Non-genetic intercellular heterogeneity has been increasingly recognized as one of the key factors in a variety
of core cellular processes including proliferation, stimulus response, carcinogenesis and drug resistance. Many diseases,
including cancer, originate in a single or a few cells. Early detection and characterization of these abnormal cells can
provide new insights into the pathogenesis and serve as a tool for better disease diagnosis and treatment. We report on a
novel technology for multiparameter physiological phenotype characterization at the single-cell level. It is based on real-time
measurements of concentrations of several metabolites by means of extracellular optical sensors in microchambers
of sub-nL volume containing single cells. In its current configuration, the measurement platform features the capability
to detect oxygen consumption rate and pH changes under normoxic and hypoxic conditions at the single-cell level. We
have conceived, designed and developed a semi-automated method for single-cell manipulation and loading into
microwells utilizing custom, high-precision fluid handling at the nanoliter scale.
We present the results of a series of measurements of oxygen consumption rates (OCRs) of single human
metaplastic esophageal epithelial cells. In addition, to assess the effects of cell-to-cell interactions, we have measured
OCRs of two and three cells placed in a single well. The major advantages of the approach are a) multiplexed
characterization of cell phenotype at the single-cell level, b) minimal invasiveness due to the distant positioning of
sensors, and c) flexibility in terms of accommodating measurements of other metabolites or biomolecules of interest.