Figure 4
ToF–SIMS data of double corneocyte layer in tape strip sample. (a) Depth profiles of proteins (black), tape (green), C24:0 (blue) and C18:1 (red) from two measurements of the same tape strip sample, attributed to a single corneocyte layer (crosses) and a double corneocyte layer (circles). Note the matching intensity maxima of the two C24:0 profiles at t ≈ 95 s, and the presence of another maximum for the double layer profile at approximately twice the sputter time, t ≈ 180 s. (b) Caffeine depth profiles of the same measurements as in (a), attributed to single (red crosses) and double (blue circles) corneocyte layers. (c) SEM micrograph of tape strip sample after 180 s sputter erosion, i.e., well over the sputter time needed to remove most of a single corneocyte layer. (d,e) SEM image as in (c) with superimposed ToF–SIMS images, showing proteins in red, tape in blue and SC lipids (C24:0 + C26:0) in green, of the same area (d) prior to sputter erosion (t = 0 s), and (e) after sputter erosion (t = 180 s).
