A Novel 3D Transmembrane Organic Electrochemical Transistor for Monitoring Growth of Fibroblast Cells

Three-dimensional cell culture and in-vitro bioelectronic systems have made significant developments for monitoring and predicting biological activity for various applications. Bioelectronic devices such as have been extensively researched based on 2D films of electrically conducting or organic semiconductor films, while tissue engineering has developed 3D structures for cell culture, such as porous scaffolds, hydrogels and fibre meshes to better mimic human tissue physiology. In this work, we present a novel bioelectronic device encompassing the benefits of both domains and is based on a 3D microporous scaffold with the conducting polymer PEDOT:PSS integrated into an organic electrochemical transistor.
The 3D scaffold serves as the separator membrane to compartmentalize different cell cultures, the tissue-like cell growth medium as well as acts as an electronic element for recording cell growth and assessing tissue integrity. We demonstrate the design, fabrication and electrical characterization of the transmembrane 3D-OECT, which demonstrates up to 20 mA drain current and was characterized for 3D scaffolds with different thicknesses (100-500 µm), different polymers to show both p-type and n-type operation, gate electrodes with different materials and different contact electrode areas.
The device can be used to continuously monitor the growth of fibroblast cells and the growth of the surrounding ECM over 10 days, with a clear electrical signal change in the drain current for static characterization and the time constant extracted from the transient response of the 3D-OECT. We have monitored the difference in cell growth for different initial cell densities (125k, 250k and 500k cells) and distinctly show different patterns in cell growth, migration and ECM production depending on the density of the cells in the scaffold. The results have been well correlated with biological assays such as immunofluorescence imaging and DNA quantification.