Measurement of physiological relevant molecules in and at individual cells with minimal disturbance of the cellular function is a key challenge in single-cell analysis. Ad­vantages of nanoscale electrochemical probes include their high spatial and tempo­ral resolution as well as a low substrate consumption. Carbon nanoelectrodes (CNEs) with a tunable radius between a few and several hundreds of nanometres can be fabricated by pyrolytic decomposition of alkane gas in glass nanopipettes. Their needle-type shape and small size enable electro­chemical measurements inside of single living cells. Two potential applications of CNEs namely for the design of nanometer-sized amperometric biosensors, and as the basis for gate-modulated reduced graphene oxide based transistors are presented.

However, the probability that a nanosensor is positioned close to a release site is tiny. Hence, we propose to combine scanning electrochemical microscopy (SECM) with bipolar electrochemistry (BPE) as a new approach to image heterogeneous electrochemical surface processes. The core of the system is a closed bipolar electrochemistry configuration comprising as the bipolar electrode (BPE) a microelectrode as SECM tip (cathodic pole of the BPE) connected with a microelectrode tip (anodic pole of the BPE) in the second half cell. Reduction processes enabled by a suitably applied feeder electrode voltage difference at the SECM tip in the sample generation/tip collection mode are transduced into an optical read-out e.g. electrochemiluminescence at the other pole which is visualized with a high sensitive CCD camera. Evidently, this configuration can be extended to multi-barrel SECM tips thus being able to simultaneously visualize the release of compounds at multiple locations while positioning the multi-barrel microelectrode above a release site of interest.

Acknowledgement: All coworkers who have contributed to this research are acknowledged namely Jan Clausmeyer, Vera Eßmann, Carla Santana Santos, Tsvetan Tarnec, Thomas Erichsen, Miriam Marquitan, Patrick Wilde, Thomas Quast, Corina Andronescu, Federica Mariani. The author is grateful to the project "Graphtivity" funded in the framework of the FLAG-ERA Joint Transnational Call (JTC) 2015 (Graphene Flagship) and the Deutsche Forschung­gemeinschaft in the framework of the cluster of excellence RESOLV (EXc1069).