Long-Term Imaging of <i>Caenorhabditis elegans</i> Using Nanoparticle-Mediated Immobilization

<div><p>One advantage of the nematode <i>Caenorhabditis elegans</i> as a model organism is its suitability for <i>in vivo</i> optical microscopy. Imaging <i>C</i>. <i>elegans</i> often requires animals to be immobilized to avoid movement-related artifacts. Immobilization has been performed by application of anesthetics or by introducing physical constraints using glue or specialized microfluidic devices. Here we present a method for immobilizing <i>C. elegans</i> using polystyrene nanoparticles and agarose pads. Our technique is technically simple, does not expose the worm to toxic substances, and allows recovery of animals. We evaluate the method and show that the polystyrene beads increase friction between the worm and agarose pad. We use our method to quantify calcium transients and long-term regrowth in single neurons following axotomy by a femtosecond laser.</p>