Insect cells as sensors for environmental toxins

The rising demand for plant-based nutrition world-wide requires the deployment of pesticides, in order to protect the crops and plant products from harmful organisms. Safe and high-quality harvests are not possible without targeted plant protection measures. On the other hand, it is a proven fact that large-area deployment of pesticides has caused a significant reduction of the insect population. The decrease of the wild bee population is especially problematic, since wild bees are significant pollinators, and as such an essential prerequisite for agricultural production. 

Multielectrode array with integrated impedance electrodes for testing insecticide effects in 96-well format
© Fraunhofer EMFT / Bernd Müller
Multielectrode array with integrated impedance electrodes for testing insecticide effects in 96-well format

Pesticides shall become more „bee-friendly“

The obvious solution to this dilemma between necessary plant protection and insect protection is the development of pesticides without insecticide effects. The Fraunhofer EMFT scientists support the development of such „bee-friendly“ pesticides by doing research on sensor technologies identifying „bee-harmful“ substances in early phases of pesticide development. The sensors are supposed to detect the insecticide effects within hours, due to their extremely short reaction times, while enabling parallel analysis of small substance libraries.

Insect cells as sensors

Moth cells on a circular electrode
© Fraunhofer EMFT
Moth cells on a circular electrode

The concept is based on the use of insect cells as sensors. The cells isolated from insects can be multiplied in the lab indefinitely, and are thus available in unlimited amounts. The cells are only few micrometers in diameter but still possess the metabolism characteristic to the insects they were originally isolated from. Exposed to a potentially harmful substance, they show how it affects cell metabolism. In order to measure these effects, the suspended, isolated insect cells are placed in a vessel with microelectrodes prepared on its bottom. These electrodes enable real-time electrochemical impedance measurements monitoring the time course of cell adhesion on the electrode surface. The adhesion process is very sensitive to harmful interferences affecting the cell metabolism, allowing for fast identification of insecticidal effects without lengthy lab times. Unlike typical biosensors, which are used to measure the concentration of a substance, this approach measures the biological impact of the substance on the cells of a certain insect species. This approach is basically applicable to cells of various insect species, so that the use of multielectrode arrays will enable the parallel assessment of insecticidal effects of a candidate compound on various insect species in the future.

Outlook: Complete efficacy profile instead of mere toxicity measurement

Scheme for testing insecticidal effects
© Fraunhofer EMFT
Scheme for testing insecticidal effects

Besides providing basic proof of an insecticide impact, the sensor technology presented here shall be applicable for multiparameter analysis of various cell functions (phenotypes) later in the project. Through modifications in the assay work flow and by applying different AC frequences in the measurement, the impedance signals reveal changes in cell proliferation, cell migration or cell motility. This would enable the compilation of a complete efficacy profile of the substance, beyond sole measurement of toxic effects.

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