Non-invasive approaches to measuring respiratory patterns using a PtTFPP based, phase-lifetime, self-referencing oxygen optrode

Optically transduced sensors (optrodes, or optodes) offer significant advantages over polarographic techniques for measuring oxygen. In biology and medicine, how we make measurements is very important, and this is especially true in terms of physiological exchange. Cellular and tissue oxygenation is a function of background concentration and respiratory demand, and in pure physical terms this is best expressed in terms of molecular flux based on Pick's law. Measuring dynamic flux from biological systems requires sensing technology that can measure activity in multiple dimensions. Here we report the development of a self-referencing oxygen optrode (SRO) for reliably making noninvasive measurements of oxygen flux from a variety of biological systems. The self-referencing microsensor technique was adapted to operate optrodic oxygen sensors through the integration of optical sensing instrumentation with software-controlled data acquisition and micro-stepping motion control. This allows the sensor to scan biologically active gradients of oxygen flux directly, as it relates to cellular and tissue respiratory activity. The technique was validated first using artificially generated oxygen gradients, which are theoretically modelled and compare with measured signals. Subsequently, the SRO was applied in basic research applications to non-invasively measure molecular oxygen flux from a variety of animal and plant systems.