Measuring the bite force of tiny nematodes using nanoparticle technology

A team of materials scientists, physicists, mechanical engineers, and molecular physiologists at Stanford University has developed nanoparticle technology that can be used to measure the force dynamics inside living things, such as worms as they chew on their food.

In a paper published in the journal Nature, the group describes how they used infrared light to excite luminescent nanocrystals in a way that allows them to measure the energy levels of cells within the C. elegans body.

Andries Meijerink of Utrecht University published a News & Views article in the same magazine issue outlining the research conducted by the California team.

As Meijerink points out, being able to measure forces inside living things could go a long way in helping us better understand internal molecular processes. Such efforts have so far been hampered by the need for remote sensing over variable ranges and scales. In a new study, the researchers found a way around such problems and measured muscle forces inside the C. elegans’ digestive tract.

This study built on previous work that showed that light from light-emitting molecules can be used for remote sensing if the emission spectrum is affected by certain physical changes such as temperature or pressure. They embedded erbium and ytterbium nanocrystals into tiny polystyrene spheres, about the same size as bacteria, and fed them to nematodes. The size of the sphere allowed it to pass through the insect’s digestive system until it reached a structure known as a grinder. A grinder, as the name suggests, grinds up the food that the insect body eats.

According to the researchers, the grinder is operated by tensing and releasing the muscles beneath it. The spheres introduced by the researchers penetrated such muscles. The researchers then monitored the nanocrystals through a small fluorescence-reading microscope while the grinder was running.

This allowed the research team to measure changes in the spectra of luminescent molecules when the worm applied the grinder. They were then able to use such changes to calculate how much energy is being used by the worm’s grinder muscles. They found that the occlusal force was approximately 10 µN.

The research team concludes by showing that their study can measure force dynamics inside organisms, suggesting that this could lead to new approaches to studying internal biological processes. .

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