title: Vehicle type affects filling of fractional laser-ablated channels imaged by optical coherence tomography.
abstract: Ablative fractional laser (AFXL) is an emerging method that enhances topical drug delivery. Penetrating the skin in microscopic, vertical channels, termed microscopic treatment zones (MTZs), the fractional technique circumvents the skin barrier and allows increased uptake of topically applied drugs. This study aims to elucidate the impact of vehicle type on the filling of MTZs from application of liquid, gel, and cream vehicles. Ex vivo pig skin was exposed to 10,600 nm fractional CO2laser at 5% density, 120 μm beam diameter, and fluences of 40 and 80 mJ/microbeam (mJ/mb). Six repetitions were performed for each of six interventions (2 fluences and 3 vehicle types, n = 36). MTZ dimensions and filling by vehicle type were evaluated by optical coherence tomography, using blue tissue dye as a contrast-enhancing agent. Outcome measure was degree of MTZ filling assessed as percentages of empty, partially filled, and completely filled MTZs (108-127 MTZs/intervention analyzed) and evaluated statistically using Kruskal-Wallis and Dunn's tests. MTZs reached mid-dermal levels of 225 μm (40 mJ/mb) and 375 μm (80 mJ/mb) penetration depths (p < 0.0001). Filling of MTZs depended on type of applied vehicle. At 80 mJ/mb, liquid (67% completely filled, p < 0.01) and gel (60%, p < 0.05) formulations filled MTZs significantly better than cream formulation (31%). At 40 mJ/mb, liquid and gel formulations filled 90% (p < 0.05) and 77% (p > 0.05) of MTZs completely versus 55% for cream formulation. Thus, filling was overall greater for more superficial MTZs. In conclusion, vehicle type affects filling of MTZs, which may be of importance for AFXL-assisted drug delivery.
authors.affiliation: Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, DK-2400, Copenhagen, NV, Denmark. olesen.uh@gmail.com.
authors.forename: Uffe Høgh
authors.initials: UH
authors.lastname: Olesen
authors.affiliation: Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, DK-2400, Copenhagen, NV, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Mogensen
authors.affiliation: Department of Dermatology, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, DK-2400, Copenhagen, NV, Denmark.
authors.forename: Merete
authors.initials: M
authors.lastname: Haedersdal
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D004337:Drug Carriers / Q000737:chemistry*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D053685:Laser Therapy; D054020:Lasers, Gas; D012867:Skin / Q000528:radiation effects; D034421:Sus scrofa; D041623:Tomography, Optical Coherence / Q000379:methods*
chemical_list: D004337:Drug Carriers
keywords: Ablative fractional laser; Contrast agent; Drug delivery; Drug vehicles; Microscopic treatment zones; Optical coherence tomography