Supramolecular co-melt adhesive, preparation and application thereof, pigment-loaded supramolecular co-melt adhesive and application of pigment-loaded supramolecular co-melt adhesive

Abstract

The invention discloses a supramolecular eutectic adhesive, preparation and application thereof, a pigment-loaded supramolecular eutectic adhesive and application of the pigment-loaded supramolecular eutectic adhesive. The supramolecular eutectic adhesive is prepared by the following method: firstly, preparing a cyclodextrin-citric acid supramolecular eutectic adhesive solution from beta-cyclodextrin, citric acid and pure water, and dehydrating to obtain the cyclodextrin-citric acid supramolecular eutectic adhesive; stirring and reacting the cyclodextrin-citric acid supramolecular eutectic adhesive and sodium lipoate at 110-130 DEG C, and then cooling to room temperature to obtain the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic adhesive. The invention provides application of the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic adhesive as an extracting agent of natural pigments or as a carrier to obtain the pigment-loaded supramolecular eutectic adhesive. The supramolecular co-melt adhesive or the pigment-loaded supramolecular co-melt adhesive can be used as an adhesive or 3D printing ink, can extract natural pigments and effectively improve the stability of the natural pigments, and has good adhesion and printing characteristics.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and specifically to a supramolecular eutectogel and its preparation and application, and a pigment-loaded supramolecular eutectogel and its application. Background Art

[0002] With the continuous promotion of the concept of green extraction and the continuous growth of the industrialization demand for natural functional factors, extraction systems with multifunctional integration characteristics have gradually become a research hotspot. In recent years, supramolecular eutectogels formed by the self-assembly of natural small molecules (such as organic acids, amino acids, cyclodextrin derivatives, etc.) through non-covalent interactions such as hydrogen bonds and with a decreased melting point have shown broad application prospects in the field of active ingredient extraction due to their advantages such as environmental friendliness, good biocompatibility, and adjustable structure. Such systems can not only achieve efficient extraction under mild conditions but also have certain structural functionality, providing a new possible path for the integration of "extraction - application".

[0003] However, the existing supramolecular eutectogel systems generally have problems such as single function and limited scope of application, and it is difficult to meet the actual needs of the integration of "extraction - application". The proline-glycerol eutectic system reported in Patent CN119633446A can improve the extraction efficiency of natural components by regulating the water content, but the system itself lacks sufficient structural viscosity and mechanical stability and is only applicable to the front-end extraction stage and is difficult to undertake subsequent loading or processing tasks, and its overall practicality is relatively limited. Patent CN119792376A proposed a method for efficiently extracting total flavonoids from Bauhinia seeds using deep eutectic solvents, showing significant advantages in green extraction, not only realizing the recycling of solvents but also tripling the extraction efficiency, and having both environmental friendliness and economy. However, its functional design is still limited to the "extraction" link and lacks a systematic consideration of the stability, storage, and carrier compatibility of the extract, making it difficult to effectively extend to subsequent application scenarios. In contrast, Patent CN119775494A made a beneficial exploration from the perspective of material construction and developed a eutectogel system based on the copolymerization of acrylamide-based and acrylic acid-based monomers and the introduction of cellulose nanocrystals for reinforcement. This material not only has excellent mechanical strength and environmental adaptability but also exhibits dual responsiveness to temperature and strain. However, due to its construction process involving multi-component polymerization and phase separation regulation, the system is complex, and it has not been systematically evaluated around the in-situ extraction and protection release of natural active ingredients, and it is still difficult to achieve a deep integration with the development of natural products.

[0004] In addition, although some supramolecular systems with strong structures have good formability and loading capacity, they generally lack the in-situ extraction function and are difficult to meet the requirement of enriching natural active substances at the source. Taking patent CN202211179578.9 as an example, the double gel system constructed therein has excellent adhesion and sustained release performance, but still needs to rely on external solvents to complete the pre-extraction of active ingredients, lacking the "extraction-loading" integration ability, which is not conducive to simplifying the operation process and improving the efficiency of green processes. Similarly, patent CN202510069170.3 achieved the effective encapsulation and controlled release of chlorogenic acid through a polypeptide self-assembly strategy, improving stability and therapeutic persistence, but also relied on the separate introduction of pre-purified components, limiting its direct applicability in scenarios of natural product raw materials. Patent CN202010017199.4, on the other hand, constructed an antibacterial composite hydrogel composed of carboxymethyl chitosan, oxidized sodium alginate and tannic acid, which has good biocompatibility, degradability and antibacterial properties and is applicable to the treatment of chronic wounds. However, the realization of its functions depends on multi-step chemical modification and complex raw material configuration, lacking the overall integration of the extraction, stabilization and forming processes of natural components. In summary, these cases show that there are still significant deficiencies in the "extraction-regulation-forming" trinity process integration of the existing material systems, and a new material platform is urgently needed to break through the technical bottlenecks of functional separation and process fragmentation.

[0005] Therefore, this study proposed and constructed a natural supramolecular eutectic gel with both high extraction ability and structural adhesion performance. This system uses β-cyclodextrin, citric acid and sodium lipoate as core components. By regulating their molar ratios, a stable hydrogen bond network can be constructed to achieve the efficient extraction of natural pigments and active compounds. While maintaining good extraction performance, this system exhibits high responsiveness to moisture, and the viscosity and rheological properties of the system can be flexibly adjusted by regulating the water content. Furthermore, the constructed eutectic gel itself has good adhesion ability and preliminary structural support ability, and can serve as both an extraction medium and a functional carrier in applications, significantly simplifying the traditional multi-step processes of "extraction-separation-loading". Summary of the Invention

[0006] To overcome the above-mentioned disadvantages and deficiencies of the prior art, the present invention discloses a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel and its preparation and applications as a natural pigment extractant, carrier, 3D printing ink and adhesive, as well as a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with natural pigments and its applications as an adhesive and 3D printing ink. The cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel can extract natural pigments and effectively improve the stability of natural pigments, and the eutectic gel has good adhesion and 3D printing properties and can be applied to food 3D printing.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel, which is prepared by the following method: First, a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectic gel solution is prepared from β-cyclodextrin, citric acid and pure water, and then dehydrated to obtain a cyclodextrin-citric acid supramolecular eutectic gel; the cyclodextrin-citric acid supramolecular eutectic gel and sodium lipoate are stirred and reacted at 110-130 °C to allow sodium lipoate to be fully embedded in the cyclodextrin-citric acid network, and then cooled to room temperature to obtain a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel; the molar ratio of β-cyclodextrin to citric acid in the feed is 1:10-1:30, the mass of pure water is 10-40 wt% of the total mass of β-cyclodextrin and citric acid, and the mass of sodium lipoate is 0.1%-1% of the mass of the cyclodextrin-citric acid supramolecular eutectic gel.

[0009] Preferably, the β-cyclodextrin, citric acid and pure water are stirred and reacted at 60 °C - 70 °C to prepare a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectic gel solution.

[0010] The cyclodextrin-citric acid supramolecular eutectic gel solution with a water content of 10-40 wt% in the present invention is in the state of a deep eutectic solvent. As the water content decreases, the fluidity of the supramolecular eutectic gel solution decreases. After dehydration, the obtained cyclodextrin-citric acid supramolecular eutectic gel loses its fluidity and becomes a solid state. The cyclodextrin-citric acid supramolecular eutectic gel can regain its fluidity when pure water is added.

[0011] In a second aspect, the present invention provides a method for preparing the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel according to the first aspect, comprising the following steps:

[0012] Step 1: Mix β-cyclodextrin and citric acid in a molar ratio of 1:10-1:30, add pure water with a mass of 10-40 wt% of the total mass of β-cyclodextrin and citric acid, stir at 60 °C - 70 °C for 2-3 hours to form a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectic gel solution, and then dehydrate to obtain a cyclodextrin-citric acid supramolecular eutectic gel;

[0013] Step 2: Add sodium lipoate to the cyclodextrin-citric acid supramolecular eutectic gel prepared in Step 1, such that the mass of sodium lipoate is 0.1%-1% of the mass of the cyclodextrin-citric acid supramolecular eutectic gel, and stir at 10-15 rpm at 110-130 °C for 10-20 minutes to allow sodium lipoate to be fully embedded in the cyclodextrin-citric acid network, and then cool to room temperature to obtain a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel.

[0014] Preferably, in Step 1, the mixing molar ratio of β-cyclodextrin and citric acid is 1:10.

[0015] Preferably, in step 1, the addition amount of pure water is 30% of the total mass of β-cyclodextrin and citric acid, the stirring temperature is 65°C, and the stirring time is 3 hours.

[0016] Preferably, in step 1, the dehydration method is rotary evaporation or freeze-drying. The further dehydration method is rotary evaporation, the vacuum degree of rotary evaporation is -0.1 Mpa, the temperature range is 60°C - 70°C, the rotary evaporation time is 0.5 - 3 hours, and the light condition is light avoidance.

[0017] Preferably, in step 2, the addition amount of sodium lipoate is 0.5% of the mass of the cyclodextrin-citric acid supramolecular eutectic gel.

[0018] Preferably, in step 2, the stirring condition is: low-speed stirring at 15 rpm for 10 minutes at 130°C.

[0019] In a third aspect, the present invention provides the application of the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel described in the first aspect as an extractant for natural pigments to obtain the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with pigments.

[0020] The specific steps of the application are as follows: Mix the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel with the natural pigment raw material, extract the natural pigment under the conditions of 60°C - 70°C, stirring and ultrasonic treatment, and remove the residue by centrifugation while it is hot after sufficient extraction to obtain the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with pigments.

[0021] The natural pigments described in the present invention can be anthocyanins, curcumin, lutein, dihydromyricetin, etc.

[0022] Preferably, the feeding mass ratio of the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel to the natural pigment raw material is 1 g : (0.5 - 5) g.

[0023] Preferably, the extraction conditions are: extraction at an ultrasonic power of 500 W for 30 - 60 minutes, and the stirring rate is 15 - 30 rpm. As a further preference, the extraction temperature is 60°C, the extraction time is 60 minutes, and the stirring frequency is 15 rpm.

[0024] In a fourth aspect, the present invention provides the application of the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel described in the first aspect as a carrier for pigments to obtain the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with pigments.

[0025] The specific steps of the application are as follows: Add an ethanol solution containing pigments to the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel, and then remove the ethanol to obtain the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with pigments.

[0026] As an implementation mode, the pigment described in the present invention is a natural pigment, which can be anthocyanin, curcumin, lutein, dihydromyricetin, etc.

[0027] Preferably, the ethanol solution containing the pigment is added in small amounts and multiple times to ensure that the pigment can be fully loaded.

[0028] Preferably, stirring is used to assist in loading the pigment into the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel.

[0029] In a fifth aspect, the present invention provides a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with a pigment obtained according to the application described in the third aspect or the fourth aspect.

[0030] In a sixth aspect, the present invention provides an application of a supramolecular eutectic gel as an adhesive, and the supramolecular eutectic gel is the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel described in the first aspect or the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with a pigment described in the fifth aspect.

[0031] The application medium of the adhesive can be wood chips, iron sheets, rubber, etc.

[0032] In a seventh aspect, the present invention provides an application of a supramolecular eutectic gel as 3D printing ink, and the supramolecular eutectic gel is the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel described in the first aspect or the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with a pigment described in the fifth aspect.

[0033] The specific application is as follows: The supramolecular eutectic gel is loaded into an extrusion 3D printer, and the printing parameters are set as: temperature 30°C - 70°C, rate 6 - 20 mm / s, nozzle diameter 0.2 - 1.5 mm, and 3D printing is carried out.

[0034] Preferably, the printing temperature is 50°C, the printing speed is 10 mm / s, and the printing nozzle diameter is 0.5 mm.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1. For the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel described in the present invention, after introducing sodium lipoate, the eutectic gel exhibits excellent structural processing properties, significantly improving the adhesiveness, texture strength and good thermal reversibility of the eutectic gel (gel-sol transition temperature 60 - 70°C) (the above results are shown in Figure 4 , and this result is obtained by Figure 4(Analysis shows that) The cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel is used as a 3D printing ink and can be adapted to an extrusion-type 3D printing device. Since there is almost no free water in the system, it avoids the problem of structural collapse caused by solvent evaporation in traditional hydrogel inks, and significantly enhances its shape retention and structural stability. The prepared eutectic gel as a 3D printing ink has good printing performance, and the printed samples have advantages such as high printing accuracy and good color / visual effect of the printed products.

[0037] 2. The cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel described in the present invention can be used as an extractant or carrier of natural pigments to obtain a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel loaded with natural pigments. Compared with the cyclodextrin-citric acid supramolecular eutectic gel without adding sodium lipoate, it can effectively improve the stability of the loaded natural pigments.

[0038] Due to its hydrophobic cavity structure, β-cyclodextrin has good ability to encapsulate guest molecules and can effectively stabilize hydrophobic active ingredients such as curcumin and lutein. On this basis, the eutectic system formed by cyclodextrin and citric acid further enhances the hydrogen bond network and supramolecular forces, constructs a denser and more stable three-dimensional network structure, enables the pigment molecules to be stably encapsulated in the system, and thus provides a lasting function release and environmental adaptability.

[0039] Introducing a small amount of sodium lipoate (0.1%-1%, based on the mass of cyclodextrin) into this system further strengthens the hydrogen bonds and hydrophobic interactions inside the system, making the supramolecular network structure more stable. The sodium lipoate molecules can be embedded in the cyclodextrin-citric acid network to form a synergistic action barrier, which not only improves the overall structural strength of the system, but also significantly enhances the resistance of the active ingredients to adverse environments such as heat and light. The stability experiment shows that at 80 °C, the sodium lipoate eutectic gel loaded with active substances (such as curcumin) can still achieve a high retention rate, far higher than the traditional emulsion or hydrogel system, indicating that this eutectic gel platform has significant advantages in the encapsulation and protection of pigment-based functional materials. Description of the Drawings

[0040] The present invention will be further described below with reference to the drawings and embodiments.

[0041] Figure 1 It is a flow chart for the preparation and application of the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel.

[0042] Figure 2 It is a comparison of the relative extraction rates of different natural pigments in the supramolecular eutectic gel system (based on an ethanol system with a volume fraction of 80%).

[0043] Figure 3Comparison of the storage stability of pigments in supramolecular eutectic gel systems and ethanol control groups under light / dark conditions for different storage times (1 - 30 days).

[0044] Figure 4 It is a rheological property test chart of the supramolecular eutectic gel prepared in Comparative Example 1 and Example 1 for comparison.

[0045] Figure 5 It is a physical picture, 3D printed physical picture and the physical picture of the product obtained by shaping of different supramolecular eutectic gels prepared in the comparative example and the example.

[0046] Figure 6 The physical pictures and corresponding fluidities of Comparative Examples 1 - 4 prepared in the present invention show that the supramolecular eutectic gel has the unique property of being able to adjust the moisture to change its form (different from traditional deep eutectic solvents and traditional small molecule eutectic gels).

[0047] Figure 7 It is a physical picture of the application of the cyclodextrin - citric acid - sodium lipoate supramolecular eutectic gel loaded with curcumin color prepared in Example 2 as an adhesive. Detailed Description of the Invention

[0048] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. It should be noted that for the processes not specifically described in detail below, those skilled in the art can implement or understand them with reference to the prior art. Reagents or instruments without indicating the manufacturer are regarded as conventional products that can be obtained through the market purchase.

[0049] The materials involved in the present invention are β - cyclodextrin, and citric acid is food - grade; the sources of the series of natural pigments mentioned (including but not limited to the sources such as, anthocyanin: purple cabbage; curcumin: turmeric; lutein: spinach; dihydromyricetin: ampelopsis grossedentata, all belong to natural and edible food and medicine materials). Sodium lipoate, finished anthocyanin, curcumin, lutein, dihydromyricetin, etc. are all analytical pure (AR) chemicals. Comparative Example 1: Preparation of cyclodextrin - citric acid supramolecular eutectic gel

[0050] Preparation reference of cyclodextrin - citric acid supramolecular eutectic gel solution and eutectic gel Figure 1 。

[0051] Step 1: Mix β - cyclodextrin (11.35 g, 0.01 mol) and citric acid (19.21 g, 0.1 mol) in a molar ratio of 1:10; add pure water (30% of the total mass of β - cyclodextrin and citric acid, that is, 9.17 g); stir magnetically at 200 rpm in a 65 °C constant temperature water bath for 3 hours to form a homogeneous and transparent cyclodextrin - citric acid supramolecular eutectic gel system with a water content of 30 wt%. As Figure 6As shown, the supramolecular eutectic gel solution has strong fluidity.

[0052] Step 2: The cyclodextrin-citric acid supramolecular eutectic gel solution with a water content of 30 wt% obtained in Step 1 was rotary evaporated at a vacuum degree of -0.1 Mpa and a temperature of 60 °C for 30 min, namely, a high-viscosity cyclodextrin-citric acid supramolecular eutectic gel was prepared. As Figure 6 shown, the supramolecular eutectic gel does not flow and presents a solidified eutectic state.

[0053] Step 3: Add the supramolecular eutectic gel to an extrusion 3D printer (model: Foodini), balance it at 50 °C for 30 min and then start printing. The printing temperature is 50 °C, the printing rate is 10 mm / s, and the nozzle diameter is 0.5 mm. See the photo of the 3D printed physical object in Figure 5 .

[0054] Control Example 2:

[0055] Step 1: Mix β-cyclodextrin (11.35 g, 0.01 mol) and citric acid (19.21 g, 0.1 mol) in a molar ratio of 1:10; add pure water (40% of the total mass of β-cyclodextrin and citric acid, namely 20.37 g); magnetically stir at 200 rpm in a 65 °C constant temperature water bath for 3 hours to form a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectic gel solution with a water content of 40 wt%. As Figure 6 shown, the eutectic gel solution has strong fluidity.

[0056] Control Example 3:

[0057] Step 1: Mix β-cyclodextrin (11.35 g, 0.01 mol) and citric acid (19.21 g, 0.1 mol) in a molar ratio of 1:10; add pure water (20% of the total mass of β-cyclodextrin and citric acid, namely 7.64 g); magnetically stir at 200 rpm in a 65 °C constant temperature water bath for 3 hours to form a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectic gel solution with a water content of 20 wt%. This eutectic gel solution is similar to the cyclodextrin-citric acid system supramolecular eutectic gel solution with a water content of 30 wt% and has strong fluidity.

[0058] Control Example 4

[0059] Step 1: Mix β-cyclodextrin (11.35 g, 0.01 mol) and citric acid (19.21 g, 0.1 mol) in a molar ratio of 1:10; add pure water (10% of the total mass of β-cyclodextrin and citric acid, namely 3.40 g); magnetically stir at 200 rpm in a 65 °C constant temperature water bath for 3 hours to form a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectic gel solution with a water content of 10 wt%. As Figure 6As shown, the eutectic gel solution is relatively viscous and flows slowly.

[0060] Example 1: Preparation of Cyclodextrin-Citric Acid-Sodium Lipoate Supramolecular Eutectic Gel

[0061] Step 1: Mix β-cyclodextrin (11.35 g, 0.01 mol) and citric acid (19.21 g, 0.1 mol) in a molar ratio of 1:10; add pure water (30% of the total mass of β-cyclodextrin and citric acid, i.e., 9.17 g); stir magnetically at 200 rpm in a 65 °C constant temperature water bath for 3 hours to form a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectic gel solution with a water content of 30 wt%.

[0062] Step 2: Rotate and evaporate the cyclodextrin-citric acid supramolecular eutectic gel solution with a water content of 30 wt% obtained in Step 1 under a vacuum of -0.1 Mpa and a temperature of 60 °C for 30 min to prepare a high-viscosity cyclodextrin-citric acid supramolecular eutectic gel.

[0063] Step 3: Add 0.015 g of sodium lipoate (the addition amount of sodium lipoate is 0.5% of the total mass of the supramolecular eutectic gel) to 3 g of the cyclodextrin-citric acid supramolecular eutectic gel, transfer the mixture to a high-temperature resistant glass reaction tube, and place it in a 130 °C oil bath, and stir at a low speed of 15 rpm for 10 minutes.

[0064] Step 4: Rapidly cool to 25 °C to obtain a pale yellow viscous cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel.

[0065] Step 5: Add the supramolecular eutectic gel to an extrusion 3D printer (model: Foodini), balance for 30 min at 50 °C and then start printing, printing temperature 50 °C, printing rate 10 mm / s, nozzle diameter 0.5 mm. See the 3D printed physical picture in Figure 5 .

[0066] Control Example 5: Curcumin Pigment Loading of Cyclodextrin-Citric Acid Supramolecular Eutectic Gel

[0067] Step 1: Prepare cyclodextrin-citric acid supramolecular eutectic gel according to the method of Control Example 1.

[0068] Step 2: Add 1.0 mg / mL curcumin ethanol solution to the above-prepared eutectic gel in small amounts and multiple times, with each addition amount of 200 μL, and continuously stir (150 rpm) at room temperature for 1 hour to make the final concentration of curcumin 0.3% (w / w), that is, prepare a supramolecular eutectic gel solution loaded with curcumin.

[0069] Step 3: Rotate and evaporate the supramolecular eutectic gel solution loaded with curcumin obtained in Step 2 under a vacuum of -0.1 Mpa and a temperature of 60 °C for 30 min, thus preparing a high-viscosity supramolecular eutectic gel loaded with curcumin and yellow in color.

[0070] Step 4: Add the supramolecular eutectic gel loaded with curcumin to an extrusion 3D printer (model: Foodini), balance it at 50 °C for 30 min, then start printing at a printing temperature of 50 °C, a printing rate of 10 mm / s, and a nozzle diameter of 0.5 mm. See the photo of the 3D printed physical object in Figure 5 Control Example 6: Loading of anthocyanin pigment with cyclodextrin-citric acid supramolecular eutectic gel

[0071] Refer to Control Example 5, the only difference is that curcumin is replaced by anthocyanin in Step 2.

[0072] Control Example 7: Loading of lutein pigment with cyclodextrin-citric acid supramolecular eutectic gel

[0073] Refer to Control Example 5, the only difference is that curcumin is replaced by lutein in Step 2.

[0074] Control Example 8: Loading of dihydromyricetin pigment with cyclodextrin-citric acid supramolecular eutectic gel

[0075] Refer to Control Example 5, the only difference is that curcumin is replaced by dihydromyricetin in Step 2.

[0076] Example 2: Loading of curcumin pigment with cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel

[0077] Step 1: Prepare a cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel according to the method of Example 1.

[0078] Step 2: Add the 1.0 mg / mL curcumin ethanol solution to the above-prepared eutectic gel in small amounts and multiple times, with a single addition amount of 200 μL, and continuously stir (150 rpm) at room temperature for 1 hour to make the final concentration of curcumin 0.3% (w / w), thus preparing a supramolecular eutectic gel solution loaded with curcumin.

[0079] Step 3: Rotate and evaporate the supramolecular eutectic gel solution loaded with curcumin obtained in Step 2 under a vacuum of -0.1 Mpa and a temperature of 60 °C for 30 min, thus preparing a high-viscosity supramolecular eutectic gel loaded with curcumin and yellow in color. See the physical object diagram of this eutectic gel in Figure 5 , showing a golden yellow color. See the application of this eutectic gel as an adhesive in Figure 7 .

[0080] Step 4: Add the supramolecular eutectic gel loaded with curcumin to an extrusion 3D printer (model: Foodini). After equilibration at 50 °C for 30 min, start printing at a printing temperature of 50 °C, a printing rate of 10 mm / s, and a nozzle diameter of 0.5 mm. See the 3D printing process and the photo of the physical object in Figure 5 .

[0081] Example 3: Loading of anthocyanin pigments in cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel

[0082] Referring to Example 2, the only difference is that curcumin is replaced by anthocyanin in Step 2.

[0083] Example 4: Loading of lutein pigments in cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel

[0084] Referring to Example 2, the only difference is that curcumin is replaced by lutein in Step 2.

[0085] Example 5: Loading of dihydromyricetin pigments in cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel

[0086] Referring to Example 2, the only difference is that curcumin is replaced by dihydromyricetin in Step 2.

[0087] Control Example 9

[0088] Mix the cyclodextrin-citric acid supramolecular eutectic gel (10.0 g in mass) prepared according to Control Example 1 with 5 g of pigment raw materials (anthocyanin: purple cabbage powder; curcumin: turmeric powder; lutein: spinach by-products; dihydromyricetin: ampelopsis grossedentata extract) respectively at a material-liquid ratio of 1:2 (g / g), perform ultrasonic extraction at 60 °C and 500 W for 60 minutes, and centrifuge (centrifugation speed: 12,000 rpm, centrifugation time: 5 minutes) to remove residues, thus obtaining the cyclodextrin-citric acid supramolecular eutectic gel loaded with the corresponding pigments. The extraction rate is determined by ultraviolet spectrophotometry (anthocyanin λ = 520 nm, curcumin λ = 425 nm, lutein λ = 445 nm, dihydromyricetin λ = 290 nm).

[0089] Example 6

[0090] The supramolecular eutectic gel of cyclodextrin-citric acid-sodium lipoate prepared according to Example 1 (10.0 g in mass) and 5 g of pigment raw materials (anthocyanin: purple cabbage powder; curcumin: turmeric powder; lutein: spinach by-products; dihydromyricetin: ampelopsis grossedentata extract) were respectively mixed at a solid-liquid ratio of 1:2 (g / g), and ultrasonically extracted for 60 minutes at 60 °C and 500 W. Subsequently, it was centrifuged at 12,000 rpm for 5 minutes to remove the residue, and the eutectic gel samples loaded with the corresponding pigments were obtained. An equal-volume ethanol (volume fraction 80%) extraction system was used as the control group, and comparative extraction was carried out under the same conditions. The supernatant after extraction was diluted and detected by ultraviolet spectrophotometry (anthocyanin λ = 520 nm, curcumin λ = 425 nm, lutein λ = 445 nm, dihydromyricetin λ = 290 nm). The pigment content was converted according to the standard curve, the extraction rate was calculated, and the relative extraction rate was further calculated with the ethanol system as the control, that is: relative extraction rate (%) = [(eutectic gel extraction rate - ethanol extraction rate) / ethanol extraction rate] × 100%.

[0091] Under the same extraction conditions, using 80% ethanol as the control extraction system, the extraction rates of four types of natural pigments were relatively low, which were: anthocyanin about 13.2% ± 1.1, curcumin 17.5% ± 0.9, lutein 15.3% ± 1.2, and dihydromyricetin 11.8% ± 1.0. This result shows that the traditional ethanol extraction system has limited efficiency in releasing and loading multiple types of pigments, especially more limited in high-polarity or structurally complex matrices.

[0092] Comparing the results of Example 9 and Example 6, with the ethanol system as the control, the relative extraction rates of the supramolecular eutectic gel of cyclodextrin-citric acid-sodium lipoate for the four types of pigments (anthocyanin 45.2% ± 1.8, curcumin 57.6% ± 1.5, lutein 49.8% ± 2.0, dihydromyricetin 41.3% ± 1.7) were on average 32.7% lower than those of the supramolecular eutectic gel of cyclodextrin-citric acid (anthocyanin 68.5% ± 2.3, curcumin 85.3% ± 2.1, lutein 72.4% ± 1.9, dihydromyricetin 63.7% ± 2.5). The results show that although the introduction of sodium lipoate results in a 32.7% decrease in the extraction rate compared with the supramolecular eutectic gel of cyclodextrin-citric acid, compared with the traditional ethanol system, both eutectic gel systems show obvious extraction enhancement effects, indicating their application potential in various polar-structured pigments. Further analysis shows that sodium lipoate may affect the pigment loading efficiency by competitively occupying the cyclodextrin cavity, and the degree of inhibition is negatively correlated with the polarity of pigment molecules.

[0093] Control Example 10: Storage stability experiment

[0094] Take the pigment-loaded cyclodextrin-citric acid supramolecular eutectic gels prepared in Comparative Examples 5 to 8 for the storage stability experiment. At different time points and under different light conditions, the mass of each group of eutectic gels is 5.0 g. Use natural pigments dissolved in ethanol as the positive control group examples (concentrations are all 1 mg / mL), namely curcumin ethanol solution (Positive Control Example 1), anthocyanin ethanol solution (Positive Control Example 2), lutein ethanol solution (Positive Control Example 3), and dihydromyricetin ethanol solution (Positive Control Example 4). The experimental temperature is 25°C, and they are treated in the dark / under light at 25°C for 1 - 30 days, and the retention rate is detected by HPLC. The liquid chromatography (HPLC) conditions are as follows: Mobile phase A / Mobile phase B: anthocyanin - acetonitrile / 0.1% formic acid water, curcumin - methanol / water, lutein - n-hexane / isopropanol, dihydromyricetin - methanol / 0.1% phosphoric acid water, flow rate 0.5 mL / min, gradient elution program: 0 min 8% B; 2 min 12% B; 10 min 20% B; 12 min 25% B; 18 min 45% B; 20 min 80% B; 30 min 8% B; injection volume 10 μL, column temperature 30°C, wavelength 520 nm.

[0095] Example 7: Storage Stability Experiment

[0096] Take the pigment-loaded cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gels prepared in Examples 2 to 5 for the storage stability experiment. At different time points and under different light conditions, the mass of each group of the series of eutectic gels is 5.0 g. The specific experimental method is the same as that of Comparative Example 10.

[0097] The storage experiment results of Comparative Example 10 and Example 7 are as Figure 3As shown, the results indicate that the ethanol system has significantly insufficient protective ability for the four pigments (anthocyanin, curcumin, lutein, dihydromyricetin). Especially under light exposure conditions, the retention rate of all pigments drops below 4.5% after 30 days of storage, fully exposing its photosensitive defect. Compared with the ethanol group, the β-cyclodextrin-sodium citrate supramolecular eutectic gel system exhibits significantly improved stability. After 30 days of light shielding, the pigment retention rate remains at 75.4% - 88.2%, and 56.7% - 68.9% of the active ingredients are retained under light exposure conditions. After introducing sodium lipoate, the system performance is further optimized: when light is shielded for 30 days, the retention rate of the four types of pigments increases to 85.7% - 93.4%, and the light stability is particularly prominent. The retention rate after 30 days of light exposure still reaches 70.4% - 80.2%, which is about 20% - 25% higher than that of the basic eutectic gel system. It is worth noting that dihydromyricetin shows the best stability in all systems, presumably related to the high adaptability of its molecular polarity and rigid structure to the cyclodextrin cavity, while lutein becomes the most easily degraded component due to its photosensitive characteristics. The antioxidant properties of sodium lipoate effectively inhibit the photo-thermal synergistic degradation. Especially during long-term light exposure storage, its ability to scavenge free radicals reduces the pigment oxidation rate by more than 40%. This data indicates that the sodium lipoate eutectic gel system can meet the shelf-life requirements of 30 days of regular light-shielded storage, but in the light exposure scenario, it is still necessary to combine with light-shielding packaging to achieve the optimal protection effect.

[0098] Example 8

[0099] Rheological property test: The Anton Paar MCR 302 rotational rheometer was used to test the cyclodextrin-citric acid supramolecular eutectic gel prepared for Control Example 1 and the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel (5 g in mass) prepared for Example 1 respectively. Angular frequency dependence test: The frequency range was from 0 to 100 rad / s, and the storage modulus (G'), loss modulus (G"), and complex viscosity (η*) of different materials were measured. From Figure 4Comparing the control example and Example 1, it can be seen that for the supramolecular eutectic gel of the β-cyclodextrin-citric acid anhydrous system, under the change of angular frequency, its storage modulus (G') and loss modulus (G") show relatively drastic fluctuations, and the intersection point of G’ and G” is near the angular frequency = 102 rad / s. Especially, the storage modulus gradually increases with the increase of angular frequency. This indicates that the rheological properties of the supramolecular eutectic gel of the β-cyclodextrin-citric acid anhydrous system prepared in the control example 1 become more obvious at a larger angular frequency, the intersection point of G’ and G” shifts to the left, and the intersection point is at the angular frequency = 101 rad / s to 102 rad / s, which indicates that there may be a certain degree of non-linearity or stress response nearby. For the supramolecular eutectic gel of cyclodextrin-citric acid-sodium thiooctanoate prepared in Example 1, the storage modulus (G') and loss modulus (G") change less with the change of angular frequency, and the increase at a higher angular frequency is relatively gentle. Moreover, the change of the complex viscosity of the supramolecular eutectic gel in Example 1 is relatively stable, which indicates that the supramolecular eutectic gel in Example 1 has more stable viscoelastic behavior and has a wider range of applications compared with the supramolecular eutectic gel in the control example 1. Temperature dependence test: Similarly, rheological tests were carried out on the above-mentioned materials under different temperature conditions (20 °C to 120 °C), and their storage modulus, loss modulus and complex viscosity were measured. From Figure 4 Comparing the control example and Example 1, it can be seen that the supramolecular eutectic gel of the control example 1 is very sensitive to temperature changes. As the temperature increases, at 40 °C - 50 °C, the storage modulus (G') and loss modulus (G") decrease significantly, and the complex viscosity also decreases greatly until it levels off. The inflection point of the change of the complex viscosity with temperature is at 40 °C - 50 °C; for the example, the inflection point of the change of the complex viscosity with temperature is at 50 °C - 60 °C. This indicates that the supramolecular eutectic gel of the control example 1 has poor thermal stability at high temperatures, and may experience enhanced fluidity or become softer, losing some of its structural stability. This indicates that the supramolecular eutectic gel of the control example 1 is not suitable for use in high-temperature environments, especially in applications that require high viscosity or high elasticity, where it may perform poorly. However, the supramolecular eutectic gel of Example 1 shows relatively mild changes when the temperature increases. The storage modulus (G') and loss modulus (G") decrease slowly, and the complex viscosity does not change drastically. This indicates that the supramolecular eutectic gel of Example 1 has good thermal stability in high-temperature environments, can maintain relatively strong structural and physical properties, and is suitable for use in applications that require high temperature resistance. Moreover, the stable rheological behavior presented above is usually associated with stronger adhesion and texture strength in the structural adhesive system. Therefore, the above results can show that the addition of sodium thiooctanoate can significantly improve the adhesion, texture strength and good thermal reversibility (gel-sol transition temperature 60 - 70 °C) of the eutectic gel.

[0100] In summary, the supramolecular eutectic gel system developed in this study fully exploits the unique advantages of β-cyclodextrin-based substances. By compounding β-cyclodextrin with citric acid, not only is the inherent inclusion ability of cyclodextrin molecules completely retained, but a new carrier system with synergistic effects is formed through supramolecular self-assembly. This unique supramolecular structure significantly enhances the stability of guest molecules through multiple action mechanisms: Firstly, the hydrophobic cavity of cyclodextrin provides a basic embedding site for pigment molecules; Secondly, the extended network formed by citric acid and cyclodextrin can generate additional coordination sites; More importantly, the dynamic hydrogen bond network in the supramolecular system can be adaptively adjusted to achieve precise inclusion of guest molecules with different sizes and polarities. This dual stabilization mechanism of "host-guest inclusion" and "supramolecular coordination" provides comprehensive protection for pigment molecules during processing and storage. It should be noted that the above embodiments are only the preferred implementation schemes of the present invention, and the protection scope of the present invention shall be subject to the claims. Any equivalent substitution or improvement based on the core concept of the present invention shall be regarded as falling within the protection scope of the present invention.

Claims

1. A cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel, characterized in that: The cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel is prepared by the following method: First, a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectogel solution is prepared from β-cyclodextrin, citric acid and pure water, and then dehydrated to obtain the cyclodextrin-citric acid supramolecular eutectogel; The cyclodextrin-citric acid supramolecular eutectogel and sodium lipoate are stirred and reacted at 110-130 °C to allow sodium lipoate to be fully embedded in the cyclodextrin-citric acid network, and then cooled to room temperature to obtain the cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel; The molar ratio of the β-cyclodextrin to citric acid in the feed is 1:10-1:30, the mass of the pure water is 10-40 wt% of the total mass of the β-cyclodextrin and citric acid, and the mass of the sodium lipoate is 0.1%-1% of the mass of the cyclodextrin-citric acid supramolecular eutectogel.

2. The cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel according to claim 1, wherein: The β-cyclodextrin, citric acid and pure water are stirred and reacted at 60 °C - 70 °C to prepare a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectogel solution.

3. A method for preparing the cyclodextrin-citric acid-sodium lipoate supramolecular eutectic gel according to claim 1 or 2, characterized in that: The preparation method includes the following steps: Step 1: Mix β-cyclodextrin and citric acid in a molar ratio of 1:10-1:30, add pure water with a mass of 10-40 wt% of the total mass of β-cyclodextrin and citric acid, stir at 60 °C - 70 °C for 2-3 hours to form a homogeneous and transparent cyclodextrin-citric acid supramolecular eutectogel solution, and then dehydrate to obtain the cyclodextrin-citric acid supramolecular eutectogel; Step 2: Add sodium lipoate to the cyclodextrin-citric acid supramolecular eutectogel prepared in Step 1, so that the mass of the sodium lipoate is 0.1%-1% of the mass of the cyclodextrin-citric acid supramolecular eutectogel, stir at a low speed of 10-15 rpm at 110-130 °C for 10-20 minutes to allow sodium lipoate to be fully embedded in the cyclodextrin-citric acid network, and then cool to room temperature to obtain the cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel.

4. The preparation method according to claim 3, characterized in that: In Step 1, the mixing molar ratio of the β-cyclodextrin to citric acid is 1:

10.

5. The preparation method according to claim 3, characterized in that: In Step 2, the addition amount of sodium lipoate is 0.5% of the mass of the cyclodextrin-citric acid supramolecular eutectogel.

6. Use of the cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel as described in claim 1 or 2 as an extractant for natural pigments to obtain a pigment-loaded cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel.

7. Use of the cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel as described in claim 1 or 2 as a carrier for pigments to obtain a pigment-loaded cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel.

8. A pigment-loaded cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel obtained according to the use described in claim 6 or 7.

9. Application of a supramolecular eutectogel as an adhesive, characterized in that: The supramolecular eutectogel is the cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel as described in claim 1 or 2 or the pigment-loaded cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel as described in claim 8.

10. Application of a supramolecular eutectogel as a 3D printing ink, characterized in that: The supramolecular eutectogel is the cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel as described in claim 1 or 2 or the pigment-loaded cyclodextrin-citric acid-sodium lipoate supramolecular eutectogel as described in claim 8.

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