Starch-based composite photocatalytic whitening hydrogel as well as preparation method and application thereof

Abstract

The invention discloses starch-based composite photocatalytic whitening hydrogel as well as a preparation method and application thereof. The preparation method comprises the following steps: compounding a cobalt-modified zirconium-based metal organic framework with oxidized starch, and then preparing the starch-based composite photocatalytic whitening hydrogel through a starch retrogradation method. The PCN-224 (Co) (at) OS composite photocatalytic whitening hydrogel with excellent photocatalytic performance and good biocompatibility is prepared through an in-situ growth method, the hydrogel has adhesion, moisture retention and stability, a more complete pore structure of a metal organic framework material is reserved, and the photocatalytic performance of the hydrogel is brought into play. Compared with traditional hydrogen peroxide blue-light whitening with poor safety, the high-efficiency, lossless and in-situ whitening of teeth is expected to be realized, and a new thought is provided for tooth whitening and development of biomedical green materials, and long-wavelength red light with high biosafety is matched to generate active oxygen to oxidize pigment molecules on the surfaces of the teeth.

Description

Technical Field

[0001] The present invention relates to the field of photocatalysis technology, and in particular to a starch-based composite photocatalytic whitening hydrogel and a preparation method and application thereof. Background Art

[0002] Currently, tooth whitening methods are divided into physical methods and chemical methods. Physical whitening methods mainly include brushing, scaling, sandblasting, etc. Although these methods can remove some pigments and dirt on the surface of the teeth, they are easy to wear the enamel and cause tooth damage, and the whitening effect is not significant, which cannot meet the patient's demand for significantly whitened teeth (Epple Matthias, Meyer Frederic, Enax Joachim. Dentistry Journal, 2019, 7(3):79). Chemical whitening is a tooth whitening method based on chemical reactions, including office tooth whitening technology, home tooth whitening materials and over-the-counter (OTC) whitening products. The principle is to use peroxide (hydrogen peroxide or carbamide peroxide) to generate oxygen free radicals during the decomposition process, which penetrate into the enamel and dentin to destroy the conjugated double bonds of organic pigment molecules, degrade them into small molecular compounds through oxidation reactions, and oxidatively bleach the enamel (Takamizawa T, Aoki R, Saegusa M, et al. Journal of Esthetic and Restorative Dentistry, 2023, 35(06): 821-833). This type of method is widely used because of its significant whitening effect.

[0003] However, the problems with traditional chemical whitening methods should not be underestimated. Peroxides are highly corrosive and oxidizing, and frequent use can lead to problems such as tooth sensitivity, enamel demineralization, and increased plaque adhesion on the crown surface (Nogueira MS, Brugnera Junior A, Bagnato VS, et al. Photomedicine and Laser Surgery, 2021, 39(6): 395-402). At the energy-assisted technology level, the blue light used to accelerate the bleaching effect of peroxide is short-wavelength light. Many studies have found that blue light can damage retinal cells (Zhang ZY, Zhang ZX, Shen M, et al. IEEE Transactions on Electron devices, 2023, 70(10): 5146-5150), inhibit the secretion of melatonin, and affect sleep quality and biological clock (Katsuhiro Mitsui, Keigo Saeki, Mingyue Sun, et al. Journal of Clinical Sleep Medicine, 2024, 20(01)). In addition, the ultraviolet rays in blue light can cause irreversible damage to immune cells (Miao XX, Yu F, Liu K. Bioactive Materials, 2022, 7: 181-191). The interweaving of the above problems exposes the essential defects of traditional technology. How to achieve fast and significant teeth whitening effects without damaging teeth or affecting health has become a difficult problem in the industry.

[0004] In recent years, many researchers have been exploring safer, more efficient and longer-lasting whitening methods and materials. These studies mainly focus on developing new whitening agents, finding natural extracts and applying various catalytic technologies. Researchers have found that papain, ficin and bromelain have the ability to whiten teeth and the whitening gel of the three proteases does not affect cell viability (Ribeiro JS, Barboza AD, Cuevas-Suárez CE, et al. Scientific Reports, 2020, 10 (01)). Turki et al. found that walnut peel extract has a significantly better whitening effect on tooth enamel than the physical polishing material - pumice powder. The use of tooth care products with added walnut peel extract has application potential in tooth whitening (Turki OH, Jafar ZJ. International Journal of Biomaterials, 2023.). However, the effect of enzyme whitening agents and natural extracts in tooth whitening treatment is not significant enough, the whitening time is long, and they are only suitable for daily care or patients with low whitening needs. Wang et al. proposed a method for whitening teeth using a piezoelectric catalytic effect. This method uses BTO nanoparticles as an abrasive and utilizes the vibrations generated by the toothbrush during brushing to stimulate the piezoelectric response of the piezoelectric material to achieve a significant whitening effect (Wang Y, Wen XR, Jia YM, et al. Nature Communications, 2020, 11(01)). However, in the oral environment, the limited source and intensity of the mechanical stress (such as ultrasound and vibration) required for piezoelectric catalysis restricts the catalytic efficiency.

[0005] As an emerging green technology, photocatalytic technology can use light energy to drive chemical reactions and has shown unique advantages in degrading pollutants (Ye ZJ, Zheng R, Li SJ, et al. Nanomaterials, 2024, 14 (20)). Introducing photocatalytic technology into dental treatment is an emerging and promising research direction, aiming to achieve the effect of whitening teeth by degrading pigment molecules on the surface of teeth through photocatalytic oxidation reactions. At present, studies have explored the potential of photocatalytic technology for tooth whitening, mainly focusing on the application of titanium dioxide in dentistry (Zhang F, Wu CX, Zhou ZY, et al. ACS Biomaterials Science & Engineering, 2018, 4: 3072-3077). However, this method still faces challenges such as low catalytic efficiency and damage to the body caused by the excitation light source when used for tooth staining treatment. In addition, powder-type photocatalysts have limitations in the application of photocatalytic teeth whitening, such as poor coverage uniformity, limited photocatalytic efficiency, inconvenient operation, and difficulty in adapting to light source equipment, resulting in poor results and user experience. Therefore, we should conduct in-depth research on photocatalytic technology, explore photocatalytic materials with excellent performance and can be excited by light sources with high safety, and develop composite hydrogel systems to take into account both photocatalytic activity and clinical applicability, so as to provide new ideas for the establishment of efficient, non-destructive, in situ teeth whitening methods. Summary of the Invention

[0006] To overcome the shortcomings and deficiencies of the aforementioned prior art, the primary objective of the present invention is to provide a starch-based composite photocatalytic whitening hydrogel, prepared by a starch retrogradation method using a cobalt-modified zirconium-based metal-organic framework (MOF) and oxidized starch. This starch-based composite photocatalytic whitening hydrogel exhibits excellent photocatalytic activity. Combined with biosafe, long-wavelength red light, it generates reactive oxygen species that oxidize tooth surface pigment molecules, resulting in a significant whitening effect. This is expected to achieve efficient, non-destructive, in-situ tooth whitening.

[0007] Another object of the present invention is to provide a starch-based composite photocatalytic whitening hydrogel prepared by the above method.

[0008] Another object of the present invention is to provide the use of the above-mentioned starch-based composite photocatalytic whitening hydrogel or the starch-based composite photocatalytic whitening hydrogel obtained by the method in teeth whitening.

[0009] The purpose of the present invention is achieved through the following solutions:

[0010] A starch-based composite photocatalytic whitening hydrogel is prepared by a starch precipitation method after a cobalt-modified zirconium-based metal-organic framework PCN-224 (Co) is composited with oxidized starch; the content of the cobalt-modified zirconium-based metal-organic framework PCN-224 (Co) is 2.47% to 6.87%; and the water content of the hydrogel is 50-80wt%.

[0011] A method for preparing a starch-based composite photocatalytic whitening hydrogel comprises the following steps:

[0012] (1) Zirconium chloride (ZrCl4) powder was dissolved in N,N-dimethylformamide (DMF) aqueous solution, and then oxidized starch (OS) was added to the above solution and stirred for reaction. After the reaction was completed, the unreacted ZrCl4 was removed by washing, and the oxidized starch-zirconium ion complex (OS-Zr) was obtained after drying. 4+ );

[0013] (2) Oxidized starch-zirconium ion complex, cobalt-tetrakis(4-carboxyphenyl)porphyrin, and benzoic acid were dissolved in a mixed solution of N,N-dimethylformamide and glacial acetic acid, and a solvothermal reaction was carried out in a hydrothermal reactor. After cooling, centrifugation, washing, and drying, a composite material of cobalt-modified zirconium-based metal-organic framework and oxidized starch (PCN-224(Co)@OS) was obtained;

[0014] (3) The composite material powder of the cobalt-modified zirconium-based metal-organic framework and oxidized starch is mixed evenly with water, then heated for gelatinization, and then transferred to a mold for cooling and molding to obtain a starch-based composite photocatalytic whitening hydrogel.

[0015] The carboxyl content of the oxidized starch in step (1) is 1.23% to 2.76%, and the molecular weight of the oxidized starch is 1.53×10 4 ~7.86×10 5 g / mol;

[0016] The mass ratio of ZrCl4 to oxidized starch in step (1) is 1:2-6;

[0017] The volume ratio of DMF to water in the N,N-dimethylformamide aqueous solution described in step (1) is 10-5:1, preferably 9:1; the amount of the N,N-dimethylformamide aqueous solution described in step (1) satisfies: 10-30 mL of N,N-dimethylformamide aqueous solution is used for every 1 g of zirconium chloride.

[0018] The stirring reaction in step (1) refers to stirring the reaction at room temperature for 6-12 hours, wherein room temperature refers to 10-35° C.; preferably, stirring the reaction at 25° C. for 6 hours. The washing in step (1) is preferably washing with anhydrous ethanol and water alternately.

[0019] The mass ratio of the oxidized starch-zirconium ion complex, cobalt-tetrakis(4-carboxyphenyl)porphyrin and benzoic acid described in step (2) is 10:1 to 4:30;

[0020] The volume ratio of N,N-dimethylformamide to glacial acetic acid in the mixed solution of N,N-dimethylformamide and glacial acetic acid described in step (2) is 12-8:1, preferably 10:1; the amount of the mixed solution of N,N-dimethylformamide and glacial acetic acid described in step (2) is such that 10-15 mL of the mixed solution of N,N-dimethylformamide and glacial acetic acid is used for every 1 g of the oxidized starch-zirconium ion complex.

[0021] The solvent thermal reaction in step (2) refers to a reaction at 120-150° C. for 20-24 hours;

[0022] After the composite material powder of the cobalt-modified zirconium-based metal-organic framework and oxidized starch described in step (3) is uniformly mixed with water, the water content thereof is 50-80 wt %, preferably 50 wt %;

[0023] The heating gelatinization in step (3) is preferably heated to 75° C. for gelatinization for 0.5-2.0 h, preferably heated to 75° C. for gelatinization for 1 h.

[0024] The content of PCN-224(Co) in the starch-based composite photocatalytic whitening hydrogel described in step (3) is 2.47% to 6.87%, wherein PCN-224(Co) refers to a cobalt-modified zirconium-based metal-organic framework.

[0025] Application of the above-mentioned starch-based composite photocatalytic whitening hydrogel in teeth whitening.

[0026] When the starch-based composite photocatalytic whitening hydrogel is used for teeth whitening, red light is used to generate active oxygen to oxidize pigment molecules on the surface of the teeth.

[0027] The beneficial effects of the present invention are:

[0028] (1) The oxidized starch hydrogel with in situ growth of PCN-224(Co) prepared by the present invention has adhesion, moisture retention and stability, and is suitable for the application scenario of photocatalytic clinic teeth whitening, and can achieve the effect of in situ teeth whitening.

[0029] (2) The present invention provides a starch-based composite photocatalytic whitening hydrogel that exhibits excellent photocatalytic activity. The first-order rate constants k for photocatalytic degradation of indigo carmine dye and rhodamine B dye can reach 3.79×10 -2 min -1 and 1.64×10 -2 min -1 , which is higher than some of the reported catalyst materials for teeth whitening.

[0030] (3) The present invention provides a starch-based composite photocatalytic whitening hydrogel that, when combined with biosafe, long-wavelength red light, exhibits excellent teeth whitening effects. Stained teeth can be visually significantly improved within 1 hour without causing significant damage to tooth enamel. Compared with conventional hydrogen peroxide whitening, which has poor safety, this method achieves highly efficient, non-destructive tooth whitening, providing new insights into the development of green materials for teeth whitening and biomedicine. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0032] Figure 1 3 is a graph showing the UV-visible absorption spectra of TCPP and CoTCPP prepared according to an embodiment of the present invention.

[0033] Figure 2 1 is an infrared spectrum of TCPP and CoTCPP prepared according to an embodiment of the present invention.

[0034] Figure 3 : is the molecular structure of CoTCPP prepared according to an embodiment of the present invention.

[0035] Figure 4 OS-Zr prepared according to Examples 1-3 of the present invention 4+ Infrared spectrum of .

[0036] Figure 5 3 are infrared spectra of PCN-224(Co)@OS, PCN-224(Co) and OS prepared according to Examples 1-3 of the present invention.

[0037] Figure 6 3 are backscattered electron / secondary electron dual-mode images of PCN-224(Co)@OS hydrogels prepared according to Examples 1-3 of the present invention, wherein A represents Example 1, B represents Example 2, and C represents Example 3.

[0038] Figure 7 is the dynamic residual rate of PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention on the enamel surface.

[0039] Figure 8 is the moisture retention rate of the PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention.

[0040] Figure 93 is a thermogravimetric analysis graph of PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention.

[0041] Figure 10 is the degradation rate of PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention.

[0042] Figure 11 The degradation rate curve (A) and degradation kinetic curve (B) of the PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention for IC, and the degradation rate curve (C) and degradation kinetic curve (D) for RhB.

[0043] Figure 12 3 is the electron paramagnetic resonance spectrum of hydroxyl radicals and superoxide radicals generated by photocatalysis of PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention.

[0044] Figure 13 Cytotoxicity of the PCN-224(Co)@OS hydrogels prepared according to Examples 1-3 of the present invention: cell viability of human gingival epithelial cells (A) and human gingival fibroblasts (B).

[0045] Figure 14 This is a diagram showing the teeth whitening effect of the PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention combined with red light irradiation.

[0046] Figure 15 The ΔE(A) and ΔWI of teeth after treatment with PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention and 30% H2O2 for different time periods D (B).

[0047] Figure 16 The Vickers hardness of the teeth before and after the PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention and 30% H2O2 whitening treatment.

[0048] Figure 17 2 is the X-ray diffraction pattern of the PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention and the teeth before and after 30% H2O2 whitening treatment.

[0049] Figure 18 2. Scanning electron micrographs of PCN-224(Co)@OS hydrogel prepared according to Examples 1-3 of the present invention and teeth before and after 30% H2O2 whitening treatment. DETAILED DESCRIPTION

[0050] The present invention will now be further described in detail with reference to the accompanying drawings and embodiments. However, it should be understood that the protection scope of the present invention is not limited to the specific embodiments.

[0051] Unless otherwise specified, all reagents used in the examples can be purchased from the market. The cells used in the experiments were human gingival fibroblasts (HGF-1) and human gingival epithelial cells (HGE), both purchased from China Center for Type Culture Collection (CCTCC).

[0052] The test method for the adhesion performance of the starch-based composite photocatalytic whitening hydrogel in the embodiment refers to the method of "Li ZK, Yu C, Kumar H, et al. The Effect of Crosslinking Degree of Hydrogels on Hydrogel Adhesion [J]. Gels, 2022, 8 (10): 682." and is slightly modified. The specific steps are as follows: Collect ex vivo teeth that meet the dental health standards established by the World Health Organization, stick them on a glass slide, and record the initial weight W0. The PCN-224 (Co) @ OS hydrogel prepared in Examples 1 to 3 is adhered to the exposed enamel surface and ensures that the contact area of ​​each group of experimental hydrogels is consistent. The initial weight is recorded as W1. Then, it is placed vertically in a 5L beaker containing artificial saliva (ISO / TR10271) at 37°C, and a magnetic stirring bar is rotated at a speed of 1000 rpm to simulate the oral environment. Take it out every 1 hour and gently absorb the surface liquid with filter paper, and then record the weight W2. The number of tests is 3. The calculation formula of the residual rate is as follows:

[0053]

[0054] The test method for the moisture retention of the starch-based composite photocatalytic whitening hydrogel in the examples was based on the method in the literature "Cai CC, Wen CY, Zhao WQ, et al. Environment-Resistant Organohydrogel-Based Sensor Enables Highly Sensitive Strain, Temperature, and Humidity Responses[J]. ACS Applied Materials & Interfaces, 2022, 14, 20, 23692-23700." with slight modifications. The specific steps are as follows: Accurately weigh an appropriate amount of PCN-224(Co)@OS hydrogel prepared in Examples 1 to 3, with the mass recorded as W1, and evenly spread it on a glass slide. The slide was placed in a constant temperature and humidity chamber (25°C, 43% humidity) and continuously irradiated with a red light source (650 nm, 50 W). The mass of the hydrogel (W2) was measured at 0, 0.5, 1.0, 1.5, and 2.0 h, and the residual moisture ratio was calculated. The test was repeated three times. The formula for calculating the moisturizing rate is as follows:

[0055]

[0056] The test method for the degradation rate of the starch-based composite photocatalytic whitening hydrogel in the embodiment refers to the method of "Gong Y, Wang P, Cao R, et al. Exudate Absorbing and Antimicrobial Hydrogel Integratedwith Multifunctional Curcumin-Loaded Magnesium Polyphenol Network for Facilitating Burn Wound Healing [J]. ACS Nano 2023, 17, 22, 22355-22370." and is slightly modified. The specific steps are as follows: The PCN-224 (Co) @ OS hydrogel prepared in Examples 1 to 3 is freeze-dried and the mass is recorded as W0. The dried hydrogel sample is placed in 37 ° C artificial saliva and soaked for different time periods, freeze-dried and weighed, and the mass is recorded as W t Three parallel experiments were set up for each group of samples. The calculation formula for the degradation rate is as follows:

[0057]

[0058] The test method for the cytotoxicity of the starch-based composite photocatalytic whitening hydrogel in the embodiment refers to the literature "Wang Y, Wang SH, Meng YZ, et al. Pyro-catalysis for tooth whitening via oral temperature fluctuation [J]. Nature Communications, 2022, 13 (1).", specifically: human gingival fibroblasts and human gingival epithelial cells were cultured to the logarithmic phase and inoculated into a 96-well plate at a cell density of 80,000 / cm 2 , adhered to the wall in a cell culture incubator at 37°C for 24 hours. After rinsing the cells with PBS buffer, 1mM, 0.5mM, and 0.25mM of the PCN-224(Co)@OS composite hydrogel solution prepared in Examples 1 to 3 were added respectively (the solvent was DMEM culture medium, pH = 7.4), and placed in an incubator for incubation for 24 hours. After reaching the time point, the cells were rinsed with PBS buffer, and 100μL of DMEM culture medium (Thermo Fisher Scientific) and 10μL of MTS cytotoxicity detection solution (Biyuntian Biotechnology Co., Ltd.) were added to each well. After incubation at 37°C for 1 to 4 hours, the absorbance of each well at 490nm was measured using an enzyme reader. No composite hydrogel solution was added to the control wells, and no cells and composite hydrogel solution were added to the blank wells. The cytotoxicity calculation formula is as follows:

[0059]

[0060] Among them, A s is the absorbance value of the experimental well, A b is the absorbance value of the blank well, A c is the absorbance value of the control well.

[0061] The test method for the photocatalytic performance of the starch-based composite photocatalytic whitening hydrogel in the embodiment refers to the literature "Wang Y, Wen XR, Jia YM, et al. Piezo-catalysis for nondestructive tooth whitening [J]. Nature Communications, 2020, 11 (1): 1328.", specifically: indigo carmine and RhB were selected as target pollutants, 0.1 g of starch-based composite photocatalytic whitening hydrogel was dispersed in 50 mL 5 mg L -1The mixed solution was stirred for 60 minutes in a dark environment to complete dark adsorption to ensure the adsorption-desorption equilibrium between the starch-based composite photocatalytic whitening hydrogel and the indigo carmine or RhB molecules. Then, it was placed in a multi-channel photochemical instrument (setting conditions: 25°C, 50W, 650nm) to induce photodegradation. At predetermined intervals, 3 mL of the suspension was taken for high-speed centrifugation (11000rpm, 8min), and the supernatant was collected and the absorbance was measured using a UV-visible spectrophotometer. A blank control group was set up in the experiment, and the operating steps were the same as above. The photodegradation rate of each starch-based composite photocatalytic whitening hydrogel was calculated as follows:

[0062] Photodegradation rate (P,%) = (1-C / C0) × 100%

[0063] Where C0 (mg / L) and C (mg / L) are the dye concentrations at the initial and illumination time t, respectively.

[0064] In order to further study the photocatalytic reaction kinetics of the composite photocatalytic whitening hydrogel, the pseudo-first-order kinetic model was used to fit the experimental data. The pseudo-first-order kinetic model is expressed as follows:

[0065] -ln(C / C0)=kt

[0066] Where C0 (mg / L) and C (mg / L) are the concentrations of the dye at time t=0 and time t, respectively, and k is the first-order rate constant, representing the slope of the straight line in the first-order reaction kinetic fitting results.

[0067] Cobalt-tetrakis (4-carboxyphenyl) porphyrin (CoTCPP) in the examples can be purchased directly (CAS No.: 108443-61-4), or can be prepared by the following method:

[0068] 0.5 mmol (0.42 g) of 5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin (TCPP-COOMe), 6.5 mmol (1.55 g) of cobalt chloride hexahydrate (CoCl2), and 50 mL of N,N-dimethylformamide (DMF) were added to a 100 mL round-bottom flask, stirred thoroughly, and reacted at 150°C for 6 h. After cooling to room temperature, 75 mL of H2O was added, filtered, and washed (25 mL of H2O each time) to yield a purple-red precipitate. The resulting solid was dissolved in chloroform (CHCl3) and extracted to yield an organic layer. Finally, the organic layer was dried over anhydrous sodium sulfate (Na2SO4) and the solvent removed by rotary evaporation under reduced pressure to yield cobalt tetraphenyl methoxycarbonylporphyrin (CoTPPCOOMe).

[0069] CoTPPCOOMe (0.4 g) was dissolved in a mixed solution of tetrahydrofuran (12.5 mL) and methanol (12.5 mL). 12.5 mL of potassium hydroxide (23.4 mmol) was slowly added to the mixed solution under magnetic stirring, and then reacted at 85°C for 12 h. After cooling to room temperature, the tetrahydrofuran and methanol in the mixed solution were removed by rotary evaporation under reduced pressure, and then 50 mL of H2O was added and heated until the solid was completely dissolved. It was then acidified with 1 M hydrogen chloride (pH ≈ 3), filtered, washed, and dried to obtain CoTCPP.

[0070] The UV-visible absorption spectra and infrared spectra of CoTCPP and porphyrin (TCPP) prepared in this example are shown in Figures 1 and 2. Figure 1 and Figure 2 As shown. Figure 1 As shown, TCPP has four characteristic absorption peaks in the visible light region. 2+ Then it decreases to 1, which is due to the high symmetry of the cobalt porphyrin ring and the close energy levels, which further reduces the Q band absorption peak, proving the successful chelation of Co metal. Figure 2 As shown, CoTCPP at 1007 cm -1 A new peak appears at 964.5cm -1 The absorption peak at disappears, indicating that the NH bond on the porphyrin ring is replaced by a Co-N bond, marking the formation of CoTCPP. Figure 1 and Figure 2 It can be seen that Co 2+ It has been combined with porphyrin to successfully prepare cobalt-tetra(4-carboxyphenyl)porphyrin, whose chemical formula is C 48 H 28 CoN4O8, molecular structure Figure 3 shown.

[0071] Example 1

[0072] (1) According to the zirconium chloride and oxidized starch (carboxyl content of 1.23%, molecular weight of 7.86×10 5 g / mol) in a mass ratio of 1:2, 5g of zirconium chloride (ZrCl4) powder was dissolved in an N,N-dimethylformamide (DMF) aqueous solution (the volume ratio of DMF to water was 9:1) to prepare a ZrCl4DMF aqueous solution with a mass concentration of 0.1g / mL. Subsequently, 10g of oxidized starch was added to the above solution and stirred at 25°C for 6h. After the reaction was completed, it was washed alternately with anhydrous ethanol and deionized water to remove the unreacted ZrCl4, and the oxidized starch-zirconium ion complex (OS1-Zr) was obtained after drying. 4+ );

[0073] (2) The prepared oxidized starch-zirconium ion complex OS1-Zr 4+ Oxidized starch-zirconium ion complex OS1-Zr, cobalt-tetra(4-carboxyphenyl)porphyrin and benzoic acid were weighed in a mass ratio of 10:1:30. 4+ 5g of cobalt-tetrakis(4-carboxyphenyl)porphyrin, 0.5g of cobalt-tetrakis(4-carboxyphenyl)porphyrin, and 15g of benzoic acid were dissolved in 55ml of a mixture of N,N-dimethylformamide and glacial acetic acid (the volume ratio of DMF to glacial acetic acid was 10:1). The mixture was then solvothermally reacted in a hydrothermal reactor at 120°C for 20h. After the reaction, the mixture was cooled, centrifuged, washed, and dried to produce a cobalt-modified zirconium-based metal-organic framework and oxidized starch composite (PCN-224(Co)@OS1).

[0074] (3) Weigh 5 g of PCN-224(Co)@OS1 powder and mix it evenly with 5 ml of deionized water (water content is 50%), then heat it to 75 °C for gelatinization for 1 h, transfer it to a mold and cool it at 4 °C to obtain a PCN-224(Co)@OS1 composite photocatalytic whitening hydrogel with a PCN-224(Co) content of 2.47%.

[0075] The oxidized starch-zirconium ion complex (OS1-Zr 4+ )'s infrared spectrum is shown in Figure 4 Compared with oxidized starch OS, OS1-Zr 4+ At 1632cm -1 The asymmetric carboxyl stretching vibration peak at 664 cm -1 A new peak appears, corresponding to the Zr-O bond. 4+ OS1-Zr was successfully prepared by coordinating Zr-O bonds with the carboxyl groups in oxidized starch. 4 + .

[0076] The infrared spectrum of the composite material of cobalt-modified zirconium-based metal-organic framework and oxidized starch (PCN-224(Co)@OS1) is shown in Figure 2. Figure 5 shown. Figure 5 PCN-224(Co) was prepared by the following method: 40 mg of zirconium chloride, 40 mg of tetrakis(4-carboxyphenyl)porphyrin, and 1.2 g of benzoic acid were added to a mixture of 0.5 mL of acetic acid and 5 mL of DMF, mixed thoroughly, and placed in a reactor at 120 degrees for 24 hours. After the reaction, the mixture was centrifuged, washed with DMF, and dried to obtain PCN-224(Co). Oxidized starch was oxidized at 1631 cm -1 The asymmetric carboxyl stretching vibration peak at 1663 cm-1 was red-shifted to 1663 cm-1 after in situ growth of PCN-224(Co). -1 , and PCN-224(Co)@OS1 at 1550cm-1 、1410cm -1 and 655cm -1 The new characteristic peaks at 370 nm correspond to the stretching vibrations of C=C, CN, and Zr-O in PCN-224(Co), respectively, demonstrating the successful preparation of PCN-224(Co)@OS1.

[0077] BSE / SE dual-mode images of PCN-224(Co)@OS1 hydrogels are shown in Figure 2. Figure 6 As shown in Figure A, the PCN-224(Co)@OS1 hydrogel exhibits a loose, porous network structure that promotes the efficient exchange of oxygen and catalytic substrates, providing channels for the release of reactive oxygen species. The composite hydrogel with a PCN-224(Co) loading of 2.47% exhibits a low network crosslink density. The bright regions (Zr / Co) in the BSE image are distributed within the oxidized starch matrix (dark regions), indicating that PCN-224(Co) is uniformly distributed throughout the hydrogel material, demonstrating the successful preparation of the PCN-224(Co)@OS1 composite photocatalytic whitening hydrogel.

[0078] The adhesion performance, moisture retention rate, thermal stability and degradation rate of the PCN-224(Co)@OS1 hydrogel obtained in this example are shown in Figure 2. Figures 7-10 As shown in Figure 2, PCN-224(Co)@OS1 hydrogel has good adhesion properties. After 6 hours, the dynamic residual rate of the enamel surface in artificial saliva at 37°C was 60.4% ( Figure 7 ). Moreover, PCN-224(Co)@OS1 hydrogel still maintained a 73.8% moisturizing rate after 2h of red light irradiation, which enabled the composite photocatalytic whitening hydrogel to continuously contact water molecules during the photocatalytic process ( Figure 8 The material structure of PCN-224(Co)@OS1 hydrogel can remain stable within the local temperature range (35-50°C) under red light irradiation ( Figure 9 At the same time, PCN-224(Co)@OS1 hydrogel has good chemical stability in the saliva environment, and 47.6% ( Figure 10 , Figure 10 Different letters indicate statistically significant differences among the groups (P<0.05).

[0079] The photocatalytic performance of the PCN-224(Co)@OS1 hydrogel obtained in this example was evaluated. Figure 11As shown. Under 650nm red light irradiation, PCN-224(Co)@OS1 composite hydrogel showed significant degradation effects on indigo carmine (IC) and rhodamine B (RhB). The degradation rate of IC reached 83.89% within 60 minutes, and the degradation rate of RhB reached 67.90% within 75 minutes. First-order reaction kinetics was used to further study the degradation of the dyes. The degradation rate constants of IC and RhB were 2.62×10 -2 min -1 , 1.41×10 -2 min -1 At the same time, PCN-224(Co)@OS1 hydrogel has good hydroxyl radical (·OH) and superoxide radical (·O2 - ) generation capacity, achieving efficient red light-driven reactive oxygen species generation (results as shown Figure 12 The above results prove that PCN-224(Co)@OS1 hydrogel has excellent photocatalytic activity because it carries the excellent bimetallic active MOF—PCN-224(Co) and has a loose pore structure that is conducive to the transport of active oxygen.

[0080] After co-culture of PCN-224(Co)@OS1 hydrogel with human gingival fibroblasts and human gingival epithelial cells, the survival rates of both cells were above 90% at all experimental concentrations (0.25-1 mM) (results shown in Figure 13 As shown, Figure 13 The same letters in the table indicate that there is no statistically significant difference between the groups (P<0.05), which proves that the starch-based composite photocatalytic whitening hydrogel has good biocompatibility.

[0081] Example 2

[0082] (1) According to the zirconium chloride and oxidized starch (carboxyl content of 1.96%, molecular weight of 3.74×10 5 g / mol) in a mass ratio of 1:4, 5g of zirconium chloride (ZrCl4) powder was dissolved in an N,N-dimethylformamide (DMF) aqueous solution (the volume ratio of DMF to water was 9:1) to prepare a ZrCl4DMF aqueous solution with a mass concentration of 0.1g / mL. Subsequently, 20g of oxidized starch was added to the above solution and stirred at 25°C for 6h. After the reaction, the unreacted ZrCl4 was removed by alternating washing with anhydrous ethanol and deionized water, and the oxidized starch-zirconium ion complex (OS2-Zr2) was obtained after drying. 4+ );

[0083] (2) The prepared oxidized starch-zirconium ion complex OS2-Zr 4+Oxidized starch-zirconium ion complex OS2-Zr, cobalt-tetra(4-carboxyphenyl)porphyrin and benzoic acid were weighed in a mass ratio of 10:4:30. 4+ 5g of cobalt-tetrakis(4-carboxyphenyl)porphyrin, 2g of cobalt-tetrakis(4-carboxyphenyl)porphyrin, and 15g of benzoic acid were dissolved in 55ml of a mixture of N,N-dimethylformamide and glacial acetic acid (the volume ratio of DMF to glacial acetic acid was 10:1). The mixture was then solvothermally reacted in a hydrothermal reactor at 150°C for 24h. After the reaction, the mixture was cooled, centrifuged, washed, and dried to produce a cobalt-modified zirconium-based metal-organic framework and oxidized starch composite (PCN-224(Co)@OS2).

[0084] (3) Weigh 5 g of PCN-224(Co)@OS2 powder and mix it evenly with 5 ml of deionized water (water content is 50%), then heat it to 75 °C for gelatinization for 1 h, transfer it to a mold and cool it at 4 °C to obtain a PCN-224(Co)@OS2 composite photocatalytic whitening hydrogel with a PCN-224(Co) content of 5.02%.

[0085] The oxidized starch-zirconium ion complex (OS2-Zr 4+ )'s infrared spectrum is shown in Figure 4 Compared with oxidized starch, OS2-Zr 4+ At 1632cm -1 The asymmetric carboxyl stretching vibration peak at 664 cm -1 A new peak appears, corresponding to the Zr-O bond. 4+ OS2-Zr was successfully prepared by coordinating the Zr-O bond with the carboxyl group in oxidized starch. 4+ .

[0086] The infrared spectrum of the composite material of cobalt-modified zirconium-based metal organic framework and oxidized starch (PCN-224(Co)@OS2) is shown in Figure 2. Figure 5 As shown. Oxidized starch at 1631cm -1 The asymmetric carboxyl stretching vibration peak at 1663 cm-1 was red-shifted to 1663 cm-1 after in situ growth of PCN-224(Co). -1 , and PCN-224(Co)@OS2 at 1550cm -1 、1410cm -1 and 655cm -1 The new characteristic peaks at 370 nm correspond to the stretching vibrations of C=C, CN, and Zr-O in PCN-224(Co), respectively, demonstrating the successful preparation of PCN-224(Co)@OS2.

[0087] BSE / SE dual-mode images of PCN-224(Co)@OS2 hydrogels are shown in Figure 2. Figure 6As shown in Figure B, the PCN-224(Co)@OS2 hydrogel exhibits a loose, porous network structure, providing channels for the release of reactive oxygen species. Compared to the PCN-224(Co)@OS1 hydrogel, the composite hydrogel with a PCN-224(Co) loading of 5.02% exhibits a higher network crosslink density. The bright regions (Zr / Co) in the BSE image are distributed within the oxidized starch matrix (dark regions), indicating that PCN-224(Co) is uniformly distributed throughout the hydrogel material, demonstrating the successful preparation of the PCN-224(Co)@OS2 composite photocatalytic whitening hydrogel.

[0088] The adhesion performance, moisture retention rate, thermal stability and degradation rate of the PCN-224(Co)@OS2 hydrogel obtained in this example are shown in Figure 2. Figure 7-10 As shown in Figure 2, PCN-224(Co)@OS2 hydrogel has good adhesion properties. After 6 hours, the dynamic residual rate on the enamel surface in artificial saliva at 37°C was 71.4% ( Figure 7 ). Moreover, PCN-224(Co)@OS2 hydrogel can maintain a moisture retention rate of 71.9% after 2h red light irradiation, which is lower than that of PCN-224(Co)@OS1 hydrogel ( Figure 8 The material structure of PCN-224(Co)@OS2 hydrogel can remain stable within the local temperature range (35-50°C) under red light irradiation ( Figure 9 At the same time, PCN-224(Co)@OS2 hydrogel has good chemical stability in the saliva environment, and 45.1% ( Figure 10 ).

[0089] The photocatalytic performance of the PCN-224(Co)@OS2 hydrogel obtained in this example was evaluated. Figure 11 As shown. Under 650nm red light irradiation, PCN-224(Co)@OS2 composite hydrogel showed significant degradation effects on indigo carmine (IC) and rhodamine B (RhB), with IC degrading by 88.66% within 60 minutes and RhB by 72.22% within 75 minutes. First-order reaction kinetics were used to further study the degradation of the dyes, and the degradation rate constants of IC and RhB were 3.18×10 -2 min -1 and 1.53×10 -2 min -1 , which is higher than that of PCN-224(Co)@OS1 hydrogel. At the same time, PCN-224(Co)@OS2 hydrogel has better hydroxyl radical (·OH) and superoxide radical (·O2 - ) generation capability (results such as Figure 12The above results demonstrate that PCN-224(Co)@OS2 hydrogel has good photocatalytic activity.

[0090] After PCN-224(Co)@OS2 hydrogel was co-cultured with human gingival fibroblasts and human gingival epithelial cells, the survival rates of both cells were above 88% at all experimental concentrations (0.25-1 mM) (results shown in Figure 13 As shown), it proves that the starch-based composite photocatalytic whitening hydrogel has good biocompatibility.

[0091] Example 3

[0092] (1) According to the zirconium chloride and oxidized starch (carboxyl content of 2.76%, molecular weight of 1.53×10 4 g / mol) was 1:6, 5g of zirconium chloride (ZrCl4) powder was dissolved in N,N-dimethylformamide (DMF) aqueous solution (the volume ratio of DMF to water was 9:1) to prepare a ZrCl4DMF aqueous solution with a mass concentration of 0.1g / mL. Subsequently, 30g of oxidized starch was added to the above solution and stirred at 25°C for 6h. After the reaction, it was washed alternately with anhydrous ethanol and deionized water to remove the unreacted ZrCl4, and the oxidized starch-zirconium ion complex (OS3-Zr) was obtained after drying. 4+ );

[0093] (2) The prepared oxidized starch-zirconium ion complex OS3-Zr 4+ Oxidized starch-zirconium ion complex OS3-Zr, cobalt-tetra(4-carboxyphenyl)porphyrin and benzoic acid were weighed in a mass ratio of 10:2:30. 4+ 5g of cobalt-tetrakis(4-carboxyphenyl)porphyrin, 1g of cobalt-tetrakis(4-carboxyphenyl)porphyrin, and 15g of benzoic acid were dissolved in 55ml of a mixture of N,N-dimethylformamide and glacial acetic acid (the volume ratio of DMF to glacial acetic acid was 10:1). The mixture was then solvothermally reacted in a hydrothermal reactor at 130°C for 22h. After the reaction, the mixture was cooled, centrifuged, washed, and dried to produce a cobalt-modified zirconium-based metal-organic framework and oxidized starch composite (PCN-224(Co)@OS3).

[0094] (3) Weigh 5 g of PCN-224(Co)@OS3 powder and mix it evenly with 5 ml of deionized water (water content is 50%), then heat it to 75°C and gelatinize it for 1 hour. Then transfer it to a mold and cool it at 4°C to obtain a PCN-224(Co)@OS3 composite photocatalytic whitening hydrogel with a PCN-224(Co) content of 6.87%.

[0095] The oxidized starch-zirconium ion complex (OS3-Zr 4+)'s infrared spectrum is shown in Figure 4 Compared with oxidized starch, OS3-Zr 4+ At 1632cm -1 The asymmetric carboxyl stretching vibration peak at 664 cm -1 A new peak appears, corresponding to the Zr-O bond. 4+ OS3-Zr was successfully prepared by coordinating Zr-O bonds with the carboxyl groups in oxidized starch. 4+ .

[0096] The infrared spectrum of the composite material of cobalt-modified zirconium-based metal organic framework and oxidized starch (PCN-224(Co)@OS3) is shown in Figure 2. Figure 5 As shown. Oxidized starch at 1631cm -1 The asymmetric carboxyl stretching vibration peak at 1663 cm-1 was red-shifted to 1663 cm-1 after in situ growth of PCN-224(Co). -1 , and PCN-224(Co)@OS3 at 1550cm -1 、1410cm -1 and 655cm -1 The new characteristic peaks at 370 nm correspond to the stretching vibrations of C=C, CN, and Zr-O in PCN-224(Co), respectively, demonstrating the successful preparation of PCN-224(Co)@OS3.

[0097] BSE / SE dual-mode images of PCN-224(Co)@OS3 hydrogels are shown in Figure 2. Figure 6 As shown in Figure C, the PCN-224(Co)@OS3 hydrogel exhibits a loose, porous network structure, providing channels for the release of reactive oxygen species. The composite hydrogel with a PCN-224(Co) loading of 6.87% exhibits the highest network crosslink density. The bright regions (Zr / Co) in the BSE image are distributed within the oxidized starch matrix (dark regions), indicating that PCN-224(Co) is uniformly distributed throughout the hydrogel, demonstrating the successful preparation of the PCN-224(Co)@OS3 composite photocatalytic whitening hydrogel.

[0098] The adhesion performance, moisture retention rate, thermal stability and degradation rate of the PCN-224(Co)@OS3 hydrogel obtained in this example are shown in Figure 2. Figure 7-10 As shown in Figure 2, PCN-224(Co)@OS3 hydrogel has the best adhesion performance, and the dynamic residual rate on the enamel surface in artificial saliva at 37℃ after 6 hours is 80.1% ( Figure 7 ). PCN-224(Co)@OS3 hydrogel can still maintain 68.6% of the moisturizing rate after 2h red light illumination, but it is lower than that of the composite photocatalytic whitening hydrogel of Examples 1 and 2 ( Figure 8The material structure of PCN-224(Co)@OS3 hydrogel can remain stable within the local temperature range (35-50°C) under red light irradiation ( Figure 9 At the same time, PCN-224(Co)@OS3 hydrogel has a certain chemical stability in the saliva environment, and 39.7% ( Figure 10 ).

[0099] The photocatalytic performance of the PCN-224(Co)@OS3 hydrogel obtained in this example was evaluated. Figure 11 As shown. Under 650nm red light irradiation, PCN-224(Co)@OS3 composite hydrogel showed the best degradation effect on indigo carmine (IC) and rhodamine B (RhB), with IC degradation rate reaching 91.96% within 60 minutes and RhB degradation rate reaching 75.23% within 75 minutes. First-order reaction kinetics was used to further study the degradation of the dyes. The degradation rate constants of IC and RhB were 3.79×10 -2 min -1 and 1.64×10 -2 min -1 , which are higher than those of the composite photocatalytic whitening hydrogels prepared in Examples 1 and 2. At the same time, PCN-224(Co)@OS3 hydrogel has the best hydroxyl radical (·OH) and superoxide radical (·O2 - ) generation capability (results such as Figure 12 The above results demonstrate that PCN-224(Co)@OS3 hydrogel has excellent photocatalytic activity.

[0100] After co-culture of PCN-224(Co)@OS3 hydrogel with human gingival fibroblasts and human gingival epithelial cells, the survival rates of both cells were above 85% at all experimental concentrations (0.25-1 mM) (results shown in Figure 13 As shown), it proves that the starch-based composite photocatalytic whitening hydrogel has good biocompatibility.

[0101] Example 4

[0102] The test method for detecting the tooth whitening effect of the starch-based composite photocatalytic whitening hydrogel obtained in Examples 1 to 3 was based on the method of "Wang Y, Wen XR, Jia YM, et al. Piezo-catalysis for nondestructive tooth whitening [J]. Nature Communications. 2020, 11 (01)" and slightly modified. The specific steps are as follows: human teeth were collected in vitro and soaked in mixed dyes (coffee, black tea, blueberry juice, cola) for 10 days to simulate natural tooth staining. In the experimental group, 0.40 g of the composite photocatalytic whitening hydrogel obtained in Examples 1 to 3 was evenly coated on the crown of the stained teeth and continuously irradiated with red light (650 nm, 50 W); in the H2O2 group, a 30% hydrogen peroxide (H2O2) solution was used instead of the composite photocatalytic whitening hydrogel obtained in Examples 1 to 3 to soak the stained teeth, and the rest of the steps were the same as those of the experimental group; the light-free control group was tested under dark conditions, and the rest of the steps were the same as those of the experimental group. After treatment for a specified period of time, each group of teeth was rinsed with deionized water, photographed, and the color change was recorded using the CIELab International Cleaning Committee color measurement system. To quantitatively analyze the effectiveness of tooth whitening, three parameters in color space were used to characterize the color change. ΔE was used to represent the degree of color change, and the color change was calculated as follows:

[0103]

[0104] Where L represents brightness, and the larger the value, the brighter the color; a represents the color value on the red-green axis, with positive numbers representing red and negative numbers representing green; b represents the color value on the blue-yellow axis, with positive numbers representing yellow and negative numbers representing blue.

[0105] Whiteness Index (WI D ) is an index developed based on the CIELab color space and can be used to evaluate dental whiteness. This index has a good correlation with visual assessment and is used to quantitatively evaluate the whiteness of teeth. D The calculation formula is as follows:

[0106] WI D =0.511L-2.324a-1.100b

[0107] Among them, WI D is the whiteness index, 0.511 is the brightness constant, 2.32 is the constant for the green to red coordinate, and 1.100 is the constant for the blue to yellow coordinate.

[0108] like Figure 14As shown, the starch-based composite photocatalytic whitening hydrogels in Examples 1 to 3 have a good teeth whitening effect when combined with red light irradiation, and stained teeth can be visually significantly improved within 1 hour. According to the standard YY / T 0825-2011 "Tooth External Bleaching Products", the bleaching efficacy of the product is acceptable when the color difference value (ΔE) of the product is ≥2, and the whiteness index difference (ΔWI D ) is larger, the whiter the teeth are. Figure 15 As shown, ΔE, ΔWI D The ΔE and ΔWI of stained teeth coated with PCN-224(Co)@OS3 hydrogel at 60 minutes after red light irradiation are proportional to the PCN-224(Co) content in the starch-based composite photocatalytic whitening hydrogel. D The values ​​were only lower than those of the H2O2 group by 2.23 and 4.30, respectively, which demonstrated that the whitening effect of the hydrogel was similar to that of the traditional peroxide whitening method and had an ideal teeth whitening effect.

[0109] Example 5

[0110] The Vickers hardness of teeth before and after the whitening treatment of the starch-based composite photocatalytic whitening hydrogel and 30% H2O2 solution prepared in Examples 1 to 3 is as follows: Figure 16 As shown in the figure, "Stained" represents teeth after staining and before whitening. The hardness of teeth treated with PCN-224(Co)@OS hydrogel was approximately 310 HV, with no significant difference in tooth hardness before and after whitening, confirming that it did not mechanically damage tooth enamel. However, treatment with a 30% H2O2 solution significantly reduced tooth hardness, causing irreversible damage to the teeth. Furthermore, there was no difference in tooth hardness between the red light-exposed and no light-exposed groups, demonstrating that the safety of starch-based composite photocatalytic whitening hydrogel combined with red light therapy is superior to traditional peroxide whitening methods.

[0111] The crystal structure of teeth before and after the starch-based composite photocatalytic whitening hydrogel and 30% H2O2 solution whitening treatment prepared in Examples 1 to 3 is shown in FIG. Figure 17 As shown in the figure, where Stained represents teeth after staining and before whitening. The crystallinity of the enamel in the H2O2 group decreased to 68.52%, while the crystallinity of the teeth using the starch-based composite photocatalytic whitening hydrogel was still above 80%. Figure 18 As shown in the scanning electron microscopy images of tooth enamel before and after starch-based composite photocatalytic whitening hydrogel and 30% H2O2 whitening treatment, it can be seen that the tooth enamel after using starch-based composite photocatalytic whitening hydrogel still presents a uniform and regular enamel surface morphology, without loose enamel surface, defects, etc.; while the enamel surface after treatment with 30% H2O2 solution becomes rough, showing varying degrees of honeycomb demineralization and irregular demineralization. This honeycomb structure will further promote plaque adhesion and increase the probability of secondary caries and re-staining.

[0112] After testing, it was found that although the traditional method of using hydrogen peroxide to whiten teeth is effective, it will lead to adverse effects such as reduced tooth hardness, destruction of the enamel crystal structure, and increased enamel surface roughness. The starch-based composite photocatalytic whitening hydrogel combined with red light irradiation has an ideal whitening effect without causing obvious damage to the enamel.

[0113] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, and these changes should be covered by the scope of protection of the present invention.

Claims

1. A starch-based composite photocatalytic whitening hydrogel, characterized in that The hydrogel is prepared by in-situ compounding of cobalt-modified zirconium-based metal-organic framework PCN-224 (Co) and oxidized starch through starch retrogradation. The carboxyl content of the oxidized starch is 1.23% to 2.76%, and the molecular weight of the oxidized starch is 1.53×10 4 ~7.86×10 5 g / mol; the content of cobalt-modified zirconium-based metal-organic framework PCN-224(Co) is 2.47% to 6.87%; the water content of the hydrogel is 50-80wt%.

2. A method for preparing a starch-based composite photocatalytic whitening hydrogel, characterized in that The following steps are involved: (1) dissolving zirconium chloride powder in an N,N-dimethylformamide aqueous solution, then adding oxidized starch to the solution and stirring for reaction, washing to remove unreacted ZrCl4 after the reaction, and drying to obtain an oxidized starch-zirconium ion complex; (2) dissolving oxidized starch-zirconium ion complex, cobalt-tetrakis(4-carboxyphenyl)porphyrin and benzoic acid in a mixed solution of N,N-dimethylformamide and glacial acetic acid, performing a solvent thermal reaction in a hydrothermal reactor, and obtaining a composite material of cobalt-modified zirconium-based metal-organic framework and oxidized starch after cooling, centrifugation, washing and drying; (3) The composite material powder of the cobalt-modified zirconium-based metal-organic framework and oxidized starch is mixed evenly with water, then heated for gelatinization, and then transferred to a mold for cooling and molding to obtain a starch-based composite photocatalytic whitening hydrogel.

3. The method for preparing the starch-based composite photocatalytic whitening hydrogel according to claim 2, characterized in that: The carboxyl content of the oxidized starch in step (1) is 1.23% to 2.76%, and the molecular weight of the oxidized starch is 1.53×10 4 ~7.86×10 5 g / mol.

4. The method for preparing the starch-based composite photocatalytic whitening hydrogel according to claim 2, wherein: The mass ratio of ZrCl4 to oxidized starch in step (1) is 1:2-6; The volume ratio of DMF to water in the N,N-dimethylformamide aqueous solution described in step (1) is 10-5:1; The stirring reaction in step (1) refers to stirring the reaction at room temperature for 6-12 hours.

5. The method for preparing the starch-based composite photocatalytic whitening hydrogel according to claim 2, characterized in that: The mass ratio of the oxidized starch-zirconium ion complex, cobalt-tetrakis(4-carboxyphenyl)porphyrin and benzoic acid described in step (2) is 10:1 to 4:30; The volume ratio of N,N-dimethylformamide to glacial acetic acid in the mixed solution of N,N-dimethylformamide and glacial acetic acid in step (2) is 12-8:

1.

6. The method for preparing the starch-based composite photocatalytic whitening hydrogel according to claim 2, characterized in that: The solvent thermal reaction in step (2) refers to a reaction at 120-150° C. for 20-24 hours.

7. The method for preparing the starch-based composite photocatalytic whitening hydrogel according to claim 2, characterized in that: After the composite material powder of the cobalt-modified zirconium-based metal-organic framework and oxidized starch described in step (3) is uniformly mixed with water, the water content thereof is 50-80 wt %.

8. The method for preparing the starch-based composite photocatalytic whitening hydrogel according to claim 2, characterized in that: The heating gelatinization in step (3) is heating to 75° C. for gelatinization for 0.5-2.0 h.

9. Use of the starch-based composite photocatalytic whitening hydrogel according to claim 1 or the starch-based composite photocatalytic whitening hydrogel prepared by the method according to any one of claims 2 to 8 in teeth whitening.

10. Use of the starch-based composite photocatalytic whitening hydrogel in teeth whitening according to claim 9, characterized in that: When the starch-based composite photocatalytic whitening hydrogel is used for teeth whitening, red light is used for irradiation to generate active oxygen to oxidize pigment molecules on the surface of the teeth.

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