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The tumour microenvironment (TME) strongly influences tumorigenesis and metastasis. Two of the most characterized properties of the TME are acidosis and hypoxia, both of which are considered hallmarks of tumours as well as critical factors in response to anticancer treatments. Currently, various imaging approaches exist to measure acidosis and hypoxia in the TME, including magnetic resonance imaging (MRI), positron emission tomography and optical imaging. In this review, we will focus on the latest fluorescent-based methods for optical sensing of cell metabolism and MRI as diagnostic imaging tools applied both in vitro and in vivo. The primary emphasis will be on describing the current and future uses of systems that can measure intra- and extra-cellular pH and oxygen changes at high spatial and temporal resolution. In addition, the suitability of these approaches for mapping tumour heterogeneity, and assessing response or failure to therapeutics will also be covered., Comment: 36 pages, 13 figures

Fine manipulation of fluid flows at the microscale has a tremendous impact on mass transport phenomena of chemical and biological processes inside microfluidic platforms. Fluid mixing in the laminar flow regime at low Reynolds is poorly effective due to the inherently slow diffusive mechanism. As a strategy to enhance mixing and prompt mass transport, here, we focus on polyelectrolyte multilayer capsules (PMCs) embodying a catalytic polyoxometalate as microobjects to create elastic turbulence and as micromotors to generate chaotic flows by fuel-fed propulsions. The effects of the elastic turbolence and of the artificial propulsion on some basic flow parameters, such as pressure and volumetric flow rate are studied by a microfluidic set-up including pressure and flow sensors. Numerical-handling and physical models of the experimental data are presented and discussed to explain the measured dependence of the pressure drop on the flow rate in presence of the PMCs. As a practical outcome of the study, a strong decrease of the mixing time in a serpentine microreactor is demonstrated. Unlike our previous reports dealing with capillarity flow studies, the present paper relies on hydrodynamic pumping experiments, that allows us to both develop a theoretical model for the understanding of the involved phenomena and demonstrate a successfully microfluidic mixing application. All of this is relevant in the perspective of developing microobject based methods to overcome microscale processes purely dominated by diffusion with potential improvements of mass trasport in microfluidic platforms., In Press, Corrected Proof

The realization of microfluidic platforms with liquid pumping and fluid transport independent on external power sources is the goal of a major part of research in the lab-on-chip (LOC) field. Autonomous pumping, indeed, has a strong impact on the cost, usability and portability of LOCs. In this context, power-free pumping is exploited herein by the use of chemically-responsive flexible thin membranes (TMs) as tool to push liquids inside the microchannels of a LOC platform. The assembled device consists of a closed poly(dimethylsiloxane) (PDMS) micro-chamber in which H2O2 dismutation occurs by an artificial catalase (ACat) system, evolving oxygen and generating a pressure gradient. This pressure is then used to push a liquid contained within an upper chamber and inject it into a tailored microfluidic channel. The two chambers are overlapped and separated by a PDMS TM, whose flexibility allows the conversion of the chemical energy into mechanical forces. Thanks to the fine-tuning of the reaction conditions by modulating the ACat catalyst and/or reagents concentrations, a precise control over the injection time and forces of the liquid can be achieved.