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The main role of mitochondria, as pivotal organelles for cellular metabolism, is the production of energy (ATP) through an oxidative phosphorylation system. During this process, the electron transport chain creates a proton gradient that drives the synthesis of ATP. One of the main features of tumoral cells is their altered metabolism, providing alternative routes to enhance proliferation and survival. Hence, it is of utmost importance to understand the relationship between mitochondrial pH, tumoral metabolism, and cancer. In this manuscript, we develop a highly specific nanosensor to accurately measure the intramitochondrial pH using fluorescence lifetime imaging microscopy (FLIM). Importantly, we have applied this nanosensor to establish differences that may be hallmarks of different metabolic pathways in breast cancer cell models, leading to the characterization of different metabophenotypes.

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Fluorescence Lifetime Imaging Microscopy (FLIM) has been employed for the detection of intracellular Zn(2+) levels, implicated in various signalling pathways, using a family of quantum dot (QD) nanosensors. The sensing mechanism was based on photoinduced electron transfer (PET) between an azacycle receptor group and the QD nanoparticles.

The binding processes of two Polo-like kinase inhibitors, RO3280 and GSK461364, to the human serum albumin (HSA) protein as well as the protonation equilibria of both compounds have been studied combining absorbance and fluorescence spectroscopy experiments together with density functional theory calculations. We found that the charge states of RO3280 and GSK461364 are +2 and +1, respectively, at the physiological pH. Nevertheless, RO3280 binds to HSA in the charge state +1 prior to a deprotonation pre-equilibrium. Binding constants to site I of HSA of 2.23 × 106 and 8.80 × 104 M–1 were determined for RO3280 and GSK461364, respectively, at 310 K. The binding processes of RO3280 and GSK461364 to HSA are entropy- and enthalpy-driven, respectively. The positive enthalpy found for the RO3280-HSA complex formation could be related to a proton pre-equilibrium of RO3280.