In Vivo Visualization of Collagen Transdermal Absorption by a Combined Second-harmonic Generation and Two-photon Excited Fluorescence Method
Abstract The transdermal administration of collagen is an important method used for wound healing and skin regeneration. However, due to the limitations of previous approaches, the process and degree of collagen transdermal absorption could only be quantitatively and qualitatively assessed in vitro. In the present study, we introduced a novel approach combining second-harmonic generation with two-photon excited fluorescence to visualize the dynamics of collagen transdermal absorption in vivo. The high resolution images showed that the exogenous recombinant human collagen permeated through the epidermis, reached the dermis and formed reticular structures in real time. We also validated these findings through traditional in vitro skin scanning and histological examination. Thus, our approach provides a reliable method of measurement for the real-time evaluation of collagen absorption and treatment effects.