title: Probing skin pigmentation changes with transient absorption imaging of eumelanin and pheomelanin.
abstract: As some of the most ubiquitous and biologically important natural pigments, melanins play essential roles in the photoprotection of skin. Changes in melanin production could potentially be useful for clinical diagnosis of the progression stage of melanoma. Previously we demonstrated a new method for imaging melanin distribution in tissue with two-color transient absorption microscopy. Here we extend this study to longer wavelengths and show that we are able to image melanin in fixed thin skin slices with higher signal-to-noise ratios (SNRs) and demonstrate epimode imaging. We show that both photothermal effects and long-lived excited states can contribute to the long-lived signal. Eumelanin and pheomelanin exhibit markedly different long-lived excited state absorption. This difference should enable us to map out their respective distribution in tissue samples with subcellular resolution. This technique could provide valuable information in diagnosing the malignant transformation of melanocytes.
authors.affiliation: Princeton University, Department of Chemistry, Princeton, New Jersey 08544, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Fu
authors.forename: Tong
authors.initials: T
authors.lastname: Ye
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Matthews
authors.forename: James
authors.initials: J
authors.lastname: Grichnik
authors.forename: Lian
authors.initials: L
authors.lastname: Hong
authors.forename: John D
authors.initials: JD
authors.lastname: Simon
authors.forename: Warren S
authors.initials: WS
authors.lastname: Warren
mesh_terms: D046169:Dermoscopy / Q000379:methods*; D006801:Humans; D008543:Melanins / Q000032:analysis*; D008545:Melanoma / Q000378:metabolism / Q000473:pathology; D036641:Microscopy, Fluorescence, Multiphoton / Q000379:methods*; D010860:Pigments, Biological / Q000032:analysis; D012867:Skin / Q000378:metabolism* / Q000473:pathology*; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology
chemical_list: D008543:Melanins; D010860:Pigments, Biological; C018362:pheomelanin; C041877:eumelanin