Spatially resolved local intracellular chemical sensing using magnetic particles

In this paper we present a new approach that allows spatially resolved local intracellular chemical sensing using a hybrid magnetic chemical sensor which can be actively manipulated inside a cell. This approach allows the sensor to be maneuvered to specific locations in the cell without the need of additional specific biochemical targeting. The approach causes minimal interference within the cell as only a single particle is needed to measure the chemical property at different sites inside the cell. In addition high differential accuracy in measuring the chemical property can be achieved as the same sensor is used to measure at different locations, and therefore the measurements are not affected by sensor-to-sensor variations. To this end we couple a chemical sensor to a magnetic particle and use magnetic tweezers to position and move the sensor inside the living cell in order to measure local chemical properties at different sites inside the cell. We illustrate the potential of this approach by moving a phagocytosed hybrid pH-sensing magnetic particle through a cell while simultaneously measuring the pH of the phagosome.