Internal 3D temperature mapping in biological systems using ratiometric light-sheet imaging and lipid-coated upconversion nanothermometers

Upconversion nanoparticles (UCNPs) are well-known for their high efficiency, photostability, near-infrared excitation, and ability to estimate temperature through ratiometric imaging of two thermally coupled fluorescence bands. This work demonstrates the feasibility of volumetric temperature mapping in internal biological systems using light-sheet fluorescence microscopy and lipid-coated UCNPs as nanothermometry markers. This approach enables real-time thermal mapping with both high spatial and temporal resolution at the cellular and subcellular levels. To validate the method, we performed 3D temperature imaging on fixed <i>Caenorhabditis elegans</i> (<i>C. elegans</i>) after UCNP ingestion. The proposed technique represents a cutting-edge method for accurate 3D analysis of temperature-driven biological processes. It holds significant potential for applications in living organisms, offering a non-invasive tool to monitor intracellular and organ-specific temperature dynamics.