It has been long known that hydrogen peroxide (H₂O₂) as an endogenous reactive oxygen species (ROS) belongs to a group of destructive molecules that can lead to protein oxidation, lipid peroxidation, and DNA damage. Whereas elevated ROS production leads to oxidative stress, it was also recently shown that at lower physiological levels, H₂O₂ acts as an intracellular signalling molecule regulating kinase-driven pathways¹. As the involvement and concentration levels of H₂O₂ at the cellular level are not fully understood, its localized detection at a cellular level is of particular importance. Fluorescent redox-sensitive dyes are frequently used for the detection of H₂O₂ at the cellular level. H₂O₂ can also be detected electrochemically, e.g. at anodic potentials (0.6 V vs. Ag/AgCl) at Platinum (Pt) electrodes. However, such high oxidation potential can be affected by co-oxidizable substances such as ascorbic acid, catecholamine etc., which may be present in biological samples².

In this contribution, we present strategies of electrochemical H₂O₂ detection avoiding such interference problems based on electrocatalytically or enzyme-modified electrodes. Modification with Platinum black³ or Prussian Blue (PB)⁴ enables the detection at lower potential such as 0.3 V vs. Ag/AgCl at Pt-black modified electrodes and 0.0 V vs Ag/AgCl at PB modified electrodes, respectively. In particular, Prussian Blue (PB) modified electrodes show higher activity and significant higher electrochemical rate constants along with enhanced sensitivity. Hyperoxia treatment is controversial particularly in traumatic brain injury (TBI), due to increased radical and catecholamine production. To study increased release of ROS, measurements at porcine granulocytes and peripheral blood mononuclear cells will be presented using such modified microelectrodes. In addition, the co-detection of catecholamines such as epinephrine using dual sensors will be addressed. In order to study release at the single cell level, we recently introduced conductive colloidal AFM-SECM probes⁵, which serve as electrochemical transducers for the modification with Platinum black or Prussian Blue (PB) allowing the accurate provisioning of the biosensor at the cell surface.

References:

[1] D. R. Gough, T. G. Cotter, Cell Death and Disease 2, e213, (2011)

[2] Y. Zang, et al., Anal. Chem., 66, 1183-1188 (1994).

[3] S. Ben-Amor et al., Electrochim. Acta 126, 171–178 (2014)

[4] A. A. Karyakin, Electroanalysis, 13, 813−819 (2001)

[5] P. Knittel, H. Zhang, C. Kranz, G. G. Wallace and M. J. Higgins, Nanoscale,8, 4475–4481 (2016)