Method for in vitro testing of the sun protection factor spf of a powder

Abstract

This application discloses an in vitro testing method for the SPF (Sun Protection Factor) of powder sunscreens, relating to the field of cosmetic efficacy evaluation technology, including the following steps: Step 1: Set a test environment with a temperature of 22-28℃ and a humidity of 40-60%; Step 2: Weigh 2.0-3.0 mg of white oil and place it on a PMMA plate, spread it evenly, and read the blank value using an SPF-290S sunscreen measurement system; Step 3: Weigh 7.0-7.9 mg of powder sunscreen product on a PMMA plate, spread it evenly, and let it stand in the dark for 15-20 minutes; Step 4: Measure the SPF value of different powder sunscreen product samples using SPF-290S, and calculate the average SPF value, STD value, and CI% value of each group of powder sunscreen products. Each group of samples is tested 4 times repeatedly; Step 5: Plot the correlation between in vitro SPF value and human SPF value for each group of powder sunscreen products, and perform linear fitting to obtain a linear equation to obtain the correlation between in vitro SPF value and human SPF value. The in vitro testing method for the SPF (Sun Protection Factor) of powder in this application is feasible, repeatable, and predictable.

Description

Technical Field

[0001] This application relates to the field of cosmetic efficacy evaluation technology, specifically to an in vitro testing method for the sun protection factor (SPF) of powder. Background Technology

[0002] Ultraviolet (UV) radiation has a wavelength range of 200-400 nm, accounting for approximately 10% of the sun's total output. Based on different biological effects, UV radiation is divided into three bands according to wavelength: UVA (320-400 nm), which has the longest wavelength but the lowest energy; UVB (280-320 nm), with a wavelength in the middle range; and UVC (200-280 nm), which has the shortest wavelength but the highest energy. Moderate UV exposure can have beneficial effects on human health; however, long-term exposure to UV radiation is considered to have a potential risk of skin cancer. Sunscreen products on the market are usually labeled with PA or SPF, or both. PA provides protection against UVA (320-400 nm), while SPF protects against UVB (280-320 nm). With increasing emphasis on sun protection, many cosmetics include sunscreen ingredients. Among these, the increasingly popular sunscreen powders and pressed sunscreens effectively prevent UV damage to the skin. Current in vitro methods for testing SPF values ​​of sunscreens only apply to non-powder sunscreen products such as sunscreen creams. Human testing of sunscreen products is expensive, time-consuming, and raises ethical concerns. Therefore, it is crucial to develop an efficient, simple, effective, and correlated in vitro method for testing the SPF values ​​of sunscreen powders with human results. Summary of the Invention

[0003] The purpose of this application is to provide an in vitro testing method for the SPF value of sunscreen powder, so as to establish an efficient, simple, effective method for in vitro testing of the SPF value of sunscreen powder that is correlated with the results of human sun protection.

[0004] To achieve the above objectives, this application discloses the following technical solution: an in vitro testing method for the SPF (Sun Protection Factor) of powder sunscreens, the method comprising the following steps:

[0005] Step 1: Set the test environment to a temperature of 22-28℃ and a humidity of 40-60%;

[0006] Step 2: Weigh 2.0-3.0 mg of white oil onto a PMMA plate, spread it evenly, and then read the blank value using a sun protection factor measurement system SPF-290S;

[0007] Step 3: Weigh 7.0-7.9mg of powder sunscreen product onto the PMMA plate, spread it evenly, and let it stand in the dark for 15-20 minutes.

[0008] Step 4: Determine the SPF value of different powder sunscreen product samples using the SPF-290S sun protection factor measurement system, and calculate the average SPF value, STD value, and CI% value of each group of powder sunscreen products. Each group of samples was tested 4 times.

[0009] Step 5: Plot the correlation between in vitro SPF values ​​and human body SPF values ​​for each group of powder sunscreen products, and perform linear fitting to obtain a linear equation, so as to obtain the correlation between in vitro SPF values ​​and human body SPF values.

[0010] Preferably, the white oil is cosmetic grade white oil.

[0011] Preferably, in step two, after placing the white oil on the PMMA plate, the user wears a finger cot to spread the white oil evenly on the PMMA plate.

[0012] Preferably, in step three, after placing the powder sunscreen product on the PMMA plate, the user wears a finger cot to spread the powder sunscreen product evenly on the PMMA plate.

[0013] Preferably, the formula for calculating the CI% value is:

[0014] in, t is the two-tailed t-value when the number of sample plates is n, n is the total number of sample plates, SD is the standard deviation of the SPF value when the number of sample plates is n, and in vitro SPF is the average in vitro SPF value obtained by measurement.

[0015] Preferably, the formula for calculating the average in vitro SPF value is as follows:

[0016] The formula for calculating the standard deviation of the SPF value is as follows:

[0017] Beneficial Effects: The in vitro testing method for the SPF of sunscreen powder in this application selects cosmetic-grade white oil as a solvent. Compared with traditional glycerin, this solvent has a lower viscosity, and its viscosity and blank value are less affected by temperature, making it a more suitable solvent. This invention uses a PMMA plate as a carrier. The PMMA plate overcomes the problem of powder leakage through the back of the skin-like film when applying sunscreen powder using the previously used 3M Transpore skin-like film tape, resulting in inaccurate powder application. This application overcomes the limitation of the existing method where the powder coating amount is 1.3 mg / cm³. 2 It addresses the issues of inaccurate, convenient, and efficient measurement of powder in sunscreen products, such as the inability to form a uniform film, excessive powder leading to powder fallout and uneven application, and poor light blocking. It also overcomes the limitations of calculating 1.3 mg / cm³ powder concentration through multiple low-dose powder concentration tests. 2The process of obtaining SPF values ​​for powder sunscreens is cumbersome and inefficient. This application only requires four repeated tests for each group of samples to obtain a CI% < 17%. Furthermore, the in vitro test results of the powder sunscreen SPF values ​​obtained by this application are correlated with human SPF values. That is, by fitting a linear equation between in vitro SPF values ​​and human SPF values, the obtained results are sufficient and predictable. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0019] Figure 1 A correlation diagram was drawn between in vitro SPF values ​​and human SPF values ​​in the embodiments of this application. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application.

[0021] In this document, the term "comprising" is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0022] This embodiment provides a simple, rapid, and efficient in vitro testing method for determining the SPF of powder sunscreens using the SPF-290S sunscreen index measurement system, and verifies the correlation between the in vitro test results of the powder sunscreen SPF value and the SPF value of human sunscreens. This application uses commercially available loose sunscreen powders of different brands and with different SPF ratings as test samples, wherein the SPF ratings of the samples are 20+, 15+, 50+, 30+, and 25+, respectively.

[0023] Example 1

[0024] Sunscreen powders with SPF ratings of 50+, 30+, and 25+ were selected as test samples.

[0025] Step 1: Set the test environment with a temperature of 22-28℃ and a humidity of 40-60%.

[0026] Step 2: Prepare a PMMA plate, weigh 2.0-3.0 mg of white oil (cosmetic grade) onto the PMMA plate, apply it evenly with a finger cot, and read the blank value using a sun protection factor measurement system SPF-290S.

[0027] Step 3: Weigh 7.0-7.9mg of powder sunscreen product onto a PMMA plate, apply it evenly while wearing a finger cot, and let it stand in the dark for 20 minutes.

[0028] Step 4: The SPF of different powder sunscreen product samples was determined using the SPF-290S sun protection factor measurement system. Each sample group underwent four repeated tests, and the average SPF value, STD value, and CI% value were calculated for each group of powder sunscreen products. The formula for calculating the CI% value is as follows: in, t is the two-tailed t-value when the number of sample plates is n, n is the total number of sample plates, SD is the standard deviation of the SPF value when the number of sample plates is n, and in vitro SPF is the average in vitro SPF value obtained from the measurement; the formula for calculating the average in vitro SPF value is: The formula for calculating the standard deviation of the SPF value is:

[0029] Example 2

[0030] Sunscreen powders with SPF ratings of 20+ and 15+ were selected as test samples.

[0031] Step 1: Set the test environment with a temperature of 22-28℃ and a humidity of 40-60%.

[0032] Step 2: Prepare a PMMA plate, weigh 2.0-3.0 mg of white oil (cosmetic grade) onto the PMMA plate, apply it evenly with a finger cot, and read the blank value using a sun protection factor measurement system SPF-290S.

[0033] Step 3: Weigh 7.0-7.9mg of powder sunscreen product onto a PMMA plate, apply it evenly while wearing a finger cot, and let it stand in the dark for 20 minutes.

[0034] Step 4: The SPF values ​​of different powder sunscreen product samples were determined using the SPF-290S sun protection factor measurement system. Each sample group underwent four repeated tests, and the average SPF value, STD value, and CI% value were calculated for each group of powder sunscreen products. The formula for calculating the CI% value is: in, t is the two-tailed t-value when the number of sample plates is n, n is the total number of sample plates, SD is the standard deviation of the SPF value when the number of sample plates is n, and in vitro SPF is the average in vitro SPF value obtained from the measurement; the formula for calculating the average in vitro SPF value is: The formula for calculating the standard deviation of the SPF value is:

[0035] Based on the measured SPF values ​​of the powder obtained in Examples 1 and 2 above, the statistical values ​​are shown in Table 1. A plot is drawn based on Table 1. Figure 1 The in vitro SPF value-human SPF value graph is shown, and a linear equation is obtained by fitting a straight line to obtain the correlation between in vitro SPF value and human SPF.

[0036] Table 1

[0037] In vitro SPF (Spectrum Per PF) In vivo SPF (body SPF value) 3.42 15 3.62 20 3.77 25 4.45 30 5.95 50

[0038] like Figure 1 The in vitro SPF value-human SPF value graph shown indicates a linear relationship between the in vitro SPF value and the human SPF value of the sunscreen powder obtained by the method of this application. A linear fit yields the equation y = 12.97x - 27.02, with a correlation coefficient of R0. 2 =0.9785, indicating a good correlation between in vitro SPF values ​​and human SPF values. Therefore, it can be clearly stated that the present application provides an in vitro testing method for powder sunscreen index (SPF) that is repeatable, feasible, efficient, and predictable. During the testing process, the CI% value of each sample group is less than 17%, and the test results are correlated with human SPF values.

[0039] Finally, it should be noted that the above description is only a preferred embodiment of this application and is not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An in vitro testing method for the sun protection factor (SPF) of powder, characterized in that, The method includes the following steps: Step 1: Set the test environment to a temperature of 22-28℃ and a humidity of 40-60%; Step 2: Weigh 2.0-3.0 mg of white oil onto a PMMA plate, spread it evenly, and read the blank value using a sun protection factor measurement system SPF-290S; the white oil is cosmetic grade white oil, and after placing the white oil on the PMMA plate, wear a finger cot to spread the white oil evenly on the PMMA plate. Step 3: Weigh 7.0-7.9 mg of the powder sunscreen product onto the PMMA plate, spread it evenly, and let it stand in the dark for 15-20 minutes; after placing the powder sunscreen product on the PMMA plate, wear finger cots to spread the powder sunscreen product evenly on the PMMA plate. Step 4: The SPF values ​​of different powder sunscreen product samples were measured using the SPF-290S sun protection factor measurement system. The average SPF value, STD value, and CI% value of each group of powder sunscreen products were calculated. Each group of samples was tested four times. The formula for calculating the CI% value is as follows: , t is the two-tailed t-value when the number of sample plates is n, n is the total number of sample plates, and SD is the standard deviation of the SPF values ​​when the number of sample plates is n. SPF is the average in vitro SPF value obtained from the measurement. Step 5: Plot the correlation between in vitro SPF values ​​and human body SPF values ​​for each group of powder sunscreen products, and perform linear fitting to obtain a linear equation, so as to obtain the correlation between in vitro SPF values ​​and human body SPF values.

2. The in vitro testing method for the SPF (Sun Protection Factor) of powder according to claim 1, characterized in that, The formula for calculating the average in vitro SPF value is as follows: , The formula for calculating the standard deviation of the SPF value is as follows: .

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