Construction and use of an integrated electrochemical device for the detection of biologically relevant compounds released from non-adherent cells: Application for the electrochemical determination of nitric oxide produced by human U937 cells

This paper reports on a conceptually new experimental device dedicated to the electrochemical measurements of nitric oxide produced by non-adherent cells. This device is constructed within a well of a standard 24-well cell culture plate. It is composed of three compartments: one for drug injection (PMA, l-NAME, DMSO or PBS); one for the positioning of the electrodes; and the third, where the non-adherent cells are introduced, allowing cell seeding, removal and eventually re-introduction for a second round of study. The NO sensor used in this study is a modified Pt-Ir/NiTSPc/Nafion^® needle-type electrode. The validation of the protocol was executed using U937 promonocytic cells. The obtained results clearly show that NO production by non-adherent U937 PMA-activated cells can be electrochemically detected without complications related to the contamination of the electrode surface during measurement by wrapping of the circulating cells around the sensitive part of the sensor. These results constitute the first example for elaborating on such an approach.