CN117643637B - A controlled release carrier for improving the bioaccessibility of curcumin and a preparation method thereof - Google Patents

Abstract

The present invention discloses a controlled release carrier for improving the bioaccessibility of curcumin and a preparation method thereof, and belongs to the field of curcumin delivery carriers. The present invention constructs succinic acid cyclodextrin ester/chitosan (SACD/CS) nanoparticles as an upper digestive tract delivery carrier of curcumin; wherein succinic acid cyclodextrin ester (SACD) promotes the dispersion of curcumin in a water matrix; chitosan (CS), as a natural polymer that is not degraded by digestive enzymes in the upper digestive tract, can fix curcumin in its macromolecular network and realize controlled release during digestion. The carrier prepared by the present invention is formed by self-assembly based on electrostatic interaction, and the preparation process is safe, simple and efficient, and has broad application prospects in the fields of food and medicine.

Description

A controlled release carrier for improving the bioaccessibility of curcumin and a preparation method thereof

Technical Field

The invention relates to a controlled release carrier for improving the bioaccessibility of curcumin and a preparation method thereof, and belongs to the field of curcumin delivery carriers.

Background technique

Curcumin is a natural phenolic compound isolated from turmeric. It has antioxidant, anti-inflammatory, anti-cancer and antibacterial physiological activities and is widely used in health fields such as food and medicine. However, curcumin has extremely poor water solubility. After being ingested orally and entering the human digestive tract, it is difficult to disperse in the digestive juice with water as the matrix. Only fully dispersed curcumin can be absorbed by intestinal epithelial cells and enter the human body. Promoting the dispersion of curcumin in digestive juice is one of the key technologies to improve its bioaccessibility.

Literature (Yao Hu, et al. Encapsulation, protection, and delivery of curcumin using succinylated-cyclodextrin systems with strong resistance to environmental and physiological stimuli, Food Chemistry, Volume 376, 2022, 131869.) By embedding curcumin in the molecular cavity of water-soluble cyclodextrin, its dispersibility in the water matrix can be effectively improved, and excellent results have been achieved. However, due to the high water solubility of the prepared curcumin-cyclodextrin inclusion complex, curcumin is immediately released after entering the digestive tract. This burst release effect causes the human body to absorb high concentrations of curcumin in a short period of time, which may produce potential toxic side effects. Therefore, the technical difficulty in improving the bioaccessibility of curcumin lies in controlling the release rate of curcumin in the digestive tract, so that it can efficiently exert its bioaccessibility.

After ingestion, curcumin passes through the upper gastrointestinal tract (mouth-stomach-small intestine) and the lower gastrointestinal tract (large intestine) in sequence, and undigested curcumin is eventually excreted from the body with feces. In the upper gastrointestinal process, curcumin dispersed into the digestive fluid under the action of digestive enzymes, bile salts, etc. can be directly absorbed by the epithelial cells of the gastrointestinal tract; while in the lower gastrointestinal process, curcumin produces a series of metabolites under the action of intestinal microorganisms, and its physiological activity also changes accordingly. The upper gastrointestinal process and the lower gastrointestinal process are two completely different processes, and the carrier that can be used in the lower gastrointestinal process may not be used for the upper gastrointestinal carrier. Generally speaking, the bioaccessibility of curcumin refers to the content of curcumin dispersed in the upper gastrointestinal tract that can be absorbed and utilized by the human body. Constructing an upper gastrointestinal delivery carrier for curcumin is currently the most promising technical means to improve the bioaccessibility of curcumin.

Literature (Wang Yurong, Feng Bin, Ju Jia, et al. Preparation and characterization of carboxymethylated Bletilla striata polysaccharide-chitosan polyelectrolyte composite membrane loaded with curcumin and its characterization [J]. Chinese Herbal Medicine, 2020, 51(4):8. DOI:10.7501/j.issn.0253-2670.2020.04.023.) discloses a method for preparing a carboxymethylated Bletilla striata polysaccharide-chitosan polyelectrolyte composite membrane loaded with curcumin, which is mainly used for oral release; CN115607524A discloses a composite nanoparticle loaded with curcumin, which is a core-shell structure, wherein curcumin and zein are the core and carboxymethyl tuckahoe polysaccharide is the shell; CN 108653721A discloses a chitosan carrier drug of a water-soluble curcumin derivative; CN104273522B discloses the preparation of a curcumin nanocomposite, which requires the use of lecithin and Tween-80 as emulsifiers; however, the present invention still faces problems such as low bioaccessibility of curcumin, high energy burden brought by lipid carriers, and the use of potentially toxic components such as small molecule emulsifiers.

Summary of the invention

[technical problem]

Curcumin carriers or complexes have problems such as "low bioaccessibility, high energy burden brought by oil carriers, and the use of potentially toxic ingredients such as small molecule emulsifiers."

[Technical solutions]

In order to solve the above problems, the present invention constructs succinic acid cyclodextrin ester/chitosan (SACD/CS) nanoparticles as an upper gastrointestinal delivery carrier of curcumin; wherein succinic acid cyclodextrin ester (SACD) promotes the dispersion of curcumin in a water matrix; chitosan (CS), as a natural polymer that is not degraded by digestive enzymes in the upper gastrointestinal tract, can fix curcumin in its macromolecular network and achieve controlled release during digestion. The carrier prepared by the present invention is formed by self-assembly based on electrostatic interaction, and the preparation process is safe, simple and efficient, and has broad application prospects in the fields of food and medicine.

The first object of the present invention is to provide a method for preparing a controlled release nanocarrier Cur-SACD/CS for improving the bioaccessibility of curcumin, comprising the following steps:

(1) Preparation of SACD/CS nanoparticles:

Slowly add the succinic acid cyclodextrin ester SACD solution to the chitosan CS solution and stir to react; then slowly add ethanol dropwise and continue stirring to promote particle formation. After the reaction is completed, separate the solid and liquid, wash and dry to obtain SACD/CS nanoparticles; wherein the mass ratio of SACD in the SACD solution to CS in the CS solution is 1:1-5;

(2) SACD/CS nanoparticles loaded with curcumin:

The SACD/CS nanoparticles are dispersed in water and hydrated to obtain a SACD/CS nanoparticle suspension; the curcumin solution is added to the SACD/CS nanoparticle suspension and stirred to react in the dark; after the reaction is completed, the solid-liquid separation and drying are performed to obtain the nanocarrier Cur-SACD/CS.

In one embodiment of the present invention, the solvent of the SACD solution in step (1) is an acetic acid-sodium acetate buffer solution with a pH of 5.3 and a concentration of 0.001-10 g/mL, more preferably 0.01 g/mL.

In one embodiment of the present invention, the preparation method of the CS solution in step (1) is: dissolving CS in a glacial acetic acid solution, and then adjusting the pH to 5.3 with a sodium hydroxide solution; wherein the dosage ratio of CS to the glacial acetic acid solution is 0.1-2 g:100 mL; the mass concentration of the glacial acetic acid solution is 0.5-1.5%; and the concentration of the sodium hydroxide solution is 0.1-0.3 mol/L.

In one embodiment of the present invention, the rate of slow addition in step (1) is 20-200 mL/min.

In one embodiment of the present invention, the stirring reaction in step (1) is carried out at 100-600 rpm for 10-30 min.

In one embodiment of the present invention, the rate of slow dripping in step (1) is 1-10 mL/min.

In one embodiment of the present invention, the ethanol in step (1) is anhydrous ethanol.

In one embodiment of the present invention, the usage ratio of CS to ethanol in step (1) is 1 g: 350-450 mL.

In one embodiment of the present invention, the stirring in step (1) is continued at 100-600 rpm for 30-90 min.

In one embodiment of the present invention, the solid-liquid separation in step (1) is performed by centrifugation or filtration to collect the SACD/CS nanoparticles therein.

In one embodiment of the present invention, the washing in step (1) is performed using an ethanol aqueous solution with a volume fraction of 60-80%, and the number of washing times is 1-5 times.

In one embodiment of the present invention, the ratio of the amount of SACD/CS nanoparticle dispersion to water in the SACD/CS nanoparticle suspension in step (2) is 0.5 g: 40-100 mL.

In one embodiment of the present invention, the hydration in step (2) is stirred at 100-300 rpm for 20-40 min.

In one embodiment of the present invention, the concentration of the curcumin solution in step (2) is 0.5-5 mg/mL; and the solvent is anhydrous ethanol.

In one embodiment of the present invention, the volume ratio of the curcumin solution to the SACD/CS nanoparticle suspension in step (2) is 0.5:40-100.

In one embodiment of the present invention, the stirring reaction in step (2) is carried out at 100-300 rpm for 2-4 hours.

In one embodiment of the present invention, the solid-liquid separation in step (2) is performed by centrifugation or filtration to collect the Cur-SACD/CS nanocarriers therein.

The second object of the present invention is the nanocarrier Cur-SACD/CS prepared by the method described in the present invention.

The third objective of the present invention is to use the nanocarrier Cur-SACD/CS prepared by the method described in the present invention in the field of food or medicine.

The fourth object of the present invention is to provide a method for improving the controlled sustained release effect and upper digestive tract release amount of curcumin, which uses the nanocarrier Cur-SACD/CS described in the present invention.

[Beneficial Effects]

(1) The present invention solves the problem of low bioaccessibility of curcumin and prepares a curcumin controlled release carrier based on electrostatic self-assembly technology. The present invention uses CS as a natural macromolecular network and self-assembles with SACD to form a SACD/CS nanoparticle carrier through electrostatic interaction. After loading curcumin, the upper gastrointestinal tract controlled release of curcumin is achieved, effectively improving the bioaccessibility of curcumin.

(2) The present invention prepares SACD/CS nanoparticles based on electrostatic self-assembly technology. Not only is the preparation process simple, green, and non-toxic, but the morphology of SACD/CS nanoparticles can be regulated by controlling the ratio of SACD to CS. In the simulated in vitro digestion process, curcumin in Cur-SACD/CS nanocarriers achieved delayed controlled delivery.

(3) The particle size of the nanocarrier Cur-SACD/CS prepared by the present invention is about 200 nm, which is much smaller than the conventional carrier size of more than 1000 nm.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is an SEM image of the SACD/CS composites prepared in Examples 1-3 and Comparative Examples 1-3, wherein: (a) Comparative Example 1 (0:5); (b) Comparative Example 2 (1:5); (c) Comparative Example 3 (3:5); (d) Example 1 (5:5); (e) Example 2 (7:5); and (f) Example 3 (9:5).

FIG. 2 is the FTIR spectra of the SACD/CS composites prepared in Examples 1-3 and Comparative Examples 2-3.

FIG3 shows the release amounts of curcumin at different stages of the in vitro simulated digestion process of curcumin, nanocarriers prepared in Examples 1-3 and Comparative Examples 1-3.

Figure 4 shows the retention rate of curcumin in the Cur-SACD/CS nanocarrier prepared in Example 1 after incubation at simulated gastric fluid pH (a), intestinal fluid pH (b), physiological salt concentration (c) and physiological temperature (d) (Ⅰ~VI indicate significant differences between samples, p<0.05).

FIG5 is a loading curve of curcumin for the nanocarriers prepared in Example 1 and Comparative Example 1.

FIG. 6 is a SEM image of the SACD/CS composite prepared in Comparative Example 4.

Detailed ways

The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

Test Methods:

1. In vitro simulated digestion and release test of Cur-SACD/CS nanocarriers:

(1) Simulated oral digestion: Disperse 1 g of the sample in 10 mL of simulated oral digestive fluid (containing 1.5 mg/mL mucin and 75 U/mL salivary amylase) and incubate at 37°C and 150 rpm for 2 min.

(2) Simulated gastric digestion: 10 mL of the reacted oral digestive fluid was added to 10 mL of simulated gastric fluid (containing 2000 U/mL pepsin and 60 U/mL gastric lipase), and then the gastric digestive fluid was adjusted to pH = 3 with 5 mol/L HCl solution, and incubated at 37°C and 150 rpm for 2 h;

(3) Simulated small intestinal digestion: 20 mL of the reacted gastric digestive fluid was adjusted to pH 7 with 5 mol/L NaOH solution, and then 20 mL of simulated small intestinal fluid (mixed pancreatic enzymes containing 10 mmol/L bile salts and 100 U/mL trypsin) was added. The small intestinal digestive fluid was adjusted to pH 7 with 5 mol/L NaOH solution again, and incubated at 37°C, 150 rpm for 2 h.

The digestive fluids after the reaction were collected at the oral, gastric, and small intestinal digestion stages, and the supernatant mixed micelles were obtained after centrifugation under low temperature conditions (4°C, 12,000 rpm, 30 min);

After the mixed micelles were demulsified with DMSO, the curcumin content was measured at a wavelength of 429 nm using a UV-vis spectrometer; this content corresponds to the curcumin released from the sample after digestion, and the release rate of curcumin can be further calculated using formula (1):

(1)

2. Stability test of Cur-SACD/CS nanocarrier:

(1) Stability of Cur-SACD/CS nanocarriers in the acidic environment of the stomach:

0.9% NaCl solution was adjusted to pH = 2.0 with 1 mol/L HCl solution, and then 10 mg Cur-SACD/CS nanocarriers were dispersed in 1 mL of the solution. After incubation at 37 °C for 2 h, the supernatant was removed by centrifugation and the precipitate was collected;

(2) Stability of Cur-SACD/CS nanocarriers in intestinal fluid pH environment:

0.9% NaCl solution was adjusted to pH = 7.0 with 1 mol/L NaOH solution, and then 10 mg Cur-SACD/CS nanocarriers were dispersed in 1 mL of the solution. After incubation at 37 °C for 2 h, the supernatant was removed by centrifugation and the precipitate was collected;

(3) Stability of Cur-SACD/CS nanocarriers at physiological ionic strength:

10 mg of Cur-SACD/CS nanocarriers were weighed and dispersed in 1 mL of 0.9% NaCl solution. After incubation at room temperature for 30 min, the supernatant was removed by centrifugation and the precipitate was collected;

(4) Stability of Cur-SACD/CS nanocarriers at physiological temperature: 10 mg of Cur-SACD/CS nanocarriers were dispersed in 1 mL of 0.9% NaCl solution and incubated at 37°C for 8 h. The supernatant was removed by centrifugation and the precipitate was collected.

Under the above conditions, an aqueous dispersion of curcumin was used as a control;

The collected precipitate was extracted with 4 mL of anhydrous ethanol to remove the remaining curcumin, and the absorbance of the extract was measured at a wavelength of 429 nm. The retention rate (RI) of curcumin in the Cur-SACD/CS nanocarrier was calculated using formula (2):

(2)

3. Drawing of curcumin loading curve of SACD/CS nanoparticles:

In order to obtain the loading curve of curcumin in the nanoparticles, samples were taken at 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 90 min, 120 min, 180 min, and 240 min of the loading process;

The absorbance of curcumin in the supernatant was measured at a wavelength of 429 nm using a UV-vis spectrometer to calculate the curcumin content in the Cur-SACD/CS nanocarrier. The curcumin loading amount (LA) and loading efficiency (LE) of the Cur-SACD/CS nanocarrier were further calculated according to formula (3) and formula (4), respectively:

(3)

(4)

The raw materials used in the embodiments and comparative examples are:

Preparation method of succinic acid cyclodextrin ester (SACD):

4 g of β-cyclodextrin, 2.96 g of succinic acid, and 4 g of sodium hypophosphite were fully dissolved in 40 mL of deionized water to prepare a mixed solution; the mixed solution was poured into a glass dish with a diameter of 160 mm and placed in a 100°C oven for drying for 4 h; the dried mixture was transferred to a 140°C oven to start dry heat esterification reaction for 20 min, and then the dish was taken out and cooled to room temperature; the crude product in the dish was then dissolved with deionized water, and the SACD was separated and precipitated with anhydrous ethanol, and then washed with anhydrous ethanol for 3 times to remove residual impurities; the purified SACD was fully dried at 50°C for 8 h and then used; the degree of substitution of the prepared SACD was 3.20 after testing;

Chitosan CS: medium viscosity, 200-400 mPa.s;

Curcumin: Purity ≥ 65%;

In the examples and comparative examples, the percentages without specific content are by mass; the reaction temperatures without specific reaction temperatures refer to room temperature reactions; and the solvents without specific solvents are water.

Example 1

A method for preparing a controlled release nanocarrier Cur-SACD/CS for improving the bioaccessibility of curcumin comprises the following steps:

(1) Preparation of SACD/CS nanoparticles:

Dissolve 1 g of CS in 100 mL of 1% glacial acetic acid solution. After the CS solution is fully dissolved, adjust the pH to 5.3 using 0.2 mol/L NaOH solution to obtain a CS solution.

1 g of SACD was dissolved in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a SACD solution;

The SACD solution was slowly added to the CS solution (50 mL/min), and the reaction was stirred at 400 rpm for 20 min. Then, 400 mL of anhydrous ethanol was slowly added dropwise (3 mL/min), and the stirring was continued at 400 rpm for 1 h to promote particle formation. After the reaction was completed, the SACD/CS nanoparticles in the solution were collected by centrifugation, washed three times with 67% ethanol aqueous solution, and dried to obtain SACD/CS nanoparticles.

(2) SACD/CS nanoparticles loaded with curcumin:

0.5 g of SACD/CS nanoparticles were dispersed in 45 mL of water and stirred at 150 rpm for 30 min for hydration to obtain a SACD/CS nanoparticle suspension;

Dispersing curcumin in anhydrous ethanol to obtain a curcumin solution with a concentration of 1 mg/mL;

0.5 mL of curcumin solution was added to 45 mL of SACD/CS nanoparticle suspension and stirred at 300 rpm for 3 h in the dark to achieve curcumin loading. After the reaction, the Cur-SACD/CS nanocarriers in the solution were collected by centrifugation and dried to obtain nanocarriers Cur-SACD/CS (SACD:CS=5:5).

Example 2

The amount of SACD in step (1) of Example 1 was adjusted to 1.4 g, and the other aspects were kept the same as in Example 1 to obtain a nanocarrier Cur-SACD/CS (SACD:CS=7:5).

Example 3

The amount of SACD in step (1) of Example 1 was adjusted to 1.8 g, and the other aspects were kept the same as in Example 1 to obtain a nanocarrier Cur-SACD/CS (SACD:CS=9:5).

Comparative Example 1

The SACD in step (1) of Example 1 is omitted, and step (1) is adjusted as follows:

Dissolve 1 g of CS in 100 mL of 1% glacial acetic acid solution. After it is fully dissolved, adjust the pH to 5.3 with 0.2 mol/L NaOH solution to obtain a CS solution.

Slowly add 400 mL of anhydrous ethanol (3 mL/min) to the CS solution, and continue stirring at 400 rpm for 1 h; collect the precipitate in the solution by centrifugation, wash it three times with 67% ethanol aqueous solution, and dry it to obtain CS nanoparticles;

The rest of the steps were the same as in Example 1 to obtain the Cur-CS carrier.

Comparative Example 2

The amount of SACD in step (1) of Example 1 was adjusted to 0.2 g, and the other parts were kept the same as in Example 1 to obtain a nanocarrier Cur-SACD/CS (SACD:CS=1:5).

Comparative Example 3

The amount of SACD in step (1) of Example 1 was adjusted to 0.6 g, and the other parts were kept the same as Example 1 to obtain a nanocarrier Cur-SACD/CS (SACD:CS=3:5).

The nanocarriers prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests, and the test results are as follows:

FIG1 is a SEM image of the SACD/CS composites prepared in Examples 1-3 and Comparative Examples 1-3, wherein (a) Comparative Example 1 (0:5); (b) Comparative Example 2 (1:5); (c) Comparative Example 3 (3:5); (d) Example 1 (5:5); (e) Example 2 (7:5); (f) Example 3 (9:5). It can be seen from FIG1 that the SACD/CS nanoparticles prepared in Example 1 have uniform microscopic morphology; the SACD/CS nanoparticles prepared in Examples 2 and 3 present a cohesive nanoparticle aggregate structure; the CS in Comparative Example 1 presents an irregular network structure without a nanoparticle structure; the SACD/CS in Comparative Example 2 only has a small amount of nanoparticle structure, and the rest is mostly a slightly cross-linked network structure; the SACD/CS in Comparative Example 3 has a large amount of nanoparticle structure, but there is still a partially cross-linked network structure between the nanoparticles.

FIG. 2 is the FTIR spectra of the SACD/CS composites prepared in Examples 1-3 and Comparative Examples 2-3. As can be seen from Figure 2: the characteristic peak associated with the NH bending vibration of the primary amine group in Example 1 red-shifted from 1589 cm ^-1 to 1579 cm ^-1 , which proves that the amino group of CS and SACD are cross-linked through electrostatic interaction to form composite nanoparticles; the characteristic peak (1589 cm ^-1 ) associated with the NH bending vibration of the primary amine group in Example 2 red-shifted from 1589 cm ^-1 to 1579 cm ^-1 , and no further red-shift was observed compared with the SACD/CS composite prepared when SACD:CS=5:5 (Example 1), indicating that the electrostatic interaction between SACD and CS has reached saturation; the characteristic peak (1589 cm ^-1 ) associated with the NH bending vibration of the primary amine group in Example 3 red-shifted from 1589 cm ^-1 to 1579 cm ^-1 , and no further red-shift was observed compared with the SACD/CS composite prepared when SACD:CS=5:5 (Example 1), indicating that the electrostatic interaction between SACD and CS has reached saturation; the characteristic peak (1589 cm ^-1 ) associated with the NH bending vibration of the primary amine group in Comparative Example 2 ) No obvious movement was observed, indicating that the electrostatic interaction between the amino group of CS and SACD was weak and could not fully meet the requirements for the formation of composite nanoparticles; in Comparative Example 3, the characteristic peak related to the NH bending vibration of the primary amine group was red-shifted from 1589 cm ^-1 to 1583 cm ^-1 , which proved that the amino group of CS and SACD were cross-linked through electrostatic interaction to form a nanoparticle structure. Compared with Example 1, the formation of the nanoparticle structure of this comparative example was still incomplete.

Figure 3 shows the curcumin release amount of curcumin, nanocarriers prepared in Examples 1-3 and Comparative Examples 1-3 at different stages of in vitro simulated digestion. As can be seen from Figure 3: the nanocarriers prepared in Examples 1, 2, and 3 disperse more curcumin into the digestive juice and can be absorbed and utilized by intestinal epithelial cells. The cumulative release rate of curcumin in the upper digestive tract reaches 75.19%, 73.25%, and 74.20%, respectively, achieving the delayed controlled delivery of curcumin in the digestive process, and showing great application potential in health fields such as food and medicine; in Comparative Example 1, during in vitro simulated digestion, the release rates of curcumin in the Cur-CS carrier in the oral cavity, stomach, and small intestinal digestive juice were 0.02%, 0.03%, and 8.46%, respectively, which were not significantly different from the release rates of unloaded curcumin (0.03%, 0.07%, and 7.94%). The cumulative release rate of curcumin in the upper digestive tract was only 8.51%, which did not have an advantage over the prior art; in Comparative Example 2, during in vitro simulated digestion, the curcumin in the Cur-SACD/CS nanocarrier was 0.02%, 0.03%, and 8.46%, respectively. The release rates of curcumin in the oral cavity, stomach and small intestine digestive juices were 0.04%, 0.45% and 12.69%, respectively, which were not significantly different from the release rates of unloaded curcumin (0.03%, 0.07% and 7.94%). The cumulative release rate of curcumin in the upper digestive tract was only 13.18%, which had no advantage over the prior art. In comparative example 3, during in vitro simulated digestion, the release rates of curcumin in the Cur-SACD/CS nanocarriers in the oral cavity, stomach and small intestine digestive juices were 3.56%, 9.88% and 19.64%, respectively, which were compared with the release rates of unloaded curcumin (0.03%, 0.07% and 7.94%). The prepared Cur-SACD/CS nanocarriers allowed more curcumin to be dispersed into the digestive juice and absorbed and utilized by intestinal epithelial cells, but the cumulative release rate of curcumin in the upper digestive tract was only 33.08%, which had no advantage over the prior art.

Figure 4 shows the retention rate of curcumin in the Cur-SACD/CS nanocarrier prepared in Example 1 after incubation under simulated gastric pH (a), intestinal pH (b), physiological salt concentration (c) and physiological temperature (d) (Ⅰ~VI indicate significant differences between samples, p<0.05). As can be seen from Figure 4: after the curcumin in the Cur-SACD/CS carrier was treated for 2 h, 12 h, 12 h and 12 h under the conditions of simulated gastric pH, intestinal pH, physiological salt concentration and physiological temperature, its retention rate changed from 88%, 24%, 35%, 19% to 88%, 72%, 70%, 63%, respectively, indicating that the stability of curcumin has been significantly improved.

Figure 5 is the loading curve of curcumin for the nanocarriers prepared in Example 1 and Comparative Example 1. As can be seen from Figure 5, the loading amount of curcumin for SACD/CS reaches 0.36 mg/g, and the loading rate is 36%, which is much higher than the loading effect of CS on curcumin.

Comparative Example 4

The chitosan in step (1) of the embodiment is adjusted to guar hydroxypropyltrimethylammonium chloride (GHC) (a synthetic cationic polysaccharide similar to chitosan), as follows:

Dissolve 1 g of GHC in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a GHC solution;

1 g of SACD was dissolved in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a SACD solution;

The SACD solution was slowly added to the GHC solution (50 mL/min), and the reaction was stirred at 400 rpm for 20 min. Then, 400 mL of anhydrous ethanol was slowly added dropwise (3 mL/min), and the stirring was continued at 400 rpm for 1 h to promote the formation of the complex. After the reaction, the SACD/GHC complex in the solution was collected by centrifugation, washed three times with 67% ethanol aqueous solution, and dried to obtain a SACD/GHC complex (morphology shown in Figure 6).

Other details are the same as those in Example 1.

The results showed that although some parts of the SACD/GHC complex had a structure similar to nanoparticles, the particles were severely adhered to each other, and the particle structure could not be observed in most other parts, but rather a smooth polymer morphology in sheets (Figure 6). When SACD/GHC was dispersed in water for loading curcumin, the SACD/GHC complex gradually dissolved and could not be used to load curcumin, nor could its controlled release effect during in vitro digestion be further explored.

Comparative Example 5

The chitosan in step (1) of the embodiment is adjusted to gum arabic, as follows:

Dissolve 1 g of gum arabic in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a gum arabic solution;

1 g of SACD was dissolved in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a SACD solution;

The SACD solution was slowly added to the gum arabic solution (50 mL/min), and the mixture was stirred at 400 rpm for 20 min. Then, 400 mL of anhydrous ethanol was slowly added dropwise (3 mL/min), and the mixture was stirred at 400 rpm for 1 h to promote the formation of the complex. After the reaction, the SACD/gum arabic complex in the solution was collected by centrifugation, washed three times with 67% ethanol aqueous solution, and dried to obtain the SACD/gum arabic complex.

Other details are the same as those in Example 1.

The results showed that when the SACD/gum arabic composite carrier was dispersed in water for loading curcumin, the SACD/gum arabic complex gradually dissolved and could not be used to load curcumin, nor could its controlled release effect during in vitro digestion be further explored.

Comparative Example 6

The chitosan in step (1) of the embodiment is adjusted to gelatin, as follows:

Dissolve 1 g of gelatin in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a gelatin solution;

1 g of SACD was dissolved in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a SACD solution;

The SACD solution was slowly added to the gelatin solution (50 mL/min), and the mixture was stirred at 400 rpm for 20 min. Then, 400 mL of anhydrous ethanol was slowly added dropwise (3 mL/min), and the mixture was stirred at 400 rpm for 1 h to promote the formation of the complex. After the reaction, the SACD/gelatin complex in the solution was collected by centrifugation, washed three times with 67% ethanol-water solution, and dried to obtain the SACD/gelatin complex.

Other details are the same as those in Example 1.

The results showed that when the SACD/gelatin composite carrier was dispersed in water for loading curcumin, the SACD/gelatin complex gradually dissolved and could not be used to load curcumin, nor could its controlled release effect during in vitro digestion be further explored.

Comparative Example 7

The CS in step (1) of Example 1 is omitted, and the specific steps are as follows:

Weigh 0.5 g of SACD in 45 mL of water and stir continuously at 150 rpm for 30 min to obtain a SACD solution;

Dispersing curcumin in anhydrous ethanol to obtain a curcumin solution with a concentration of 1 mg/mL;

Take 0.5 mL of curcumin solution and add it to 45 mL of SACD solution. Protect from light and stir at 300 rpm for reaction.

The results showed that: due to the strong water solubility of SACD, after curcumin was loaded into SACD, it was completely dissolved and its release effect during in vitro digestion could not be further explored.

Comparative Example 8

The SACD in Example 1 is adjusted to be a cyclodextrin derivative, octenyl succinate cyclodextrin ester (OSACD) (which has similar branching groups to SACD and is expected to be used in food);

The preparation method of cyclodextrin derivative octenyl succinate cyclodextrin ester (OSACD) is as follows:

β-cyclodextrin was dissolved in water to a mass fraction of 10%, and stirred at 50°C and 300 rpm for 2 h. Then, an ethanol dilution of octenyl succinic anhydride (diluted 4 times) was added dropwise to the solution. The process was completed within 2 h, and a 3% NaOH solution was used to control the pH of the reaction system to 8.5. After the pH of the system became constant, the pH of the reaction system was adjusted to 6.5 with a 3% hydrochloric acid solution. The obtained mixture was dried and then fully washed with ethanol, and dried again to obtain the product OSACD.

Other details are the same as those in Example 1.

The results showed that OSACD could not form a complex with CS and could not be used to load curcumin, nor could its controlled release effect during in vitro digestion be further explored.

Comparative Example 9

The curcumin loading step in Example 1 was adjusted to be encapsulated simultaneously during the nanoparticle formation process, as follows:

1 g of CS was dissolved in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a CS solution;

1 g of SACD was dissolved in 100 mL of acetic acid-sodium acetate buffer at pH 5.3 to obtain a SACD solution;

Dispersing curcumin in anhydrous ethanol to obtain a curcumin solution with a concentration of 1 mg/mL;

The SACD solution was slowly added into the CS solution (50 mL/min) and stirred at 400 rpm for 20 min to obtain a SACD/CS self-assembly solution.

0.5 mL of curcumin solution was added to 400 mL of anhydrous ethanol, and then the ethanol solution containing curcumin was slowly added dropwise (3 mL/min) to the SACD/CS self-assembly solution, and stirring was continued at 400 rpm for 1 h to promote particle formation; after the reaction, the Cur-SACD/CS nanocarriers in the solution were collected by centrifugation, washed three times with 67% ethanol aqueous solution, and dried to obtain Cur-SACD/CS nanocarriers (SACD: CS = 5:5).

The results showed that the loading rate of curcumin in SACD/CS nanocarriers using the simultaneous encapsulation method was only about 3%, indicating that the simultaneous encapsulation method is not suitable for loading curcumin in SACD/CS nanoparticles.

Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims (6)

1. A method for preparing a controlled release nanocarrier Cur-SACD/CS for improving the bioaccessibility of curcumin, characterized in that it comprises the following steps: (1) Preparation of SACD/CS nanoparticles: Succinic acid cyclodextrin ester SACD solution is slowly added to chitosan CS solution and stirred for reaction; then ethanol is slowly added dropwise and stirring is continued to promote particle formation. After the reaction is completed, solid-liquid separation, washing and drying are performed to obtain SACD/CS nanoparticles; wherein the mass ratio of SACD in SACD solution to CS in CS solution is 1:1; (2) SACD/CS nanoparticles loaded with curcumin: The SACD/CS nanoparticles are dispersed in water and hydrated to obtain a SACD/CS nanoparticle suspension; the curcumin solution is added to the SACD/CS nanoparticle suspension and stirred to react in the dark; after the reaction is completed, the solid-liquid separation and drying are performed to obtain a nanocarrier Cur-SACD/CS; Wherein, the dosage ratio of SACD/CS nanoparticles and water in the SACD/CS nanoparticle suspension is 0.5 g: 40-100 mL; The volume ratio of curcumin solution and SACD/CS nanoparticle suspension was 0.5:40-100; The concentration of curcumin solution is 0.5-5 mg/mL. 2. The method according to claim 1, characterized in that the concentration of the SACD solution in step (1) is 0.001-10 g/mL. 3. The method according to claim 1, characterized in that the preparation method of the CS solution in step (1) is: dissolving CS in a glacial acetic acid solution, and then adjusting the pH to 5.3 with a sodium hydroxide solution; wherein the dosage ratio of CS to the glacial acetic acid solution is 0.1-2 g: 100 mL. 4. The method according to claim 1, characterized in that the ethanol in step (1) is anhydrous ethanol. 5. The nanocarrier Cur-SACD/CS prepared by the method according to any one of claims 1 to 4. 6. Use of the nanocarrier Cur-SACD/CS according to claim 5 in the preparation of food or medicine.