This chapter focuses on two specific areas of organic mixed ion–electron conductors: surfaces and scaffolds for controlling cell cultures, and “iontronic”-controlled delivery of ions and biomolecules. It draws on iontronic technology based on ion exchange materials, which is compatible with physiological salt concentrations. Iontronics is attractive for bioelectronic applications, as it provides a means for the manipulation of flows of ions and charged biomolecules – species that can possess chemical and biological functionality. The organic electronic ion pump (OEIP) is a delivery device where charged (bio)molecules are transported within a polyelectrolyte membrane. The electronic control of the delivery flux, together with micrometer-sized channel outlets, enables OEIPs to achieve high spatiotemporal resolution; biomolecule delivery can be tightly controlled to a specific site and dose amount. High spatiotemporal control of ion and biomolecule concentrations is attractive for a wide range of in vitro studies of biological systems.??