Luminescent molecular thermometers for the ratiometric sensing of intracellular temperature

Abstract

<jats:title>Abstract</jats:title><jats:p>Recently, numerous luminescent molecular thermometers that exhibit temperature-dependent emission properties have been developed to measure the temperatures of tiny spaces. Intracellular temperature is the most interesting and exciting applications of luminescent molecular thermometers because this temperature is assumed to be correlated with all cell events, such as cell division, gene expression, enzyme reaction, metabolism, and pathogenesis. Among the various types of temperature-dependent emission parameters of luminescent molecular thermometers, the emission intensity ratio at two different wavelengths is suitable for accurate and accessible intracellular temperature measurements. In this review article, luminescent molecular thermometers that exhibit a temperature-dependent emission intensity ratio in living cells are summarized, and current progress in intracellular thermometry is outlined.</jats:p>

Whither Magnetic Hyperthermia? A Tentative Roadmap

“…Luminescence thermometers are probably the best option for non-contact high spatial resolution thermometry in general [155] and intracellular thermometry in particular [156]. There are several types of luminescent thermometric probes according to their nature: luminescent molecules (organic molecules such as dyes, proteins like green fluorescence protein, GFP), inorganic compounds (quantum dots, Si-dots, nanodiamond, lanthanides) or hybrid molecular or particulate materials.…”

“…There are several ways to implement luminescence nanothermometry into a magnetic nanoheater: the dual-particle approach and the single-particle approach [157]. There are also several kinds of temperature measuring [155][156][157]169]: indirect single temperature value, direct instant, continuous measurements of temperature changes, and in situ ratiometric absolute temperature measurements. In the next section, we will consider the best available options so far for magnetic hyperthermia applications.…”

“…As introduced in Section 7.2, several types of materials have been proposed as temperature nanoprobes [156], some of them have been even used for intracellular thermometry [170], i.e., ER thermo yellow [171], but only a few have been actually used in local magnetic hyperthermia studies [170]. For instance, reports of a 15 • C temperature gradient were reported on Mn-ferrite NPs attached to the membrane of HEK 293 cells 15 s after the application of AC fields using DyLight549 as a thermometric probe [164].…”

“…Moreover, the simultaneous use of nanoheaters and nanothermometers could be employed to investigate phenomena of heat transfer at the nanoscale, which is actually an unexplored territory and the object of intense debate, especially concerning intracellular heat transfer [153,154]. The recent development of rare-earth-doped luminescent MNPs has introduced a new field in thermal biosensing, implying less invasive experiments, not only in living cells but also in more challenging small animal models [155][156][157][158]. Joining thermometry and heating at the nanoscale can also be particularly interesting for the development of high-performance non-invasive hyperthermia therapy based on the local heating of specific intracellular sites to provoke cell apoptosis, without the need of overall massive heating of the whole cancer tumor.…”

Thermo-Responsive Fluorescent Polymers with Diverse LCSTs for Ratiometric Temperature Sensing through FRET

“…To a solution of BOBPYOH (2 mmol, 0.86 g) and triethylamine (3 mmol, 0.3 g) in dichloromethane (20 mL) acryloyl chloride (20 mmol, 1.8 g) was added slowly and stirred for 0.5 h at 0 • C. Then the reaction was stirred further at room temperature for 12 h. The mixture was treated with water and the organic layer was separated. The aqueous layer was extracted with dichloromethane and the combined organic layer was washed with saturated aqueous NH 4 Cl, brine, and dried over anhydrous Na 2 SO 4 . The solvent was removed by rotary evaporation and the residue was purified by silica gel column chromatography (dichloromethane/n-hexane = 10:1) to afford BOBPYBX (yield was 35.5%).…”