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The ablative fractional coagulation zone influences skin fluorescence intensities of topically applied test molecules—An in vitro study with fluorescence microscopy and fluorescence confocal microscopy
Author(s) -
Banzhaf Christina A.,
Ortner Vinzent K.,
Philipsen Peter A.,
Haedersdal Merete
Publication year - 2019
Publication title -
lasers in surgery and medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 112
eISSN - 1096-9101
pISSN - 0196-8092
DOI - 10.1002/lsm.23034
Subject(s) - fluorescence , confocal microscopy , fluorescence microscope , microscopy , confocal , analytical chemistry (journal) , materials science , sodium fluorescein , optical microscope , chemistry , biomedical engineering , fluorescein , scanning electron microscope , chromatography , optics , pathology , medicine , physics , composite material
Background Ablative fractional laser (AFL) increases uptake of topically applied skin agents. The coagulation zone (CZ) surrounding vertically ablated channels may influence uptake of drugs. Objectives To investigate impact of CZ thickness on skin fluorescence intensities (FI) of a hydrophilic molecule by means of fluorescence microscopy (FM) and fluorescence confocal microscopy (FCM). Second, to compare FI of hydrophilic and lipophilic test molecules by FCM. Study Design/Methods and Materials Microchannels with CZ thicknesses of 0, 20, and 80 µm were generated by microneedles or AFL (10,600 nm). Channels were 700 µm deep and number of channels kept constant per skin area. After 4 hours of incubation, FI induced by sodium fluorescein ( NAF , hydrophilic, logarithmic partition‐coefficient (logP) = −1.52, MW = 376.26) were quantified in both CZ and surrounding skin by FM (0–1,500 µm) and FCM (0–90 µm). FI of NAF and carboxyfluorescein ( CAF , lipophilic, logP = 2.9, MW = 376.32) were compared by FCM. Results By FM, NAF‐induced FI were higher in CZ than in surrounding skin ( P ≤ 0.001). Highest NAF‐FI were induced in skin pretreated with a thin CZ (CZ–20 µm), assessed by both FM and FCM and in particular, FI were higher than in skin pretreated with no CZ (CZ–0 µm) (FM P ≤ 0.041, FCM P < 0.012). Skin FI remained constant to a depth of 500 µm, which corresponded to approximate depth of microchannels (CZ–0 µm, CZ–20 µm, CZ –80 µm: 0–500 µm P ≥ 0.107). In accordance with FM data, FCM showed higher FI within CZ than in surrounding skin, but gradually decreased to zero at a depth of 90 µm. NAF‐FI were higher than CAF‐FI ( P ≤ 0.036), and highest CAF‐FI were induced by CZ–0 µm and CZ–20 µm compared to CZ–80 µm ( P ≤ 0.009). Conclusions The influence of the CZ thickness on skin FI differs between small hydrophilic and lipophilic test molecules. Results may have clinical relevance for laser‐assisted drug delivery. Lasers Surg. Med. 51:68–78, 2019. © 2018 Wiley Periodicals, Inc.