Sunscreen moisturizing nano-composite hydrogel as well as preparation method and application thereof

Abstract

The invention discloses a sunscreen moisturizing nano composite hydrogel and a preparation method and application thereof, and the preparation method comprises the following steps: adding a flower-like titanium dioxide nano material and a vinyl-containing hydrophilic monomer into water, and carrying out ultrasonic dissolution under the protection of nitrogen to obtain a precursor solution of the hydrogel; and irradiating the precursor solution of the hydrogel under a high-pressure ultraviolet lamp to obtain the sunscreen and moisturizing nano composite hydrogel. The sunscreen and moisturizing nano-composite hydrogel is simple in formula component and convenient in preparation process, sunscreen and moisturizing functions can be realized without adding extra humectants and sunscreen agents, and the sunscreen and moisturizing nano-composite hydrogel has good economical efficiency and universality and provides a new idea for preparation of the sunscreen and moisturizing hydrogel.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel biomaterials, and particularly relates to a sunscreen and moisturizing nanocomposite hydrogel, its preparation method and application. Background Technology

[0002] As the largest organ in the human body, the skin forms the first crucial line of defense against external physical, chemical, and biological aggressors. Its integrity and health not only form the basis for maintaining the body's internal homeostasis but also directly affect an individual's appearance and mental well-being. The core of the skin barrier function lies in the stratum corneum, composed of keratinocytes and intercellular lipids, which work together to regulate transepidermal water loss and prevent the invasion of harmful substances. However, in daily life, the skin constantly faces challenges from various internal and external factors, the two most significant threats being ultraviolet radiation and skin moisture loss. On the one hand, ultraviolet radiation, especially UVA (320-400nm) and UVB (290-320nm), is the main culprit behind a series of pathological changes, including photoaging, sunburn, hyperpigmentation, and even skin cancer. Therefore, photoprotection has become an indispensable part of modern skin care. Sunscreen is the most direct and effective way to achieve photoprotection, blocking or absorbing UV radiation through physical shielding or chemical absorption, thereby protecting the skin.

[0003] On the other hand, dehydration or dryness is another common skin problem. It not only causes discomfort such as tightness, roughness, flaking, and itching, but more importantly, it damages the skin barrier function, increasing the skin's susceptibility to external irritants. Factors such as low environmental humidity, excessive cleansing, aging, and certain medications (such as the epidermal growth factor receptor inhibitor erlotinib) can all lead to dry skin. Therefore, using moisturizers to replenish and lock in skin moisture is a fundamental skincare step for maintaining healthy skin and delaying aging.

[0004] Given that UV radiation and skin dehydration are two major challenges that need to be addressed simultaneously in daily skincare, developing multifunctional skincare products that combine sun protection and moisturizing functions has become an important trend in cosmetic research and development. These products not only simplify skincare routines and improve consumer convenience and compliance, but also provide more comprehensive skin protection through synergistic effects. However, existing high-efficiency, stable, and skin-friendly cosmetic formulations are complex to manufacture and costly. Traditional sunscreens, such as creams and lotions, while widely used, are often unpopular with consumers due to their oily and heavy texture, especially in hot and humid climates or for oily, acne-prone skin types. Furthermore, safety concerns regarding some chemical sunscreens, such as skin irritation, allergic contact dermatitis, and potential endocrine disruption effects, have also raised widespread concerns.

[0005] Gel formulations have emerged as a highly attractive cosmetic matrix. Gels, especially hydrogels, are favored for their refreshing, oil-free, easy-to-apply, quick-drying, and excellent moisturizing properties. Their three-dimensional network structure can hold a large amount of water, providing an immediate cooling and hydrating sensation to the skin upon application. Hydrogels with sun protection and moisturizing effects are particularly popular. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a method for preparing a sunscreen and moisturizing nanocomposite hydrogel, which can achieve sunscreen and moisturizing functions without the need to add additional moisturizers and sunscreens.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing a sunscreen and moisturizing nanocomposite hydrogel includes the following steps:

[0009] (1) Add flower-shaped titanium dioxide nanomaterials and vinyl-containing hydrophilic monomers to water and dissolve them by ultrasonication under nitrogen protection to obtain a precursor solution of hydrogel;

[0010] (2) The precursor solution of the hydrogel was irradiated under a high-pressure ultraviolet lamp to obtain a sunscreen and moisturizing nanocomposite hydrogel.

[0011] The method for preparing the sunscreen and moisturizing nanocomposite hydrogel of the present invention uses flower-shaped titanium dioxide nanomaterials as photoinitiators. Under ultraviolet light irradiation, water is catalyzed to generate free radicals (such as hydroxyl radicals ·OH), and free radical polymerization reaction containing vinyl hydrophilic monomers is initiated in situ. This forms a core-shell nanocomposite polymer structure unit with titanium dioxide material as the center and polymer chains wrapped around it. The abundant hydrogen bonding between polymer chains forms a three-dimensional hydrogel network. No initiator or crosslinking agent needs to be added during the entire reaction process.

[0012] Preferably, in step (1), the vinyl-containing hydrophilic monomer is at least one of acrylamide, N-isopropylacrylamide, hydroxyethylacrylamide, acrylic acid, and polyethylene glycol (meth)acrylate.

[0013] Preferably, in step (1), the flower-shaped titanium dioxide nanomaterial is obtained by hydrothermal reaction in a high-pressure reactor with potassium titanium oxalate as the titanium source and hydrogen peroxide added.

[0014] In a preferred embodiment, the molar ratio of potassium titanium oxalate to hydrogen peroxide is 1:100-250; the hydrothermal reaction temperature is 120-160°C; and the reaction time is 6-10 hours.

[0015] The flower-shaped titanium dioxide nanomaterials of this invention exhibit abundant hydroxyl groups on their surface, which is a key factor affecting their surface chemical activity. Compared with ordinary spherical titanium dioxide nanoparticles, the surface hydroxyl density of flower-shaped TiO2 is 30-50% higher. This high specific surface area provides more exposed sites, which is beneficial for converting free water molecules into bound water.

[0016] During the preparation of precursor solutions, increasing the content of hydrophilic monomers can increase the length of polymer molecular chains. Therefore, adjusting the length of polymer chains in structural units can improve the mechanical strength of hydrogels and optimize their stability. The length of polymer chains plays a positive role in structural stability.

[0017] Preferably, in step (1), the mass concentration of the flower-shaped titanium dioxide nanomaterial in the precursor solution is 0.2-0.4%, the mass concentration of the vinyl-containing hydrophilic monomer is 10-30%, and the water content is 60-85%.

[0018] Preferably, in step (1), the temperature of the ultrasound is 30-40℃, the frequency is 35-45kHz, and the duration is 3-10min.

[0019] Preferably, in step (2), the irradiation conditions are irradiation under a 365nm, 300W high-pressure ultraviolet lamp for 20-30 minutes.

[0020] This invention also provides a sunscreen and moisturizing nanocomposite hydrogel, prepared by the above-described preparation method. The sunscreen and moisturizing nanocomposite hydrogel prepared by this invention is composed of core-shell polymer nanocomposite structural units with flower-like titanium dioxide nanostructures as the core and hydrophilic polymer chains as the shell. The polymer chains intertwine to form a three-dimensional gel network structure.

[0021] This invention also provides the application of the above-mentioned sunscreen and moisturizing nanocomposite hydrogel in cosmetics. The sunscreen and moisturizing nanocomposite hydrogel prepared by this invention achieves multi-level hydrogen bonding between structural unit chains. The flower-like structure of nano-titanium dioxide converts free water in the gel into bound water, achieving excellent water retention performance. Furthermore, the semiconductor properties of nano-titanium dioxide allow valence band electrons to absorb ultraviolet light and transition to the conduction band, converting light energy into electron kinetic energy consumption, which can shield ultraviolet light, thereby achieving sun protection function.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The preparation method of the sunscreen and moisturizing nanocomposite hydrogel of the present invention mainly uses flower-shaped titanium dioxide nanomaterials as photoinitiators. Under ultraviolet light irradiation, the nanomaterials catalyze the generation of free radicals from water, which initiates the free radical polymerization reaction of vinyl hydrophilic monomers, forming a core-shell polymer nanocomposite structure unit with flower-shaped titanium dioxide nanomaterials as the core and hydrophilic polymer chains as the shell. The abundant hydrogen bonding between the polymer chains forms a three-dimensional network of hydrogel. Unlike traditional sunscreen and moisturizing gels, the nanocomposite hydrogel of the present invention is composed of nanoscale nanocomposite polymer structure units. The multi-level hydrogen bonding between polymer chains and the nanoscale size effect endow the gel with good stability. At the same time, the flower-shaped structure of the nano-titanium dioxide converts free water into bound water, realizing the moisturizing property of the gel. Furthermore, the semiconductor properties of the flower-shaped titanium dioxide nanostructure itself allow valence band electrons to absorb ultraviolet light and jump to the conduction band, converting light energy into electron kinetic energy consumption, which can shield ultraviolet light, thereby achieving the sunscreen function.

[0024] (2) The formulation of the sunscreen and moisturizing nanocomposite hydrogel of the present invention is simple and the preparation process is convenient. It can achieve sun protection and moisturizing functions without the need to add additional moisturizers and sunscreens. It has good economy and universality, and provides a new idea for the preparation of sunscreen and moisturizing hydrogels. Attached Figure Description

[0025] Figure 1 Transmission electron microscopy (TEM) image of synthesized flower-like nano-TiO2;

[0026] Figure 2 The infrared spectrum of the synthesized flower-like nano-TiO2;

[0027] Figure 3 TEM image of a sunscreen and moisturizing nanocomposite hydrogel;

[0028] Figure 4 Stress-strain curves of hydrogels with different TiO2 concentrations (left), different water contents (middle), and different AM monomer concentrations (right);

[0029] Figure 5 The results show the water retention properties of the hydrogels in the examples and comparative examples;

[0030] Figure 6 Optical photograph of the experiment for studying the sun protection properties of the nanocomposite hydrogel (left), and HE staining results of the rat's back (right). Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Synthesis of Flower-like Titanium Dioxide Nanomaterials

[0033] Take a certain amount of 0.05 mol / L potassium titanium oxalate aqueous solution, then add an appropriate amount of hydrogen peroxide aqueous solution to make the molar ratio of potassium titanium oxalate to hydrogen peroxide 1:200, and add a certain amount of hydrochloric acid solution to adjust the pH of the mixed solution to 4. After the above solution is quickly stirred evenly, the solution color changes from transparent to dark red. After the mixed solution reacts completely, continue stirring for a certain period of time. Transfer the obtained mixed solution to a reaction vessel and heat it at 150℃ for 8 hours, then stop heating. After natural cooling, separate the solid precipitate from the solution, wash the precipitate several times with anhydrous ethanol and deionized water, and then dry it at 70℃ to obtain the flower-shaped titanium dioxide nanomaterial powder sample.

[0034] Figure 1 Transmission electron microscopy (TEM) images of flower-shaped nano-titanium dioxide are shown (at different magnifications). From Figure 1 As can be seen, the synthesized nano-titanium dioxide has a flower-like structure, is uniform in size, and is concentric and layered in the shape of petals, with a particle size of 200 nm.

[0035] Figure 2 The infrared absorption spectrum of the synthesized flower-like nano-TiO2 was obtained from... Figure 2 As can be seen from this, flower-like TiO2 at 3400 cm⁻¹ -1 and 1630cm -1 Strong absorption peaks appear nearby, corresponding to the stretching and bending vibrations of OH groups in the surface adsorbed water, respectively; while at 3700-3650 cm⁻¹... 1 The characteristic peaks within this range are attributed to the vibrations of the Ti-OH groups. Compared to spherical TiO2 nanoparticles, flower-shaped TiO2 has a 30-50% higher surface hydroxyl density, and this higher specific surface area provides more exposed sites, which is beneficial for converting free water molecules into bound water.

[0036] Example 1:

[0037] (1) Add the flower-shaped titanium dioxide nanomaterial and the vinyl-containing hydrophilic monomer acrylamide (AM) to 5 mL of water, and dissolve them by sonication for 5 min under nitrogen protection. Adjust the added mass of monomer acrylamide and titanium dioxide nanomaterial to 20% and 0.4% of the total solution mass, respectively, to obtain the precursor solution of hydrogel.

[0038] (2) The precursor solution of the hydrogel was irradiated under a high-pressure ultraviolet lamp (365nm, 300W) for 25min to prepare a sunscreen and moisturizing nanocomposite hydrogel (TFA). The stress of the gel prepared in this example was 25kPa, and the strain was up to 50 times the original length, which showed good stretchability and mechanical strength.

[0039] Figure 3 A TEM image of the sunscreen and moisturizing nanocomposite hydrogel is shown. As can be seen from the image, the sunscreen and moisturizing nanocomposite hydrogel prepared in this embodiment is composed of core-shell polymer nanocomposite structural units.

[0040] Example 2: Optimization of mass concentration of flower-shaped titanium dioxide nanomaterials

[0041] (1) Add flower-shaped titanium dioxide nanomaterials and vinyl-containing hydrophilic monomer acrylamide to 5 mL of water, sonicate for 5 min under nitrogen protection and dissolve. Keep the added mass of monomer acrylamide at 20% of the total solution mass. Change the amount of flower-shaped titanium dioxide nanomaterials so that the added mass of flower-shaped titanium dioxide nanomaterials is 0.1%, 0.2%, 0.4% and 0.8% of the total solution mass, respectively, to obtain precursor solutions of hydrogels with different titanium dioxide concentrations;

[0042] (2) The precursor solutions of the obtained hydrogels with different titanium dioxide concentrations were irradiated under a high-pressure ultraviolet lamp (365nm, 300W) for 25min to prepare sunscreen and moisturizing nanocomposite hydrogels with different titanium dioxide concentrations.

[0043] Example 3: Optimization of the mass concentration of monomeric acrylamide

[0044] (1) Add flower-shaped titanium dioxide nanomaterials and vinyl-containing hydrophilic monomer acrylamide to 5 mL of water, sonicate for 5 min under nitrogen protection and dissolve. Keep the added mass of flower-shaped titanium dioxide nanomaterials at 0.4% of the total solution mass. Change the amount of monomer acrylamide so that the added mass of monomer acrylamide is 10%, 20% and 40% of the total solution mass, respectively, to obtain precursor solutions of hydrogels with different monomer concentrations.

[0045] (2) The precursor solutions of the hydrogels with different monomer concentrations were irradiated under a high-pressure ultraviolet lamp (365nm, 300W) for 25min to prepare sunscreen and moisturizing nanocomposite hydrogels with different monomer concentrations.

[0046] Example 4: Optimization of water content

[0047] (1) Flower-shaped titanium dioxide nanomaterials and vinyl-containing hydrophilic monomer acrylamide were added to a certain mass of water, keeping the added mass of flower-shaped titanium dioxide nanomaterials at 0.4% of the total solution mass and the added mass of monomer acrylamide at 20% of the total solution mass. The water content was adjusted to 50%, 67%, 75%, 80%, 85% and 87.5% of the total solution mass to obtain hydrogel precursor solutions with different water contents.

[0048] (2) The hydrogel precursor solutions with different water contents were irradiated under a high-pressure ultraviolet lamp (365nm, 300W) for 25min to prepare sunscreen and moisturizing nanocomposite hydrogels with different water contents.

[0049] Example 5:

[0050] The vinyl-containing hydrophilic monomer was replaced with N-isopropylacrylamide instead of acrylamide, and the rest was the same as in Example 1. The gel prepared in this example had a strain up to 53 times that of the original gel and a stress of 26 kPa, exhibiting good stretchability and mechanical strength.

[0051] Comparative Example 1:

[0052] The flower-shaped titanium dioxide nanomaterials were replaced with spherical titanium dioxide nanomaterials (purchased from Jiangsu Xianfeng Nanomaterials Technology Co., Ltd., China; model: 100359, size 200nm), and the rest was the same as in Example 1, to obtain a hydrogel (TA). The strain of the gel prepared in this comparative example was 70 times that of the original gel. Although it had good tensile properties, its stress was only 3kPa, and its mechanical strength was poor.

[0053] Comparative Example 2:

[0054] (1) Add spherical titanium dioxide nanomaterials, acrylamide and water-retaining agent LiCl to 5 mL of water, and dissolve by sonication for 5 min under nitrogen protection. Adjust the added mass of monomer acrylamide, spherical titanium dioxide nanomaterials and water-retaining agent LiCl to 20%, 0.4% and 20% of the total solution mass, respectively, to obtain the precursor solution of hydrogel.

[0055] (2) The precursor solution of the hydrogel was irradiated under a high-pressure ultraviolet lamp (365nm, 300W) for 25min to obtain hydrogel (TAL). The strain of the gel prepared in this comparative example is 70 times that of the original gel. Although it has good tensile properties, its stress is 9kPa and its mechanical strength is poor.

[0056] Experimental Example: Performance Testing

[0057] (1) Mechanical properties of hydrogels

[0058] The hydrogel prepared in the examples was cut into rectangular strips 15 mm long, 5 mm wide, and 3 mm thick. These strips were then placed in the tensile and compressive strength testing fixture of a 50 N force sensor for tensile property testing. The mechanical properties of the hydrogel were evaluated using a tensile testing machine at room temperature. The tensile stress of the hydrogel was calculated as follows: Stress = F × L / L0, where F, L, and L0 represent the force, the real-time length between the fixtures, and the initial length of the sample, respectively. Strain was defined as the deformation length divided by the initial length of the sample.

[0059] The results are as follows Figure 4 As shown, with the addition of flower-shaped titanium dioxide nanomaterials, the stress of the hydrogel gradually increases. However, if the amount of flower-shaped titanium dioxide nanomaterials is too large, it will affect the polymerization efficiency initiated by ultraviolet light, resulting in a reduction in its stress. Therefore, the preferred mass concentration of flower-shaped titanium dioxide nanomaterials is 0.2-0.4%.

[0060] As the content of acrylamide (AM) monomer increases, the strain properties of the hydrogel improve. However, excessive acrylamide content reduces free radical initiation efficiency, thereby decreasing the polymer chain length and affecting its stretchability. Therefore, an acrylamide mass concentration of 10-30% is preferred, within which the hydrogel exhibits good stretchability and mechanical strength.

[0061] Increasing the H2O content increases the tensile stress of the gel and decreases the tensile strain. However, too much H2O will prevent the formation of TFA gel. Therefore, the preferred water content in this invention is 60-85%.

[0062] (2) Study on the water retention of hydrogels

[0063] The hydrogel samples prepared in Example 1 and Comparative Examples 1-2 were weighed and recorded as m0. Then, the hydrogel samples were placed at room temperature and weighed at regular intervals and recorded as m. t Three replicates were prepared for each sample group. The water retention capacity (Q) of the hydrogel was calculated using the following formula:

[0064]

[0065] See results Figure 5Compared to the hydrogel (TA) prepared in Comparative Example 1, the TFA hydrogel prepared in Example 1 showed a water retention rate of only 20% after being placed at 60°C for 8 hours. After 24 hours, the TFA hydrogel still maintained a water retention rate of up to 60%, while the TA hydrogel lost 80%. The water retention of the hydrogel (TFA) of this invention is comparable to that of the hydrogel (TAL) in Comparative Example 2, which added the water-retaining agent LiCl. This indicates that the water retention performance of the TFA hydrogel prepared in this invention is significantly better than that of Comparative Example 1, and it does not require the addition of an additional water-retaining agent, thus demonstrating good economic efficiency.

[0066] (3) Study on the sun protection properties of hydrogels

[0067] Six-week-old female SD rats, weighing 18-22g, were randomly selected. All mice were housed for three days to acclimatize, then anesthetized and randomly divided into two groups (control group and gel group). Hair was removed from the backs of mice in each group using a hair removal cream, followed by washing with warm water. After the skin dried, it was disinfected with alcohol swabs. Before UV irradiation, the sunscreen and moisturizing nanocomposite hydrogel (TFA) prepared in Example 1 was applied to the backs of mice in the gel group, while the control group received no treatment. The backs of mice in each group were then exposed to 240mJ cm⁻² UV radiation (365nm, 8W) for 5 minutes daily for 7 days. Forty-eight hours after the experiment, all animals were sacrificed. The back skin of the mice was peeled off, fixed with 10% neutral buffered formalin, and stained with hematoxylin and eosin (H&E).

[0068] The results are as follows Figure 6 As shown, the control group exhibited relatively severe skin tissue damage, including severe acanthosis and epidermal hyperplasia; while the gel group, protected by the gel, did not show significant pathological skin damage or epidermal hyperplasia. This demonstrates that the hydrogel prepared in this invention has excellent UV shielding capabilities and provides good sun protection.

Claims

1. A method for preparing a sunscreen and moisturizing nanocomposite hydrogel, characterized in that, Includes the following steps: (1) Add flower-shaped titanium dioxide nanomaterials and a vinyl-containing hydrophilic monomer to water and dissolve them by ultrasonication under nitrogen protection to obtain a precursor solution of hydrogel; (2) The precursor solution of the hydrogel was irradiated under a high-pressure ultraviolet lamp to obtain a sunscreen and moisturizing nanocomposite hydrogel.

2. The preparation method of the sunscreen and moisturizing nanocomposite hydrogel according to claim 1, characterized in that: In step (1), the vinyl-containing hydrophilic monomer is selected from at least one of acrylamide, N-isopropylacrylamide, hydroxyethylacrylamide, acrylic acid, and polyethylene glycol (meth)acrylate.

3. The preparation method of the sunscreen and moisturizing nanocomposite hydrogel according to claim 1, characterized in that: In step (1), the flower-shaped titanium dioxide nanomaterial is obtained by hydrothermal reaction in a high-pressure reactor with potassium titanium oxalate as the titanium source and hydrogen peroxide added.

4. The preparation method of the sunscreen and moisturizing nanocomposite hydrogel according to claim 3, characterized in that: The molar ratio of potassium titanium oxalate to hydrogen peroxide is 1:100~250; the hydrothermal reaction temperature is 120~160℃, and the reaction time is 6~10h.

5. The preparation method of the sunscreen and moisturizing nanocomposite hydrogel according to claim 1, characterized in that: In step (1), the mass concentration of the flower-shaped titanium dioxide nanomaterial in the precursor solution is 0.2-0.4%, the mass concentration of the vinyl-containing hydrophilic monomer is 10-30%, and the water content is 60-85%.

6. The preparation method of the sunscreen and moisturizing nanocomposite hydrogel according to claim 1, characterized in that: In step (1), the temperature of the ultrasound is 30-40℃, the frequency of the ultrasound is 35-45kHz, and the duration of the ultrasound is 3-10min.

7. The preparation method of the sunscreen and moisturizing nanocomposite hydrogel according to claim 1, characterized in that: In step (2), the irradiation conditions are irradiation under a 365nm, 300W high-pressure ultraviolet lamp for 20-30 minutes.

8. A sunscreen and moisturizing nanocomposite hydrogel, prepared by the preparation method according to any one of claims 1-7.

9. The sunscreen and moisturizing nanocomposite hydrogel according to claim 8, characterized in that, The sunscreen and moisturizing nanocomposite hydrogel is composed of core-shell polymer nanocomposite structural units with flower-like titanium dioxide nanostructures as the core and hydrophilic polymer chains as the shell. The polymer chains intertwine to form a three-dimensional gel network structure.

10. The application of the sunscreen and moisturizing nanocomposite hydrogel according to claim 8 or 9 in cosmetics.

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