Microfabricated electrochemical probe for the rapid detection of proteins released by cells

We present a microfabricated electrochemical probe (EP) designed for the detection of biomolecules released by dissociated cells and which is operated on an inverted microscope with real time imaging. The characteristics of the EP are (i) a geometry with a flat, blunt tip that is 200 mum wide, and (ii) two nanoelectrodes that are 200 nm thick, 30 mum long, and spaced 30 mum from one another. The two electrodes are sandwiched between two photopatterned SU-8 layers. The blunt tip corresponds to the cutting plane obtained by dicing through the SU-8 layers and the electrodes. Thus the electrodes are exposed at the dicing surface only and the width of the electrodes is defined by the metal thickness. The EP was characterized electrochemically, and antibodies were immobilized on one nanoelectrode by a selective functionalization using diazonium-adduct electro-addressing to provide specificity against an antigen. The expected concentration at the probe electrodes of molecules released by the cell was calculated using finite element modeling as a function of (i) the gap between the probe and the cell and (ii) the release rate, and shows strong dependency on both parameters.