Temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles as well as preparation method and application thereof
By preparing temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles, the stability and release control issues of plant essential oils in packaging were solved, achieving efficient encapsulation and controllable release, and improving the antioxidant properties of essential oils.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-03-27
AI Technical Summary
Plant essential oils are highly volatile and unstable, resulting in a high loss rate when combined with packaging materials, making it difficult to effectively protect their active ingredients and control their release.
We employ temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles, and through hydrophobic modification, amination modification, polymer grafting, and gallic acid grafting, we construct a partitioned functional system with internal hydrophobicity and external hydrophilicity, to achieve efficient encapsulation and controllable release of essential oils.
It improves the solubility and bioavailability of essential oils, enhances their storage stability and antibacterial and antioxidant properties, and achieves efficient encapsulation and controllable release of essential oils, with an antioxidant efficiency of over 92%.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of new materials, and particularly relates to a temperature-pH dual-responsive anti-oxidation type hollow mesoporous silica nanoparticle and a preparation method and application thereof. BACKGROUND
[0002] Essential oils, as a natural plant extract, have been widely used in many fields such as medical care, beauty and skin care, daily chemical products, etc. due to their diverse pharmacological activities and aromatic properties. Natural plant essential oils have aromatic odor, low toxicity and good antibacterial and antioxidant properties. However, the physical properties such as high volatility and instability of plant essential oils result in a high loss rate when they are combined with packaging materials.
[0003] Nano-silicon dioxide (SiO2) is a non-crystalline inorganic non-metallic material with good biocompatibility, no toxicity and no pollution, and has mesoscopic system characteristics such as small size effect, surface and interface effect and macroscopic quantum tunneling effect. The molecular state of nano-silicon dioxide is a three-dimensional network structure with [SiO4] tetrahedron as a basic structural unit. The oxygen and silicon atoms are directly connected by a covalent bond, the bond energy is as high as 460 kJ / mol, the structure is firm, and the thermal expansion coefficient is only 3×10 –5 ~ 5×10 –5 / K, which has stable physical and chemical properties, porosity, high temperature resistance and low dielectric properties. In addition, the surface of nano-silicon dioxide has unsaturated residual bonds and different states of hydroxyl groups, and the skeleton can be replaced or doped by other chemical atoms, so that it can be further functionalized by other functional groups. It has broad application prospects in many fields such as electronic packaging, industrial catalysis, energy and chemical industry, biological pharmaceuticals, diagnostic medicine, drug delivery and environmental protection.
[0004] The use of nano-materials to encapsulate plant essential oils can improve the solubility and bioavailability of essential oils, protect the active ingredients and control the release of essential oils, improve the storage stability and antibacterial and antioxidant properties of essential oils. The slow-release effect can also significantly improve the antioxidant and antibacterial effects of essential oils. SUMMARY
[0005] In view of the problems and deficiencies in the prior art, the purpose of the present application is to provide a temperature-pH dual-responsive anti-oxidation type hollow mesoporous silica nanoparticle and a preparation method and application thereof.
[0006] To achieve the above purpose, the present application adopts the following technical scheme: The present application provides a preparation method of a temperature-pH dual-responsive anti-oxidation type hollow mesoporous silica nanoparticle, comprising the following steps: S1, hydrophobic modification of hollow mesoporous silica nanoparticles (HMSNs) by using octadecyltrimethoxysilane to obtain hydrophobically modified hollow mesoporous silica nanoparticles (HMSNs-C18 ); S2, for HMSNs-C 18 Amination modification yields HMSNs-C 18 -NH2, for the HMSNs-C 18 -NH2 was used as an initiator to fix the HMSNs-C 18 -Br; for the HMSNs-C 18 -Br was used for grafting with poly(N-isopropylacrylamide) (PNIPAM) to obtain HMSNs-C 18 -PNIPAM-Br, for the HMSNs-C 18 -PNIPAM-Br was grafted with polyacrylic acid (PAA) to obtain HMSNs-C 18 -PNIPAM-b-PAA; S3, in HMSNs-C 18 Grafting gallic acid (GA) onto PNIPAM-b-PAA yields temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles (HMSNs-C). 18 -PNIPAM-b-PAA-GA).
[0007] Preferably, in step S3, the specific operation of grafting gallic acid is as follows: The HMSNs-C 18 -PNIPAM-b-PAA is added to solvent A to obtain HMSNs-C 18 -PNIPAM-b-PAA dispersion; Gallic acid is dissolved in solvent B to obtain a gallic acid solution, and an activator is added to the gallic acid solution for activation treatment to obtain an activated gallic acid solution; The activated gallic acid solution is added to the HMSNs-C 18 The PNIPAM-b-PAA dispersion was reacted at room temperature for 2–4 h. After the reaction was completed, the precipitate was collected, washed, and dried to obtain temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles.
[0008] Preferably, the gallic acid and HMSNs-C 18 The molar ratio of -PNIPAM-b-PAA is 1:(1~4); the activator is a mixture of EDC and NHS.
[0009] Preferably, the molar ratio of gallic acid to activator is 1:(1-3); the molar ratio of EDC to NHS is 1:(1-2).
[0010] Preferably, in step S1, the specific operation of the hydrophobic modification is as follows: HMSNs are added to solvent C to obtain an HMSNs dispersion. Under an inert gas atmosphere, octadecyltrimethoxysilane and a catalyst are added to the HMSNs dispersion, and the reaction is carried out at 100°C. After the reaction is completed, the reaction solution is subjected to alcohol precipitation and the precipitate is collected. The precipitate is washed and then mixed with toluene to obtain a suspension. The suspension is subjected to alcohol precipitation and the precipitate is collected. The precipitate is dried to obtain HMSNs-C. 18 ; Preferably, in step S2, the specific process of the amination modification is as follows: HMSNs-C activated with hydrochloric acid... 18 Adding to solvent D yields HMSNs-C 18 The dispersion was mixed with 3-aminopropyltriethoxysilane and refluxed at 100–110 °C for 12–16 h under an inert atmosphere. After the reaction was complete, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -NH2; Preferably, in step S2, the specific process of the initiator immobilization treatment is as follows: The HMSNs-C 18 -NH2 is added to solvent E to obtain HMSNs-C 18 -NH2 dispersion, under light-protected conditions at 0–4°C, to HMSNs-C 18 Triethylamine and 2-bromoisobutyryl bromide were added to an NH2 dispersion, and the reaction was carried out at room temperature in the dark. After the reaction was completed, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -Br; Preferably, in step S2, the specific operation of the PNIPAM grafting treatment is as follows: HMSNs-C 18 -Br is added to solvent F to obtain HMSNs-C 18 -Br dispersion, into HMSNs-C 18 NIPAM monomer, CuBr, and PMDETA were added to the -Br dispersion, and the mixture was stirred at 60–80 °C for 24–48 h under an inert gas atmosphere. After the reaction was completed, the precipitate was collected, washed, and lyophilized to obtain HMSNs-C. 18 -PNIPAM-Br; Preferably, in step S2, the specific operation of the PAA grafting treatment is as follows: HMSNs-C 18 -PNIPAM-Br is added to solvent G to obtain HMSNs-C 18 -PNIPAM-Br dispersion; to HMSNs-C 18tBA monomer, CuBr, and PMDETA were added to the PNIPAM-Br dispersion. After freezing, vacuuming, and nitrogen purging for deoxygenation, the reaction was carried out at 80–82 °C for 24–48 h. After the reaction was completed, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -PNIPAM-b-PtBA; HMSNs-C 18 -PNIPAM-b-PtBA is added to solvent H to obtain HMSNs-C 18 -PNIPAM-b-PtBA dispersion; to HMSNs-C 18 Trifluoroacetic acid was added to the PNIPAM-b-PtBA dispersion, and the mixture was stirred at room temperature. After the reaction was complete, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -PNIPAM-b-PAA.
[0011] Preferably, in the hydrophobic modification process, the catalyst is ethylenediamine or tripropylamine, the concentration of HMSNs in the HMSNs dispersion is 1-10 mg / mL, and the molar ratio of the catalyst to octadecyltrimethoxysilane is 1:(1-10). Preferably, during the amination modification process, 3-aminopropyltriethoxysilane reacts with HMSNs-C 18 The mass ratio is 1:(10~20); Preferably, during the initiator immobilization process, HMSNs-C 18 The ratio of -NH2, triethylamine and 2-bromoisobutyryl bromide is 1 g : (250-270) μL : (300-350) μL; Preferably, during the PNIPAM grafting process, the NIPAM monomer and HMSNs-C 18 The mass ratio of -Br is (10~15):1, the molar ratio of CuBr to NIPAM monomer is (0.01~0.02):1, and the molar ratio of PMDETA to CuBr catalyst is (4~5):1; Preferably, during the PAA grafting process, HMSNs-C 18 The ratio of -PNIPAM-Br, tBA monomer, CuBr and PMDETA is 0.1 g:(2-3) g:(0.02-0.03) g:(30-50) μL; Preferably, solvents A, B, C, D, E, F, G, and H are all organic solvents.
[0012] The second aspect of the present invention provides temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles prepared by the method described in the first aspect above.
[0013] The third aspect of this invention provides the application of the temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles described in the second aspect above in the encapsulation of essential oils.
[0014] A fourth aspect of the present invention provides a method for encapsulating essential oils, comprising the following steps: (1) Dispersion adjustment: The temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles described in the second aspect above are added to water to obtain a suspension. The pH of the suspension is adjusted to 5.0 to 6.5, and the suspension is heated to 32 to 35°C. (2) Essential oil loading: The essential oil was added to the suspension and mixed well. First, it was stirred and adsorbed at 32–35℃ and pH 5.0–6.5, then ultrasonically impregnated. After ultrasonic impregnation, the pH was adjusted to neutral, the precipitate was collected by centrifugation, and lyophilized to obtain the encapsulated essential oil (HMSNs-C). 18 -PNIPAM-b-PAA-GA@EO).
[0015] Preferably, the mass ratio of the temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles to the essential oil is (1-4):100.
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention employs a "relative to the inside and friendly to the outside" partitioned functionalization strategy to design a partitioned functionalized temperature-pH dual-response antioxidant gating system: (1) The surface of the internal cavity is modified with hydrophobic octadecylsilane (C18) to improve the affinity of essential oils and achieve a theoretical loading of ≥85%.
[0017] (2) The inner wall of the mesoporous channel is grafted with an interpenetrating network polymer of poly(N-isopropylacrylamide) (PNIPAM) and polyacrylic acid (PAA) to form a dual-response gating system of temperature (32-35℃) and pH (5.0-6.5). Under skin temperature (32-35℃) and slightly acidic environment (pH 5.5-6.0), the PNIPAM chain contracts, the PAA is protonated, and the pores open, achieving controllable release in 8-72 hours. Under normal temperature and neutral conditions, the polymer chain extends to close the pores, preventing essential oil leakage and oxygen penetration.
[0018] (3) The pore opening is modified with phenolic hydroxyl antioxidant groups (such as gallic acid esters) to construct an oxygen free radical scavenging barrier, providing a chemical protective layer that can effectively scavenge oxygen free radicals and prevent essential oil oxidation. Antioxidant efficiency ≥92%. Attached Figure Description
[0019] Figure 1 The gallic acid grafting rate of Examples 1 to 4 of the present invention; Figure 2 The gallic acid grafting rate of Examples 3, 5 and 6 of the present invention; Figure 3 The gallic acid grafting rate of Examples 5, 7 and 8 of the present invention; Figure 4 This is the cumulative release curve of the essential oil in this invention. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0021] (a) Gallic acid and HMSNs-C 18 Effect of the molar ratio of -PNIPAM-b-PAA on the grafting rate of gallic acid To investigate the relationship between gallic acid and HMSNs-C 18 The effect of the molar ratio of -PNIPAM-b-PAA on the grafting rate of gallic acid was investigated in Examples 1 to 4 of this invention. The gallic acid and HMSNs-C in Examples 1 to 4 were compared. 18 The molar ratios of -PNIPAM-b-PAA are 1:1, 1:2, 1:3, and 1:4, respectively, as detailed below: Example 1: A method for preparing temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles, the specific steps of which are as follows: S1, C18 silanization chamber: 0.050 mol of dried HMSNs was added to 200 mL of diphenyl ether and ultrasonically dispersed for 50 minutes to obtain an HMSNs dispersion with a concentration of 1–10 mg / mL. Under nitrogen protection, the HMSNs dispersion was placed in a 100℃ oil bath, and 0.016 mol of octadecyltrimethoxysilane (octadecyltrimethoxysilane was first subjected to vacuum distillation for 2 hours to remove water) and 0.0016 mol of tripropylamine catalyst were added. The mixture was heated and reacted for 20 hours under stirring. After the reaction, the resulting mixture was precipitated with ethanol, and the precipitate was collected by centrifugation. The precipitate was washed three times to thoroughly remove impurities adhering to its surface. Finally, the precipitate was dispersed in toluene at a solid-liquid ratio of 1:10–1:50, precipitated with methanol, and the solid phase was collected by centrifugation again. The separated solid phase was placed in a vacuum oven and dried at room temperature for 24 hours to obtain HMSNs-C 18 .
[0022] The preparation steps of hollow mesoporous silica nanoparticles are as follows: 0.64 g of hexadecyltrimethylammonium bromide (CTAB), 60 mL of ethanol, and 2 mL of a mixed silicon source (composed of 0.6 mL of tetraethyl silicate, 0.6 mL of 1,2-bis(triethoxysilyl)ethane, and 0.8 mL of cyclohexane) are mixed evenly at room temperature. 100 mL of water is added, and the mixture is stirred for 60 min. Then, 1 mL of concentrated ammonia is added, and the mixture is stirred for 2.5 h. After the reaction is complete, the mixture is centrifuged at 8000 r / min for 10 min, and the precipitate is washed three times with ethanol. Then, it is resuspended in a 1:9 hydrochloric acid-ethanol solution and refluxed for 12 h. After the reaction is complete, the mixture is centrifuged at 8000 r / min for 10 min, and the precipitate is washed twice with ethanol and twice with water. Finally, it is resuspended in water and freeze-dried to obtain hollow mesoporous silica nanoparticles (HMSNs).
[0023] S2, ATRP grafting temperature-pH responsive polymers: S21, Amination modification: HMSNs-C 18 Dispersed in ethanol, ultrasonically dispersed for 30 minutes, refluxed with 3M hydrochloric acid for 6 hours to activate surface silanol groups (Si-OH), centrifuged and washed until neutral, and vacuum dried to obtain activated HMSNs-C 18 Take 1g of activated HMSNs-C 18 Dispersed in 100 mL of anhydrous toluene, then 0.15 g of 3-aminopropyltriethoxysilane (APTES) was added to the activated HMSNs-C 18 Surface amination was performed under nitrogen protection and refluxed at 110°C for 12 hours. After the reaction, the precipitate was collected by centrifugation and washed several times with ethanol to remove unreacted APTES. The washed precipitate was then dried to obtain amination-treated mesoporous silica nanoparticles (HMSNs-C). 18 -NH2).
[0024] S22, Initiator fixation: Take 1.0 g HMSNs-C 18 -NH2 was ultrasonically dispersed in an appropriate amount of toluene to obtain a dispersion. Under stirring in an ice-water bath in the dark, 270 μL of triethylamine and 335 μL of 2-bromoisobutyryl bromide (BIBB) were slowly added dropwise to the dispersion. After the addition was complete, the mixture was moved to room temperature and stirred for 12 hours in the dark. During the reaction, the round-bottom flask was wrapped with lead foil to prevent the bromine from reacting with light. 2-Bromoisobutyryl bromide releases hydrogen bromide (HBr) during the reaction, which is an acidic substance. Triethylamine, as an organic base, neutralizes these acidic byproducts, preventing them from interfering with the reaction system and ensuring the smooth progress of the reaction. After the reaction, the product was washed twice with anhydrous ethanol and centrifuged, then dried in a vacuum drying oven to obtain HMSNs-C with an initiator on its surface.18 -Br.
[0025] S23, Grafted PNIPAM: Take 1.0 g of HMSNs-C with surface initiator. 18 -Br was dispersed in 100 mL of a mixed solvent (composed of 50 mL tetrahydrofuran and 50 mL isopropanol) to obtain a dispersion. 10.0 g of N-isopropylacrylamide (NIPAM) monomer, 0.122 g of cuprous bromide (CuBr) catalyst, and 0.825 g of pentamethyldiethylenetriamine ligand (PMDETA) were added to the dispersion. Under inert gas (argon) protection, the reaction system was placed in an oil bath at 60–80 °C and stirred for 24–48 hours. After the reaction was completed, the mixture was cooled and then ultrasonically washed with THF and acetone (using a pulse mode of 30 seconds on and 30 seconds off, not continuous sonication). Unreacted monomers and catalysts were removed by centrifugation (5000 rpm, 10 minutes) or filtration. The precipitate was then lyophilized (-50 °C, vacuum <10 Pa, vacuum drying for 24–48 hours) to obtain HMSNs-PNIPAM-Br (Br is retained at the chain ends for secondary initiation).
[0026] S24, PAA grafting: Surface-initiated ATRP grafting of PtBA: Take 0.1 g HMSNs-C 18 -PNIPAM-Br was dispersed in 15 mL of anisole, and 0.02 mol (approximately 2.56 g) of tBA monomer, 0.028 g of CuBr, and 40 μL of PMDETA were added. The mixture was deoxygenated using a cycle of freezing, vacuuming, and nitrogen purging, and reacted at 80 °C for 24–48 hours. After washing and purification, HMSNs-C was obtained. 18 -PNIPAM-b-PtBA block copolymer. Selective hydrolysis of PtBA: 0.1 g HMSNs-C 18 -PNIPAM-b-PtBA was dispersed in 20 mL of dichloromethane, and 5 mL of trifluoroacetic acid (TFA) was added. The mixture was stirred at room temperature for 12 hours, centrifuged, and washed to obtain HMSNs-C. 18 -PNIPAM-b-PAA.
[0027] S3, grafting rate gallic acid: 1g HMSNs-C 18 -PNIPAM-b-PAA was dispersed in 50 mL of ethanol and sonicated for 10-30 min to ensure uniform dispersion of nanoparticles, yielding HMSNs-C. 18-PNIPAM-b-PAA dispersion. Dissolve 0.34 g gallic acid in 50 mL of dichloromethane, add 0.46 g EDC and 0.28 g NHS, and stir for 30 minutes to obtain an activated gallic acid solution. Add the activated gallic acid solution to HMSNs-C 18 In the PNIPAM-b-PAA dispersion, gallic acid and HMSNs-C 18 The molar ratio of -PNIPAM-b-PAA is 1:1, and the carboxyl group of gallic acid reacts with HMSNs-C. 18 The hydroxyl groups on the surface of -PNIPAM-b-PAA reacted at room temperature for 2 hours. After the reaction, the supernatant was discarded by centrifugation, and the precipitate was collected and washed three times with ethanol and water to remove unreacted gallic acid, activator, and byproducts. Then, it was dried in a vacuum drying oven at room temperature for 24 hours to obtain temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles (denoted as: HMSNs-C). 18 -PNIPAM-b-PAA-GA).
[0028] Example 2: Example 2 is basically the same as Example 1, except that in step S3, gallic acid and HMSNs-C 18 The molar ratio of -PNIPAM-b-PAA is 1:2.
[0029] Example 3: Example 3 is basically the same as Example 1, except that in step S3, gallic acid and HMSNs-C 18 The molar ratio of -PNIPAM-b-PAA is 1:3.
[0030] Example 4: Example 4 is basically the same as Example 1, except that in step S3, gallic acid and HMSNs-C 18 The molar ratio of -PNIPAM-b-PAA is 1:4.
[0031] Calculation of HMSNs-C prepared in Examples 1 to 4 18 Gallic acid grafting rate in -PNIPAM-b-PAA-GA, results are shown in [link to data]. Figure 1 .Depend on Figure 1 It can be seen that Example 3 has the highest grafting rate, and the optimal molar ratio of gallic acid to other substances is 1:3.
[0032] (II) Effect of reaction time on gallic acid grafting rate To investigate the effect of reaction time on the grafting rate of gallic acid, Examples 5 and 6 were conducted in this invention. The reaction times for Examples 5 and 6 were 3 hours and 4 hours, respectively. The details are as follows: Example 5: The content of Example 5 is basically the same as that of Example 3, except that the reaction time in step S3 is 3 hours.
[0033] Example 6: The content of Example 6 is basically the same as that of Example 3, except that the reaction time in step S3 is 4 hours.
[0034] Calculation of HMSNs-C prepared in Examples 3, 5 and 6 18 Gallic acid grafting rate in -PNIPAM-b-PAA-GA, results are shown in [link to data]. Figure 2 .Depend on Figure 2 It can be seen that Example 5 has the highest grafting rate and the optimal reaction time is 3 hours.
[0035] (III) Effect of the molar ratio of gallic acid to activator on the grafting rate of gallic acid To investigate the effect of the molar ratio of gallic acid to activator on the grafting rate of gallic acid, Examples 7 and 8 were conducted in this invention. The molar ratios of gallic acid to activator in Examples 7 and 8 were 1:2 and 1:3, respectively. The details are as follows: Example 7: The content of Example 7 is basically the same as that of Example 5, except that in step S3, the molar ratio of gallic acid to activator is 1:2.
[0036] Example 8: The content of Example 8 is basically the same as that of Example 5, except that in step S3, the molar ratio of gallic acid to activator is 1:3.
[0037] Calculation of HMSNs-C prepared in Examples 5, 7 and 8 18 Gallic acid grafting rate in -PNIPAM-b-PAA-GA, results are shown in [link to data]. Figure 3 .Depend on Figure 3 It can be seen that Example 7 has the highest grafting rate, and the optimal molar ratio of gallic acid to activator is 1:2.
[0038] Comparative Example 1: The content of Comparative Example 1 is basically the same as that of Example 7, except that: no hydrophobic modification is performed on HMSNs, and temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles (denoted as: HMSNs-PNIPAM-b-PAA-GA) are obtained without hydrophobic modification.
[0039] Comparative Example 2: Comparative Example 2 is basically the same as Example 7, except that the gallic acid grafting treatment in step S3 is not performed, thus obtaining temperature-pH dual-responsive hollow mesoporous silica nanoparticles (denoted as: HMSNs-C). 18 -PNIPAM-b-PAA).
[0040] Example 9: A method for encapsulating essential oils, with the following specific steps: (1) Take 400 mg of HMSNs-C prepared in Example 7 18 -PNIPAM-b-PAA-GA nanoparticles were added to deionized water to prepare a suspension of 10 mg / mL. The pH of the suspension was adjusted to 5.0-6.5 using 0.1M hydrochloric acid or sodium hydroxide solution. The pH-adjusted suspension was placed in a constant temperature water bath and the temperature was controlled at 32-35℃. (2) Add 10g of essential oil (EO) to the suspension system of step (1), stir evenly, and first adsorb for 24 hours at 32-35℃ and pH 5.0-6.5 to allow the essential oil to be fully adsorbed into the pores of the nanoparticles. Then, ultrasonically oscillate and impregnate at a frequency of 25-35kHz for 10-12 hours. After ultrasonic oscillation and impregnation, adjust the pH to neutral, centrifuge at 3000-4000 r / min for 10-20 min, discard the supernatant (containing unadsorbed essential oil), collect the precipitate, dry it, and obtain the encapsulated essential oil (denoted as: HMSNs-C). 18 -PNIPAM-b-PAA-GA@EO).
[0041] Comparative Example 3: The content of Comparative Example 3 is basically the same as that of Example 9, except that the nanoparticles used in step (1) to encapsulate the essential oil are HMSNs-PNIPAM-b-PAA-GA of Comparative Example 1, and the encapsulated essential oil is prepared (denoted as: HMSNs-PNIPAM-b-PAA-GA@EO).
[0042] Comparative Example 4: Comparative Example 4 is basically the same as Example 9, except that the nanoparticles used in step (1) to encapsulate the essential oil are HMSNs-C from Comparative Example 2. 18 -PNIPAM-b-PAA, to obtain encapsulated essential oil (denoted as: HMSNs-C) 18 -PNIPAM-b-PAA@EO).
[0043] The HMSNs-C prepared by this invention 18 Performance testing of -PNIPAM-b-PAA-GA: 1. Essential oil loading capacity The essential oil loading rates of test examples 9, 3, and 4 are shown in Table 1.
[0044] Table 1 Essential oil loading rates of Example 9, Comparative Example 3 and Comparative Example 4 Table 1 shows that the essential oil loading rate of the unmodified HMSNs-PNIPAM-b-PAA-GA@EO was 60.3%, while that of the hydrophobically modified HMSNs-C 18 The essential oil loading rate of HMSNs-C18-PNIPAM-b-PAA-GA@EO is 87.5%. Essential oils are hydrophobic substances. Modifying the surface of the hollow mesoporous nanoparticles with hydrophobic octadecylsilane (C18) improves the affinity for essential oils, thus significantly increasing the essential oil loading rate to achieve a theoretical loading of ≥85%. After hydrophobic modification, the essential oil loading rate of HMSNs-C18-PNIPAM-b-PAA@EO without gallic acid is 72.4%, lower than that of HMSNs-C18-PNIPAM-b-PAA@EO with hydrophobic modification and gallic acid attachment. 18 The -PNIPAM-b-PAA-GA@EO loading rate indicates that grafting gallic acid has a certain impact on the loading rate. This may be because the gallic acid structure contains 3 phenolic hydroxyl groups and 1 carboxyl group, which enhances hydrogen bonding. The essential oil components are rich in phenols, alcohols, aldehydes, etc., which form a multi-point hydrogen bond network, improving adsorption capacity and increasing the essential oil loading rate.
[0045] Antioxidant properties The free radical scavenging rates of the essential oil, Example 9, Comparative Example 3, and Comparative Example 4 were tested, and the results are shown in Table 2.
[0046] Table 2. Free radical scavenging rates of essential oils, Example 9, Comparative Example 3, and Comparative Example 4 Table 2 shows that the antioxidant capacity of the essential oils was not inhibited after grafting; in fact, it was somewhat enhanced. This may be due to the good water dispersibility of HMSN, which allows the essential oils to be more evenly dispersed in the system during testing, thus improving their free radical scavenging ability. After GA modification, the scavenging ability against DPPH and ABTS free radicals was improved, with scavenging rates exceeding 90%. This indicates that grafted GA can effectively scavenge free radicals and prevent the oxidation of essential oils.
[0047] Temperature-pH dual-response essential oil release performance The release of essential oils was carried out in phosphate-buffered saline (PBS) at pH 5.5 and pH 7, respectively. The nanoparticles were added to the PBS and continuously stirred at 25°C and 35°C. At different time points, the PBS was removed and the same volume of fresh solution was added. Absorbance was measured, the essential oil content was calculated, and cumulative essential oil release curves were plotted. Results are shown below. Figure 4 As shown.
[0048] Depend on Figure 4 It is observed that the release rate of essential oils is fastest and the final release amount is highest, reaching approximately 98%, at pH=5.5 and 35℃. This is because in the slightly acidic environment of 35℃ and pH=5.5, the PNIPAM chains contract and PAA protonates, opening the pores and allowing the essential oils to be released more quickly from the internal cavities. However, at pH=7 and 25℃, under neutral conditions at room temperature, the polymer chains extend and close the pores, hindering the release of essential oils. Therefore, the release rate of essential oils is slowest under these conditions, and the final release amount is only 36.5%. At pH=5.5 and 25℃ and pH=7 and 35℃, the influence of the polymer chains causes the pores to open only partially. Although essential oils can still be partially released, their release rate is higher than at pH=7 and 25℃, but lower than at pH=5.5 and 35℃.
[0049] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention. Those skilled in the art can modify or make equivalent substitutions to the technical solutions of the present invention based on the concept of the present invention, without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles, characterized in that, Includes the following steps: S1. HMSNs were hydrophobically modified using octadecyltrimethoxysilane to obtain HMSNs-C 18 ; S2, for HMSNs-C 18 Amination modification was performed to obtain HMSNs-C 18 -NH2, for the HMSNs-C 18 -NH2 was used as an initiator to fix the HMSNs-C 18 -Br; for the HMSNs-C 18 -Br was subjected to PNIPAM grafting to obtain HMSNs-C 18 -PNIPAM-Br, for the HMSNs-C 18 -PNIPAM-Br was subjected to PAA grafting to obtain HMSNs-C 18 -PNIPAM-b-PAA; S3, in HMSNs-C 18 Grafting gallic acid onto PNIPAM-b-PAA yields temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles.
2. The method for preparing temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles according to claim 1, characterized in that, In step S3, the specific operation of grafting gallic acid is as follows: The HMSNs-C 18 -PNIPAM-b-PAA is added to solvent A to obtain HMSNs-C 18 -PNIPAM-b-PAA dispersion; Gallic acid is dissolved in solvent B to obtain a gallic acid solution, and an activator is added to the gallic acid solution for activation treatment to obtain an activated gallic acid solution; The activated gallic acid solution is added to the HMSNs-C 18 The PNIPAM-b-PAA dispersion was reacted at room temperature for 2–4 h. After the reaction was completed, the precipitate was collected, washed, and dried to obtain temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles.
3. The method for preparing temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles according to claim 2, characterized in that, The gallic acid and HMSNs-C 18 The molar ratio of -PNIPAM-b-PAA is 1:(1~4); the activator is a mixture of EDC and NHS.
4. The method for preparing temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles according to claim 3, characterized in that, The molar ratio of gallic acid to activator is 1:(1-3); the molar ratio of EDC to NHS in the activator is 1:(1-2).
5. The method for preparing temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles according to any one of claims 1-4, characterized in that, In step S1, the specific operation of the hydrophobic modification is as follows: HMSNs are added to solvent C to obtain an HMSNs dispersion. Under an inert gas atmosphere, octadecyltrimethoxysilane and a catalyst are added to the HMSNs dispersion, and the reaction is carried out at 100°C. After the reaction is completed, the reaction solution is subjected to alcohol precipitation and the precipitate is collected. The precipitate is washed and then mixed with toluene to obtain a suspension. The suspension is subjected to alcohol precipitation and the precipitate is collected. The precipitate is dried to obtain HMSNs-C. 18 ; In step S2, the specific process of the amination modification is as follows: HMSNs-C activated with hydrochloric acid... 18 Adding to solvent D yields HMSNs-C 18 The dispersion was mixed with 3-aminopropyltriethoxysilane and refluxed at 100–110 °C for 12–16 h under an inert atmosphere. After the reaction was complete, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -NH2; In step S2, the specific process of the initiator immobilization treatment is as follows: The HMSNs-C 18 -NH2 is added to solvent E to obtain HMSNs-C 18 -NH2 dispersion, under light-protected conditions at 0–4°C, to HMSNs-C 18 Triethylamine and 2-bromoisobutyryl bromide were added to an NH2 dispersion, and the reaction was carried out at room temperature in the dark. After the reaction was completed, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -Br; In step S2, the specific operation of the PNIPAM grafting process is as follows: HMSNs-C 18 -Br is added to solvent F to obtain HMSNs-C 18 -Br dispersion, into HMSNs-C 18 NIPAM monomer, CuBr, and PMDETA were added to the -Br dispersion, and the mixture was stirred at 60–80 °C for 24–48 h under an inert gas atmosphere. After the reaction was completed, the precipitate was collected, washed, and lyophilized to obtain HMSNs-C. 18 -PNIPAM-Br; In step S2, the specific operation of the PAA grafting process is as follows: HMSNs-C 18 -PNIPAM-Br is added to solvent G to obtain HMSNs-C 18 -PNIPAM-Br dispersion; to HMSNs-C 18 tBA monomer, CuBr, and PMDETA were added to the PNIPAM-Br dispersion. After freezing, vacuuming, and nitrogen purging for deoxygenation, the reaction was carried out at 80–82 °C for 24–48 h. After the reaction was completed, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -PNIPAM-b-PtBA; HMSNs-C 18 -PNIPAM-b-PtBA is added to solvent H to obtain HMSNs-C 18 -PNIPAM-b-PtBA dispersion; to HMSNs-C 18 Trifluoroacetic acid was added to the PNIPAM-b-PtBA dispersion, and the mixture was stirred at room temperature. After the reaction was complete, the precipitate was collected, washed, and dried to obtain HMSNs-C. 18 -PNIPAM-b-PAA.
6. The method for preparing temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles according to claim 5, characterized in that, In the hydrophobic modification process, the catalyst is ethylenediamine or tripropylamine, the concentration of HMSNs in the HMSNs dispersion is 1-10 mg / mL, and the molar ratio of the catalyst to octadecyltrimethoxysilane is 1:(1-10). During the amination modification process, 3-aminopropyltriethoxysilane reacts with HMSNs-C 18 The mass ratio is 1:(10~20); During the initiator immobilization process, HMSNs-C 18 The ratio of -NH2, triethylamine and 2-bromoisobutyryl bromide is 1 g : (250-270) μL : (300-350) μL; During the PNIPAM grafting process, NIPAM monomers and HMSNs-C 18 The mass ratio of -Br is (10~15):1, the molar ratio of CuBr to NIPAM monomer is (0.01~0.02):1, and the molar ratio of PMDETA to CuBr catalyst is (4~5):1; In the specific operation of the PAA grafting treatment, HMSNs-C 18 The ratio of -PNIPAM-Br, tBA monomer, CuBr and PMDETA is 0.1 g:(2-3) g:(0.02-0.03) g:(30-50) μL.
7. The method for preparing temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles according to claim 6, characterized in that, Solvents A, B, C, D, E, F, G, and H are all organic solvents.
8. Temperature-pH dual-responsive antioxidant hollow mesoporous silica nanoparticles prepared by the method according to any one of claims 1-7.
9. The application of the temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles as described in claim 8 in the encapsulation of essential oils.
10. A method for encapsulating essential oils, characterized in that, Includes the following steps: (1) Dispersion adjustment: The temperature-pH dual-response antioxidant hollow mesoporous silica nanoparticles of claim 8 are added to water to obtain a suspension, the pH of the suspension is adjusted to 5.0 to 6.5, and the suspension is heated to 32 to 35°C; (2) Essential oil loading: Add the essential oil to the suspension and mix well. First, stir and adsorb under the conditions of 32-35℃ and pH 5.0-6.5, then impregnate with ultrasonic vibration. After the ultrasonic vibration impregnation is completed, adjust the pH to neutral, centrifuge to collect the precipitate, freeze dry, and obtain the encapsulated essential oil.