Micro-oxygraph device for biosensoristic applications

Oxygen consumption rate (OCR) is a significant parameter helpful to determine in vitro respiratory efficiency of living cells. Oxygen is an excellent oxidant and its electrocatalytic reduction on a noble metal allows to accurately detect it. By means of micro fabrication technologies, handy, low-cost and disposable chip can be attained, minimizing working volumes and improving sensitivity and response-time. With this respect, here is presented a micro-oxygraph device (MOD), based on Clark's electrode principle, displaying many advantageous features comparing to other systems. This lab-on-chip platform is composed of: a three microelectrode detector equipped with a micro-grooved electrochemical cell, sealed with a polymeric reaction chamber. Standard photolithographic and thermal evaporation processes were used to fabricated Au working/counter electrodes and Ag/AgCl reference electrode on a glass slide. A micro-channel was realized by photoresist lift-off technique and a polydimethylsiloxane (PDMS) nano-porous membrane was integrated as oxygen permeable septum (OPM) between the probe and the micro reaction chamber. The chip was characterized by cyclic voltammetry, selecting a potential of -0.8 V for electrochemical measurement. Reproducibility (? response 0.54 µA ± 0.06 SD) and average response time (39.6 sec ± 0.5 SD) were assessed by periodic injection and suction of 0.1 M Na2S2O4. OCR measurements on 3T3 cells, subjected, in real time, to chemical stress on the respiratory chain were able to show that this chip lets to perform consistent metabolic analysis.