Near-Infrared-Light-Assisted Photothermal Polymerization for Transdermal Hydrogelation and Cell Delivery

Photopolymerization of hydrogels has been widely used to encapsulate cells and support their growth in 3D environments. However, common light sources (i.e., ultraviolet and visible light) strongly interact with biological systems and are therefore inappropriate for in vivo applications, such as transdermal polymerization. Using near infrared (NIR) light that minimally interacts with living tissues, this study investigates NIR light-assisted photothermal polymerization (NAPP) of diacrylated polyethylene glycol (PEGDA), in which interactions between NIR light and gold nanorods activate a thermal initiator (i.e., AIPH), resulting in generation of radicals for polymerization of PEGDA. Gelation parameters, including precursor concentrations and NIR power, are investigated to minimize the use of initiator and temperature increases (<43 °C) during NAPP. Cell viability is as high as 80% after NAPP-based encapsulation. Incorporation of polyethylene glycol (PEG) modified with a cell-adhesive peptide moiety (Arg-Gly-Asp) into the gel system further enables prolongation of cell viability during incubation up to 7 d. NAPP results in successful transdermal gelation and good viability of the transplanted cells. Thus, this new cell encapsulation approach, demonstrated for the first time in this study, will benefit various applications, including cell delivery and remote control over cellular environments.