Influence of experimental parameters on in vitro human skin permeation of Bisphenol A

Bisphenol A (BPA) in vitro skin permeation studies have shown inconsistent results, which could be due to experimental conditions. We studied the impact of in vitro parameters on BPA skin permeation using flow-through diffusion cells with ex-vivo human skin (12 donors, 3–12 replicates). We varied skin status (viable or frozen skin) and thickness (200, 400, 800 μm), BPA concentrations (18, 250 mg/l) and vehicle volumes (10, 100 and 1000 μl/cm2). These conditions led to a wide range of BPA absorption (2%–24% after 24 h exposure), peak permeation rates (J = 0.02–1.31 μg/cm2/h), and permeability coefficients (Kp = 1.6–5.2 × 10−3 cm/h). This is the first time steady state conditions were reached for BPA aqueous solutions in vitro (1000 μl/cm2 applied at concentration 250 mg/l). A reduction of the skin thickness from 800 and 400 μm to 200 μm led to a 3-fold increase of J (P 0.05). Previously frozen skin led to a 3-fold increase in J compared to viable skin (P