Piezoelectric nano-enzyme material with core-shell structure and application of piezoelectric nano-enzyme material in oral care

Abstract

The invention discloses a core-shell structure piezoelectric nano-enzyme material and application thereof in oral care, which can generate active oxygen through piezoelectric effect under the action of mechanical stress to realize double effects of tooth whitening and antibiosis. The technology does not need external source energy input, avoids dependence of traditional photocatalysis and chemical bleaching technologies, and is simple and convenient to operate, green and safe. Through in-situ generation of cerium oxide on the surface, the material has dual enzyme activity, effectively balances the antibacterial effect and biological safety, and prevents excessive damage to enamel. In addition, the stability and catalytic efficiency of the material are remarkably improved in a complex oral environment, and the problem of failure of a traditional material is avoided. The technology can be widely applied to oral care products such as toothpaste, mouth wash and antibacterial gel, has remarkable industrialization potential and can bring innovation to the global oral care market.

Description

Technical Field

[0001] This invention relates to the field of nanocomposite materials technology, and in particular to a core-shell structured piezoelectric nanoenzyme material and its application in oral care. Background Technology

[0002] With the increasing demands of modern oral care, teeth whitening and oral antibacterial properties have become core concerns. While traditional teeth whitening techniques are effective in removing surface stains to some extent, they often suffer from oxidative damage and short-lived results. Oral antibacterial techniques, on the other hand, face challenges such as limited antibacterial spectrum and increasing drug resistance. Therefore, resolving the contradiction between teeth whitening and oral antibacterial properties simultaneously has become a pressing technical challenge in the field of oral care.

[0003] The rise of nanotechnology has offered new solutions to this problem, especially the development of nanozyme technology, which has made smart materials combining catalytic activity and functional regulation a research hotspot. Nanozyme materials, with their enzyme-like catalytic activity and good biocompatibility, have shown great potential in the fields of teeth whitening and antibacterial applications. In particular, piezoelectric catalytic nanomaterials not only possess catalytic functions but can also generate surface charges or electric fields under mechanical stress, thereby driving or enhancing catalytic reactions. They can release large amounts of ·OH free radicals through ultrasonic or mechanical stimulation, powerfully oxidizing and decomposing tooth surface pigments and exerting strong antibacterial effects, providing a completely new approach for efficient and safe teeth whitening. However, existing whitening technologies still have many limitations, especially in terms of oral microecological balance. For example, high concentrations of hydrogen peroxide may disrupt the balance of oral flora while removing stains, leading to a decrease in the number of beneficial bacteria and even causing oral microecological disorders. While abrasive toothpaste can physically remove surface stains, it cannot effectively remove plaque and lacks an effective solution to the correlation between bacterial pigment deposition and tooth discoloration. Therefore, overcoming the problems of oxidative damage and narrow antibacterial spectrum in traditional whitening technologies has become an important direction for current technological research and development.

[0004] Based on the above issues, nanoenzyme materials, especially piezoelectric catalytic nanomaterials, have become a research focus in the field of oral care due to their controllable reaction characteristics, biocompatibility, and catalytic activity. Utilizing the piezoelectric effect to convert mechanical energy into catalytic power not only avoids the dependence on light sources and chemical energy in traditional technologies but also addresses the dual needs of antibacterial and whitening by dynamically balancing the generation and removal of reactive oxygen species. However, existing nanomaterials exhibit poor stability in the complex oral environment and are prone to failure due to environmental changes. While traditional antibacterial materials (such as nano-silver and zinc oxide) possess certain bactericidal effects, they typically lack synergistic effects related to whitening mechanisms, and some materials exhibit cytotoxicity, limiting their application. Therefore, developing an antibacterial and whitening material with long-lasting stability and synergistic effects is particularly important.

[0005] To address these technical challenges, this invention proposes an innovative solution based on barium titanate-based piezoelectric composite nanoenzyme materials. By combining the piezoelectric effect, nanoenzyme catalysis, and antioxidant functions, a mechanically stress-driven antibacterial whitening system is constructed. This system can achieve teeth whitening and plaque removal by generating reactive oxygen species without external energy, while effectively protecting tooth enamel, overcoming many shortcomings of existing technologies. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, one of the objectives of this invention is to provide a core-shell structured piezoelectric nanoenzyme material and its application in oral care.

[0007] One objective of this invention is achieved through the following technical solution: a core-shell structured piezoelectric nanoenzyme material comprising a core layer composed of barium titanate (BaTiO3) nanocrystals and a cerium oxide (CeO2) nanoshell layer in situ coated on the surface of the core layer; under mechanical stress, the material generates active oxygen (·OH) through the piezoelectric effect of barium titanate, while cerium oxide generates active oxygen (·OH) through CeO2. 3+ / Ce 4+ Redox cycles remove excess free radicals.

[0008] Furthermore, the cerium oxide shell endows the material with dual enzyme activity of superoxide dismutase (SOD) and catalase (CAT).

[0009] Furthermore, the cerium oxide shell has a thickness of 5-50 nm and forms a lattice-matched heterogeneous interface with the barium titanate core layer.

[0010] A method for preparing the core-shell structured piezoelectric nanoenzyme material according to any one of claims 1-3, comprising the following steps:

[0011] (a) A solution of tetrabutyl titanate in alcohol was mixed with an aqueous solution of barium hydroxide, and a complexing agent was added to carry out a hydrothermal reaction to obtain barium titanate nanocrystals.

[0012] (b) The barium titanate nanocrystals obtained in step (a) are dispersed in an aqueous solution containing a surfactant, a cerium salt solution is added and the pH is adjusted to ≥9, and a precursor is obtained after the reaction.

[0013] (c) The precursor is calcined in an inert atmosphere to form a core-shell structured material with a cerium oxide shell.

[0014] As a further improvement to the above technical solution:

[0015] The hydrothermal reaction temperature in step (a) is 200-240℃ and the reaction time is 18-30h; the cerium salt in step (b) is cerium nitrate and the surfactant is sodium dodecyl sulfate (SDS); the calcination temperature in step (c) is 400-600℃ and the holding time is 1-3h.

[0016] An oral care composition comprising the core-shell structured piezoelectric nanoenzyme material according to any one of claims 1-3, wherein the mass fraction is 0.1-10 wt%.

[0017] As a further improvement to the above technical solution:

[0018] The composition is toothpaste, mouthwash, dental whitening gel, denture cleaner, or oral patch.

[0019] Mechanical stress is applied by brushing teeth or ultrasonic vibration to drive the core-shell structured piezoelectric nanoenzyme material to achieve the following:

[0020] (i) Decomposes pigments on the tooth surface;

[0021] (ii) Disruption of dental plaque biofilm;

[0022] (iii) Protect tooth enamel from oxidative damage.

[0023] A method for synergistic teeth whitening and antibacterial treatment involves applying the oral care composition of claim 6 to the tooth surface and applying mechanical stress to generate ·OH free radicals from the core-shell structured piezoelectric nanoenzyme material, which decomposes pigments and bacteria. At the same time, cerium oxide is used to remove excess free radicals to maintain the oral microecological balance.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] This invention provides an intelligent antibacterial and teeth whitening technology based on barium titanate-based piezoelectric composite nanoenzyme materials. This technology generates active oxygen through the piezoelectric effect under mechanical stress, achieving a dual effect of teeth whitening and antibacterial properties. This technology requires no external energy input, avoiding reliance on traditional photocatalysis and chemical bleaching techniques, and is simple, green, and safe to operate. By generating cerium oxide in situ on the surface, the material possesses dual enzyme activity, effectively balancing antibacterial effects and biocompatibility, preventing excessive damage to tooth enamel. Furthermore, the material's stability and catalytic efficiency are significantly improved in complex oral environments, avoiding the failure problems of traditional materials. This technology can be widely applied to oral care products such as toothpaste, mouthwash, and antibacterial gels, possessing significant industrialization potential and bringing innovation to the global oral care market.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0027] Figure 1 Transmission electron microscopy image and energy-dispersive X-ray spectrum of barium titanate-loaded cerium oxide piezoelectric nanoparticles;

[0028] Figure 2 XRD pattern of barium titanate-supported cerium oxide piezoelectric nanoparticles;

[0029] Figure 3 Figure showing the degradation of methylene blue dye by reactive oxygen species generated from barium titanate-supported cerium oxide piezoelectric nanoparticles.

[0030] Figure 4 CCK-8 cytotoxicity of barium titanate-loaded cerium oxide piezoelectric nanoparticles;

[0031] Figure 5 Blood agar plate coating image of barium titanate-loaded cerium oxide piezoelectric nanoparticles for the removal of common oral pathogens;

[0032] Figure 6 Scanning electron microscope image of barium titanate-loaded cerium oxide piezoelectric nanoparticles for clearing common oral pathogens;

[0033] Figure 7 The graph shows the total antioxidant capacity of barium titanate-supported cerium oxide piezoelectric nanoparticles. Detailed Implementation

[0034] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0035] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0037] Example 1: Please refer to Figure 1 The material comprises a core layer composed of barium titanate (BaTiO3) nanocrystals and a cerium oxide (CeO2) nanoshell layer in situ coated on the surface of the core layer. Under mechanical stress, the material generates active oxygen (·OH) through the piezoelectric effect of barium titanate, while cerium oxide reacts through CeO2. 3+ / Ce 4+ Redox cycles remove excess free radicals.

[0038] The cerium oxide shell endows the material with dual enzyme activity of superoxide dismutase (SOD) and catalase (CAT).

[0039] The cerium oxide shell has a thickness of 5-50 nm and forms a lattice-matched heterogeneous interface with the barium titanate core layer.

[0040] A method for preparing core-shell structured piezoelectric nanoenzyme materials includes the following steps:

[0041] (a) A solution of tetrabutyl titanate in alcohol was mixed with an aqueous solution of barium hydroxide, and a complexing agent was added to carry out a hydrothermal reaction to obtain barium titanate nanocrystals.

[0042] (b) The barium titanate nanocrystals obtained in step (a) are dispersed in an aqueous solution containing a surfactant, a cerium salt solution is added and the pH is adjusted to ≥9, and a precursor is obtained after the reaction.

[0043] (c) Calcination of the precursor in an inert atmosphere to form a core-shell structured material with a cerium oxide shell.

[0044] In step (a), the hydrothermal reaction temperature is 200-240℃ and the reaction time is 18-30h; in step (b), the cerium salt is cerium nitrate and the surfactant is sodium dodecyl sulfate (SDS); in step (c), the calcination temperature is 400-600℃ and the holding time is 1-3h.

[0045] The oral care composition of this embodiment has a mass fraction of 0.1-10 wt%.

[0046] The composition may be toothpaste, mouthwash, dental whitening gel, denture cleaner, or oral patch.

[0047] Mechanical stress is applied by brushing teeth or ultrasonic vibration to drive core-shell structured piezoelectric nanoenzyme materials to achieve the following:

[0048] (i) Decomposes pigments on the tooth surface;

[0049] (ii) Disruption of dental plaque biofilm;

[0050] (iii) Protect tooth enamel from oxidative damage.

[0051] In this embodiment, the teeth whitening and antibacterial synergistic treatment method involves applying an oral care composition to the tooth surface and applying mechanical stress, causing the core-shell structured piezoelectric nanoenzyme material to generate ·OH free radicals that decompose pigments and bacteria. At the same time, cerium oxide removes excess free radicals to maintain the oral microecological balance.

[0052] Example 2:

[0053] Material synthesis

[0054] Preparation of barium titanate cores:

[0055] Add 8.5g of tetrabutyl titanate (dissolved in 20mL of ethanol) dropwise to 11.04g of Ba(OH)2·8H2O (dissolved in 25mL of water);

[0056] Add 5 mL of diethanolamine and react hydrothermally at 220 °C for 24 h.

[0057] Centrifugation and washing followed by drying at 60°C yielded the BaTiO3 precursor.

[0058] In-situ growth of cerium oxide shells:

[0059] Disperse 1g BaTiO3 in 100mL of water containing 0.1g SDS and sonicate for 30min;

[0060] Add 0.87g Ce(NO3)3·6H2O (dissolved in 50mL water) dropwise, adjust pH to 9, and react for 2h;

[0061] After centrifugation, washing, and drying, the material was calcined at 500°C for 2 hours under argon atmosphere to obtain the core-shell material.

[0062] The preparation method of core-shell structured piezoelectric nanoenzyme materials includes the following steps, with specific details and parameters as follows:

[0063] Step (a): Preparation of barium titanate (BaTiO3) nanocrystals

[0064] Reagent preparation: Add 8.5g tetrabutyl titanate (dissolved in 20mL ethanol) dropwise to 11.04g Ba(OH)2·8H2O (dissolved in 25mL water), and add 5mL diethanolamine as a complexing agent.

[0065] Reaction conditions: The hydrothermal reaction was carried out at 220℃ for 24 h. After the reaction was completed, the product was centrifuged, washed, and dried at 60℃ to obtain the BaTiO3 precursor.

[0066] Step (b): In-situ growth of cerium oxide (CeO2) shell

[0067] Reagent preparation: Disperse 1g of BaTiO3 obtained in step (a) in 100mL of water containing 0.1g of sodium dodecyl sulfate (SDS) and sonicate for 30min; add 0.87g of Ce(NO3)3·6H2O (dissolved in 50mL of water) dropwise, adjust the pH to 9, and react for 2h.

[0068] Reaction conditions: Reaction at room temperature, pH adjusted to ≥ 9.

[0069] Step (c): Calcination and shaping

[0070] Processing conditions: After centrifuging, washing and drying the precursor obtained in step (b), it is calcined at 500°C for 2 hours in an argon atmosphere to form a core-shell structure material coated with a cerium oxide shell.

[0071] Parameter range: calcination temperature can be 400-600℃, holding time is 1-3h (in the example, calcination is carried out at 500℃ for 2h).

[0072] core components

[0073] Core layer: Barium titanate (BaTiO3) nanocrystals, forming the main framework of the material. Shell layer: Cerium oxide (CeO2) nanoshell layer, in situ coated on the surface of the core layer, with a thickness of 5-50 nm (the shell thickness in this example is about 20 nm).

[0074]

[0075]

[0076] The application of this material in the field of oral care is mainly reflected in the following aspects:

[0077] Application: It can be added as an active ingredient to oral care compositions such as toothpaste, mouthwash, dental whitening gel, denture cleaner or oral patches, with a mass fraction of 0.1-10 wt% (2 wt% was added to toothpaste in the example).

[0078] Mechanism of action: Applying mechanical stress through brushing teeth or ultrasonic vibration drives the material to produce the following effects:

[0079] It breaks down pigments on the surface of teeth (such as coffee stains and tea stains) to achieve teeth whitening.

[0080] It disrupts dental plaque biofilm, inhibits the growth of oral pathogens such as Streptococcus mutans and Porphyromonas gingivalis, and has a high antibacterial rate.

[0081] Cerium oxide protects tooth enamel from oxidative damage by scavenging excess free radicals through its dual enzyme activity (SOD and CAT).

[0082] Example 3: Application Example (Oral Care Performance Test)

[0083] Experimental subjects: human extracted tooth model, Streptococcus mutans, and Porphyromonas gingivalis.

[0084] Experimental process

[0085] Teeth whitening: Apply toothpaste containing 2wt% of the material to a toothpaste stained with coffee / tea, simulate brushing with a toothbrush machine (pressure 150g, 2min), and measure the whitening effect (ΔE value) with a colorimeter.

[0086] Antibacterial properties: The material suspension (100 μg / mL) was incubated with the bacterial solution for 24 h, and the inhibition rate was calculated by plate counting method.

[0087] Enamel protection: The Vickers hardness of the enamel surface was tested before and after whitening treatment, and the surface morphology was observed by SEM.

[0088]

[0089]

[0090] Preparation method details and component ratios:

[0091] Hydrothermal reaction parameter range: The hydrothermal reaction temperature in step (a) can be 200-240℃, and the reaction time can be 18-30h (220℃ and 24h are used in the example).

[0092] Cerium salt and surfactant: In step (b), the cerium salt is fixed as cerium nitrate, and the surfactant is sodium dodecyl sulfate (SDS), with a mass ratio of 0.1:1 (0.1g SDS: 1g BaTiO3) to BaTiO3.

[0093] Core-shell structure control: The thickness of the CeO2 shell can be controlled by adjusting the amount of Ce(NO3)3·6H2O. For example, in the example, 0.87g of Ce(NO3)3·6H2O corresponds to a shell thickness of about 20nm. Theoretically, when the shell thickness is 5-50nm, the amount of Ce(NO3)3·6H2O can be adjusted proportionally.

[0094] Experimental procedure and data:

[0095] Experiment 1: Characterization of core-shell structure (supporting claims 1-3)

[0096] Experimental process

[0097] 1. Sample preparation:

[0098] Experimental group: BaTiO3@CeO2 core-shell material was synthesized according to Example 1.

[0099] Control group 1: Pure BaTiO3 nanoparticles (without CeO2 coating)

[0100] Control group 2: Physically mixed BaTiO3 + CeO2 (mass ratio 1:0.2)

[0101] 2. Testing Method:

[0102] TEM / EDS: Morphology observed using a Hitachi HT7800 transmission electron microscope, elemental distribution analyzed using an Oxford X-Max N80 energy dispersive spectrometer.

[0103] XPS: ThermoScientificK-Alpha Analysis Ce 3+ / Ce 4+ Proportion

[0104] XRD: RigakuSmartLab diffractometer (Cu-Kα radiation) characterization of lattice matching.

[0105] Experimental results

[0106]

[0107] Experiment 2: Piezoelectric Catalysis and Free Radical Regulation Performance (Supporting Claims 1-2, 8) Experimental Procedure

[0108] 1. OH generation ability (detected by TA colorimetric probe):

[0109] 20 mg of the material was dispersed in 10 mL of 0.5 mMMTA solution. Ultrasonic stress (40 kHz, 50 W) was applied to simulate the mechanical stress of brushing teeth. Samples were taken from 0 to 30 min and the absorbance change of the ·OH-TA adduct was detected by UV spectrophotometer (detection wavelength = 320 nm).

[0110] 2. Free radical scavenging ability (DPPH method):

[0111] The material reacted with 0.2 mM DPPH ethanol solution for 30 min.

[0112] The rate of decrease in absorbance was measured at 517 nm.

[0113] Experimental results

[0114]

[0115] Experiment 3: Oral Care Performance Test (Supporting Claims 6-9)

[0116] Experimental process

[0117] Teeth whitening effect (human extracted tooth model):

[0118] Coffee / tea stained teeth (n=10) → Apply toothpaste containing 2wt% of the material → Simulate brushing with an ultrasonic toothbrush (pressure 150g, 2min) → Measure whitening effect (ΔE value) with a colorimeter

[0119] Antibacterial properties (ISO20743:2013):

[0120] Bacterial strains: Fusobacterium nucleatum, Porphyromonas gingivalis (ATCC33277)

[0121] Material suspension (100 μg / mL) was co-incubated with bacterial culture for 24 h → inhibition rate was calculated by plate count method.

[0122] Enamel protection (microhardness and SEM):

[0123] Vickers hardness test of tooth enamel surface before and after whitening treatment (load 50g, 15s)

[0124] SEM observation of surface morphology changes

[0125] Experimental results

[0126]

[0127]

[0128] Experiment 4: Oral Microecological Balance Assessment (Supporting Claim 9)

[0129] Experimental process

[0130] Probiotic survival rate: Oral probiotics (L. reuteri DSM17938) were co-cultured with the materials, and the change in 16S rRNA gene copy number was detected by qPCR.

[0131] Microbial diversity: Shannon index analysis using 16S rRNA high-throughput sequencing (Illumina MiSeq) after interaction of human saliva microbiota with materials.

[0132]

[0133] Experimental conclusions

[0134] 1. Structural advantages: The core-shell structure (right 1) improves the piezoelectric output efficiency through the lattice matching interface (XRD mismatch < 3%), and the CeO2 shell thickness of 20nm (right 3) optimizes the free radical scavenging ability (DPPH scavenging rate 89.2%).

[0135] 2. Synergistic Function: Piezoelectric catalysis and dual-enzyme activity (Right 2) achieve high ·OH yield (18.7 μM·min) -1 ·g -1 It combines dynamic scavenging (concentration decreased by 43.6% after 10 min) to solve the problem of oxidative damage.

[0136] 3. Application effect: The toothpaste containing 2wt% of the material has a ΔE value of 6.8 under mechanical stress, and the antibacterial rate against Fusobacterium nucleatum and P. gingivalis is >90% (material concentration 100μg / mL), and the loss of tooth enamel hardness is only 2.1%.

[0137] 4. Ecological safety: Significantly protects the survival of probiotics (92.5%) and maintains microbial diversity (Shannon index 4.71), which is superior to all control groups.

[0138] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A core-shell structured piezoelectric nanoenzyme material, characterized in that: The material comprises a core layer composed of barium titanate (BaTiO3) nanocrystals and a cerium oxide (CeO2) nanoshell layer in situ coated on the surface of the core layer. Under mechanical stress, the material generates active oxygen (·OH) through the piezoelectric effect of barium titanate, while cerium oxide reacts through CeO2. 3+ / Ce 4+ Redox cycles remove excess free radicals.

2. The core-shell structured piezoelectric nanoenzyme material according to claim 1, characterized in that: The cerium oxide shell endows the material with dual enzyme activity of superoxide dismutase (SOD) and catalase (CAT).

3. The core-shell structured piezoelectric nanoenzyme material according to claim 1 or 2, characterized in that: The cerium oxide shell has a thickness of 5-50 nm and forms a lattice-matched heterogeneous interface with the barium titanate core layer.

4. A method for preparing a core-shell structured piezoelectric nanoenzyme material according to any one of claims 1-3, characterized in that... Includes the following steps: (a) A solution of tetrabutyl titanate in alcohol was mixed with an aqueous solution of barium hydroxide, and a complexing agent was added to carry out a hydrothermal reaction to obtain barium titanate nanocrystals. (b) The barium titanate nanocrystals obtained in step (a) are dispersed in an aqueous solution containing a surfactant, a cerium salt solution is added and the pH is adjusted to ≥9, and a precursor is obtained after the reaction. (c) The precursor is calcined in an inert atmosphere to form a core-shell structured material with a cerium oxide shell.

5. The preparation method according to claim 4, characterized in that: The hydrothermal reaction temperature in step (a) is 200-240℃ and the reaction time is 18-30h; the cerium salt in step (b) is cerium nitrate and the surfactant is sodium dodecyl sulfate (SDS); the calcination temperature in step (c) is 400-600℃ and the holding time is 1-3h.

6. An oral care composition, characterized in that... The core-shell structured piezoelectric nanoenzyme material according to any one of claims 1-3 has a mass fraction of 0.1-10 wt%.

7. The oral care composition according to claim 6, characterized in that: The composition is toothpaste, mouthwash, dental whitening gel, denture cleaner, or oral patch.

8. The method of applying the oral care composition according to claim 6 or 7, characterized in that: Mechanical stress is applied by brushing teeth or ultrasonic vibration to drive the core-shell structured piezoelectric nanoenzyme material to achieve the following: (i) Decomposes pigments on the tooth surface; (ii) Disruption of dental plaque biofilm; (iii) Protect tooth enamel from oxidative damage.

9. A method for synergistic treatment of teeth whitening and antibacterial properties, characterized in that: The oral care composition of claim 6 is applied to the tooth surface and mechanical stress is applied to cause the core-shell structured piezoelectric nanoenzyme material to generate ·OH free radicals to decompose pigments and bacteria, while cerium oxide removes excess free radicals to maintain the oral microecological balance.

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