Resumen de In vivo luminescence thermometry: Addressing the tissue-induced perturbations
In this thesis, we concentrated our discussion on the reliability of luminescence thermometry under in vivo conditions. For that research area, the accuracy provided by luminescent thermometers is dependent on two main parameters: (i) the brightness of the probes, and (ii) the optical response from the tissue where the signal travels through. In this sense, this thesis provided five pieces of work that touched on these aspects. The first of these works brings the proposal of a new synthesis method capable of enhancing the brightness of near-infrared emitting Ag2S NPs (material of choice for the whole thesis) by irradiating them in a chloroform dispersion with femtosecond laser pulses. The formation of a protective AgCl shell on the surface of such Ag2S NPs, leading to a significant increment in the quantum yield (80-fold increment) and fluorescence lifetime (over 20 times). The second work defied the long-held assumption that the low attenuation coefficients of tissues in the so-called Near-Infrared Biological Windows (NIR BWs) had little to no impact on the signal provided by luminescent thermal probes. In fact, erroneous thermal readouts as large as 11 ºC were observed. At this point, it became pivotal to propose new methodologies to account for these artifacts or, by the very least, minimize their effect on the interpretation of the data. Three different approaches were shown to be effective in this regard: (i) the concomitant use of multiple thermometric parameters, (ii) the use of calibrations provided by computational simulations of heat diffusion, and (iii) the utilization of fluorescence lifetime as the sensing parameter. The third, however, stood out as it enhanced the accuracy of the thermal reading at the experimental level. The results here presented unequivocally signal the reestablishment of luminescence thermometry as a reliable technique for biomedical applications.
