Upon buffer addi on, a glass-gel interface, represen ng the water penetra on front, is visible as a discrete change in the shade of color within the film (Figure , visible at 1, 2 and 5 min). The buffer coefficient values in the coefficients plots provide addi onal evidence of this water penetra on front, also at the la er me points. The water penetra on was, however, much slower for the ASD with 60% drug loading than for both the 20 and 40% drug loadings, with the penetra on front appearing at approximately -17 µm, -27 µm, -42 µm, -55 µm, -76 µm, -84 µm and -94 µm from the original interface at 1, 2, 5, 10, 15, 20 and 30 min, respec vely (also see Figure , in the Suppor ng Informa on). In addi on to the slower water penetra on, the buffer coefficient values suggest the water concentra on in the gel was also lower across the gel phase at all me points, presumably due to the higher content of the hydrophobic drug. Water penetra on was also associated with gradual film swelling up to approximately 18 µm a er 30 min. Interes ngly, the swelling is on the same order of magnitude as the lower drug loadings, and appears to be limited by the drug enriched matrix surface at all three drug loadings.