Unveiling in Vivo Subcutaneous Thermal Dynamics by Infrared Luminescent Nanothermometers

Abstract

The recent development of core/shell engineering of rare earth doped luminescent nanoparticles has ushered a new era in fluorescence thermal biosensing, allowing for the performance of minimally invasive experiments, not only in living cells but also in more challenging small animal models. Here, the potential use of active-core/active-shell Nd(3+)- and Yb(3+)-doped nanoparticles as subcutaneous thermal probes has been evaluated. These temperature nanoprobes operate in the infrared transparency window of biological tissues, enabling deep temperature sensing into animal bodies thanks to the temperature dependence of their emission spectra that leads to a ratiometric temperature readout. The ability of active-core/active-shell Nd(3+)- and Yb(3+)-doped nanoparticles for unveiling fundamental tissue properties in in vivo conditions was demonstrated by subcutaneous thermal relaxation monitoring through the injected core/shell nanoparticles. The reported results evidence the potential of infrared luminescence nanothermometry as a diagnosis tool at the small animal level.

LaF3 core/shell nanoparticles for subcutaneous heating and thermal sensing in the second biological-window

“…TEM images also reveal similar size distributions and shapes to those reported by our group in previous works also dealing with LaF 3 NPs fabricated by the same procedure. 11 Nevertheless, this does not affect the working principle demonstrated here. Additionally, the core/shell nature of the LaF 3 NPs synthesized by the adopted procedure has been previously demonstrated by both energy-dispersive X-ray (EDX) and electron paramagnetic resonance (EPR) techniques.…”

“…As a consequence, there has been an increasing interest in the design of multifunctional luminescent NPs capable of simultaneous heating and thermal sensing under single power excitation as they would constitute significant building blocks toward the achievement of real controlled PTTs as well as subcutaneous studies. 11 Despite the continuously growing list of systems that could operate as simultaneous NHs and nanothermometers (NThs), including polymeric NPs, quantum dots, nanodiamonds, metallic NPs, and rare earth-doped NPs, only a few of them show real potential of working subcutaneously. [12][13][14] This is so because most of them operate in the visible spectrum domain, where optical penetration into tissues is minimal.…”

“…Electronic mail: daniel.jaque@uam.es doped LaF 3 NPs and (ii) the infrared luminescence thermal sensing of Neodymium and Ytterbium co-doped core-shell LaF 3 NPs. 11,32 The multifunctional agent here developed aim to join both functionalities in a single nanostructure. The NPs presented herein are based on a core/shell structure with an Yb 3þ doped core (concentration of 10 mol.…”

“…A detailed description of the synthesis procedure can be found elsewhere. 11 By analyzing transmission electron microscopy (TEM) experiments carried out in both single-core and core/shell LaF 3 NPs (not shown for the sake of brevity) we have estimated a core diameter of 15 nm and a shell thickness of 4.5 nm. TEM images also reveal similar size distributions and shapes to those reported by our group in previous works also dealing with LaF 3 NPs fabricated by the same procedure.…”

“…Additionally, the core/shell nature of the LaF 3 NPs synthesized by the adopted procedure has been previously demonstrated by both energy-dispersive X-ray (EDX) and electron paramagnetic resonance (EPR) techniques. 11,33 Under the proposed scheme (see Figure 1(b)), the shell would act as a donor unit absorbing the 808 nm radiation through the 4 I 9/2 ! 4 F 5/2 Nd 3þ absorption.…”