Thermal Properties of Lipid Bilayers Determined Using Upconversion Nanothermometry

Abstract

Luminescent nanomaterials have shown promise for thermal sensing in bio-applications, yet little is known of the role of organic coatings such as supported lipid bilayers on the thermal conductivity between the nanomaterial and its environment. Additionally, since the supported lipid bilayer mimics the cell membrane, its thermal properties are fundamentally important to understand the spatial variations of temperature and heat transfer across membranes. Herein we describe a new approach that enables direct measurement of these thermal properties using a LiYF4:Er 3+ /Yb 3+ upconverting nanoparticle encapsulated within a conformal supported lipid bilayer and dispersed in water as a temperature probe yielding the temperature gradient across the bilayer. The thermal conductivity of lipid bilayer was measured as function of the temperature, being 0.20±0.02 W·m -1 ·K -1 at 300 K. For the uncapped nanoparticles dispersed in water, the temperature dependence of the thermal conductivity was also measured in the 300-314 K range as [0.63-0.69]±0.11 W·m -1 ·K -1 . Using a lumped elements model, we calculate the directional heat transfer at each of the system interfaces, namely nanoparticle-bilayer and bilayer-nanofluid, opening a new avenue to understand the membrane biophysical properties as well as the thermal properties of organic and polymer coatings.

Probing and manipulating embryogenesis via nanoscale thermometry and temperature control

“…Independent simulations confirmed that heat-convection effects are negligible on these length scales, and we did not observe clearly distinguishable features caused by variations in the local thermal conductivity within the cell. This is presumably because the cell environment is predominantly water, while cell membranes are thin and have thermal conductivities on the same order of magnitude as water (41). By overlaying the temperature map with early embryo images, the average and nucleus temperatures of different cells can be calculated (SI Appendix, Fig.…”

Remarkable Thermal Conductivity Enhancement in Carbon-Based Ionanofluids: Effect of Nanoparticle Morphology

“… 13 Thus, it can be considered as a thermal bridge between base liquid and solid nanoparticle, increasing the thermal conductivity of nanofluids/ionanofluids. 28 , 29 The molecular dynamics studies showed that several solvation layers are near the nanocarbon–IL interface, and both cations and anions were found in the first interfacial layer interacting with the carbon nanomaterials. 14 , 30 Moreover, molecular dynamics studies showed that IL forms different structures inside of CNTs depending on nanotubes diameter.…”

In situ measurement of intracellular thermal conductivity using heater-thermometer hybrid diamond nanosensor

“…One of the essential factors in the calculation is the thermal conductivity, a parameter determining the heat flux and usually assumed to be about 1 Wm -1 K -1 , similar to a watery environment. However, Bastos et al have used upconverting nanoparticles 25 to measure the thermal conductivity of a single lipid bilayer and reported a value of 0.2 Wm -1 K -1 . Theoretically, the thermal conductivity in cells can be about six times smaller than that in water when the boundary heat resistance, or Kapitza resistance is considered 24 .…”