Abstracts

Interaction of living organisms with their environments happens constantly through mechanical forces, as signals, spanning different orders of magnitude which range from the Newton scale at the organ level to the nanoNewton (nN) forces that drive tumor progression, all the way down to the picoNewton (pN) forces related to cell adhesion. Measuring forces at the (sub)cellular level in physiological conditions constitutes a difficult task, but it will bring understanding of biological processes to create new biomedical tools. In that framework, some of the currently applied techniques (atomic force or traction force microscopies; optical tweezers) imply removal of the cell from its medium (non-realistic approach to gather useful knowledge) or require difficult and time-consuming calibrations.Luminescent nanoprobes are promising candidates for nanomanometry because they rely on light emission changes for sensing and have small size. This combination allows measurements to be performed remotely and in a minimally invasive way. Among them, quantum dots (QDs) have emerged as prime nanosensors. This is because quantum confinement effects at the nanoscale allow tuning the optical properties of QDs by controlling their size, hence making them sensitive to applied mechanical forces. Given the surface area of QDs (diameter usually below 10 nm), they GPa-pressure they can monitor translates to single-QD measured forces in the nN-to-μN magnitude, characteristic of biomechanical forces of interest. Specifically, QDs made of copper indium sulfide (CIS) are uniquely attractive for the development of luminescence nanomanometry approaches targeting biological applications. One advantage offered by this material is its lower toxicity compared to Cd- and Pb-based QDs. More essentially for their sensing role, the emission of CIS QDs can be tuned by tweaking different parameters like size, chemical composition, crystal structure, and core/shell architecture.We have studied two series of CIS QDS samples prepared changing their size – by tuning the reaction time – and composition – by varying the amount of copper introduced in the reaction mixture. Investigation in a diamond anvil cell revealed that CIS QDs with an intermediate size (2.8-4.0 nm) afforded a lack of hysteresis, good sensitivity, and a larger operational working range. Control of the stoichiometry of CIS QDs of the selected size via the introduction of copper vacancies, then, allows to simultaneously increase the photoluminescence quantum yield (up to 7%) and the sensitivity (up to.5% GPa−1 for pressures < 0.5 GPa) to externally applied mechanical pressure. CIS QDs can perform as luminescent nanomanometers in pressure and force range of interest for biology, while keeping at minimum concerns over their toxicity, thanks to the lack of metals like cadmium and lead. Future efforts will be devoted to the transfer of CIS QDs to aqueous media and investigating their performance as luminescent nanomanometers in biological systems.