<p>We report the fundamental electrical characteristics of an organic electrochemical transistor (OECT) with a porous-structured PEDOT:PSS channel, which was simply fabricated by freeze-drying, for biosensing applications. The fabricated device not only showed typical OECT characteristics but also responded to various cations and hydrogen peroxides with the change in each of their concentrations. Such electrical responses were substantially based on the variation in the redox state of PEDOT. The porous-structured channel can be utilized as an electroactive scaffold for 3D cell cultures, allowing the electrical monitoring of cellular functions based on ion fluxes and redox reactions.</p> Graphical abstract <p></p>