Accumulation and detection of secreted proteins from single cells for reporter gene assays using a local redox cycling-based electrochemical (LRC-EC) chip device.

A lab-on-a-chip device is described for the electrochemical detection of alkaline phosphatase (ALP) secreted by transformed single HeLa cells. Detection on the chip device is based on local redox cycling at 256 individually addressable sensor points. Ring-disk electrodes (generator/collector) are arranged at individual sensor points to amplify the signal due to redox-cycling with only 32 connector pads. The surface of each sensor point is modified with antibodies for secreted alkaline phosphatase (SEAP) immobilization, which facilitates separation and detection of SEAP. Separation of SEAP from HeLa cells enables elimination of endogenous ALP and prevents HeLa cells from damage due to exposure to high level pH used during electrochemical detection. The large number of sensor points enables the simultaneous analysis of a large amount of single cells using the chip. The system is useful for gene reporter assays and for the detection of several types of secreted proteins.