There are several physical parameters intrinsically related to human health. For instance, certain temperature fluctuations can be used as an early indicator of the development of diseases, such as degenerative processes of the nervous system, acute inflammation caused by infectious agents, and cardiovascular diseases.[1] Hence, thermal monitoring of tissues and organs has emerged as a valuable tool for early detection of threatening diseases.[2,3] Among the main requirements to carry out it, it must be performed remotely, without perturbing the temperature of the tissue while measuring, also avoiding physical alterations of the organ under investigation. [4]
Luminescence thermometry represents an alternative technique that overcomes the limitations affecting other methods (invasiveness; only reporting surface temperature). It is based on the use of luminescent nanothermometers (LNThs) (nanoparticles (NPs), proteins, or dyes whose luminescence is strongly temperature-dependent) as remote thermal reporters. [5,6]. At some point LNThs have been applied for remote thermal sensing in animal models [7] enabling, for instance, non-invasive monitoring of brain activity,[8] diagnosis of ischemic tissues,[19] detection of inflammation processes, and control of thermal therapies of solid tumors.[10,11]
However, in vivo luminescence thermometry is still not yet a completely reliable technique. Not only the presence of biological tissues in the optical path significantly reduces the amount of detected luminescence;[6] more importantly, they induce spectral distortions that yield inaccurate thermal readouts.[12] A way around these conundrums may be to switch detection of the outcoming signal from the spectral domain to the time-based one.
In this work, the robustness of relying on lifetime of the luminescence is evaluated, through near infrared nanoprobes - Ag2S semiconductor nanoparticles (NPs)- as lifetime-LNThs was initially evaluated through ex vivo experiments and simple numerical calculations. After ascertaining the negligible impact of tissue extinction coefficient in the lifetime-based thermal readout, the actual potential of Ag2S NPs as τ-LNThs for thermal monitoring of internal organs, in our case the liver, was demonstrated in an in vivo inflammation model.
Aside from temperature, another biomedically relevant aspect is how the mechanical forces control the function of organisms and mediate the interaction between biological systems and their environments. Knowledge of these forces will increase the understanding of biological processes and can support the development of novel diagnostic and therapeutic procedures.[13,14] Current approaches to measuring forces over a broad range of values are invasive and lack versatility. A promising way to overcome these hurdles is luminescent nanomanometry. Quantum dots (QDs) specifically have optical properties that depend on their size because of the quantum confinement, which makes them responsive to applied forces. Here, a thorough study is conducted on the nanomanometry performance (pressure-dependent photoluminescence) of CuInS2 QDs in the red/near-infrared range. [15, 16] That feature can enable the measurement of mechanical forces in the range of physiological relevance in a remote and minimally invasive way. It is shown that tuning size and stoichiometry can simultaneously enhance the CuInS2 QDs’ brightness and response to applied pressure. Hence, this line of research is providing design guidelines on how fundamental parameters assist the quest for better luminescent nanomanometers.