Figure 3
3D distributions of caffeine and JAD in lipid matrix versus corneocytes. (a) Fraction of actives detected in the top lipid region relative to the combined top lipid and corneocyte regions, estimated from the depth profiles as the ratio of measured intensities in the lipid region (t = 0–7 s) to total intensities in the lipid and corneocyte region (t = 0–62 s). The protein results represent the expected ratio for corneocyte localization, whereas higher values correspond to increasing fractional localization to the lipid matrix. Mean values and error bars corresponding to +/− 1 standard deviation (N = 3). (b) Depth profiles (from TS2) of JAD (red), protein (blue) and C18:1 (green), together with a fit to the JAD profile (black) given by a weighted sum of the protein profile and C18:1. (c) Depth profile of caffeine (same measurement as in (b)), where the black line is a fit using the protein depth profile only. (d) Ion images acquired from tape strip sample (TS2) after t = 60, 90 and 120 s of sputter erosion, showing proteins, tape, C18:1 and overlay images of caffeine (red) and JAD (green). Note the correlation between the distributions of C18:1 and JAD, whereas the distribution of caffeine is homogeneous across the protein-covered parts of the surface.
