New <i>in vitro</i> SPF Evaluation Method for Hydrophilic Sunscreen Samples

Abstract

ploying measurements such as in vitro SPF 10) , in vitro UVA-PF 11) , and the determination of the critical wavelength for Broad Spectrum approval 12) . These all require that sample sunscreens be applied to a roughened cosmetic standard PMMA UV evaluation plate 13−15) , to allow measurement of the UV transmission passed through the sunscreen layer. However, in a previous study, the surface roughness of the cosmetic standard PMMA UV evaluation plate was found to alter UV transmission 16) . In addition,

Investigation on the Validity of <i>in vitro</i> Sun Protection Factor and Ultraviolet-A Protection Factor Evaluation Method for Sunscreen Samples

“…samples and their comparison with their in vivo UVA-PF According to our recently proposed new in vitro SPF evaluation method 8) , in vitro SPF of the two hydrophilic sunscreen samples 1 and 2 were evaluated. Samples were applied on hydroxyalkyl cellulose-coated quartz plates using linear motor coating machine and four-side applicator, in a manner similar to our previously published report 8) . The UV absorbance of the applied layer was measured using LAMBDA 850＋ in the range between 290 nm and 400 nm in 1 nm increment.…”

“…The coefficient of adjustment, C, was then evaluated by making the values of in vitro SPF thus calculated using equation (7) equal to in vivo SPF. The values of in vitro UVA-PF of both sunscreen samples were calculated by substituting the value of C into equation (8) . For the spectral irradiance, I (λ ) , both Colipa 1994 and UV-SSR, were substituted into the equation ( 7) and (8) .…”

<i>In vitro</i> Evaluation Method of UV Protecting Ability of Sunscreens: Clarifying and Overcoming Problems to Develop New Method

“…We have developed two types of hydrophilic substrate, super-hydrophilic plate (SHP plate) 49,50) and hydroxyalkyl cellulose coated plate (HCC plate) 52,53) . Contact angle of water on a quartz plate was in a range between 70 to 80 deg, and SHP plate was prepared by Corona-discharge treatment on a flat square quartz plate using Laboratory Corona Treater (BD-20AC, Electro-Technic Products) .…”

“…In the case of evaporating water from the aqueous solution of hydroxyalkyl cellulose spread on the SHP plate, various drying patterns were found to be generated (Fig. 8) 52) . Thus, special care had to be taken for the preparation of flat and uniform film of hydroxyalkyl cellulose 53) .…”

“…In addition to those studies to verify the problems on in vitro evaluation method of UV protecting ability of sunscreens 34−36, 48−51) , attempts were made to establish reliable and reproducible in vitro evaluation method of UV protecting ability of sunscreens 52) . New type of plate was developed by coating the super-hydrophilic plate by polysaccharide.…”