In vitro evaluation of sun protection factors of sunscreen agents using a novel UV spectrophotometric technique

Abstract

A method for the in vitro determination of low- and high-value sun protection factors (SPF) of sunscreens using artificial substrates and a novel pseudo double beam (PDB) mode of operation of a standard double beam UV spectrophotometer is described. The method allows transmittance to be calculated from detector responses of reference and sample beams measured at different gain levels and facilitates the accurate quantification of low levels of electromagnetic radiation transmitted through highly absorbing samples. The spectrophotometer was modified to hold quartz diffusing plates on which a substrate [Transpore adhesive tape or human stratum corneum obtained from a skin surface biopsy (SSB)] and the sunscreens to be tested were applied. The PDB mode of operation increased the effective linear range of the detector response of the spectrophotometer by a factor of approximately 20000-fold, enabling the in vitro SPF determination technique to be applied to both high and low SPF value sunscreens. Eight commercial sunscreens with known SPF values ranging from 4 to 77, previously determined by in vivo methods, were tested in vitro using both test substrates and correlations between the in vivo and in vitro values were determined. SPF values determined using the in vitro method correlated well with the known in vivo results (Transpore tape, R(2) = 0.611; SSB, R(2) = 0.7928). The in vitro SPF obtained for one of the tested products differed substantially from the cited in vivo SPF value. Independent in vitro and in vivo re-evaluation of the SPF of this product matched the value predicted by the present method much more closely than the originally cited in vivo value. All determined SPFs were ordered correctly in comparison to in vivo ranking and the technique appeared to correctly identify a sunscreen that had a labelled SPF value that was significantly higher than its true SPF.

A new hair follicle-derived human epidermal model for the evaluation of sunscreen genoprotection

“…Moreover, determination of SPF is a tedious and time-consuming process that requires participation of human volunteers. Numerous works have been devoted to the development of in vitro techniques as complementary tools to SPF [6][7][8][9][10][11][12][13][14][15]. These approaches mostly rely on the induction of UVB and/or UVA-activated molecular pathways in cutaneous cells as endpoints for the evaluation of the photoprotection afforded by sunscreens following topical application.…”

Teucrium polium L. extract adsorbed on zinc oxide nanoparticles as a fortified sunscreen

“…[2021222324] The Transpore ® tape from a part, excluding the first or last 60 cm of a roll, was used. Transpore ® 3M, a surgical tape manufactured by the 3M Company, was used as a substrate for its reported similar topography and sunscreen distribution to the human skin.…”

In Vitro Evaluation of Sunscreens: An Update for the Clinicians

“…There is no official, standardized, harmonized published method accepted for SPF labeling by authorities. Among these methods, the National Institute of Public Health (NIPH) method [22], the Výzkumný ústav organických syntéz (VUOS) (Research Institute for Organic Syntheses) method [23], a method using artificial substrates and a novel pseudodouble beam mode of operation of a standard double beam UV spectrophotometer [24], and the SONING method [25]. NIPH method [22] measures the attenuation of UVB intensity on a defined layer of a sunscreen product, using an UVA/UVB source, a sheet of Mikelanta covering paper with 2 mg/cm 2 of product applied with an ungloved finger, and a radiometer for UVB radiation intensity measurement.…”

“…The VUOS method [23] uses a surgical tape posed on a quartz layer with 1.2 mg/cm 2 of product applied; a spectrophotometer then measures the transmittance and the SPF is calculated. The method described by Bleasel and Aldous [24] uses diffusing plates made of quartz with Transpore adhesive tape or human stratum corneum obtained from a skin surface biopsy as substrate. A pseudodouble beam mode of operation of a standard double beam UV spectrophotometer is utilized, greatly increasing the effective linear range of the detector response of the spectrophotometer.…”