Far infrared dressing with inhibiting skin itching and its preparation method

Abstract

The application discloses a far-infrared dressing with skin itching inhibition and a preparation method thereof, and belongs to the technical field of dressings. Functionalized tourmaline powder and modified luteolin are mixed and stirred to obtain composite functional particles; sodium alginate and deionized water are mixed, swelled and stirred and dispersed to obtain a hydrogel base solution; glycerol and the composite functional particles are added into the hydrogel base solution and stirred and dispersed to obtain a composite system; the composite system is vacuum-deaerated to obtain a gel matrix; and the gel matrix is subjected to coating treatment and sterilization in sequence to obtain the far-infrared dressing. The composite functional particles are constructed through step-by-step modification, and the far-infrared dressing has the effects of far-infrared physiotherapy, itching relief and antibiosis, the active ingredients have good skin retention and are not prone to irritation, and the far-infrared dressing can cooperatively improve local circulation and repair the skin barrier.

Description

Technical Field

[0001] This invention relates to the field of dressing technology, specifically to a far-infrared dressing that inhibits skin itching and its preparation method. Background Technology

[0002] Skin itching accompanied by localized pain is common in eczema, dry and sensitive skin, and postoperative wounds. Far-infrared dressings are a mainstream care product, but existing products have significant shortcomings. Far-infrared powders have few active sites on their surface, relying solely on physical adsorption to carry active ingredients, making them prone to detachment and ineffectiveness; the sharp edges of the powder can easily scratch damaged skin, and they only provide basic heat therapy effects without antipruritic or antibacterial capabilities. Natural antipruritic ingredients have poor water solubility, easily agglomerate and deteriorate in hydrogels, have weak adhesion and penetration abilities, and cannot prevent secondary infections of wounds.

[0003] Invention patent CN104147632A discloses a chitosan wound dressing with specific cell adhesion, which has several limitations. Pain relief relies solely on the action of chitosan itself, lacks far-infrared physiotherapy pathways, and has limited ability to improve local circulation. Itching relief depends on film-forming physical isolation, lacks anti-inflammatory and antipruritic components, and has a short duration of action. The film-forming protective strength is limited, and it is not well adapted to skin with damaged barriers, resulting in a relatively single functional dimension.

[0004] Most commercially available dressings simply mix powders and active ingredients, resulting in poor compatibility between the two phases. They are prone to separation and precipitation during storage, and their effects are merely additive without synergy. The release of active ingredients is uncontrollable, easily irritating the skin in the early stages and quickly losing effectiveness in the later stages. Furthermore, they lack an integrated antibacterial and repair design, making it difficult to break the cycle of itching, scratching, and infection. They also have separate effects for pain relief and itch relief, resulting in short duration of action.

[0005] Therefore, providing a far-infrared dressing that provides long-lasting relief from pain and inhibits skin itching is an important problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a far-infrared dressing that inhibits skin itching and a method for preparing the same.

[0007] Specifically, the technical solution of the present invention includes the following:

[0008] A method for preparing a far-infrared dressing that inhibits skin itching, the method comprising the following steps:

[0009] Functionalized tourmaline powder and modified luteolin were mixed and stirred to obtain composite functional particles;

[0010] Sodium alginate and deionized water were mixed and swollen, and then stirred and dispersed to obtain a hydrogel-based solution.

[0011] Glycerol and composite functional particles were added to the hydrogel base liquid and stirred to disperse to obtain a composite system;

[0012] The composite system was degassed under vacuum to obtain a gel matrix;

[0013] The far-infrared dressing is prepared by sequentially coating and sterilizing the gel matrix.

[0014] Furthermore, the preparation method of the functionalized tourmaline powder includes the following steps:

[0015] Hydroxylated tourmaline was obtained by mixing tourmaline powder and hydrogen peroxide solution and reacting them.

[0016] Thiolized tourmaline was obtained by mixing and stirring hydroxylated tourmaline with 3-mercaptopropyltriethoxysilane.

[0017] Functionalized tourmaline powder was obtained by mixing and stirring mercapto-modified tourmaline, citronellal, and azobisisobutyronitrile.

[0018] Furthermore, the concentration of the hydrogen peroxide solution is 30 wt%.

[0019] Furthermore, the weight ratio of the tourmaline micro powder to the hydrogen peroxide solution is 10:50~70.

[0020] Furthermore, the conditions for the mixed reaction of the tourmaline micro powder and hydrogen peroxide solution include a reaction temperature of 110~130℃ and a reaction time of 6~8h.

[0021] Furthermore, the weight ratio of the hydroxylated tourmaline to 3-mercaptopropyltriethoxysilane is 10:0.13~0.16.

[0022] Furthermore, the conditions for the mixed and stirred reaction of the hydroxylated tourmaline and 3-mercaptopropyltriethoxysilane include a reaction temperature of 100-110°C and a reaction time of 22-24 h.

[0023] Furthermore, the weight ratio of the mercapto-modified tourmaline, citronellal, and azobisisobutyronitrile is 10:1.2~2.0:0.05~0.07.

[0024] Furthermore, the conditions for the mixed and stirred reaction of the mercapto-modified tourmaline, citronellal, and azobisisobutyronitrile include a reaction temperature of 65-75°C and a reaction time of 5-7 hours.

[0025] Furthermore, the preparation method of the modified luteolin includes the following steps:

[0026] Luteolin and sodium chloroacetate were mixed and stirred to produce carboxymethyl luteolin;

[0027] The amino-containing luteolin was obtained by mixing and stirring carboxymethyl luteolin, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide and ethylenediamine.

[0028] Modified luteolin was obtained by mixing and stirring amino-containing luteolin and cyanamide.

[0029] Furthermore, the weight ratio of luteolin to sodium chloroacetate is 10:0.5~0.7.

[0030] Furthermore, the conditions for the mixed stirring reaction of luteolin and sodium chloroacetate include a reaction temperature of 55-65°C and a reaction time of 4-6 hours.

[0031] Further, the weight ratio of carboxymethyl luteolin, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide and ethylenediamine is 10:1.2~2.0:0.7~1.3:1.5~2.5.

[0032] Furthermore, the conditions for the mixed stirring reaction of carboxymethyl luteolin, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide, and ethylenediamine include a reaction temperature of 24-26°C and a reaction time of 12-16 h.

[0033] Furthermore, the weight ratio of aminoluteolin and cyanamide is 10:0.8~1.2.

[0034] Furthermore, the reaction conditions for the mixed stirring reaction containing aminoluteolin and cyanamide include a reaction temperature of 90-100°C and a reaction time of 7-8 hours.

[0035] Furthermore, the weight ratio of the functionalized tourmaline powder to the modified luteolin is 10:1.0~1.5.

[0036] Furthermore, the reaction conditions for the mixed stirring reaction of the functionalized tourmaline powder and modified luteolin include a reaction temperature of 24~26℃ and a reaction time of 10~14h.

[0037] Furthermore, the conditions for the swelling of the sodium alginate and deionized water include a swelling temperature of 24-26°C and a swelling time of 22-24 hours.

[0038] Furthermore, the conditions for mixing and dispersing the sodium alginate and deionized water after swelling include a stirring temperature of 50-60°C and a stirring time of 30-50 min.

[0039] Furthermore, the weight ratio of sodium alginate, deionized water, glycerin and composite functional particles is 2.0~2.5:83~86:4~6:7~9.

[0040] Furthermore, the conditions for adding glycerol and dispersing the composite functional particles include a stirring speed of 800~120 r / min and a stirring time of 20~30 min.

[0041] Furthermore, the vacuum degassing conditions include a vacuum degree of 0.06~0.08MPa and a degassing time of 15~30min.

[0042] Furthermore, the conditions for the coating process include a coating thickness of 0.4 to 0.6 mm.

[0043] Furthermore, the sterilization is performed using cobalt-60 gamma ray irradiation, with the sterilization dose controlled at 25~30 kGy.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0045] (1) In this invention, tourmaline powder is sequentially activated by hydroxylation, grafted with mercaptosilane, and click-grafted with citronellol: hydroxylation improves the inertness of the powder surface and increases the density of reaction sites; mercaptosilane forms a flexible coating layer to passivate the sharp edges of the particles and reduce the risk of itching caused by physical friction; the mercapto-ene click reaction covalently anchors citronellol, which can alleviate the problem of easy volatilization and loss of citronellol, and exert an immediate cooling and antipruritic effect, while reserving aldehyde reaction sites. Moreover, the surface modification does not destroy the crystal structure of tourmaline, and can retain its core effects of far-infrared circulation promotion and pain relief. Luteolin is sequentially modified by carboxymethylation, amination, and partial guanidinolation: carboxymethylation improves water solubility and improves its dispersion uniformity in the hydrogel matrix; amination introduces primary amino reaction sites, providing a structural basis for covalent bonding; partial guanidinolation can enhance skin adhesion, promote transdermal absorption, and endow it with certain broad-spectrum antibacterial properties, improving the related shortcomings of natural luteolin for external use.

[0046] (2) In this invention, functionalized tourmaline powder and modified luteolin form composite functional particles through Schiff base reaction. The organic outer layer can improve the compatibility between inorganic powder and hydrogel matrix, reduce stratification and sedimentation and the phenomenon of sudden release of active ingredients, and improve storage stability. Citronellol can provide immediate relief, luteolin exerts a long-lasting anti-inflammatory and antipruritic effect, and far-infrared rays accelerate the metabolism of pruritus and pain-causing substances. The three complement each other in terms of duration of action and target. The anti-inflammatory effect and the far-infrared circulation-promoting effect promote each other and jointly help repair the skin barrier. The antibacterial effect of guanidine can reduce the risk of pruritus-infection cycle. Particle passivation and covalent grafting reduce the risk of skin irritation and are suitable for sensitive and barrier-damaged skin. The final dressing has the effects of far-infrared analgesia, multiple antipruritic effects, anti-inflammatory and antibacterial effects, and barrier repair. It has a fast onset and long duration of action and is suitable for various scenarios of skin itching accompanied by pain. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below through embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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.

[0048] Unless otherwise stated, all raw materials and reagents used in this invention are commercially available or can be prepared by known methods.

[0049] Preparation Example 1

[0050] The preparation method of functionalized tourmaline powder includes the following steps:

[0051] Ten parts by weight of tourmaline micro powder were sieved through a 300-mesh standard sieve and dispersed in 50 parts by weight of a 30 wt% hydrogen peroxide solution. The mixture was stirred at 200 r / min for 15 min and then ultrasonically treated at 200 W for 20 min to obtain a dispersion. The dispersion was transferred to a hydrothermal reactor lined with polytetrafluoroethylene, sealed, and placed in a forced-air drying oven at 110 °C for 6 h. After the reaction was completed, the mixture was cooled to 26 °C and centrifuged at 6000 r / min for 15 min to collect the precipitate. The precipitate was washed four times with deionized water, dried under vacuum at 60 °C for 12 h, ground, and passed through a 100-mesh sieve to obtain hydroxylated tourmaline.

[0052] Ten parts by weight of hydroxylated tourmaline were dispersed in 80 parts by weight of mixed solvent (V anhydrous ethanol:V deionized water = 9:1). The pH was adjusted to 4.0, and the mixture was stirred at 200 r / min for 10 min. Then, 0.13 parts by weight of 3-mercaptopropyltriethoxysilane were added under a nitrogen atmosphere. The mixture was heated to 100 °C and stirred for 22 h. After the reaction was completed, the mixture was cooled to 26 °C, and the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with anhydrous ethanol, dried under vacuum at 60 °C for 12 h, ground, and passed through a 100-mesh sieve to obtain mercaptolated tourmaline.

[0053] Ten parts by weight of mercapto-modified tourmaline were dispersed in 80 parts by weight of anhydrous ethanol. After stirring at 300 r / min for 15 min, 1.2 parts by weight of citronellal and 0.05 parts by weight of azobisisobutyronitrile were added under a nitrogen atmosphere. The mixture was heated to 65 °C and stirred at 200 r / min for 5 h. After the reaction was completed, the mixture was cooled to 26 °C and centrifuged at 6000 r / min for 15 min to collect the precipitate. The precipitate was washed three times with anhydrous ethanol and then centrifuged at 6000 r / min for 15 min to collect the precipitate. After washing the precipitate three times with anhydrous ethanol, the mixture was vacuum dried at 60 °C for 12 h and then ground and passed through a 100-mesh sieve to obtain functionalized tourmaline powder.

[0054] Preparation Example 2

[0055] The preparation method of functionalized tourmaline powder includes the following steps:

[0056] Ten parts by weight of tourmaline micro powder were sieved through a 300-mesh standard sieve and dispersed in 60 parts by weight of a 30 wt% hydrogen peroxide solution. The mixture was stirred at 250 r / min for 17 min and then ultrasonically treated at 250 W for 25 min to obtain a dispersion. The dispersion was transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and placed in a forced-air drying oven at 120 °C for 7 h. After the reaction was completed, the mixture was cooled to 26 °C and centrifuged at 6000 r / min for 15 min to collect the precipitate. The precipitate was washed four times with deionized water, vacuum dried at 60 °C for 12 h, ground, and sieved through a 100-mesh sieve to obtain hydroxylated tourmaline.

[0057] Ten parts by weight of hydroxylated tourmaline were dispersed in 100 parts by weight of mixed solvent (V anhydrous ethanol:V deionized water = 9:1). The pH was adjusted to 4.5, and the mixture was stirred at 300 r / min for 10 min. Then, 0.145 parts by weight of 3-mercaptopropyltriethoxysilane were added under a nitrogen atmosphere. The mixture was heated to 105 °C and stirred for 23 h. After the reaction was completed, the mixture was cooled to 26 °C, and the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with anhydrous ethanol, dried under vacuum at 60 °C for 12 h, ground, and passed through a 100-mesh sieve to obtain mercaptolated tourmaline.

[0058] Ten parts by weight of mercapto-modified tourmaline were dispersed in 90 parts by weight of anhydrous ethanol. After stirring at 400 r / min for 17 min, 1.6 parts by weight of citronellal and 0.06 parts by weight of azobisisobutyronitrile were added under a nitrogen atmosphere. The mixture was heated to 70 °C and stirred at 300 r / min for 6 h. After the reaction was completed, the mixture was cooled to 26 °C and centrifuged at 6000 r / min for 15 min to collect the precipitate. The precipitate was washed three times with anhydrous ethanol and then centrifuged at 6000 r / min for 15 min to collect the precipitate. After washing the precipitate three times with anhydrous ethanol, the mixture was vacuum dried at 60 °C for 12 h and then ground and passed through a 100-mesh sieve to obtain functionalized tourmaline powder.

[0059] Preparation Example 3

[0060] The preparation method of functionalized tourmaline powder includes the following steps:

[0061] Ten parts by weight of tourmaline micro powder were sieved through a 300-mesh standard sieve and dispersed in 70 parts by weight of a 30 wt% hydrogen peroxide solution. The mixture was stirred at 300 r / min for 20 min and then ultrasonically treated at 300 W for 30 min to obtain a dispersion. The dispersion was transferred to a polytetrafluoroethylene-lined hydrothermal reactor, sealed, and placed in a forced-air drying oven at 130℃ for 8 h. After the reaction was completed, the mixture was cooled to 26℃ and centrifuged at 6000 r / min for 15 min to collect the precipitate. The precipitate was washed four times with deionized water, dried under vacuum at 60℃ for 12 h, ground, and passed through a 100-mesh sieve to obtain hydroxylated tourmaline.

[0062] Ten parts by weight of hydroxylated tourmaline were dispersed in 120 parts by weight of mixed solvent (V anhydrous ethanol:V deionized water = 9:1). The pH was adjusted to 5.0, and the mixture was stirred at 400 r / min for 10 min. Then, 0.16 parts by weight of 3-mercaptopropyltriethoxysilane were added under a nitrogen atmosphere. The mixture was heated to 110 °C and stirred for 24 h. After the reaction was completed, the mixture was cooled to 26 °C, and the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with anhydrous ethanol, dried under vacuum at 60 °C for 12 h, ground, and passed through a 100-mesh sieve to obtain mercaptolated tourmaline.

[0063] Ten parts by weight of mercapto-modified tourmaline were dispersed in 100 parts by weight of anhydrous ethanol. After stirring at 500 r / min for 20 min, 2.0 parts by weight of citronellal and 0.07 parts by weight of azobisisobutyronitrile were added under a nitrogen atmosphere. The mixture was heated to 75 °C and stirred at 400 r / min for 7 h. After the reaction was completed, the mixture was cooled to 26 °C and centrifuged at 6000 r / min for 15 min to collect the precipitate. The precipitate was washed three times with anhydrous ethanol and then centrifuged at 6000 r / min for 15 min to collect the precipitate. After washing the precipitate three times with anhydrous ethanol, it was vacuum dried at 60 °C for 12 h and then ground and passed through a 100-mesh sieve to obtain functionalized tourmaline powder.

[0064] Preparation Example 4

[0065] The preparation method of modified luteolin includes the following steps:

[0066] 10 parts by weight of luteolin were dispersed in 90 parts by weight of a mixed solvent (V anhydrous ethanol:V deionized water = 3:2), stirred at 200 r / min for 10 min, and the pH was adjusted to 8.8 with 1 mol / L sodium hydroxide solution. 0.5 parts by weight of sodium chloroacetate were added under a nitrogen atmosphere, the temperature was raised to 55 °C and the reaction was stirred for 4 h. After the reaction was completed, the temperature was cooled to 26 °C, the pH was adjusted to 6.5, 300 parts by weight of anhydrous ethanol were added and allowed to stand for 4 h. The precipitate was collected by filtration, washed 3 times with anhydrous ethanol, and dried under vacuum at 60 °C for 16 h to obtain carboxymethyl luteolin.

[0067] Ten parts by weight of carboxymethyl luteolin were dispersed in 200 parts by weight of 2-morpholine ethanesulfonic acid buffer at pH 5.5. After dispersion at 150 r / min for 15 min under nitrogen protection, 1.2 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 0.7 parts by weight of N-hydroxysuccinimide were added. After activation by stirring at 24 °C for 20 min, 1.5 parts by weight of ethylenediamine were added dropwise over 30 min. After the addition was completed, the reaction was stirred for 12 h. After the reaction was completed, the reaction solution was placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 72 h. Then, it was freeze-dried at -50 °C for 24 h to obtain amino-containing luteolin.

[0068] Ten parts by weight of amino-containing luteolin and 0.8 parts by weight of cyanamide were dispersed in 150 parts by weight of deionized water. The pH was adjusted to 3.4 with 6 mol / L hydrochloric acid solution. The mixture was heated to 90 °C and stirred at 200 r / min for 7 h. After the reaction was completed, 90 wt% of water was removed by vacuum distillation at 60 °C. The mixture was then placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 72 h. Finally, it was freeze-dried at -50 °C for 24 h to obtain modified luteolin.

[0069] Preparation Example 5

[0070] The preparation method of modified luteolin includes the following steps:

[0071] Ten parts by weight of luteolin were dispersed in 90 parts by weight of a mixed solvent (V anhydrous ethanol:V deionized water = 3:2), stirred at 250 r / min for 12 min, and the pH was adjusted to 9.2 with 1 mol / L sodium hydroxide solution. 0.6 parts by weight of sodium chloroacetate were added under a nitrogen atmosphere, the temperature was raised to 60 °C and the reaction was stirred for 5 h. After the reaction was completed, the temperature was cooled to 26 °C, the pH was adjusted to 7.0, 300 parts by weight of anhydrous ethanol were added and allowed to stand for 4 h. The precipitate was collected by filtration, washed three times with anhydrous ethanol, and dried under vacuum at 60 °C for 16 h to obtain carboxymethyl luteolin.

[0072] Ten parts by weight of carboxymethyl luteolin were dispersed in 250 parts by weight of 2-morpholine ethanesulfonic acid buffer at pH 5.7. After dispersion by stirring at 200 r / min for 17 min under a nitrogen atmosphere, 1.6 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1.0 parts by weight of N-hydroxysuccinimide were added. After activation by stirring at 25 °C for 25 min, 2.0 parts by weight of ethylenediamine were added dropwise over 35 min. After the addition was completed, the reaction was stirred for 14 h. After the reaction was completed, the reaction solution was placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 72 h. Finally, it was freeze-dried at -50 °C for 24 h to obtain amino-containing luteolin.

[0073] Ten parts by weight of amino-containing luteolin and 1.0 part by weight of cyanamide were dispersed in 175 parts by weight of deionized water. The pH was adjusted to 3.5 with 6 mol / L hydrochloric acid solution. The mixture was heated to 95℃ and stirred at 250 r / min for 7.5 h. After the reaction was completed, 90 wt% of water was removed by vacuum distillation at 60℃. The mixture was then placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 72 h. Finally, it was freeze-dried at -50℃ for 24 h to obtain modified luteolin.

[0074] Preparation Example 6

[0075] The preparation method of modified luteolin includes the following steps:

[0076] Ten parts by weight of luteolin were dispersed in 90 parts by weight of a mixed solvent (V anhydrous ethanol:V deionized water = 3:2), stirred at 300 r / min for 15 min, and the pH was adjusted to 9.5 with 1 mol / L sodium hydroxide solution. 0.7 parts by weight of sodium chloroacetate were added under a nitrogen atmosphere, the temperature was raised to 65 °C and the reaction was stirred for 6 h. After the reaction was completed, the temperature was cooled to 26 °C, the pH was adjusted to 7.5, 300 parts by weight of anhydrous ethanol were added and allowed to stand for 4 h. The precipitate was collected by filtration, washed three times with anhydrous ethanol, and dried under vacuum at 60 °C for 16 h to obtain carboxymethyl luteolin.

[0077] Ten parts by weight of carboxymethyl luteolin were dispersed in 300 parts by weight of 2-morpholine ethanesulfonic acid buffer at pH 6.0. After dispersion at 250 r / min for 20 min under nitrogen protection, 2.0 parts by weight of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and 1.3 parts by weight of N-hydroxysuccinimide were added. After activation by stirring at 26 °C for 30 min, 2.5 parts by weight of ethylenediamine were added dropwise over 40 min. After the addition was completed, the reaction was stirred for 16 h. After the reaction was completed, the reaction solution was placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 72 h. Then, it was freeze-dried at -50 °C for 24 h to obtain amino-containing luteolin.

[0078] Ten parts by weight of amino-containing luteolin and 1.2 parts by weight of cyanamide were dispersed in 200 parts by weight of deionized water. The pH was adjusted to 3.6 with 6 mol / L hydrochloric acid solution. The mixture was heated to 100℃ and stirred at 300 r / min for 8 h. After the reaction was completed, 90 wt% of water was removed by vacuum distillation at 60℃. The mixture was then placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed in deionized water for 72 h. Finally, it was freeze-dried at -50℃ for 24 h to obtain modified luteolin.

[0079] Preparation Example 7

[0080] The preparation method of functionalized tourmaline powder includes the following steps:

[0081] In Preparation Example 3, 3-mercaptopropyltriethoxysilane was replaced with an equal weight of 3-aminopropyltriethoxysilane, while other operations remained the same as in Preparation Example 3.

[0082] Preparation Example 8

[0083] The preparation method of functionalized tourmaline powder includes the following steps:

[0084] In Preparation Example 3, citronellal was replaced with an equal mass of menthol, and all other operations were the same as in Preparation Example 3.

[0085] Preparation Example 9

[0086] The preparation method of functionalized tourmaline powder includes the following steps:

[0087] The hydroxyl activation step in Preparation Example 3 was removed, and mercaptosilane grafting was performed directly. Other operations were the same as in Preparation Example 3.

[0088] Preparation Example 10

[0089] The preparation method of modified luteolin includes the following steps:

[0090] The guanidinolation step of luteolin in Preparation Example 6 was removed, and aminoated luteolin was directly grafted. Other operations were the same as in Preparation Example 6.

[0091] Preparation Example 11

[0092] The preparation method of functionalized tourmaline powder includes the following steps:

[0093] Remove citronellal from Preparation Example 3, and keep the other operations the same as in Preparation Example 3.

[0094] Example 1

[0095] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0096] Ten parts by weight of the functionalized tourmaline powder prepared in Preparation Example 1 were dispersed in 90 parts by weight of phosphate buffer solution at pH 5.4. The mixture was stirred at 300 r / min for 15 min to obtain a suspension. The suspension was stirred at 150 r / min at 24 °C under a nitrogen atmosphere. One part by weight of the modified luteolin prepared in Preparation Example 4 was added, and the mixture was stirred for another 10 h. After the reaction was completed, the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with deionized water and then freeze-dried at -50 °C for 24 h to obtain composite functional particles.

[0097] 2.0 parts by weight of sodium alginate were dispersed in 83 parts by weight of deionized water. After standing at 24°C for 22 hours to swell, the temperature was raised to 50°C and stirred at 300 r / min for 30 min to obtain a hydrogel base solution. 4 parts by weight of glycerol were added to the hydrogel base solution and stirred for 15 min to obtain a moisturizing gel. Then, 7 parts by weight of composite functional particles were added and stirred at 800 r / min for 20 min to obtain a composite system. The composite system was placed in a vacuum degassing machine and degassed at a vacuum of 0.06 MPa for 15 min to obtain a gel matrix.

[0098] The gel matrix was transferred to the coating machine's feed trough and evenly coated onto a substrate with a basis weight of 50 g / m². 2 The medical nonwoven fabric backing layer has a coating thickness controlled at 0.4mm, and after coating, it is covered with a layer with a basis weight of 70g / m². 2 The polyethylene release film is rolled flat and then fed into a slitting device to be cut into finished dressings according to commonly used clinical specifications. After being cut, the dressings are sealed in aluminum-plastic composite bags and then sterilized by cobalt-60 gamma irradiation with a sterilization dose controlled at 25 kGy to obtain far-infrared dressings that can inhibit skin itching.

[0099] Example 2

[0100] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0101] Ten parts by weight of the functionalized tourmaline powder prepared in Preparation Example 1 were dispersed in 90 parts by weight of phosphate buffer solution at pH 5.4. The mixture was stirred at 320 r / min for 16 min to obtain a suspension. The suspension was stirred at 180 r / min at 24 °C under a nitrogen atmosphere. 1.2 parts by weight of the modified luteolin prepared in Preparation Example 5 were added. The mixture was stirred and reacted for 11 h. After the reaction was completed, the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with deionized water and then freeze-dried at -50 °C for 24 h to obtain composite functional particles.

[0102] 2.1 parts by weight of sodium alginate were dispersed in 83.9 parts by weight of deionized water. After standing at 24°C for 22.5 h to swell, the temperature was raised to 52°C and stirred at 350 r / min for 35 min to obtain a hydrogel base solution. 4.5 parts by weight of glycerol were added to the hydrogel base solution and stirred for 16 min to obtain a moisturizing gel. Then, 7.5 parts by weight of composite functional particles were added and stirred at 900 r / min for 22 min to obtain a composite system. The composite system was placed in a vacuum degassing machine and degassed at a vacuum of 0.065 MPa for 18 min to obtain a gel matrix.

[0103] The gel matrix is ​​transferred to the coating machine trough and evenly coated onto a 50 g / m² medical nonwoven fabric backing layer with a coating thickness controlled at 0.45 mm. After coating, a 70 g / m² polyethylene release film is applied. After being rolled flat, the film is sent to a slitting device and cut into finished dressing pieces according to commonly used clinical specifications. The slit dressings are then sealed in aluminum-plastic composite bags and sterilized by cobalt-60 gamma irradiation at a dose controlled at 26 kGy to obtain far-infrared dressings that inhibit skin itching.

[0104] Example 3

[0105] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0106] Ten parts by weight of the functionalized tourmaline powder prepared in Preparation Example 2 were dispersed in 90 parts by weight of phosphate buffer solution with pH 5.5. The mixture was stirred at 350 r / min for 17 min to obtain a suspension. The suspension was stirred at 200 r / min at 25 °C under a nitrogen atmosphere. 1.25 parts by weight of the modified luteolin prepared in Preparation Example 5 were added. The mixture was stirred and reacted for 12 h. After the reaction was completed, the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with deionized water and then freeze-dried at -50 °C for 24 h to obtain composite functional particles.

[0107] 2.25 parts by weight of sodium alginate were dispersed in 84.75 parts by weight of deionized water. After standing at 25°C for 23 hours to swell, the temperature was raised to 55°C and stirred at 400 r / min for 40 minutes to obtain a hydrogel base solution. 5 parts by weight of glycerol were added to the hydrogel base solution and stirred for 17 minutes to obtain a moisturizing gel. Then, 8 parts by weight of composite functional particles were added and stirred at 1000 r / min for 25 minutes to obtain a composite system. The composite system was placed in a vacuum degassing machine and degassed at a vacuum of 0.07 MPa for 22 minutes to obtain a gel matrix.

[0108] The gel matrix is ​​transferred to the coating machine trough and evenly coated onto a 50 g / m² medical nonwoven fabric backing layer with a coating thickness controlled at 0.5 mm. After coating, a 70 g / m² polyethylene release film is applied. After being rolled flat, the film is sent to a slitting device and cut into finished dressing pieces according to commonly used clinical specifications. The slit dressings are then sealed in aluminum-plastic composite bags and sterilized by cobalt-60 gamma irradiation with a sterilization dose controlled at 27.5 kGy to obtain a far-infrared dressing that inhibits skin itching.

[0109] Example 4

[0110] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0111] Ten parts by weight of the functionalized tourmaline powder prepared in Preparation Example 2 were dispersed in 90 parts by weight of phosphate buffer solution at pH 5.5. The suspension was stirred at 370 r / min for 18 min and stirred at 220 r / min at 25 °C under a nitrogen atmosphere. 1.4 parts by weight of the modified luteolin prepared in Preparation Example 6 were added and the reaction was continued to be stirred for 13 h. After the reaction was completed, the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with deionized water and then freeze-dried at -50 °C for 24 h to obtain composite functional particles.

[0112] 2.4 parts by weight of sodium alginate were dispersed in 85.1 parts by weight of deionized water. After standing and swelling at 25°C for 23.5 h, the temperature was raised to 57°C and stirred at 450 r / min for 45 min to obtain a hydrogel base solution. 5.5 parts by weight of glycerol were added to the hydrogel base solution and stirred for 18 min to obtain a moisturizing gel. Then, 8.5 parts by weight of composite functional particles were added and stirred at 1100 r / min for 27 min to obtain a composite system. The composite system was placed in a vacuum degassing machine and degassed at a vacuum of 0.075 MPa for 26 min to obtain a gel matrix.

[0113] The gel matrix is ​​transferred to the coating machine trough and evenly coated onto a 50 g / m² medical nonwoven fabric backing layer with a coating thickness controlled at 0.55 mm. After coating, a 70 g / m² polyethylene release film is applied. After being rolled flat, the film is sent to a slitting device and cut into finished dressing pieces according to commonly used clinical specifications. The slitting dressings are then sealed in aluminum-plastic composite bags and sterilized by cobalt-60 gamma irradiation with a sterilization dose controlled at 28.5 kGy to obtain a far-infrared dressing that inhibits skin itching.

[0114] Example 5

[0115] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0116] Ten parts by weight of the functionalized tourmaline powder prepared in Preparation Example 3 were dispersed in 90 parts by weight of phosphate buffer solution at pH 5.6. The mixture was stirred at 400 r / min for 20 min to obtain a suspension. The suspension was stirred at 250 r / min at 26 °C under a nitrogen atmosphere. 1.5 parts by weight of the modified luteolin prepared in Preparation Example 6 were added. The mixture was stirred and reacted for 14 h. After the reaction was completed, the precipitate was collected by centrifugation at 6000 r / min for 15 min. The precipitate was washed three times with deionized water and then freeze-dried at -50 °C for 24 h to obtain composite functional particles.

[0117] 2.5 parts by weight of sodium alginate were dispersed in 86 parts by weight of deionized water. After standing at 26°C for 24 hours to swell, the temperature was raised to 60°C and stirred at 500 r / min for 50 min to obtain a hydrogel base solution. 6 parts by weight of glycerol were added to the hydrogel base solution and stirred for 20 min to obtain a moisturizing gel. Then, 9 parts by weight of composite functional particles were added and stirred at 1200 r / min for 30 min to obtain a composite system. The composite system was placed in a vacuum degassing machine and degassed at a vacuum of 0.08 MPa for 30 min to obtain a gel matrix.

[0118] The gel matrix is ​​transferred to the coating machine trough and evenly coated onto a 50 g / m² medical nonwoven fabric backing layer with a coating thickness controlled at 0.6 mm. After coating, a 70 g / m² polyethylene release film is applied. After being rolled flat, the film is sent to a slitting device and cut into finished dressing pieces according to commonly used clinical specifications. The slit dressings are then sealed in aluminum-plastic composite bags and sterilized by cobalt-60 gamma irradiation with a sterilization dose controlled at 30 kGy to obtain a far-infrared dressing that inhibits skin itching.

[0119] Comparative Example 1

[0120] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0121] The functionalized tourmaline powder prepared in Example 3 of Example 5 was replaced with the functionalized tourmaline powder prepared in Example 7, and other operations were kept the same as in Example 5.

[0122] Comparative Example 2

[0123] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0124] The functionalized tourmaline powder prepared in Example 3 of Example 5 was replaced with the functionalized tourmaline powder prepared in Example 8, and other operations were kept the same as in Example 5.

[0125] Comparative Example 3

[0126] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0127] The modified luteolin obtained in Preparation Example 6 of Example 5 was replaced with an equal mass of unmodified luteolin, and all other operations were the same as in Example 5.

[0128] Comparative Example 4

[0129] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0130] The functionalized tourmaline powder prepared in Example 3 of Example 5 was replaced with an equal mass of tourmaline micro powder, and other operations were kept the same as in Example 5.

[0131] Comparative Example 5

[0132] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0133] The functionalized tourmaline powder prepared in Example 3 of Example 5 was replaced with the functionalized tourmaline powder prepared in Example 9, and other operations were kept the same as in Example 5.

[0134] Comparative Example 6

[0135] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0136] The modified luteolin obtained in Preparation Example 6 of Example 5 was replaced with the modified luteolin obtained in Preparation Example 10, and all other operations were the same as in Example 5.

[0137] Comparative Example 7

[0138] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0139] The step of covalently grafting functionalized tourmaline powder and modified luteolin with Schiff base in Example 5 was omitted, and the mixture was directly physically mixed. Other operations were the same as in Example 5.

[0140] Comparative Example 8

[0141] A method for preparing a far-infrared dressing that can suppress skin itching includes the following steps:

[0142] The functionalized tourmaline powder prepared in Example 3 of Example 5 was replaced with the functionalized tourmaline powder prepared in Example 11, and other operations were kept the same as in Example 5.

[0143] Performance testing

[0144] The far-infrared dressings prepared in Examples 1-5 and Comparative Examples 1-8 were subjected to various performance tests, and the test methods are as follows:

[0145] Far-infrared normal emissivity: Refer to the test method in GB / T30127-2013, and use a far-infrared emissivity tester to test the normal emissivity in the 8~14μm band;

[0146] 8-hour skin retention rate of active ingredients: Using a Franz vertical diffusion cell, with isolated porcine abdominal skin as a barrier, luteolin was extracted from the skin after being kept at 32℃ for 8 hours and quantitatively determined. The proportion of the retained amount to the total load was then calculated.

[0147] Staphylococcus aureus inhibition rate: The inhibition rate against Staphylococcus aureus ATCC6538 was tested using the shaking method in GB / T20944.3-2008.

[0148] Skin irritation score: Referring to the test method in GB / T16886.10-2017, a rabbit skin irritation test was used. Skin reactions were recorded at 24h, 48h, and 72h, and the average irritation score was calculated. The lower the score, the less irritating the skin.

[0149] Itching inhibition rate: Using a guinea pig histamine-induced itching model, the number of scratches and latency within 30 minutes were recorded, and the itching inhibition rate was calculated with the blank group as the control.

[0150] Pain threshold elevation rate: The analgesic effect was evaluated using the mouse hot plate test. The temperature of the intelligent hot plate instrument was set to 55±0.5℃. The pain response endpoint was defined as the appearance of the mouse licking its hind paw. The baseline pain threshold (time of onset of pain response) was measured before drug administration in each group of mice. The test dressing was applied to the skin of the plantar hind paw of the mice. The pain threshold was measured again 30 minutes after drug administration. The pain threshold elevation rate was calculated using the formula: Pain threshold elevation rate = (Pain threshold after drug administration - Baseline pain threshold before drug administration) / Baseline pain threshold before drug administration × 100%. Ten parallel mice were set up in each group.

[0151] The test results are shown in Table 1.

[0152] Table 1. Performance Test Results

[0153] Far-infrared normal emissivity 8h skin retention rate Staphylococcus aureus inhibition rate Skin irritation score Itching suppression rate Pain threshold elevation rate Example 1 0.88 72.30% 85.20% 0.21 64.70% 32.50% Example 2 0.89 73.80% 87.10% 0.18 67.20% 35.10% Example 3 0.9 75.40% 88.90% 0.15 69.80% 37.80% Example 4 0.905 76.90% 90.30% 0.13 72.10% 40.20% Example 5 0.91 78.20% 91.80% 0.11 74.50% 42.60% Comparison 1 0.89 62.10% 86.30% 0.32 55.30% 33.60% Comparative Example 2 0.9 74.80% 88.50% 0.17 58.60% 36.20% Comparative Example 3 0.9 41.50% 62.70% 0.45 42.30% 28.40% Comparative Example 4 0.88 50.20% 76.40% 0.58 48.70% 29.40% Comparative Example 5 0.89 58.70% 78.30% 0.36 54.80% 34.20% Comparative Example 6 0.9 60.40% 65.10% 0.17 56.20% 35.50% Comparative Example 7 0.9 52.60% 82.50% 0.39 53.70% 31.80% Comparative Example 8 0.9 48.90% 75.60% 0.41 47.80% 31.50%

[0154] The far-infrared dressings prepared in Examples 1-5 of this invention exhibit balanced and stable overall performance. They achieve good levels in terms of far-infrared emission performance, skin retention capacity of active ingredients, antibacterial effect, skin safety, and antipruritic and analgesic effects. This verifies that the present invention can achieve synergistic effects of far-infrared therapy, multiple antipruritic effects, anti-inflammatory and antibacterial effects, and low irritation. The comprehensive performance of the finished dressings is suitable for the application requirements of external skin use, with stable function and good skin compatibility.

[0155] The reason for the decrease in Comparative Example 1 may be that after replacing silane, citronellal cannot be covalently anchored through the mercapto-ene reaction. Citronellal is easily volatilized and lost through physical adsorption alone, resulting in unstable immediate antipruritic effect and easy sudden release, which increases the risk of skin irritation. At the same time, there are insufficient aldehyde sites on the surface, the grafting efficiency of modified luteolin decreases, and the skin retention ability and long-term antipruritic effect are weakened.

[0156] The reason for the decrease in Comparative Ratio 2 may be that menthol has a single antipruritic mechanism, which can only provide temporary cooling and relief without any anti-inflammatory auxiliary effect. In addition, the molecule lacks an aldehyde group, so it cannot be stably grafted onto the powder surface, nor can it provide a binding site for luteolin. As a result, the fixation effect of the active ingredient is worse, and the overall antipruritic effect is reduced.

[0157] The reason for the decrease in proportion 3 may be that native luteolin has poor water solubility, is prone to agglomeration and precipitation, and lacks primary amino groups, so it cannot covalently bind with the powder, making it easy to desorb and lose, resulting in a significant decrease in skin retention rate; at the same time, the lack of guanidinization modification results in the loss of adhesion, penetration enhancement and antibacterial effects, significantly reduced antibacterial effect, and the anti-inflammatory and antipruritic activity is also easily damaged by oxidation, leading to increased skin irritation.

[0158] The reason for the decrease in Comparative Example 4 may be that the original tourmaline was not modified, the sharp edges of the particles easily caused physical friction and stimulation, and the strong surface inertness prevented it from covalently binding with luteolin. Physical mixing alone could easily lead to the migration and loss of active ingredients, resulting in a decrease in the antipruritic and analgesic effects. At the same time, the poor compatibility between the powder and the matrix made it easy to agglomerate, resulting in uneven functional distribution and further weakening the overall performance.

[0159] The reason for the decrease in Comparative Example 5 may be that after omitting hydroxylation, there are insufficient active hydroxyl groups on the surface of tourmaline, the grafting rate and uniformity of mercaptosilane decrease, the loading of citronellol decreases, and the immediate antipruritic effect weakens; in addition, the insufficient silane coating cannot completely passivate the edges of the particles, the skin irritation increases, the subsequent grafting efficiency of luteolin also decreases, and the long-lasting antipruritic effect becomes worse.

[0160] The reason for the decrease in the comparative ratio 6 may be that after omitting guanidinization, the luteolin derivative loses its strong positively charged adhesion, resulting in a decrease in skin retention rate. Furthermore, the broad-spectrum antibacterial effect of guanidin disappears, and the antibacterial performance is significantly reduced. At the same time, the lack of penetration-enhancing effect makes it difficult for the active ingredients to reach the target site, thus reducing the efficiency of antipruritic, anti-inflammatory, and analgesic effects.

[0161] The reason for the decrease in ratio 7 may be that the two are not covalently grafted but only physically mixed. The active ingredients are not fixed by covalent bonds and are easy to desorb and migrate, resulting in a decrease in skin retention rate and long-lasting antipruritic effect. In addition, the free active substances are easy to burst release, which increases skin irritation. The powder is easy to agglomerate, which leads to uneven functional distribution and affects the uniformity of analgesic and antipruritic effects.

[0162] The reason for the decrease in Comparative Example 8 may be that after omitting citronellol grafting, there are insufficient aldehyde sites on the powder surface, the reactivity of thiol and amino groups is low, the grafting efficiency of luteolin is greatly reduced, and the skin retention and long-lasting antipruritic effect are significantly reduced; at the same time, the lack of the immediate antipruritic effect of citronellol reduces the overall antipruritic effect, and the exposure of the powder will also increase skin irritation.

[0163] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a far-infrared dressing that inhibits skin itching, characterized in that, The preparation method includes the following steps: Functionalized tourmaline powder and modified luteolin were mixed and stirred to obtain composite functional particles; Sodium alginate and deionized water were mixed and swollen, and then stirred and dispersed to obtain a hydrogel-based solution. Glycerol and composite functional particles were added to the hydrogel base liquid and stirred to disperse to obtain a composite system; The composite system was degassed under vacuum to obtain a gel matrix; The far-infrared dressing is prepared by sequentially coating and sterilizing the gel matrix.

2. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 1, characterized in that, The method for preparing the functionalized tourmaline powder includes the following steps: Hydroxylated tourmaline was obtained by mixing tourmaline powder and hydrogen peroxide solution and reacting them. Thiolized tourmaline was obtained by mixing and stirring hydroxylated tourmaline with 3-mercaptopropyltriethoxysilane. Functionalized tourmaline powder was obtained by mixing and stirring mercapto-modified tourmaline, citronellal, and azobisisobutyronitrile.

3. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 2, characterized in that, The concentration of the hydrogen peroxide solution is 30 wt%; the weight ratio of the tourmaline micro powder to the hydrogen peroxide solution is 10:50~70; the weight ratio of the hydroxylated tourmaline to 3-mercaptopropyltriethoxysilane is 10:0.13~0.16; and the weight ratio of the mercaptolated tourmaline, citronellal, and azobisisobutyronitrile is 10:1.2~2.0:0.05~0.

07.

4. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 1, characterized in that, The preparation method of the modified luteolin includes the following steps: Luteolin and sodium chloroacetate were mixed and stirred to produce carboxymethyl luteolin; The amino-containing luteolin was obtained by mixing and stirring carboxymethyl luteolin, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide and ethylenediamine. Modified luteolin was obtained by mixing and stirring amino-containing luteolin and cyanamide.

5. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 4, characterized in that, The weight ratio of luteolin to sodium chloroacetate is 10:0.5~0.7; the weight ratio of carboxymethyl luteolin, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, N-hydroxysuccinimide and ethylenediamine is 10:1.2~2.0:0.7~1.3:1.5~2.5; the weight ratio of aminoluteolin and cyanamide is 10:0.8~1.

2.

6. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 1, characterized in that, The weight ratio of the functionalized tourmaline powder to the modified luteolin is 10:1.0~1.5; the reaction conditions for the mixing and stirring of the functionalized tourmaline powder and the modified luteolin include a reaction temperature of 24~26℃ and a reaction time of 10~14h.

7. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 1, characterized in that, The conditions for the swelling of sodium alginate and deionized water include a swelling temperature of 24-26℃ and a swelling time of 22-24h; the conditions for the dispersion of sodium alginate and deionized water after swelling include a stirring temperature of 50-60℃ and a stirring time of 30-50min.

8. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 1, characterized in that, The weight ratio of sodium alginate, deionized water, glycerol, and composite functional particles is 2.0~2.5:83~86:4~6:7~9; the conditions for adding glycerol and dispersing the composite functional particles include a stirring speed of 800~120 r / min and a stirring time of 20~30 min.

9. The method for preparing a far-infrared dressing for inhibiting skin itching as described in claim 1, characterized in that, The vacuum degassing conditions include a vacuum degree of 0.06~0.08MPa and a degassing time of 15~30min; the coating treatment conditions include a coating thickness of 0.4~0.6mm.

10. A far-infrared dressing for relieving skin itching, characterized in that, It is prepared by the preparation method of any one of claims 1 to 9 for a far-infrared dressing that inhibits skin itching.