Combining CdTe/CdS/ZnS Quantum Dot Fluorescence Temperature Measurements with Double-Helix Point Spread Function Axial Location for Intracellular 3D Thermograms

Intracellular three-dimensional (3D) thermal mapping is a valuable technical tool for answering fundamental scientific questions about cellular thermal behavior and subcellular diagnostic therapy. The best method for achieving intracellular 3D thermal imaging is to collect intracellular temperature response while also obtaining a 3D position for the corresponding location. However, temperature measurement in cell space has not been accurately characterized due to the difficulty in accurately locating the 3D position in microregions. In this article, we developed a QD-based intracellular 3D thermal imaging system by combining QD fluorescence thermometry with double-helical point spread function (DH-PSF)-based axial localization. Liposome transfection was used to achieve the cellular uptake of CdTe/CdS/ZnS QDs in HOS cells. Five QDs’ temperatures with spatial distribution in living cells were realized in the axial range of 1.35 μm by collecting the thermosensitive fluorescence emission of discrete QDs and the axial imaging localization information, and their 3D thermal image distribution was mapped. Measurements and analysis show that the combination of QD fluorescence thermometry and axial localization of DH-PSF enables the acquisition of thermal image information in intracellular 3D microregions. Using this system, temperature variations at 3D locations in living cells exposed to ionomycin Ca²⁺ stress were also monitored. The method described in this article can be applied broadly to the study of intracellular space thermal response and thermal regulation.