol / L of a Ce (NO3) 3·6H2O solution and 0.05-0.2 mol / L of a hexamethylenetetramine solution are mixed according to a volume ratio of 1: 0.5-8, 10: 1-3 mg / mL of polypyrrole nanoparticles are added, 4-10 times the volume of water and 4-10 times the volume of anhydrous ethanol are added, and reaction is performed at 55-70℃ for 1.5-3 hours to obtain PPy@CeO2 NPs nanoparticles. 2.The method according to claim 1, characterized in that: in the step S2, the mixed solution is washed with water and anhydrous ethanol for 2-3 times after reaction is completed. 3.The method according to claim 1, characterized in that: the mass ratio of polyvinyl alcohol to water is 1: 83.33, and the molar ratio of polyvinyl alcohol to FeCl3 is 1: 1.

28. 4.The method according to claim 1, characterized in that: in the step S2, the Ce (NO3) 3·6H2O solution is 0.1 mol / L, the hexamethylenetetramine solution is 0.1 mol / L, and the Ce (NO3) 3·6H2O solution and the hexamethylenetetramine solution are mixed according to a volume ratio of 1:

2. S2. The alkaline environment provided by hexamethylenetetramine makes Ce 3+ oxidized into CeO2 nanoparticles, mixed with polypyrrole nanoparticles, coated on the surface of polypyrrole nanoparticles, and PPy@CeO2 NPs nanoparticles are obtained; 5.The method according to claim 4, characterized in that: in the step S2, 10: 1.5 mg / mL of polypyrrole nanoparticles are added to the mixture of the Ce (NO3) 3·6H2O solution and the hexamethylenetetramine solution after the mixture is prepared. 6.The application of PPy@CeO2 NPs nanoparticles prepared by the method according to any one of claims 1-5 in preparing photothermal conversion agents and photodynamic therapy reagents. ​ ​ ​ ​ ​ ​ ​ ​ ​

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