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Topic Name: Penn Engineers Create Carbon Nanopipettes that may useful for Concurrently Measuring Electrical Signals of Cells during Fluid Injection

Category: Nanobiotechnology

Research persons: Pennsylvania Research Team

Location: University of Pennsylvania, United States

Details

University of Pennsylvania engineers and physicians have developed a carbon nanopipette thousands of times thinner than a human hair that measures electric current and delivers fluids into cells. Researchers developed this tiny carbon-based tool to probe cells with minimal intrusion and inject fluids without damaging or inhibiting cell growth.

Glass micropipettes are found in almost every cell laboratory in the world but are fragile at small scales, can cause irreparable cell damage and cannot be used as injectors and electrodes simultaneously. Haim Bau, a professor in the Department of Mechanical Engineering and Applied Mechanics at Penn, and his team developed tiny carbon-based pipettes that can be mass-produced to eliminate the problems associated with glass micropipettes. Although they range in size from a few tens to a few hundred nanometers, they are far stronger and more flexible than traditional glass micropipettes. If the tip of a carbon nanopipette, or CNP, is pressed against a surface, the carbon tip bends and flexes, then recovers its initial shape. They are rigid enough to penetrate muscle cells, carcinoma cells and neurons.

Researchers believe the pipettes will be useful for concurrently measuring electrical signals of cells during fluid injection. In addition, the pipettes are transparent to X rays and electrons, making them useful when imaging even at the molecular level. Adding a functionalized protein to the pipette creates a nanoscale biosensor that can detect the presence of proteins.

“Penn’s Micro-Nano Fluidics Laboratory now mass-produces these pipettes and uses them to inject reagents into cells without damaging the cells,” Bau said. "We are ultimately interested in developing nanosurgery tools to monitor cellular processes and control or alter cellular functions. We feel CNPs will help scientists gain a better understanding of how a cell functions and help develop new drugs and therapeutics."

Just as important as the mechanical properties of carbon nanopipettes, however, is the ease of fabrication, said Michael Schrlau, a doctoral candidate and first author of the study, “Carbon Nanopipettes for Cell Probes and Intracellular Injection,” published in the most recent issue of Nanotechnology. “After depositing a carbon film inside quartz micropipettes, we wet-etch away the quartz tip to expose a carbon nanopipe. We can simultaneously produce hundreds of these integrated nanoscale devices without any complex assembly,” he said.

The next challenge for researchers is fully utilizing the new tools in nanosurgery.
"We will need to go beyond the proof-of-concept, development stage into the utilization stage," Schrlau said. "This includes finding the appropriate collaborations across engineering, life science and medical disciplines."

Note for Micropipettes 
Micropipettes are tools constructed from glass tubing for microinjection, micromanipulation and measuring purposes. Many types and sizes of glass tubing are available, mainly in three different compositions: borosilicate, aluminosilicate and quartz. Each composition has its own unique properties and the right selection is determined by the application it is used for. Micropipettes are mainly used in biological and chemistry experiments. Normal glass pipettes which are used in chemical labs are not highly accurate for volumes less than 2ml, but micropipettes (autopipettes) are both accurate and precise. Various sizes of micropipettes allow for accurate measurements of volumes less than 1µl, or as large as 1000µl (1ml).

Note for Biosensor
A biosensor is a device for the detection of an analyte that combines a biological component with a physicochemical detector component.
It consists of 3 parts:

• the sensitive biological element (biological material (eg. tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc), a biologically derived material or biomimic) The sensitive elements can be created by biological engineering.
• the transducer in between (associates both components)
• the detector element (works in a physicochemical way; optical, piezoelectric electrochemical, thermometric, or magnetic.)

The most widespread example of a commercial biosensor is the blood glucose biosensor, which uses an enzyme to break blood glucose down. In doing so it transfers an electron to an electrode and this is converted into a measure of blood glucose concentration. The high market demand for such sensors has fueled development of associated sensor technologies.

Note for Carbon Nanotube
Carbon nanotubes (CNTs) are allotropes of carbon. A single-walled carbon nanotube (SWNT) is a one-atom thick sheet of graphite (called graphene) rolled up into a seamless cylinder with diameter on the order of a nanometer. This results in a nanostructure where the length-to-diameter ratio exceeds 1,000,000. Such cylindrical carbon molecules have novel properties that make them potentially useful in many applications in nanotechnology, electronics, optics and other fields of materials science. They exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Inorganic nanotubes have also been synthesized.
Nanotubes are members of the fullerene structural family, which also includes buckyballs. Whereas buckyballs are spherical in shape, a nanotube is cylindrical, with at least one end typically capped with a hemisphere of the buckyball structure. Their name is derived from their size, since the diameter of a nanotube is in the order of a few nanometers (approximately 1/50,000th of the width of a human hair), while they can be up to several millimeters in length. Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs).

The research was supported by an NSF-STTR grant with Vegrandis LLC and the Commonwealth of Pennsylvania through the Nano Technology Institute.