The measurement of pH is important throughout many biological systems, but there are limited available technologies to enable its periodical monitoring in the complex, small volume, media often used in cell culture experiments across a range of disciplines. Herein, pad printed electrodes are developed and characterised through modification with: a commercially available fullerene multiwall carbon nanotube composite applied in Nafion, casting of hydrophobic ubiquinone as a pH probe to provide the electrochemical signal, and coated in Polyethylene glycol to reduce fouling and potentially enhance biocompatibility, which together are proven to enable the determination of pH in cell culture media containing serum. The ubiquinone oxidation peak position (E) provided an indirect marker of pH across the applicable range of pH 6-9 (R = 0.9985, n = 15) in complete DMEM. The electrochemical behaviour of these sensors was also proven to be robust; retaining their ability to measure pH in cell culture media supplemented with serum up to 20% (v/v) [encompassing the range commonly employed in cell culture], cycled > 100 times in 10% serum containing media and maintain > 60% functionality after 5 day incubation in a 10% serum containing medium. Overall, this proof of concept research highlights the potential applicability of this, or similar, electrochemical approaches to enable to detection or monitoring of pH in complex cell culture media.

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The use of bioelectronics is a quickly evolving and developing field offering novel application to solve problems across numerous biological disciplines. Cancer research has focussed on various biomarkers as a means for detection and for potential therapeutic treatments. Several therapies and medications focus on influencing redox state within the cellular environment, with some of these therapies utilising cyclic redox components, allowing for repeated oxidation/reduction at target sites. This offers great potential for electrical (DC and AC) and electrochemical control over the intracellular redox environment. Herein explores the redox circuits in cancer and its metabolism, the influence of mediated oxidative stress in redox altered environments, therapeutics that target specific redox pathways and their redox active proteins, and the implementation of electrochemical interrogation to control the cellular redox environment to manipulate cancer metabolism.

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