In vitrodetection ofsuperoxide anions released from cancer cells based on potassium-doped carbon nanotubes–ionic liquid composite gels

Abstract

A newly developed electrochemical biosensor for the determination of superoxide anions (O₂˙⁻) released from cancer cells using potassium-doped multi-walled carbon nanotubes (KMWNTs)–1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆) ionic liquid composite gels is demonstrated. The KMWNTs–[BMIM]PF₆ can electrocatalyze oxygen reduction to generate a strong current signal in neutral solution. Compared with KMWNTs without [BMIM]PF₆ or MWNTs–[BMIM]PF₆ composites, the KMWNTs–[BMIM]PF₆ can enhance the oxygen reduction peak current by 6.2-fold and 2.8-fold, which greatly increases the detection sensitivity of oxygen. Then, O₂˙⁻ biosensors are fabricated by mixing superoxide dismutase (SOD) in the KMWNTs–[BMIM]PF₆ gels via monitoring oxygen produced by an enzymic reaction between SOD/O₂˙⁻ without the help of electron mediators. The resulting biosensors show a linear range from 0.04 to 38 μM with a high sensitivity of 98.2 μA mM⁻¹, and a lower detection limit of 0.024 μM. The common interferents such as hydrogen peroxide (H₂O₂), ascorbic acid (AA), uric acid (UA), and metabolites of neurotransmitters, do not interfere with the detection of O₂˙⁻. The proposed biosensor is tested to determine O₂˙⁻in vitro and from liver cancer and leukemia cells and shows good application potential in biological electrochemistry.