In vivo two-photon imaging of topically applied care cosmetics and pharmaceuticals in human skin

Abstract

We applied femtosecond laser multiphoton tomographs, including the novel system MPTcompact with its chiller-free fiber laser positioned inside the measurement head, for multimodal imaging of in vivo human skin of volunteers, that had been exposed to topically applied sunscreens, UV stains, care cosmetics, and pharmaceuticals. Signals are based on two-photon excited and time-resolved fluorescence (FLIM), Second Harmonic Generation (SHG), and confocal reflection. In particular, SHG signals have been detected from silver nanoparticles in mineral sunscreen. Of particular interest was the distribution of the exogenous compounds within the upper epidermis such as the stratum corneum as an efficient skin barrier. The lateral resolution was 300 nm and the time resolution was 250 picoseconds. In addition, the autofluorescence based on NADH and keratin detection was imaged.

On the quantitative analysis of lamellar collagen arrangement with second-harmonic generation imaging

“…Today, SHG is the de facto imaging technique for imaging collagen and assessing tissue organization in healthy and pathological conditions. Its potential to aid in the diagnosis of dermatological diseases [ 2 ], evaluate the influence of topical creams [ 3 , 4 ], or to differentiate between healthy and tumor tissue [ 5 , 6 ] was already demonstrated. However, ophthalmology has been the main area of application.…”