Detection of theophylline utilising portable electrochemical sensors

The electrochemical oxidation of theophylline (TP) is investigated utilising screen-printed electrodes. Through thorough investigation of pH, we propose a reaction mechanism, finding that the oxidation of TP is stable over a wide pH range, in particular under acidic conditions. Conversely under alkaline conditions, theophylline fouls the electrode surface. The screen-printed carbon sensors are applied towards the electroanalytical sensing of TP with a remarkable amount of success in aqueous solution at physiological pH. The screen-printed sensors have been shown to be applicable to the detection of TP at unharmful, medicinally relevant (55–110 mM), and toxic concentrations in aqueous media at physiological pH. Thus this work presents a proof-of-concept approach towards TP detection utilising sensors commonly implemented in point-of-care applications

L-Cysteine determination in embryo cell culture media using Co (II)-phthalocyanine modified disposable screen-printed electrodes

Thiol-containing compounds such as L-cysteine have been demonstrated to play an important role in metabolism and cellular growth, acting as powerful antioxidants. Consequently, their analytical determination in biological media has received a considerable amount of attention. In this work, an electrochemical sensor for the accurate electroanalytical determination of L-cysteine is proposed, based upon a Co(II)-phthalocyanine bulk modified disposable screen-printed graphite electrode (CoPc-SPE). Cyclic (CV) and Square Wave (SWV) voltammetry experiments have demonstrated an excellent electrocatalytic activity towards the electrochemical oxidation of L-cysteine using CoPc-SPEs within optimum neutral or basic pH. Moreover, the SWV response of L-cysteine is found to exhibit a linear range of 2.6–200 μM, with a low limit of detection of 4 μM (S/N = 3) and a sensitivity of 0.78 μA cm− 2 μM− 1. Coefficient of variation for reproducibility and repeatability of L-cysteine determination using the CoPc-SPE are 3 and 0.4%, respectively. The effect of inherent interferences such as naturally occurring amino acids, cystine and cysteic acid has been also evaluated. Finally, the applicability of the L-cysteine electrochemical sensor based upon CoPc-SPEs has been successfully demonstrated for the first time for the assessment of L-cysteine in a complex embryo cell culture medium

Electroanalytical overview: The electroanalytical detection of theophylline

In this overview, we explore the electroanalytical determination of theophylline. Theophylline finds use as a bronchodilator for treating diseases such as asthma and chronic obstructive pulmonary disease (COPD). There is a need to measure the concentration of theophylline in pharmaceuticals for QA/QC purposes as well as in plasma samples to ensure the doses of theophylline are at the correct therapeutic levels. If the concentration levels of theophylline deviate from the therapeutic levels (10–20 µg/mL for asthma), then patients can experience adverse effects. As such, there is a desire to progress from traditional laboratory based techniques to portable rapid testing. In this overview, we review the endeavours directed to the development of theophylline electroanalytical sensors, noting current and future trends