Fig. 3.

Relative skin recovery of model biomarkers. The relative skin recovery of: (a) interleukin (IL)-1α, (b) IL-6, (c) IL-17 and (d) tumour necrosis factor (TNF)-α calculated from the absolute skin recovery of the biomarkers with background tissue levels subtracted and the concentration of the corresponding reference solutions injected: IL-1α: 0, 233, 700 and 2,100 pg/ml; IL-6: 0, 384, 960 and 2,400 pg/ml; IL-17: 0, 560, 1,400 and 3,500 pg/ml; and TNF-α: 0, 561, 1,404 and 3,510 pg/ml. Dialysate concentrations were determined by enzyme-linked immunoassay (ELISA). Data are depicted as individual samples (triplicate probes for each biomarker concentration injected and every setup was repeated in skin specimens from 3 donors) with mean ± standard deviation. Symbols represent different skin donors (● D4, ▪ D18, ▴ D20). Open symbols indicate values below the lower limit of quantification (LLOQ) and × denotes outliers, which were omitted from statistical analyses. p-values are obtained from a 2-way analysis of variance (ANOVA) followed by Tukey’s multiple comparison test comparing the mean relative skin recoveries after injection of different reference solutions.