A glassy carbon (GC) electrode modified with a CoTPP (5, 10, 15, 20-meso tetraphenylporphyrin cobalt (II)) film was prepared and used as a dissolved oxygen electrochemical sensor. The as-prepared electrode was characterized using atomic force microscopy (AFM) and cyclic voltammetry (CV). The electrochemical behaviour of the CoTPP/GC modified electrode for oxygen reduction in 0.1 mol L-1 KNO3 aqueous solution was compared to that of a bare GC electrode and a decrease in overpotential (similar to 0.30 V) and onset potential (similar to 0.15 V) was noticed. The proposed platform was used as an electrochemical sensor for dissolved oxygen detection, and analytical parameters such as reproducibility, repeatability and long-term stability were determined. The usefulness of the developed sensor was demonstrated by continuous amperometric monitoring of mitochondrial oxygen consumption and the results agreed well with those obtained in parallel measurements performed using a commercial high-resolution "Clark-type" electrode. (C) 2016 Elsevier B.V. All rights reserved.