Non-Invasive Method for Quantitative Evaluation of Exogenous Compound Deposition on Skin

Abstract

Topical application of active compounds on skin is common to both pharmaceutical and cosmetic industries. Quantification of the concentration of a compound deposited on the skin is important in determining the optimum formulation to deliver the pharmaceutical or cosmetic benefit. The most commonly used techniques to date are either invasive or not easily reproducible. In this study, we have developed a noninvasive alternative to these techniques based on spectrofluorimetry. A mathematical model based on diffusion approximation theory is utilized to correct fluorescence measurements for the attenuation caused by endogenous skin chromophore absorption. The limitation is that the compound of interest has to be either fluorescent itself or fluorescently labeled. We used the method to detect topically applied salicylic acid. Based on the mathematical model a calibration curve was constructed that is independent of endogenous chromophore concentration. We utilized the method to localize salicylic acid in epidermis and to follow its dynamics over a period of 3 d.

Morphological characterization of solar lentigines by in vivo reflectance confocal microscopy: a longitudinal approach

“…The fluorescence intensity is inversely proportional to the skin colour . Therefore, each fluorescence measurement was normalized to its reflectance value at 345 nm, as described elsewhere .…”

Antiaging Action of Retinol: From Molecular to Clinical

“…The excitation source was a xenon arc lamp. A detailed description of the instrumentation is given elsewhere [15] . Measurements were performed by placing the fiberoptic probe in contact with the skin site of interest.…”

“…For a review of the skin fluorescence maxima see Kollias et al [18] . The second scan corresponds to acquisition of a diffuse reflectance spectrum and was used to normalize the fluorescence spectrum, in order to account for variations in skin native pigmentation (skin pigmentation attenuates the detected fluorescence signal) [15,19] . The correction was necessary especially for wavelengths 1 315 nm.…”

Effects of Cosmetic Formulations Containing Hydroxyacids on Sun-Exposed Skin: Current Applications and Future Developments

“…However, this CIE L*a*b* system is inadequate to discriminate erythema masked by higher melanin content, and therefore measuring skin chromophores, such as melanin, oxyhemoglobin and deoxyhemoglobin, by DRS is highly desirable for defining the MED noninvasively. Several studies have been published on the use of DRS, which prove that it can be applied as an adjunct to aid in the prediction and measurement of MEDs for HA UV effects [29–31]. …”