Figure 7. 3D mapping of fluorescently labeled Ag nanoparticles in cleared human skin tissues after 24 h exposure.

Biotinylated Ag nanoparticles (~20 nm) labeled with Alexa Fluor 647-conjugated streptavidin were applied to wounded human skin biopsies, then imaged in 3D on a light sheet fluorescent microscope (LSFM) after tissue immunolabeling and clearing. Large deposits of Ag ENMs remaining in and around the wound site are visible in both (a) 3D reconstruction and (b) optical sections of a wounded skin biopsy. (c-f) No apparent Ag localization was observed in regions with hair follicles and sweat glands at the wound surface (h, green = 488 nm autofluorescence). White arrowheads indicate the epidermal boundary of the wound site. Wound diameter = 2 mm. (g) Within the wound site (top view), 85% of exposed dermal surface area is covered by Ag ENMs, while only 2% of intact epidermal surface area is covered (503 light sheet sections from 2 wounded skin samples). (h) Ag ENMs remained confined to the superficial papillary dermis and did not permeate into the deeper dermal layers (mean < 500 μm; 12 ENMs from 4 light sheet sections of 2 wounded skin samples). Error bars are SEM.