Abstract:
Small multi-cellular organisms such as nematodes are emerging models for a variety of biomedical applications. Small size, optical transparency of organs, ease of culture, and the capability to develop and respond to environmental parameters make them attractive models for a variety of cellular, genetic and pharmacological studies. This work demonstrates the unique features of dielectrophoresis, the induced motion of polarisable particles in non-uniform electric fields, to manipulate embryonic nematodes in a microfluidic platform. The system took advantage of curved chromium/gold microelectrodes patterned on a glass slide to produce dielectrophoresis, and a polymeric microchamber integrated onto the glass slide to harbour nematodes. The microchamber was filled with a 200 µm of nematode sample while the microelectrodes were energised with an AC signal of 8-10 Vp-p and 20 MHz. The nematodes eggs exhibited positive dielectrophoretic response, and were immobilised at the delta-shaped region between the curved microelectrodes within 10-15 minutes. After immobilisation process, the magnitude of AC signal was reduced to 3-4 Vp-p to minimise the negative impact of electric field, facilitate the normal embryo development, and eventually hatching of nematode eggs within 2-6 hours. The trapping force was not strong enough to immobilise the nematode worms at the microelectrodes. However, reducing the frequency to 0.1-1 MHz led to immediate immobilisation and stretching of worms between the microelectrodes. The demonstrated system enables the real-time, non-invasive imaging of developing multi-cellular organisms, and studying the response of eggs/worms to different chemical stimuli.