Development of a versatile in vitro platform for studying biological systems using micro-3D printing and scanning electrochemical microscopy.

We report a novel strategy for studying a broad range of cellular behaviors in real time by combining two powerful analytical techniques, micro-3D printing and scanning electrochemical microscopy (SECM). This allows one, in microbiological studies, to isolate a known number of cells in a micrometer-sized chamber with a roof and walls that are permeable to small molecules and observe metabolic products. In such studies, the size and spatial organization of a population play a crucial role in cellular group behaviors, such as intercellular interactions and communication. Micro-3D printing, a photolithographic method for constructing cross-linked protein microstructures, permits one to compartmentalize a small population of microbes by forming a porous roof and walls around cells in situ. Since the roof and walls defining the microchamber are porous, any small molecules can freely diffuse from the chamber to be detected and quantified using SECM. The size of the chamber and the roof permeability can be obtained by SECM using a small probe molecule, ferrocenemethanol (FcMeOH). The chamber permeability to FcMeOH can be tuned by varying printing parameters that influence the cross-linking density of the proteinaceous material. These analyses establish a versatile strategy as a sensitive platform to quantitatively monitor small molecules produced by microbes.