Insects are a major part of the planet's ecosystem and their vital role as pollinators
for agriculture is undisputed. Alongside factors as climate change or loss of habitats,
rising use of pesticides emerges as a key threat to insect populations. For fighting
this man‐made problem, development of an easy, fast, sensitive, and non‐invasive
biosensor for determining pesticide toxicity may help to ban harmful substances and
formulations. Here, a biosensor based on Sf21 (Spodoptera frugiperda) insect cells as
sensors and electric cell‐substrate impedance sensing (ECIS) as physical transducer is
described. Sf21 cell suspensions and well‐defined pesticide solutions were mixed
immediately before seeding on planar gold‐film electrodes. The capacitance at
20 kHz was recorded as a function of time as a measurand for cell adhesion
providing dose–response profiles of pesticide impact. For future in‐field applications,
decoupling of the cell culture routines from the actual cytotoxicity assay is
mandatory. Thus, suspensions of Sf21 cells were cryopreserved at –80°C in the
wells of multielectrode arrays and thawed anytime for conducting the assays. Five
pesticides were tested for their concentration‐dependent cytotoxicity expressed as
EC50 values by ECIS and validated using the well‐established WST‐1 cell viability
assay. Results were found to be in good agreement. Our studies revealed cytotoxic
effects of some pesticides sold for home usage far below the recommended
concentration and were found to be more toxic than formulations sold for
agricultural industry only.