Figure 5. Impact of skin phototypes on biomedical optics.

a, Decreased energy of 680 nm, 800 nm, and 1064 nm lasers due to light absorption by mimicked skin phototypes. The error bars represent the standard deviation of three individual samples. Photograph shows 3D-bioprinted skin phantoms with different skin phototypes (from Fitz. 1 to 6). b, μ_a and μ_s΄ (solid lines) values of Fitz. 1, 3, and 5 skin phantoms. The dotted lines represent the tunable range of μ_a and μ_s΄ by adjusting PDA content in the epidermis. c, PA image of MB dye covered by Fitz. 1, 3, and 5 skin phantoms. Yellow dotted area remained uncovered showing no decrease in the laser power. The scale bars (x, y, z) represent 4 mm. d, PA signal attenuation of MB and ICG dyes by Fitz. 1, 3, and 5 skin phantoms. The error bars represent the standard deviation of six regions of interests. e, PA image of MB dye in a 5-mm-thick phantom covered by Fitz. 1, 3, and 5 skin phantoms. The scale bars (x, y, z) represent 4 mm. f, PA signal attenuation of MB and ICG dyes at different imaging depths from 1 to 5 mm. MB and ICG dyes (10 mM) were covered by Fitz. 1, 3, and 5 skin phantoms. The error bars represent the standard deviation of six regions of interest. g, PA signal attenuation of real human blood. Human blood in the blood vessel scaffold was covered by Fitz. 1, 3, and 5 skin phantoms. Yellow-dotted area remained uncovered as a negative control. The error bar represents the standard deviation of six regions of interest. h, Fluorescence attenuation of Cy5.5 and ICG dye by mimicked skin phototypes. Insert images show that Cy5.5 and ICG dyes were covered by phantoms with different skin phototypes from Fitz. 2 (left) to the Fitz. 5 (right). The scar bar represents 5 mm. i, Impact of skin phototypes on photothermal therapy. NIR-I (808 nm) and NIR-II (1064 nm) lasers were used for the test. Fitz. 0 indicates the phantom without synthetic melanin. The experiments in a, d, f, g, h, and i were repeated independently three times with similar results.