Fig. 2

mSHS can increase the load of PpIX and coumarin 6 dramatically and enhanced skin penetration of coumarin and PpIX in vitro. a Visualization of mSHS@PpIX at different concentration of the PpIX. Scale bar was 100 µm. b Visualization of mSHS@coumarin 6 at different concentration of the coumarin 6. Scale bar was 100 µm. c Skin penetration of PpIX using SHS and mSHS in vitro. SC denotes 1–10 tape strip, Epi denotes the epidermis, Der denotes the dermis, and Rec denotes the receptor. ***represents p < 0.001. d Coumarin 6 penetrates different skin layer in vitro. e Visualization of skin delivery of PpIX. Scale bar was 100 µm f Visualization of skin delivery of coumarin 6. g The internalization of PpIX in B16 cells over time. Scale bar was 50 µm. h Cell viability of B16 cells at different concentrations of PpIX