MEMS Device to Monitor Biological Oxygen Uptake at Arrays of Single Cells and Small Cell Clusters

Abstract

Oxygen uptake by a cell is indicative of metabolic processes which are modulated by extracellular stimuli and is characteristic of a cells physiological status. In this work, a MEMS platform with an array of microsensors to monitor these processes at cell constructs is being developed. An array of Pt microring electrodes has been fabricated to quantitatively assess oxygen uptake by normal and pharmacologically manipulated BAC1.2F5 macrophage cells positioned at cell attachment sites inside the microrings. An amperometric pulsing protocol was implemented to reduce interference with cellular metabolism caused by depletion of oxygen during the measurement. We were able to detect changes as small as 1% in oxygen concentration in the vicinity of single cells and small cell clusters. Thus, the approach can be used for sensitive indication of oxygen uptake by cell(s) and its modulation by environmental factors such as pharmacological agents, and interaction with adjacent cells. Moreover, parallel experiments at different cell attachment sites are made feasible by the sensor array. This can provide multiple data sets for biostatistics in the same amount of time that is required to get a single data set.

Electrochemical mapping of oxygenation in the three-dimensional multicellular tumour hemi-spheroid

“…As shown in our earlier work [75] at a single cell pO 2 is about 19% in air-saturated medium. Oxygen levels around 15% were found at a cluster of five cells.…”

“…It is noted that an analogous approach was used earlier in our work to determine oxygen consumption by a single cell [75]. Here, the cell is surrounded by a microfabricated ring ultramicroelectrode.…”

“…A diffusional overlap between adjacent electrodes is negligible despite their closeness to each other. From the duration of the O 2 reduction peak (about 1 s, from [75]), the diffusion coefficient of molecular oxygen in buffer (2.1 × 10 −5 cm 2 s −1 ) and the fact that there is a considerable edge effect at the 50 µm disc electrodes, it is estimated that the extension of the oxygen depletion is less than half of the distance between two electrodes (not shown).…”