Monitoring proliferative activities of hormone-like odorants in human breast cancer cells by gene transcription profiling and electrical impedance spectroscopy

The human estrogen receptor alpha (ER!) mediates the proliferative action of hormones in breast cancer cells by regulating the expression of target genes to control cellular functions. Current methodologies do not permit a real-time assessment of these processes in living cells. We overcome this limitation using electrical cell-substrate impedance sensing for measuring ER!-regulated signaling processes indicative of the onset of cell proliferation to target them for compound screenings. We report that hormone like odorants regulate, similarly as natural estrogen, ER!-mediated gene expression involved in mitogenic and developmental processes in MCF7 breast cancer cells. An odorant concentration-dependent switch in cell responses was detectable already 10–15 h post-stimulation, providing rapid quanti!cation of hormonal activity before cell division occurred. Though ER! exhibits complex regulatory roles our noninvasive approach captures its activity for accelerated screenings of compounds promoting breast cancer cell proliferation expanding the analysis of ER! signaling networks

Real-time high-sensitivity impedance measurement interface for tethered BLM biosensor arrays

This paper presents a switched-capacitor (SC) current integrator circuit for impedance measurement of tethered bilayer lipid membrane (tBLM) biosensors. The circuit comprises a small number of high performance components enabling enhanced experimental flexibility and reliability. The sensitivity is improved significantly by suppressing the output offset through pseudo-differential operation, using R-C components for the reference impedance. The sensing and reference electrodes are excited with low-amplitude differential voltage pulses and the current response to membrane resistance (RM) change of the tBLM biosensor is converted to voltage by a precision, low-noise SC integrator available as a single-package IC. Tests with both electrical models and actual biosensors demonstrated that the proposed circuit operates with high sensitivity and can be used in single chip versions for low-cost and high-sensitive tBLM biosensor arrays, featuring multiple electrode sites

Impedance spectroscopy of ion channels in tethered lipid bilayers

A review. The efficient anal. of the function of ion channels is an important task in many different fields ranging from (bio)analytics and drug-screening to nanoelectronics. Here, the modulation of the channel activity of a synthetic ligand gated ion channel by a specific antibody is measured in tethered lipid bilayers by impedance spectroscopy. Tethered single lipid bilayers with exceptionally high elec. resistances suitable for the detection of a few channels are presented. [on SciFinder (R)

Investigating the function of ion channels in tethered lipid membranes by impedance spectroscopy

A review. The function of biol. important ion channels can be measured in supported lipid membranes by impedance spectroscopy. This approach offers substantial advantages over traditional electrophysiol. measurements. In this article, we present an overview of the field, with a special emphasis on the reconstitution of ion channels in lipid bilayers tethered to gold electrodes and the modulation of their channel activity by specific ligand binding. [on SciFinder (R)

Calcium(2+)-sensitive monolayer electrodes

A Ca2+ sensor based on the admittance change of synthetic membranes supported on derivatized silicon electrodes is reported. The ion-sensitive membranes consist of mixed monolayers of phospholipid and the Ca2+-ligand ETH 1001. The electrodes are characterized electrochem. and their sensor performances are described. Through ion complexation by the neutral ligand, elec. charges are incorporated in the low-dielec.-const. environment of the sensitive layer. The no. of charged complexes and thus the membrane admittance depend on the ion content of the electrolyte. The membrane response to Ca2+ and the competitive binding of other cations are studied. A noncompetitive process is obsd. if several ionophores, each one specific for a different ion, are incorporated in the membrane. Mixed layers with tetradecyl-18-crown-6 and ETH 1001 show both K+ and Ca2+ sensitivity. These electrodes allow direct comparison with a previously reported K+ sensor based on tetradecyl-18-crown-6. [on SciFinder (R)

Determination of the surface concentration of crown ethers in supported lipid membranes by capacitance measurements

The attachment of a tetradecyl chain to the ionophore 18-crown-6 leads to a stronger interaction with a supported lipid monolayer. Some C14-18-crown-6 mols. introduced in the aq. phase are incorporated in the phospholipid membrane. This process is used to produce ionophore contg. lipid monolayers of detd. compn. at the surface of an electrode. The ionophore content and the sensitivity to K+ of these layers are detd. by capacitance measurements. [on SciFinder (R)

A synthetic membrane protein in tethered lipid bilayers for immunosensing in whole blood

Tethered lipid bilayers, containing a transmembrane synthetic ligand-gated ion channel (SLIC), have been formed on gold surfaces. The SLIC was designed as a highly selective receptor and reporter protein to detect antibodies in whole blood, which are of importance in malaria diagnosis. The specific binding of the antibody to the sensor surface was monitored on-line with label-free surface-sensitive techniques either optically by surface plasmon resonance in whole blood or electrically by measuring the channel activity of SLIC in blood serum. We demonstrate the feasibility of a highly sensitive and easily applicable whole blood biosensor on the basis of simple commercially available components. The sensor might find applications in the field of infectious diseases such as point-of-care diagnostics of malaria, high content quality control of blood samples of donors, or monitoring the efficacy of vaccination. (C) 2009 Elsevier Inc. All rights reserved