A kind of natural polyphenol-based nanodots and a preparation method thereof

Abstract

The embodiment of the application discloses a kind of natural polyphenol-based nanodots and its preparation method and application.The method comprises: under stirring condition, slowly add the concentration of 20.0-30.0mg / mL ferric chloride aqueous solution to the concentration of 1.0-3.0mg / mL natural polyphenol aqueous solution, continue stirring 1-4h, then carry out filtration, dialysis and freeze-drying processing in sequence, obtain the natural polyphenol-based nanodots, wherein the volume ratio of the natural polyphenol aqueous solution and ferric chloride aqueous solution is 5-15:1.The application uses water as reaction medium, avoids using organic solvent, and does not need additional stabilizer, reduces the complexity of raw material use, and can obtain nanodots with uniform shape and uniform distribution by simple stirring at lower temperature.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of natural biomass nanomaterials, and in particular to a kind of nano-dot based on natural polyphenol and a preparation method thereof. BACKGROUND

[0002] Natural polyphenols refer to a large number of compounds extracted from plants, which are composed of catechol and / or galloyl groups, including tea polyphenols, tannins, lignans, etc. Based on its outstanding structure and function, natural polyphenol-based materials have received extensive attention and have been developed through various processing methods from different angles. It is reported that catechol groups can form dynamic covalent bonds with boric acid, and this dynamic bond has the response ability to pH value and cis-diol. Secondly, the quinone group generated by the oxidation of catechol and galloyl group can react with other functional groups such as thiol and amino group through Schiff base reaction and / or Michael addition to endow it with additional functions. Catechol and galloyl group can be chelated with metal ions to form metal-phenol network complexes, in which a large database including metal ions and polyphenols has been involved to prepare functional materials based on metal-phenol network. In addition, catechol and galloyl group can be joined in some non-covalent interactions, such as hydrogen bonding, electrostatic interaction, conjugated stacking, hydrophobic interaction and cation-π interaction. Due to these rich structural and functional characteristics, various multi-dimensional functional materials have been developed for biomedical, surface engineering, energy and environmental science.

[0003] Among natural polyphenols, catechol groups can be converted between phenol and quinone, and with the assistance of metal ions, a bi-redox catalytic system of polyphenol and metal ions has been used to rapidly prepare hydrogel at room temperature with ultrafast speed through free radical polymerization (Chem. Mater. 2019, 31, 5625-5632; Compos. Sci. Technol. 2022, 221, 109345; CN109400779B). However, the catalytic system directly mixed by natural polyphenol and metal ions often needs a higher concentration when used to prepare gel, and the subsequent possible leakage may bring unpredictable accidents. Therefore, it is still difficult to improve the catalytic efficiency of the bi-redox catalytic system based on natural polyphenol and metal ions to prepare multifunctional hydrogel.

[0004] One possible approach is to prepare natural polyphenol and metal ion nanoparticle materials, which have been reported in some reports, such as ACS Cent. Sci. 2022, 8, 10-21; Mater. Horiz., 2021, 8, 1314-1322: 66 mg of PVP (polyvinylpyrrolidone, as a stabilizer) is dissolved in 5 mL of methanol, 1 mL of iron chloride solution (containing 20 mg of iron chloride) is added dropwise, 5 min later, 1 mL of natural polyphenol solution (containing 10 mg of natural polyphenol) is added dropwise, and then stirred for 3 h. The existing method uses an organic solvent, and a stabilizer needs to be added during preparation. These complex preparation processes are not conducive to achieving the goal of sustainable development, and may cause potential biological toxicity and environmental pressure.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] To this end, the embodiments of the present application provide a natural polyphenol-based nanoparticle and a preparation method thereof.

[0007] To achieve the above-mentioned purpose, the embodiments of the present application provide the following technical solutions:

[0008] According to a first aspect of the embodiments of the present application, the present application provides a preparation method of a natural polyphenol-based nanoparticle, the method comprising:

[0009] Under stirring, a ferric chloride aqueous solution with a concentration of 20.0-30.0 mg / mL is slowly added to a natural polyphenol aqueous solution with a concentration of 1.0-3.0 mg / mL, and stirring is continued for 1-4 h, and then filtration, dialysis and freeze-drying treatment are sequentially performed to obtain the natural polyphenol-based nanoparticle, wherein the volume ratio of the natural polyphenol aqueous solution to the ferric chloride aqueous solution is 5-15:1.

[0010] The present application studies the concentration of the natural polyphenol aqueous solution and the ferric chloride aqueous solution, as well as the dropwise adding sequence. Under the above conditions, the nanoparticle with uniform morphology and stability can be obtained, and the iron content in the prepared nanoparticle is low (less than 2%), and the remaining is biomass molecules of natural plant origin, which greatly improves the biological safety and usability of the material. It should be noted that the ferric chloride mentioned in the present application refers to ferric chloride hexahydrate.

[0011] Further, the concentration of the natural polyphenol aqueous solution is 1.39 mg / mL, the concentration of the ferric chloride aqueous solution is 25.0 mg / mL, and the volume ratio of the natural polyphenol aqueous solution to the ferric chloride aqueous solution is 9:1.

[0012] The present application further finds that, without using a stabilizer, stirring conditions (including speed and temperature), and dropping speed are key parameters for controlling the morphology of the nanodots, too slow stirring or too fast dropping causes too high local iron concentration, and iron cannot be dispersed quickly to form precipitated aggregates, too fast stirring or too slow dropping causes the solution to be unstable, and is not conducive to forming nanodots with uniform morphology. In some preferred embodiments, the stirring speed is 300-500 rpm, and the temperature is 5-40℃; the adding speed of the aqueous ferric chloride solution is 1 drop / s. In some specific embodiments, the stirring speed is preferably 400 rpm, and the temperature is preferably 25℃.

[0013] Further, the filtration uses a filter membrane with a pore size of 0.22 microns.

[0014] Further, the dialysis has a molecular weight cut-off of 1000-14000 daltons, and a time of 2-7 days. The dialysis operation is to remove some oligomers that have not grown into nanodots, and the molecular weight selection is to balance the purification speed and sample loss (the larger the molecular weight cut-off, the faster the speed, the shorter the time, but the greater the loss of nanodots).

[0015] Further, the freeze-drying conditions are: placing the liquid in the dialysis bag in liquid nitrogen for 10-20 min, then immediately taking it out and placing it in a freeze dryer, under a cold trap temperature of less than -50℃ and a vacuum degree of less than 10 Pa, for 3-7 days. Research finds that using liquid nitrogen for quick freezing is to maintain the original morphological characteristics of the nanodots. If a refrigerator (relatively slow freezing) is used, perfect crystals may be formed due to slow freezing of water, and the structure of the nanodots may be destroyed.

[0016] Further, the natural polyphenol is gallic acid, epigallocatechin gallate, epicatechin, chlorogenic acid, or pyrogallic acid.

[0017] According to a second aspect of the embodiments of the present application, the present application provides a nanodot based on a natural polyphenol, which is prepared by the method according to any one of the above.

[0018] The embodiments of the present application have the following advantages:

[0019] 1. The preparation method of the nanodot based on a natural polyphenol provided by the present application uses water as a reaction medium, avoids using organic solvents, and does not need to add additional stabilizers, thereby reducing the complexity of raw material use, and obtaining nanodot materials with uniform shape and uniform distribution through simple stirring at a relatively low temperature.

[0020] 2. The nanodot based on a natural polyphenol provided by the present application has excellent catalytic ability, and can catalyze various vinyl monomers to form a hydrogel at a relatively low concentration at room temperature.

[0021] 3、The preparation method of the hydrogel is simple, fast, universal, and can form the hydrogel in situ in a space with different shapes. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only exemplary, and for those skilled in the art, other drawings can be obtained from the provided drawings without creative labor.

[0023] Figure 1 The scanning electron microscope image (upper row, scale 100 nm) and the enlarged detail image (lower row, scale 2 nm) provided for the embodiment of the present application are shown in the following figure:

[0024] Figure 2 The TEM photo provided for the comparative example 1 of the present application is shown in the following figure:

[0025] Figure 3 The dynamic light scattering test results provided for the embodiment of the present application are shown in the following figure:

[0026] Figure 4 The particle size statistical test results provided for the embodiment of the present application are shown in the following figure:

[0027] Figure 5 The dynamic light scattering test results before and after the embodiment of the present application is placed at 25℃ for 24 hours are shown in the following figure:

[0028] Figure 6 The schematic diagram of the nanodot catalyzing the polymerization of different monomers into a gel provided for the embodiment of the present application is shown in the following figure:

[0029] Figure 7 The nanodot catalyzing the formation of hydrogels with different shapes from acrylamide provided for the embodiment of the present application is shown in the following figure:

[0030] Figure 8 The nanodot and free monomer catalyzing the formation of hydrogels from acrylamide provided for the embodiment of the present application is shown in the following figure. DETAILED DESCRIPTION

[0031] The embodiments of the present application are described below by specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in the description. Obviously, the described embodiments are part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0032] In the embodiments of the present application, the natural polyphenol monomers (gallic acid, purity ≥ 99%; chlorogenic acid, purity ≥ 95%; epigallocatechin gallate, purity ≥ 98%; epicatechin, purity ≥ 97%; pyrogallic acid, purity ≥ 99%) and the vinyl monomers (acrylic acid, purity AR; acrylamide, purity AR; poly(ethylene glycol) diacrylate, average molecular weight 1000) are purchased from Shanghai Aladdin Bio-Chem Technology Co., Ltd.; iron trichloride hexahydrate (purity AR) is purchased from Chengdu Kelong Chemical Co., Ltd.

[0033] Example 1 Preparation of gallic acid nanodots

[0034] (1) 15 mL of water was used to dissolve 15 mg of gallic acid, and ultrasonic treatment was performed for 30 min to obtain liquid 1.

[0035] (2) 1 mL of water was used to dissolve 20 mg of iron trichloride hexahydrate, and ultrasonic treatment was performed for 5 min to obtain liquid 2.

[0036] (3) Liquid 1 was subjected to magnetic stirring at 400 rpm at room temperature (25°C), and then liquid 2 was slowly added to liquid 1 at a rate of about 1 drop / s, and after the addition was completed, the reaction was stirred for 2 h.

[0037] (4) The reaction liquid obtained in step (3) was filtered using a filter membrane with a pore size of 0.22 microns, and then the filtrate was subjected to dialysis treatment using a dialysis bag with a molecular weight cut-off of 3500 daltons for 3 days, and finally the liquid in the dialysis bag was subjected to freeze-drying treatment. The specific process is as follows: the liquid in the dialysis bag was placed in liquid nitrogen and frozen for 15 min, then immediately taken out and placed in a freeze dryer, and the cold trap temperature was less than -50°C, the vacuum degree was less than 10 Pa, and the treatment was continued for 5 days to obtain nanodots.

[0038] Example 2 Preparation of epigallocatechin gallate nanodots

[0039] (1) 9 mL of water was used to dissolve 12.5 mg of epigallocatechin gallate, and ultrasonic treatment was performed for 30 min to obtain liquid 1.

[0040] (2) 1 mL of water was used to dissolve 25 mg of iron trichloride hexahydrate, and ultrasonic treatment was performed for 5 min to obtain liquid 2.

[0041] (3) Liquid 1 was subjected to magnetic stirring at 400 rpm at room temperature (25°C), and then liquid 2 was slowly added to liquid 1 at a rate of about 1 drop / s, and after the addition was completed, the reaction was stirred for 2 h.

[0042] (4) The reaction solution obtained in step (3) is filtered using a filter membrane with a pore size of 0.22 microns, and then the filtrate is dialyzed using a dialysis bag with a molecular weight cut-off of 3500 daltons for 3 days. Finally, the liquid in the dialysis bag is freeze-dried. The specific process is as follows: the liquid in the dialysis bag is frozen in liquid nitrogen for 15 min, then immediately taken out and placed in a freeze dryer, under a cold trap temperature of less than -50°C and a vacuum degree of less than 10 Pa for 5 days, to obtain the nanodots.

[0043] Example 3 Preparation of epicatechin nanodots

[0044] (1) 9 mg of epicatechin is dissolved in 9 mL of water and ultrasonically treated for 30 min to obtain liquid 1.

[0045] (2) 25 mg of ferric chloride hexahydrate is dissolved in 1 mL of water and ultrasonically treated for 5 min to obtain liquid 2.

[0046] (3) Liquid 1 is magnetically stirred at room temperature (25°C) at 400 rpm, and then liquid 2 is slowly added to liquid 1 at a rate of about 1 drop / s. After the addition is complete, the reaction is stirred for another 2 h.

[0047] (4) The reaction solution obtained in step (3) is filtered using a filter membrane with a pore size of 0.22 microns, and then the filtrate is dialyzed using a dialysis bag with a molecular weight cut-off of 3500 daltons for 3 days. Finally, the liquid in the dialysis bag is freeze-dried. The specific process is as follows: the liquid in the dialysis bag is frozen in liquid nitrogen for 15 min, then immediately taken out and placed in a freeze dryer, under a cold trap temperature of less than -50°C and a vacuum degree of less than 10 Pa for 5 days, to obtain the nanodots.

[0048] Example 4 Preparation of chlorogenic acid nanodots

[0049] (1) 10 mg of chlorogenic acid is dissolved in 5 mL of water and ultrasonically treated for 30 min to obtain liquid 1.

[0050] (2) 20 mg of ferric chloride hexahydrate is dissolved in 1 mL of water and ultrasonically treated for 5 min to obtain liquid 2.

[0051] (3) Liquid 1 is magnetically stirred at room temperature (25°C) at 400 rpm, and then liquid 2 is slowly added to liquid 1 at a rate of about 1 drop / s. After the addition is complete, the reaction is stirred for another 2 h.

[0052] (4) The reaction solution obtained in step (3) was filtered using a filter membrane with a pore size of 0.22 micrometers. Then, the filtrate was dialyzed for 3 days using a dialysis bag with a molecular weight cutoff of 3500 Daltons. Finally, the liquid in the dialysis bag was freeze-dried. The specific process was as follows: the liquid in the dialysis bag was placed in liquid nitrogen and frozen for 15 minutes. Then, it was immediately taken out and placed in a freeze dryer. The freeze dryer was kept at a cold trap temperature of less than -50°C and a vacuum degree of less than 10 Pa for 5 days to obtain nanodots.

[0053] Example 5: Preparation of Pyrogalic Acid Nanodots

[0054] (1) Dissolve 27 mg of pyrogallol in 9 mL of water and sonicate for 30 min to obtain liquid 1.

[0055] (2) Dissolve 20 mg of ferric chloride hexahydrate in 1 mL of water and sonicate for 5 min to obtain liquid 2.

[0056] (3) Liquid 1 was magnetically stirred at 400 rpm at room temperature (25℃), and then Liquid 2 was slowly added to Liquid 1 at a rate of about 1 drop / s. After the addition was completed, the mixture was stirred for 2 hours.

[0057] (4) The reaction solution obtained in step (3) was filtered using a filter membrane with a pore size of 0.22 micrometers. Then, the filtrate was dialyzed for 3 days using a dialysis bag with a molecular weight cutoff of 3500 Daltons. Finally, the liquid in the dialysis bag was freeze-dried. The specific process was as follows: the liquid in the dialysis bag was placed in liquid nitrogen and frozen for 15 minutes. Then, it was immediately taken out and placed in a freeze dryer. The freeze dryer was kept at a cold trap temperature of less than -50°C and a vacuum degree of less than 10 Pa for 5 days to obtain nanodots.

[0058] Comparative Example 1: Preparation of Gallic Acid Nanodots

[0059] (1) Dissolve 60 mg of gallic acid in 15 mL of water and sonicate for 30 min to obtain liquid 1.

[0060] (2) Dissolve 20 mg of ferric chloride hexahydrate in 1 mL of water and sonicate for 5 min to obtain liquid 2.

[0061] (3)-(5) Same as Example 1.

[0062] Test Example 1

[0063] The products prepared in Examples 1-5 and Comparative Example 1 were characterized by transmission electron microscopy to observe the morphology of the nanodots and to count their particle size. The results showed that the products prepared in Examples 1-5 had a size of less than 5 nm, exhibited a distinct layered structure, and had an interlayer spacing of approximately 0.21 nm. Figure 1 The product prepared in Comparative Example 1 was an aggregate with a random morphology.Figure 2 The above shows that the method provided by the embodiments of the present application can prepare nanodots with uniform shape and uniform distribution.

[0064] The size of the products prepared in Examples 1-5 was detected by a dynamic light scattering particle size instrument, and the results show that the size of the product of Example 1 is about 6.1 nm, the size of the product of Example 2 is about 2.7 nm, the size of the product of Example 3 is about 3.6 nm, the size of the product of Example 4 is about 3.1 nm, and the size of the product of Example 5 is about 5.0 nm. Figure 3 The above shows that there is a significant difference in the diameters of the nanodots prepared from different monomers, but the regularity is basically the same as the result of the transmission electron microscope. Figure 4

[0065] Test Example 2

[0066] Taking Examples 2 and 3 as typical cases, the size of the products was detected by a dynamic light scattering particle size instrument after being placed in an environment of 25℃ for 24 hours. The results show that the particle size of the products of Examples 2 and 3 remains relatively stable and does not change significantly. Figure 5 The above shows that the nanodots prepared by the method provided in the embodiments of the present application have good stability.

[0067] Examples 6-8: Gallic acid-based nanodots catalyze polymerization of different monomers into hydrogels

[0068] The specific steps are as follows: each material is weighed according to the amount ratio in Table 1 for standby; the nanodots, the monomer and the crosslinking agent (methylene bisacrylamide) are dispersed in 9 mL of water, and ultrasonic treatment is performed for 3 min to form liquid 3; ammonium persulfate is dispersed in 1 mL of water, and ultrasonic treatment is performed for 3 min to form liquid 4; liquid 4 is quickly added to liquid 3, and after being quickly shaken, it is left to stand or poured into a mold, and a hydrogel can be formed after 5 min, as shown in Figures 6-7 .

[0069] Table 1: Formulas corresponding to Examples 6-8

[0070]

[0071] The results show that the gallic acid-based nanodots can quickly catalyze the polymerization of acidic, basic and neutral vinyl monomers to form hydrogels at room temperature.

[0072] ​To illustrate the advantage of the natural polyphenol-based nanodot material provided by the present application in catalytic ability, we determined the chemical composition of the nanodot by inductively coupled plasma atomic emission spectrometer, and formulated the experimental scheme of Example 9 and Comparative Example 2 so that the contents of gallic acid and iron elements were the same, as shown in Table 2. The specific steps are as follows: the components contained in the catalytic system, acrylamide, and a crosslinking agent (methylene bisacrylamide) dispersion solution were dispersed in 4.5 mL of water, and ultrasonic treatment was performed for 3 min to form liquid 5. 1 mg of ammonium persulfate was dissolved in 0.5 mL of water, and ultrasonic treatment was performed for 3 min to form liquid 6. Liquid 6 was quickly added to liquid 5, and after quick shaking, it was left to stand for 5 min, as shown in Figure 8

[0073] The results show that, under the premise that other reaction conditions remain unchanged, the nanodot material cannot catalyze the formation of a hydrogel by vinyl monomers by being split into a single natural polyphenol monomer and iron particles.

[0074] Table 2 Formulation corresponding to Example 9 and Comparative Example 2

[0075]

[0076] Compared with the prior art, the nanodot material of the present application can effectively catalyze the polymerization of acidic, basic and neutral vinyl monomers at room temperature under low catalyst concentration without other auxiliary conditions. In Example 9, the final prepared gel contains only about 20 μg / mL of natural polyphenol and 1 μg / mL of iron ion, which can minimize the subsequent leakage problem of the catalytic components, and provides a new method and idea for the polymerization and preparation of hydrogels.

[0077] Although the present application has been described in detail in the foregoing with general description and specific embodiments, some modifications or improvements can be made on the basis of the present application, which is obvious to those skilled in the art. Therefore, these modifications or improvements made on the basis of not deviating from the spirit of the present application, all belong to the scope of protection claimed by the present application.​

Claims

1. Use of natural polyphenol-based nanodots as catalysts in the preparation of hydrogels by catalyzing the polymerization of vinyl monomers, characterized in that, The preparation method of the nanodots comprises the following steps: Under stirring, a ferric trichloride aqueous solution with a concentration of 20.0-30.0 mg / mL is slowly added into a natural polyphenol aqueous solution with a concentration of 1.0-3.0 mg / mL, and the stirring is continued for 1-4 hours, and then the obtained product is subjected to filtration, dialysis and freeze-drying in sequence to obtain the nanodots based on natural polyphenols, wherein the volume ratio of the natural polyphenol aqueous solution to the ferric trichloride aqueous solution is 5-15:

1. The stirring speed is 300-500 rpm, and the temperature is 5-40℃; and the ferric trichloride aqueous solution is added at a speed of 1 drop / s.

2. Use according to claim 1, characterized in that, The concentration of the natural polyphenol aqueous solution is 1.39 mg / mL, the concentration of the ferric trichloride aqueous solution is 25.0 mg / mL, and the volume ratio of the natural polyphenol aqueous solution to the ferric trichloride aqueous solution is 9:

1.

3. Use according to claim 1, characterized in that, The filtration is performed by using a filter membrane with a pore size of 0.22 microns.

4. Use according to claim 1, characterized in that, The dialysis is performed at a molecular weight cut-off of 1000-14000 daltons for 2-7 days.

5. The use according to claim 1, characterized in that, The freeze-drying is performed by freezing the obtained dialysis product in liquid nitrogen for 10-20 minutes, then immediately taking out and placing in a freeze dryer, and continuously performing freeze-drying at a cold trap temperature less than -50℃ and a vacuum degree less than 10 Pa for 3-7 days.

6. Use according to claim 1, characterized in that, The natural polyphenol is gallic acid, epigallocatechin gallate, epicatechin, chlorogenic acid or pyrogallic acid.

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