Development of a hydrogel-enabled impedance biosensor for cellular spheroid monitoring

Three-dimensional (3D) cellular models require sensing approaches capable of probing volumetric features beyond conventional cell-electrode interfaces. This thesis presents a bioelectronic impedance sensing platform combining PEDOT:PSS microelectrodes with micropatterned hydrogel, with the aim of extending the spatial sensitivity of impedance measurements towards 3D cellular structures. A microfabrication protocol was developed to integrate the electrode, PEDOT:PSS and hydrogel into a single device, and the resulting platform was electrically and biologically characterized. The spatial sensing capability was investigated using a vertically displaced insulating rod as a controlled model object. Numerical modelling was used to interpret these results and explore the response to cellular spheroids, combining Finite Volume Method (FVM) simulations of the electric field and current distribution with equivalent-medium modelling of spheroid impedance. Overall, this work demonstrates the physical principle and echnological feasibility of hydrogel-mediated spatial confinement of impedance sensing, while providing a basis for optimizing the device geometry towards a balance between electrical performance and the biological requirements of 3D cellular models.