Self-monitored photothermal nanoparticles based on core–shell engineering

Abstract

The continuous development of nanotechnology has resulted in the actual possibility of the design and synthesis of nanostructured materials with pre-tailored functionabilities. Nanostructures capable of simultaneous heating and local thermal sensing are in strong demand as they would constitute a revolutionary solution to several challenging problems in bio-medicine, including the achievement of real time control during photothermal therapies. Several approaches have been demonstrated to achieve simultaneous heating and thermal sensing at the nanoscale. Some of them lack of sufficient thermal sensitivity and others require complicated synthesis procedures for heterostructure fabrication. In this study, we demonstrate how single core/shell dielectric nanoparticles with a highly Nd(3+) ion doped shell and an Yb(3+),Er(3+) codoped core are capable of simultaneous thermal sensing and heating under an 808 nm single beam excitation. The spatial separation between the heating shell and sensing core provides remarkable values of the heating efficiency and thermal sensitivity, enabling their application in single beam-controlled heating experiments in both aqueous and tissue environments.

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

“…For the first experiment, an infrared thermal camera was coupled to the optical set-up in order to record the temperature of the tissue's surface and to demonstrate the differences between subtissue and surface temperatures (the latter being expected to be lower due to heat diffusion processes). 3,32,33 The steady state subtissue and surface temperatures were recorded for different 808 nm power densities and in both cases, a linear relationship was experimentally found (see Figure 3(b)). As expected, there are remarkable differences between subtissue and surface temperature, as demonstrated in previous studies dealing with ex vivo and in vivo PTTs based on heating nanoparticles.…”

“…expected to provide heating capabilities to the nanostructure. 33,36 In order to corroborate this possibility and to demonstrate the dominant role played by Nd 3þ concentration in the light-to-heat efficiency of our NPs, a simple control experiment was conceived. Different core/shell NPs presenting the same Yb 3þ concentration into the core (10 mol.…”

“…As expected, there are remarkable differences between subtissue and surface temperature, as demonstrated in previous studies dealing with ex vivo and in vivo PTTs based on heating nanoparticles. 3,32,33 Since the infrared thermal camera fails to provide a value for the subcutaneous temperature, the use of NThs is extremely necessary for the achievement of an accurate and remote control over PTTs.…”

“…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.…”

Nd 3+ ions in nanomedicine: Perspectives and applications

“…In these NPs, the green Er 3þ emission from the core exhibited better performance at around room temperature, while the NIR emission features of the Nd 3þ :Yb 3þ doped shell were found to be more suitable for temperatures higher than those in the physiological range. Recently E. C. Ximendes et al have also used a core/shell strategy to develop self-monitored photothermal NPs [82]. They used LaF 3 :Er 3þ ,Yb 3þ (core)/LaF 3 :Nd 3þ (shell) NPs capable of simultaneous heating, deep tissue imaging and thermal sensing in the visible range all under 808 nm single beam excitation.…”