Spearhead Nanometric Field-Effect Transistor Sensors for Single-Cell Analysis.

Nanometric field-effect-transistor (FET) sensors are made on the tip of spear-shaped dual carbon nanoelectrodes derived from carbon deposition inside double-barrel nanopipettes. The easy fabrication route allows deposition of semiconductors or conducting polymers to comprise the transistor channel. A channel from electrodeposited poly pyrrole (PPy) exhibits high sensitivity toward pH changes.

Electrochemical nanoprobes for single-cell analysis.

The measurement of key molecules in individual cells with minimal disruption to the biological milieu is the next frontier in single-cell analyses. Nanoscale devices are ideal analytical tools because of their small size and their potential for high spatial and temporal resolution recordings. Here, we report the fabrication of disk-shaped carbon nanoelectrodes whose radius can be precisely tuned within the range 5-200 nm.

Local delivery of molecules from a nanopipette for quantitative receptor mapping on live cells.

Using nanopipettes to locally deliver molecules to the surface of living cells could potentially open up studies of biological processes down to the level of single molecules. However, in order to achieve precise and quantitative local delivery it is essential to be able to determine the amount and distribution of the molecules being delivered. In this work, we investigate how the size of the nanopipette, the magnitude of the applied pressure or voltage, which drives the delivery, and the distance to the underlying surface influences the number and spatial distribution of the delivered molecules.

Topographical and electrochemical nanoscale imaging of living cells using voltage-switching mode scanning electrochemical microscopy.

We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements.

Realizing the biological and biomedical potential of nanoscale imaging using a pipette probe.

Cells naturally operate on the nanoscale level, with molecules combining together to form complex molecular machines, which can work together to enable normal cell function or go wrong as in the case of many diseases. Visualizing these key processes on the nanoscale has been difficult and two main approaches have been used to date; nanometer resolution imaging of fixed cells using electron microscopy, or imaging live cells using optical or fluorescence microscopy, with a resolution of a few hundred nanometers. Scanning probe microscopy has the potential to allow live cells to be imaged at nanoscale resolution and a noncontact method based on the use of a nanopipette probe has been developed over the last 10 years that allows both topographic and functional imaging.