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A NEW IN-VITRO METHOD FOR DETERMINATION OF EFFICACY OF SUN CARE PRODUCTS

IP.com Disclosure Number: IPCOM000240603D
Publication Date: 2015-Feb-11

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The IP.com Prior Art Database

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William J. Davis: ATTORNEY

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Page 01 of 11

RESEARCH DISCLOSURE

A NEW IN-VITRO METHOD FOR DETERMINATION OF EFFICACY OF SUN CARE PRODUCTS

Xin Qu, Xiao- min Zhao, and Zhi-hua Chen

ASI Shanghai Technical Center, Ashland Inc., Shanghai, China

This research disclosure relates to a new in-vitro test method for determining the efficacy of sun care products. The test method is based on UV [Ultra Violet] dosage cumulate response using Gafchromic film. The test is more accurate, cost effective, reproducible, and does not employ UV spectrophotometer compared to the current test methods.

The potential of UV radiation causing skin damage rises exponentially with decreasing wavelength or on long exposure. The damage caused [Skin burn or skin erythema] is measured as minimal erythema dose [MED]. Both in-vivo and in-vitro test methods are used to determine the sun care products efficacy.

Generally, an in-vivo test method involves measuring dosage of UV radiation required to cause MED (sunburn/erythema) on skin with the sunscreen on, as a multiple of the dosage required without sunscreen by the SPF (Equation 1).

with

without

     Dosage SPF
= Dosage

Sunscreen

Sunscreen

MED

(Equation 1)

The in-vivo test method is expensive, time consuming, affected by skin types, and subjective to human observation of skin erythema. In-vitro SPF test involves the measurement of the spectral transmittance of a sunscreen applied to a transparent substrate material. The transmittance of the sunscreen is the ratio of spectral transmittance through a defined amount of sunscreen applied. The measured spectral power distribution is then weighted by the defined solar spectrum and erythemal effectiveness functions to yield the calculated in vitro SPF (Equation 2). This method is

MED


Page 02 of 11

based on UV spectral transmission measurements, and has no UV dosage cumulating response.

SPF =

λ λ

= =

400 290

nm nm

E

(

λ

)


*

I

(

λ

)


*

d

λ

(Equation 2)

Where: E(λ) = Erythema action spectrum (CIE-1987)

I(λ) = Spectral irradiance of the UV source (SSR or SPF testing)

A0(λ) = Mean monochromatic absorbance measurements per plate of the test product layer before UV exposure;
dλ = Wavelength step (1nm)

Thus, to overcome the setbacks of the above methods, a new in-vitro test method for sun care product based on UV dosage cumulate response is developed using Gafchromic films. The Gafchromic film is a radiochromic film which consists of a single or double layer of radiation sensitive organic microcrystal monomers and is set on a thin polyester base with a transparent coating. The radiochromic film instantly changes the color on exposure to ionizing radiation. No chemical or physical processing is needed. The color of the Gafchromatic films is changed upon irradiation. Darkness of the film is increased with increasing absorbed dose thus any further processing to develop or fix the image is not required.. Various types of Gafchromic films can be prepared by changing sizes [with sensitive layer in the range of 5-30µm], shap...