阅读说明：本技术 一种生物粘附型邻苯二酚木质素/化学防晒剂微胶囊及其制备与应用 (Bioadhesive catechol lignin/chemical sun-screening agent microcapsule and preparation and application thereof ) 是由 钱勇 张艾程 邱学青 杨东杰 卢铭津 楼宏铭 于 2021-07-28 设计创作，主要内容包括：本发明公开了一种生物粘附型邻苯二酚木质素/化学防晒剂微胶囊及其制备与应用。本发明采用原位生成Lewis酸法对木质素进行结构改性得到邻苯二酚木质素,再对邻苯二酚木质素进行碱溶、透析和浓缩得到邻苯二酚木质素溶液,最后将邻苯二酚木质素溶液与防晒剂、表面活性剂超声空化,得到邻苯二酚木质素/化学防晒剂微胶囊乳液。本发明木质素/化学防晒剂微胶囊的紫外吸收性能优异,生物粘附性、耐水性和优异的抗渗透性能,解决了传统防晒剂的耐水性差、易渗透等问题。(The invention discloses a bioadhesive catechol lignin/chemical sun-screening agent microcapsule, and a preparation method and an application thereof. According to the invention, structural modification is carried out on lignin by adopting an in-situ generated Lewis acid method to obtain catechol lignin, then alkali dissolution, dialysis and concentration are carried out on the catechol lignin to obtain catechol lignin solution, and finally ultrasonic cavitation is carried out on the catechol lignin solution, a sun-screening agent and a surfactant to obtain catechol lignin/chemical sun-screening agent microcapsule emulsion. The lignin/chemical sunscreen agent microcapsule has excellent ultraviolet absorption performance, biological adhesion, water resistance and excellent anti-permeability performance, and solves the problems of poor water resistance, easy permeability and the like of the traditional sunscreen agent.)

1. A preparation method of a bioadhesive catechol lignin/chemical sunscreen microcapsule is characterized by comprising the following steps:

(1) dissolving lignin in a polar solvent, deoxidizing, heating to 80-200 ℃, adding halogenated alkane and/or halogen acid, carrying out reflux reaction for 8-24 hours, purifying, and drying to obtain catechol lignin;

(2) adding catechol lignin into an alkali solution with the pH value of 10-13, adjusting the pH value of the system to be neutral, performing dialysis treatment, and concentrating to obtain a catechol lignin solution;

(3) compounding the catechol lignin solution with a sun-screening agent and a surfactant, performing ultrasonic cavitation to obtain catechol lignin/chemical sun-screening agent microcapsule emulsion, and centrifuging to obtain the biological adhesion type catechol lignin/chemical sun-screening agent microcapsule.

2. The preparation method of the bioadhesive catechol lignin/chemical sun-screening agent microcapsule according to claim 1, wherein the weight ratio of the lignin to the halogenated alkane and/or the halogen acid in the step (1) is 1-10: 6-24;

the concentration of the catechol lignin solution obtained after concentration in the step (2) is 5-10 wt%;

the weight ratio of the catechol lignin solution to the sun-screening agent in the step (3) is 1: 1-10: 1;

and (3) adding the surfactant in an amount which is 1-15% of the total weight of the catechol lignin solution and the sun-screening agent.

3. The method for preparing a bioadhesive catechol lignin/chemical sunscreen microcapsule according to claim 2, wherein the weight ratio of the lignin to the haloalkane and/or hydrohalic acid in step (1) is 1: 1-1: 5;

the weight ratio of the catechol lignin solution to the sun-screening agent in the step (3) is 1: 1-4: 1.

4. The method for preparing a bioadhesive catechol lignin/chemical sunscreen microcapsule according to claim 1, wherein the lignin in step (1) is at least one of solvent-based lignin, enzymatic lignin and alkali lignin;

the halogenated alkane in the step (1) is at least one of iodocyclohexane and bromocyclohexane, and the hydrohalic acid is at least one of hydroiodic acid and hydrobromic acid;

the sunscreen agent of step (3) is at least one of UVA and UVB type sunscreen agents;

and (3) the surfactant is at least one of tween, alkyl polyglycoside and sucrose ester.

5. The method of claim 4, wherein the alkali lignin is at least one of wood pulp alkali lignin, bamboo pulp alkali lignin, wheat straw pulp alkali lignin, reed pulp alkali lignin, bagasse pulp alkali lignin, asparagus pulp alkali lignin and cotton pulp alkali lignin;

the sunscreen agent in the step (3) is at least one of avobenzone, ethylhexyl methoxycinnamate, homosalate and oxybenzone.

6. The preparation method of the bioadhesive catechol lignin/chemical sun-screening agent microcapsule according to claim 1, wherein the temperature of the reflux reaction in the step (1) is 100-160 ℃, and the time is 8-12 hours;

and (4) performing ultrasonic cavitation at 200-1500W for 1-20 min.

7. The preparation method of the bioadhesive catechol lignin/chemical sun-screening agent microcapsule according to claim 6, wherein the temperature of the reflux reaction in the step (1) is 120-160 ℃;

and (4) ultrasonic cavitation in the step (3) is 400-1000W ultrasonic cavitation for 3-10 min.

8. The preparation method of the bioadhesive catechol lignin/chemical sun-screening agent microcapsule according to claim 1, wherein the weight ratio of the lignin and the polar solvent in the step (1) is 1-10: 5-50, wherein the polar solvent is at least one of N, N-dimethylformamide, dimethyl sulfoxide and acetone;

the oxygen removal treatment in the step (1) comprises the following steps: repeatedly vacuumizing and filling nitrogen for treatment;

the volume ratio of the weight of the catechol lignin to an alkali solution with the pH value of 10-13 in the step (2) is 1g: 10-40 mL, and the alkali solution with the pH value of 10-13 is at least one of a NaOH solution and a KOH solution;

the dialysis treatment in the step (2) is carried out for 3-7 days, and the dialysate is water;

centrifuging the catechol lignin/chemical sun-screening agent microcapsule emulsion obtained in the step (3) for 20-40 min at 5000-15000 r/min to obtain the lignin/chemical sun-screening agent microcapsule.

9. A bioadhesive catechol lignin/chemical sunscreen microcapsule obtainable by the method of any one of claims 1 to 8.

10. Use of a bioadhesive catechol lignin/chemical sunscreen microcapsule according to claim 9 in the field of chemical sun protection.

Technical Field

The invention belongs to the field of fine chemicals, and particularly relates to a bioadhesive catechol lignin/chemical sun-screening agent microcapsule, and preparation and application thereof.

Background

Proper sunlight irradiation is beneficial to human bodies, but excessive ultraviolet irradiation can stimulate the skin and generate free radicals, and the free radicals further induce cell membranes to generate peroxidation, so that the skin is aged and relaxed, and even the skin cancer can be caused. Illumination radiation having a wavelength of 10 to 400nm is internationally called ultraviolet radiation. The ultraviolet radiation can be divided into UVA wave band (320-400 nm), UVB wave band (290-320 nm), UVC wave band (100-290 nm) and EUV (10-100nm) according to international inertial ultraviolet radiation. UVC is absorbed by the ozone layer already in high altitude, so that the human body cannot be injured. But more than 90% UVA and about 1% to 10% UVB are still able to pass through the atmosphere to the earth's surface. Ultraviolet rays in the UVA band have strong penetrating performance and can reach the dermis layer of a human body, so that melanin is deposited, and the skin of the human body is aged and damaged due to long-term accumulation. The penetration performance of UVB wave band ultraviolet rays is weak, and the UVB wave band ultraviolet rays are mostly absorbed by human epidermal cells, but the UVB wave band ultraviolet rays can cause damage to skin due to relatively high energy, and the phenomena of reddening, blisters and the like occur. Ultraviolet radiation, whether in the UVB or UVA band, causes the generation of Reactive Oxides (ROS) in the human body, and the presence of ROS further damages cells.

Sunscreen products such as creams, sprays, etc. applied to the skin surface can reduce or prevent the damage of ultraviolet radiation. Sunscreens are largely classified into physical sunscreens and chemical sunscreens, depending on the principle of protection. The sunscreen ingredients of physical sunscreens are generally metal oxide particles such as titanium dioxide, zinc oxide, and the like, which are less comfortable to use and are prone to photocatalytic reactions. Thus, chemical sunscreens account for 80% of the market. The main components of the chemical sunscreen agent are generally aromatic small molecules with ultraviolet absorption, such as avobenzone, xylon-3, cinnamate, etc., but these small molecules easily permeate the skin and cause anaphylaxis. Under the irradiation of ultraviolet rays, even a small amount of physical or chemical sunscreen agent penetrates into the skin to cause the generation of Reactive Oxygen Species (ROS), which in turn damages cellular components and causes DNA damage. The problem of penetration of small molecule sunscreens has become an urgent problem to be solved in the field of sunscreens. Deng et al effectively solved the problem of sunscreen penetration by using aldehyde hyperbranched polyglycidyl ether with bioadhesive properties as a wall material to wrap small molecule sunscreens to form microcapsules (Nature Materials,2015,14, 1278).

Lignin is the highest content of natural polymers containing benzene rings. In addition, lignin contains a large number of phenolic hydroxyl groups, benzene rings, carbonyl groups and other structures, and the structures all have certain ultraviolet absorption capacity, so that the lignin also has good ultraviolet absorption resistance, and in addition, the phenolic hydroxyl groups in the lignin also have certain free radical scavenging function (Industrial crops and products,2011,33, 259-276). The applicant innovatively develops the lignin into natural polymer sunscreen and applies the natural polymer sunscreen to the field of sunscreen and skin care. Due to random agglomeration, the lignin has limited direct application sun-screening performance, but has good synergistic effect with a small-molecular sun-screening agent, and the sun-screening performance and the light stability can be greatly improved by adding the sun-screening cream. Therefore, the applicant prepares a lignin/sunscreen agent composite nanocapsule by coating avobenzone and cinnamate with lignin, regulates the addition ratio of the lignin and the sunscreen agent, strengthens the synergistic effect, and can maintain the SPF of the sunscreen cream prepared by adding 10 wt% of the lignin/sunscreen agent composite nanocapsule to be up to 408 and for 8 hours (ACS Applied biological Materials,2018,1, 1276).

The lignin/sun-screening agent composite nanocapsule has excellent and stable ultraviolet resistance, and provides a new idea for developing natural polymer sun-screening cream. However, the lignin-based microcapsules have relatively small particle size and very weak biological adhesion capability, and still have the hidden trouble of skin penetration, and the water resistance of the lignin-based microcapsules is poor. Therefore, the lignin needs to be modified by adhesion, so as to improve the water and permeability resistance of the lignin/sunscreen composite nanocapsule, and further improve the safety of the lignin-based sunscreen agent.

The polydopamine can simulate melanin to block ultraviolet radiation to cause skin damage, but the polydopamine is relatively high in cost, self-polymerization reaction of the dopamine is easy to occur, the reaction is difficult to control, and the process of grafting the polydopamine to lignin is relatively complex.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention aims to provide a preparation method of a bioadhesive type catechol lignin/chemical sun-screening agent microcapsule.

The lignin contains a large number of potential methoxyl structures in the structure, and good feasibility is provided for constructing more catechol structures by the lignin. According to the invention, the lignin is structurally modified by adopting an in-situ generated Lewis acid method, so that the catechol structure in the lignin structure is obviously increased, the biological adhesion performance, the ultraviolet resistance and the oxidation resistance of the lignin are improved, and the stability of the lignin-based microcapsule is further improved.

The invention also aims to provide a bioadhesive catechol lignin/chemical sun-screening agent microcapsule prepared by the method.

The invention further aims to provide application of the bioadhesive catechol lignin/chemical sun-screening agent microcapsule.

The purpose of the invention is realized by the following technical scheme:

a preparation method of a bioadhesive catechol lignin/chemical sunscreen microcapsule comprises the following steps:

(1) dissolving lignin in a polar solvent, deoxidizing, heating to 80-200 ℃, adding halogenated alkane and/or halogen acid, carrying out reflux reaction for 8-24 hours, purifying, and drying to obtain catechol lignin;

(2) adding catechol lignin into an alkali solution with the pH value of 10-13, adjusting the pH value of the system to be neutral, performing dialysis treatment, and concentrating to obtain a catechol lignin solution;

(3) compounding the catechol lignin solution with a sun-screening agent and a surfactant, performing ultrasonic cavitation to obtain catechol lignin/chemical sun-screening agent microcapsule emulsion, and centrifuging to obtain the biological adhesion type catechol lignin/chemical sun-screening agent microcapsule.

Preferably, the weight ratio of the lignin to the halogenated alkane and/or the halogen acid in the step (1) is 1-10: 6-24; the weight ratio of the lignin to the polar solvent is 1-10: 5-50; more preferably 3 to 6: 30.

more preferably, the weight ratio of the lignin to the haloalkane and/or hydrohalic acid in step (1) is 1: 1-1: 5; more preferably 3 to 6: 9-15.

Preferably, the lignin in the step (1) is at least one of solvent-based lignin, enzymatic lignin and alkali lignin.

More preferably, the alkali lignin is at least one of wood pulp alkali lignin, bamboo pulp alkali lignin, wheat straw pulp alkali lignin, reed pulp alkali lignin, bagasse pulp alkali lignin, asparagus pulp alkali lignin and cotton pulp alkali lignin.

The lignin obtained by industrially treating and separating it using different treatment means is generally called industrial lignin. The division and naming is generally based on the different ways of processing and separation of the lignin. Different lignins differ greatly in structure, reactive functional group content and species. Industrial lignin can be divided into four major groups: enzymatic hydrolysis of lignin: the enzymatic hydrolysis lignin is lignin which is obtained by depolymerizing and dissolving lignin raw materials by using cellulase and hemicellulose, alkali lignin: the alkali lignin mainly comes from waste liquid of alkaline pulping such as sulfate method and alkyl-alkali method, organic solvent lignin: the organic solvent lignin is lignin extracted from plants by organic reagents such as methanol, ethanol, acetone and the like under a high-temperature environment, and is characterized in that lignin sulfonate: the lignosulfonate is derived from sulfite pulping waste liquor, and has good water solubility and wide application prospect.

Preferably, the polar solvent in step (1) is at least one of N, N-dimethylformamide, dimethyl sulfoxide and acetone.

Preferably, the oxygen removing treatment in the step (1) is as follows: and repeatedly vacuumizing and filling nitrogen for treatment.

Preferably, the halogenated alkane in the step (1) is at least one of iodocyclohexane and bromocyclohexane, and the hydrohalic acid is at least one of hydroiodic acid and hydrobromic acid.

Preferably, the temperature of the reflux reaction in the step (1) is 100-160 ℃, and the time is 8-12 hours; more preferably 120 to 160 ℃.

Preferably, the purification method in step (1) is: washing the reaction product mixture with n-hexane to remove unreacted halogenated alkane and/or hydrohalic acid, then dropwise adding the reaction solution into saturated sodium metabisulfite solution, filtering, retaining precipitate and washing.

Preferably, the volume ratio of the weight of the catechol lignin to the alkaline solution with the pH value of 10-13 in the step (2) is 1g: 10-40 mL.

Preferably, in the step (2), the alkali solution with a pH of 10-13 is at least one of a NaOH solution and a KOH solution.

Preferably, the dialysis treatment in the step (2) is carried out for 3-7 days, the dialysate is water, and the conductivity of the dialysate is similar to or consistent with that of deionized water after dialysis.

Preferably, the concentration of the catechol lignin solution obtained after concentration in the step (2) is 5-10 wt%.

Preferably, the weight ratio of the catechol lignin solution to the sun-screening agent in the step (3) is 1: 1-10: 1, and more preferably 1: 1-4: 1; most preferably 7: 3.

preferably, the addition amount of the surfactant in the step (3) accounts for 1-15% of the total weight of the catechol lignin solution and the sun-screening agent; more preferably 7%.

Preferably, the sunscreen agent of step (3) is at least one of a UVA and UVB type sunscreen agent; more preferably at least one of avobenzone, ethylhexyl methoxycinnamate, homosalate and oxybenzone; if the sunscreen contains both UVA and UVB types, then the UVA type needs to be dispersed and dissolved into the UVB type sunscreen.

Preferably, the surfactant in step (3) is at least one of tween, alkyl polyglycoside and sucrose ester.

Preferably, the ultrasonic cavitation in the step (3) is 200-1500W for 1-20 min; more preferably 400-1000W ultrasonic cavitation for 3-10 min.

Preferably, the catechol lignin/chemical sunscreen agent microcapsule emulsion in the step (3) may be washed by centrifugation to remove excessive catechol lignin, so as to obtain demethylated lignin/chemical sunscreen agent microcapsule.

More preferably, the speed of the centrifugation is 5000-15000 r/min, and the time of the centrifugation and water washing is 20-40 min.

The invention provides a bioadhesive catechol lignin/chemical sun-screening agent microcapsule prepared by the method.

The bioadhesive catechol lignin/chemical sun-screening agent microcapsule is an amphiphilic spherical structure, has the particle size of 100-800nm, has excellent ultraviolet absorption performance and good stability, and has good adhesive property, thus having excellent water resistance and anti-seepage performance.

The invention provides an application of the bioadhesive type catechol lignin/chemical sun-screening agent microcapsule in the field of chemical sun-screening. The chemical sun protection does not take a living body as a sun protection object.

More preferably in the preparation of sunscreens.

The lignin is a natural polymer with good ultraviolet resistance, and has good biocompatibility and oxidation resistance. After the lignin is subjected to demethylation chemical modification, the content of phenolic hydroxyl in the lignin can be remarkably improved, and the modified lignin is easier to perform cross-linking reaction with a chemical sunscreen agent and the like when the chemical sunscreen agent is embedded by ultrasonic cavitation. The invention promotes the dispersion of the oil phase and the water phase by adding the surfactant, so that the size of the microcapsule can reach the nanometer level, and the ultraviolet scattering effect can be enhanced. In addition, due to the promotion of phenolic hydroxyl in the structure of the catechol lignin, the structure of the catechol in lignin molecules is greatly increased, so that the obtained microcapsule has good permeation resistance and water resistance, and the use efficiency and safety of the microcapsule are improved.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the lignin has good ultraviolet resistance and oxidation resistance, the biocompatibility is good, the phenolic hydroxyl active sites in molecules are increased by more than 60% after the lignin is subjected to chemical modification, so that the ultraviolet resistance of the lignin is obviously enhanced, the small-molecule chemical sun-screening agent can be effectively embedded to be used for synergetic sun-screening by utilizing free radical crosslinking in the ultrasonic cavitation process, the photolysis resistance of the small-molecule chemical sun-screening agent is improved, and the lasting sun-screening is realized.

(2) The catechol lignin prepared by the in-situ demethylation method has bionic adhesion performance, and the mutual conversion of catechol and quinoid structures enables more stable semiquinone free radicals to appear, so that the method can play a role in removing external free radicals, and remarkably improves the oxidation resistance of the lignin. The small-molecule sunscreen agent coated by the catechol lignin can effectively resist the phenomenon that the small-molecule chemical sunscreen agent damages the skin after photodegradation, and realizes safe sunscreen.

(3) The catechol structure distributed on the surface of the biological adhesion type microcapsule of the catechol lignin/chemical sun-screening agent endows the microcapsule with good adhesion performance and anti-permeability performance, improves the use efficiency and safety, solves the problems that the traditional sun-screening agent has poor water resistance, is easy to permeate into skin to hurt human bodies and the like, and realizes safe and efficient sun-screening and skin care.

Drawings

FIG. 1 is a nuclear magnetic hydrogen spectrum of an alkali lignin feedstock and catechol alkali lignin from example 1.

FIG. 2 is a microcapsule of catechol lignin obtained in example 1.

FIG. 3 is a Fourier infrared spectrum of the catechol lignin obtained in example 1 and the original lignin.

FIG. 4 is an ultraviolet spectrum of the bioadhesive microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen agent and the ultraviolet spectrum of the alkali lignin/chemical sunscreen agent microcapsule sunscreen cream in the range of 290-400 nm obtained in example 1.

FIG. 5 is a laser confocal test chart of bioadhesive microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen obtained in example 1 and of alkali lignin/chemical sunscreen microcapsule sunscreen cream.

FIG. 6 is an ultraviolet spectrum of the bioadhesive microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen agent obtained in example 1 and the ultraviolet spectrum of the catechol alkali lignin/chemical sunscreen agent microcapsule sunscreen cream of comparative example 1 in the range of 290-400 nm.

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

Those who do not specify specific conditions in the examples of the present invention follow conventional conditions or conditions recommended by the manufacturer. The raw materials, reagents and the like which are not indicated for manufacturers are all conventional products which can be obtained by commercial purchase.

Example 1

(1) Dissolving 3g of alkali lignin in 30mL of N, N-dimethylformamide solution, repeatedly vacuumizing and filling nitrogen in a reaction device for three times, isolating air, heating at 120 ℃ for 15min, then slowly adding 10mL of iodocyclohexane under stirring, and then refluxing for reaction for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the catechol alkali lignin.

(2) And (3) adding the obtained catechol alkali lignin into 50mL of NaOH solution with the pH value of 12 for dissolving, slowly adjusting the pH value of the solution to be neutral, dialyzing the solution for 6 days, and concentrating the dialyzate when the conductivity of the dialyzate is close to the same as that of deionized water to obtain the catechol alkali lignin solution with the concentration of 5 wt%.

(3) Weighing 7g of catechol lignin solution with the weight percent of 5g, adding 3g of a mixture of ethylhexyl methoxycinnamate and avobenzone (the mass ratio is 4:1) and 0.7g of tween, carrying out ultrasonic cavitation for 3min under the condition that the ultrasonic power is 400W to obtain a biological adhesion type microcapsule of catechol alkali lignin/chemical sun-screening agent, and centrifuging for 30min at 10000r/min to obtain the biological adhesion type microcapsule of catechol alkali lignin/chemical sun-screening agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen agent.

FIG. 1 is a nuclear magnetic hydrogen spectrum of an alkali lignin feedstock and catechol alkali lignin from example 1. Compared with alkali lignin, the proton peak of methoxyl at 3.73ppm in the nuclear magnetic hydrogen spectrum of catechol alkali lignin is almost negligible, which indicates that the original methoxyl is almost completely converted into phenolic hydroxyl.

FIG. 2 is a microcapsule of catechol lignin obtained in example 1. The obvious color of the microcapsule prepared by the catechol lignin is darker, which shows that the content of phenolic hydroxyl in the lignin is obviously increased.

Figure 3 is a fourier infrared spectrum of the produced catechol lignin and the original alkali lignin. The catechol lignin was found to be 3389cm in comparison to the original lignin^-1The absorption peak signal is obviously enhanced, which shows that the hydroxyl content of the structure of the lignin is greatly increased under the demethylation of the iodocyclohexane. The positions and intensities of other absorption peaks in the fourier spectrum did not change significantly, indicating that the demethylation process did not cause damage to the main structure of the lignin.

Fig. 4 is an ultraviolet spectrum diagram of the bioadhesion type microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen obtained in example 1 and the original lignin/chemical sunscreen microcapsule sunscreen cream (obtained by changing catechol alkali lignin in step (3) of example 1 into alkali lignin) in the range of 260 to 400nm, measured by a japanese shimadzu UV-2550 ultraviolet-visible spectrophotometer. As can be seen from the figure, the ultraviolet transmittance of the biological adhesion type microcapsule sunscreen cream of the catechol alkali lignin/chemical sunscreen agent is obviously lower than that of the alkali lignin/chemical sunscreen agent microcapsule sunscreen cream, which shows that the biological adhesion type microcapsule sunscreen cream has better ultraviolet blocking effect. Converted to the ultraviolet protection index (SPF), the SPF of the bioadhesive microcapsule sunscreen of the alkali lignin catechol/chemical sunscreen was 235, while the SPF of the alkali lignin/chemical sunscreen microcapsule sunscreen was 64.

FIG. 5 is a laser confocal test chart of bioadhesive microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen obtained in example 1 and of alkali lignin/chemical sunscreen microcapsule sunscreen cream. The adhesion performance of the biological adhesion type microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen agent and the adhesion performance of the alkali lignin/chemical sunscreen agent microcapsule sunscreen cream to skin are tested by using a laser confocal microscope. The alkali lignin/chemical sunscreen agent microcapsule sunscreen cream prepared by replacing the catechol lignin in the step 3 in the embodiment 1 with the original alkali lignin has poor adhesion performance with skin, the blue fluorescence signal of the surface lignin is weak, which proves that the microcapsules adhered to the surface of the skin are washed away, and the biological adhesion type microcapsule sunscreen cream of the catechol alkali lignin/chemical sunscreen agent can still keep a strong fluorescence signal after washing, which proves that the lignin has more phenolic hydroxyl groups on the surface after demethylation compared with the original lignin, and the adhesion performance is obviously improved.

Example 2

(1) 5g of alkali lignin is dissolved in 30mL of N, N-dimethylformamide solution, the reaction device is subjected to repeated vacuum-nitrogen filling treatment for three times, air is isolated, the reaction device is heated at 150 ℃ for 15min, then 12mL of hydrobromic acid is slowly added under stirring, and then reflux reaction is carried out for 8 hours. And after the reaction liquid is cooled, n-hexane is used as a detergent to wash away unreacted hydrobromic acid. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the catechol alkali lignin.

(2) And (3) adding the obtained catechol alkali lignin into 50mL of NaOH solution with the pH value of 11 for dissolving, slowly adjusting the pH value of the solution to be neutral, dialyzing the solution for 5 days, and concentrating the dialyzate when the conductivity of the dialyzate is close to the same as that of deionized water to obtain the catechol alkali lignin solution with the concentration of 10 wt%.

(3) Weighing 7g of 10 wt% catechol lignin solution, adding 3g of a mixture of ethylhexyl methoxycinnamate and avobenzone (the mass ratio is 4:1) and 0.7g of alkyl polyglycoside, performing ultrasonic cavitation for 3min under the condition that the ultrasonic power is 1000W to obtain a bioadhesive microcapsule of catechol alkali lignin/chemical sun-screening agent, and centrifuging for 30min at 8000r/min to obtain the bioadhesive microcapsule of catechol alkali lignin/chemical sun-screening agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen agent.

The results of the nmr hydrogen spectroscopy, the microcapsule preparation process, the fourier infrared spectroscopy, the uv-vis spectroscopy, and the laser confocal measurement, which were the same as those of example 1, were substantially the same as those of fig. 1, fig. 2, fig. 3, fig. 4, and fig. 5, respectively. The bioadhesive microcapsule sunscreen of the catechol alkali lignin/chemical sunscreen had an SPF value of 211.

Example 3

(1) Dissolving 5g of enzymatic hydrolysis lignin in 30mL of N, N-dimethylformamide solution, repeatedly vacuumizing and filling nitrogen for three times in a reaction device, isolating air, heating at 100 ℃ for 15min, then slowly adding 15mL of bromocyclohexane under the condition of stirring, and then carrying out reflux reaction for 10 hours. And after the reaction liquid is cooled, n-hexane is taken as a detergent, and unreacted bromocyclohexane is washed away. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the catechol enzymatic hydrolysis lignin.

(2) And (3) adding the obtained catechol enzymatic hydrolysis lignin into 50mL of KOH solution with the pH value of 13 for dissolving, slowly adjusting the pH value of the solution to be neutral, dialyzing the solution for 7 days, and concentrating the dialyzate when the conductivity of the dialyzate is close to the same as that of deionized water to obtain a catechol alkali lignin solution with the concentration of 8 wt%.

(3) Weighing 7g of 8 wt% catechol lignin solution, adding 3g of a mixture of homosalate and avobenzone (the mass ratio is 4:1) and 0.7g of sucrose ester, performing ultrasonic cavitation for 4min under the condition that the ultrasonic power is 800W to obtain a bioadhesive microcapsule of catechol alkali lignin/chemical sun-screening agent, and centrifuging for 25min at 10000r/min to obtain the bioadhesive microcapsule of catechol enzymolysis lignin/chemical sun-screening agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol enzymatic hydrolysis lignin/chemical sunscreen agent.

The results of the nmr hydrogen spectroscopy, the microcapsule preparation process, the fourier infrared spectroscopy, the uv-vis spectroscopy, and the laser confocal measurement, which were the same as those of example 1, were substantially the same as those of fig. 1, fig. 2, fig. 3, fig. 4, and fig. 5, respectively. The SPF value of the bioadhesive microcapsule sunscreen cream of the catechol alkali lignin/chemical sunscreen agent is 184.

Example 4

(1) 6g of enzymatic lignin is dissolved in 30mL of N, N-dimethylformamide solution, the reaction device is subjected to repeated vacuum-nitrogen filling treatment for three times, air is isolated, the mixture is heated at 160 ℃ for 15min, then 9mL of hydroiodic acid is slowly added under the condition of stirring, and then the reaction is refluxed for 12 hours. After the reaction liquid is cooled, n-hexane is used as a detergent to wash away unreacted hydroiodic acid. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the demethylated enzymatic hydrolysis lignin.

(2) And (3) adding the obtained demethylation enzymatic hydrolysis lignin into 50mL of KOH solution with the pH value of 12 for dissolving, slowly adjusting the pH value of the solution to be neutral, dialyzing the solution for 7 days, and concentrating the dialyzate when the conductivity of the dialyzate is nearly consistent with that of deionized water to obtain the demethylation enzymatic hydrolysis lignin solution with the concentration of 5 wt%.

(3) Weighing 7g of 5 wt% catechol lignin solution, adding 3g of a mixture of homosalate and avobenzone (the mass ratio is 4:1) and 0.7g of alkyl polyglycoside, performing ultrasonic cavitation for 6min under the condition that the ultrasonic power is 700W to obtain a bioadhesive microcapsule of catechol enzymatic hydrolysis lignin/chemical sun-screening agent, and centrifuging for 40min at 5000r/min to obtain the bioadhesive microcapsule of catechol enzymatic hydrolysis lignin/chemical sun-screening agent. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea limited company) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol enzymatic hydrolysis lignin/chemical sunscreen agent.

The results of the nmr hydrogen spectroscopy, the microcapsule preparation process, the fourier infrared spectroscopy, the uv-vis spectroscopy, and the laser confocal measurement, which were the same as those of example 1, were substantially the same as those of fig. 1, fig. 2, fig. 3, fig. 4, and fig. 5, respectively. The SPF value of the bioadhesive microcapsule sunscreen cream of the catechol enzymatic hydrolysis lignin/chemical sunscreen agent is 188.

Comparative example 1

(1) 3g of alkali lignin was dissolved in 30mL of N, N-dimethylformamide solution, heated at 120 ℃ for 15min, and then 15mL of iodocyclohexane was slowly added under stirring, followed by reflux reaction for 12 hours. And after the reaction liquid is cooled, using n-hexane as a detergent to wash away unreacted iodocyclohexane. And then, dropwise adding the reaction solution into a saturated sodium metabisulfite solution, filtering, retaining and washing the precipitate, and then carrying out freeze drying to obtain the catechol alkali lignin.

(2) And (3) adding the obtained catechol alkali lignin into 50mL of NaOH solution with the pH value of 12 for dissolving, slowly adjusting the pH value of the solution to be neutral, dialyzing the solution for 6 days, and concentrating the dialyzate when the conductivity of the dialyzate is nearly consistent with that of deionized water to obtain a catechol alkali lignin solution with the concentration of 5 wt%.

(3) Weighing 7g of catechol lignin solution with the weight percent of 5g, adding 3g of a mixture of ethylhexyl methoxycinnamate and avobenzone (the mass ratio is 4:1) and 0.7g of tween, carrying out ultrasonic cavitation for 3min under the condition that the ultrasonic power is 400W to obtain a biological adhesion type microcapsule of catechol alkali lignin/chemical sun-screening agent, and centrifuging for 30min at 10000r/min to obtain the catechol alkali lignin/chemical sun-screening agent microcapsule. The microcapsules are mixed with blank cream (Nivea deep moisturizing hand cream, Nivea (Shanghai) Co., Ltd.) without sunscreen active ingredients according to the mass ratio of 1:9 to prepare the biological adhesion type microcapsule sunscreen cream of catechol alkali lignin/chemical sunscreen agent.

FIG. 6 is a UV-VIS spectrum of the catechol lignin/chemical sunscreen microcapsule sunscreen cream obtained in this comparative example. It can be seen from the figure that oxygen participates in the reaction process due to no air isolation in the reaction process, and the obtained phenolic hydroxyl group is further oxidized, so that the content of the phenolic hydroxyl group is not obviously improved, and the SPF of the subsequently prepared catechol lignin/chemical sunscreen agent microcapsule sunscreen cream is 69 and is not obviously improved.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.