High-resolution thermal sensing and bioimaging at the cellular level and in animal models (in vivo applications) is interesting for both early diagnosis and controlled treatment via photothermal conversion. Despite excellent in vitro results have been obtained with visible emitting luminescent nanothermometers, their application for in vivo studies is very limited due to the reduced penetration depth of visible light in biological tissues. This can be overcome if materials with emission and absorption bands lying in the so-called first and second biological windows, corresponding to the 650-950 and 1000-1350 nm spectral ranges, respectively, where tissue scattering and absorption are minimized. Here we present the last results we obtained in luminescence nanothermometry and bioimaging in the first and second biological spectral windows using specially oxide-based materials, such as monoclinic double tungstates and tetragonal Gd vanadate nanoparticles doped with Tm3+, Ho3+, and Nd3+, in some cases sensitized with Yb3+. The results show that high thermal sensitivity can be obtained in the first biological window with Tm3+, Yb3+:GdVO4@SiO2 nanoparticles using up-conversion excitation mechanisms, and that the inert shell plays an important role in improving the thermal sentivity and resolution. We will also show that Nd3+:KGd(WO4)2 capped with APTES molecules can be used for luminescent thermometry with good sensitivity in both the first and second biological windows. Furthermore, these nanoparticles can also be used for bioimaging specially in the first biological window, achieving a penetration depth of ~1 cm. Tm3+,Ho3+:KLu(WO4)2 nanoparticles have been explored also as luminescent thermometers and bioprobes in these spectral ranges. The results achieved indicate that these nanoparticles can also be used as photothermal agents. In this field, we used an integrating sphere to determine in an easy and fast way the photothermal conversion efficiency of photothermal agents, including Au nanoparticles and graphene derivatives.

New luminescence nanothermometers in different biological windows

253rd National Meeting (2017)

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