Nanomaterial-based electrochemical sensors and optical probes for detection and imaging of peroxynitrite: a review

Peroxynitrite (PON for short) is a powerful nitrating, nitrosating and oxidative agent for cellular constituents. In vivo, PON is formed through the diffusion-controlled reaction between superoxide radical (O2•-) and nitric oxide (•NO). This critical review (with 67 refs.) covers the state of the art in nanomaterial-based (a) detection and imaging of PON inside cells and (b) monitoring of cellular events such as cellular oxidative burst by using optical or electrochemical methods. It starts with the formation, fate and pathophysiology of PON in vivo. The next part summarizes nanomaterial based electrochemical microsensors featuring nanofilms and nanostructured electrodes, nanospheres, 3D nanostructures and graphene-supported catalysts. A following chapter covers techniques based on optical nanoprobes, starting with nanomaterials used in optical detection of PON (including quantum dots, carbon dots, fluorescent organic polymer dots, rare earth nanocrystals including upconversion nanoparticles, iron oxide nanoparticles, gold nanoparticles, and fluorophore-modified nanoporous silicon). This is followed by subsections on strategies for optical detection of PON (including color changes, fluorescence quenching, activation and recovery), and on schemes for optimized spatial and temporal resolution, for improving sensitivity, selectivity, and (photo)stability. We then address critical issues related to biocompatibility, pharmacokinetics, give a number of representative practical applications and discuss challenges related to PON detection. The review concludes with a discussion of latest developments and future perspectives.