Quantitatively Monitoring In Situ Mitochondrial Thermal Dynamics by Upconversion Nanoparticles

Abstract

Temperature dynamics reflect the physiological conditions of cells and organisms. Mitochondria regulate the temperature dynamics in living cells as they oxidize the respiratory substrates and synthesize ATP, with heat being released as a byproduct of active metabolism. Here, we report an upconversion nanoparticle-based thermometer that allows the in situ thermal dynamics monitoring of mitochondria in living cells. We demonstrate that the upconversion nanothermometers can efficiently target mitochondria, and the temperature-responsive feature is independent of probe concentration and medium conditions. The relative sensing sensitivity of 3.2% K–1 in HeLa cells allows us to measure the mitochondrial temperature difference through the stimulations of high glucose, lipid, Ca2+ shock, and the inhibitor of oxidative phosphorylation. Moreover, cells display distinct response time and thermodynamic profiles under different stimulations, which highlight the potential applications of this thermometer to study in situ vital processes related to mitochondrial metabolism pathways and interactions between organelles.

Spatiotemporally Mapping Thermodynamics of Lysosomes and Mitochondria using Cascade Organelle-Targeting Upconversion Nanoparticles

“…FCCP is an inhibitor of mitochondrial oxidative phosphorylation, as it disrupts the ATP synthesis by transporting protons across the mitochondrial inner membrane [34]. LysoDots and MitoDots not only revealed the significant increase of both the lysosomal and mitochondrial temperature by almost 3~7 °C in the first 10 min after adding 10 μM FCCP (P < 0.0001 by Students' t-test, Figure 4G, magenta and orange lines), but also mitochondria release a large amount of heat, which is consistent with the previous observation [26], but with higher accuracy using MitoDots. A clear delay by approximately 1~2 min in the time domain during the process of both temperature increase (0-6 min) and decrease (10-14 min) between lysosomes and mitochondria.…”

Opto-thermal technologies for microscopic analysis of cellular temperature-sensing systems

“…Finally, there remains substantial room for the development of advanced optical heaters and thermometers. Intracellular thermometry reported 1 °C or greater local temperature gradients in both stimulated and non-stimulated cells at the organelle level, such as in nuclei (Okabe et al 2012;Nakano et al 2017) (see also Vu et al 2021 for the controversial result), mitochondria (Okabe et al 2012;Kiyonaka et al 2013;Homma et al 2015;Nakano et al 2017;Huang et al 2018Huang et al , 2021Chrétien et al 2018Chrétien et al , 2020Savchuk et al 2019;Di et al 2021), and ER/SR (Kiyonaka et al 2013;Arai et al 2014;Itoh et al 2016;Hou et al 2017;Kriszt et al 2017;Oyama et al 2020). However, these experimental results largely contradict to the estimates based on the theories of macroscopic heat transfer, which expect the local temperature rises of the orders of 10 −4 to 10 −5 °C.…”

Post-functionalization of drug-loaded nanoparticles prepared by polymerization-induced self-assembly (PISA) with mitochondria targeting ligands

“…Several mitochondriotropic moieties such as dequalinium (DQA), triphenylphosphonium (TPP), and mitochondrial penetrating peptides and proteins have been linked to nanotechnology. DQA and TPP are both cationic and lipophilic molecules and therefore able to easily pass the mitochondrial membrane [ 15 – 19 ]. TPP is the most-studied mitochondrial targeting agent and has shown to accumulate 1000 times more in the mitochondrial matrix than in the cytosol [ 20 ].…”