Detection of tumor necrosis factor (TNF-α) in cell culture medium with label free electrochemical impedance spectroscopy

Here we present an electrochemical impedance spectroscopy (EIS) based biosensor to detect TNF-α as part of an integrated platform to detect toxicity caused by inflammatory responses in cell culture systems. EIS based biosensors offer label free and low cost solution over conventional methods such as ELISA and have the potential to be integrated with cell culture systems for real time cell monitoring. The biosensor was fabricated on a silicon substrate with an array of gold electrodes which was functionalized with a self assembled monolayer of dithiobis-succinimidyl propionate (DSP). Results indicated that the biosensor was more sensitive (∼57 fM) than ELISA (∼890 fM), and achieved a proportionally decreasing response while detecting TNF-α (1 pg/ml to 100 pg/ml) in culture media. Ethanol amine was used to reduce non specific binding which was confirmed with interferon-γ (IFN-γ) in a competitive assay. Dose response curves were elicited by introducing lipopolysacchride (LPS) in Jurkat cell culture and the supernatant showed an exponential increase in TNF-α production, as detected by the biosensor. Time course results indicated that the biosensor reached a saturation limit after 24 h. Overall, the biosensor has the potential to provide a minimally invasive solution to assess inflammatory responses in real time in integrated cell culture systems.