Abstract
We present non-faradaic electrochemical recordings of exocytosis from populations of mast and chromaffin cells using chemoreceptive neuron MOS (CνMOS) transistors. In comparison to previous cell-FET-biosensors, the CνMOS features control (CG), sensing (SG) and floating gates (FG), allows the quiescent point to be independently controlled, is CMOS compatible and physically isolates the transistor channel from the electrolyte for stable long-term recordings. We measured exocytosis from RBL-2H3 mast cells sensitized by IgE (bound to high-affinity surface receptors FcεRI) and stimulated using the antigen DNP-BSA. Quasi-static I-V measurements reflected a slow shift in surface potential () which was dependent on extracellular calcium ([Ca]o) and buffer strength, which suggests sensitivity to protons released during exocytosis. Fluorescent imaging of dextran-labeled vesicle release showed evidence of a similar time course, while un-sensitized cells showed no response to stimulation. Transient recordings revealed fluctuations with a rapid rise and slow decay. Chromaffin cells stimulated with high KCl showed both slow shifts and extracellular action potentials exhibiting biphasic and inverted capacitive waveforms, indicative of varying ion-channel distributions across the cell-transistor junction. Our approach presents a facile method to simultaneously monitor exocytosis and ion channel activity with high temporal sensitivity without the need for redox chemistry.
Highlights
Released compounds from mast cells impinge on cells expressing specific receptors [Fig. 1(c)] and elicit a downstream response
The readout current and V floating gates (FG) is re-calibrated to this defined level by modulating the control gate (CG) bias
Degranulation in mast cells and action potential activity in chromaffin cells were monitored through quasi-static surface potential measurements, high resolution transient recordings and impedance spectroscopy using chemoreceptive neuron MOS transistor (Cν MOS) transistors
Summary
Released compounds from mast cells impinge on cells expressing specific receptors (such as the histamine receptor on smooth muscle cells) [Fig. 1(c)] and elicit a downstream response. We extend the approach to measuring depolarization induced activity from chromaffin cells where it can function as an electronic post-synaptic sensor [Fig. 1(d)] Such a system provides a test bench for fundamental exocytotic analysis by monitoring release from vesicles and action potential’s with high temporal resolution, which is paramount in understanding cellular kinetics and establishing rapid screening procedures and sets a promising route towards future artificial synapse systems and ionic-electronic interfacing circuitry. Changes in ionic activity sets up a potential within the cleft which capacitively influences the transistor output[19], while chemical changes at the transistor surface such as pH or molecular binding may directly influence the net surface charge[26] Limitations of this approach include the lack of independent control over the transistor’s operating point. One drawback is that, top metal interfaces lack chemical specificity to ionic and molecular adsorption, unless specific functionalized coatings are used
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