Functionalized Bioink with Optical Sensor Nanoparticles for O2 Imaging in 3D‐Bioprinted Constructs

Research on 3D bioprinting of living cells has strong focus on printable biocompatible materials and monitoring of cell growth in printed constructs, while cell metabolism is mostly measured in media surrounding the constructs or by destructive sample analyses. Bioprinting is combined with online imaging of O2 by functionalizing a hydrogel bioink via addition of luminescent optical sensor nanoparticles. Rheological properties of the bioink enable 3D printing of hydrogel layers with uniform response to O2 concentration. Co‐immobilization of sensor nanoparticles with green microalgae and/or mesenchymal stem cells does not affect cell viability over several days. Interference from microalgal autofluorescence on the O2 imaging is negligible, and no leakage or photobleaching of nanoparticles is observed over 2–3 days. Oxygen dynamics due to respiration and photosynthesis of cells can be imaged online and the metabolic activity of different cell types can be discriminated in intact 3D structures. Bioinks containing chemical sensor particles enable noninvasive mapping of cell metabolism and spatiotemporal dynamics of their chemical microenvironment in 3D‐printed structures. This major advance now facilitates rapid evaluation of cell activity in printed constructs as a function of structural complexity, metabolic interactions in mixed species bioprints, and in response to external incubation conditions. Bioinks can be functionalized by addition of luminescent O2 sensing nanoparticles, and show excellent printability and biocompatibility in 3D bioprinting. This enables imaging of the spatiotemporal dynamics of O2 concentration, which can be mapped across complex 3D‐bioprinted constructs containing living cells. Such sensor‐functionalized bioinks facilitate a wide range of novel applications in 3D bioprinting and additive manufacturing.