Upconverting microgauges reveal intraluminal force dynamics in vivo

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Physiology

Background:

• Muscle action potentials drive physiological processes in luminal structures.
• Current non-invasive techniques struggle to measure forces within these internal body structures.
• Developing new tools is crucial for understanding luminal organ function.

Purpose of the Study:

• To introduce novel, non-toxic, ingestible mechanosensors for studying luminal forces.
• To quantitatively assess feeding forces in living Caenorhabditis elegans (C. elegans) using these sensors.
• To explore the potential of these sensors for broader physiological research.

Main Methods:

• Fabrication of optical 'microgauges' using upconverting nanoparticles (NaY_0.8Yb_0.18Er_0.02F₄@NaYF₄) in polystyrene microspheres.
• In vitro characterization using optical and atomic force microscopy to establish force-response relationship.
• In vivo application in C. elegans, combining fluorescence imaging and non-invasive electrophysiology.

Main Results:

• Microgauges demonstrated a linear, hysteresis-free response to force, altering the ratio of emitted red to green light.
• Adult C. elegans generate feeding bite forces of approximately 10 µN.
• Measured bite forces align with muscle activity and correspond to stresses capable of lysing bacterial food.

Conclusions:

• Ingestible optical microgauges offer a novel, non-invasive method for quantifying forces in luminal organs.
• This technology enables detailed study of feeding mechanics in C. elegans.
• Microgauges hold potential for investigating neuromuscular stresses in various physiological conditions and diseases.