C arbon nanopipettes (CNPs), nanoprobes that integrate carbon nanotubes (CNTs) into larger easily maneuverable devices, provide a viable means of performing cell surgery with carbon-based nanostructures. Taking advantage of the nanoscopic tubular geometry and unique material properties of CNTs, CNPs facilitate minimally invasive cell probing, low-volume intracellular fluid injection, sensitive electrical measurements of cell signals, and other unique analytical abilities not possible with traditional glass-based cell probing technology. In this technology review, we highlight the cell probing applications where CNPs were used as nanoneedles for intracellular injection and nanoelectrodes for cell electrophysiology. Besides summarizing the proven capabilities of CNPs, the intent of this review is to encourage further development of CNTbased devices and related nanotechnology for novel cell probing and bioanalytical applications. ( JALA 2010;15:145-51)
INTRODUCTIONRecently, there has been a growing interest across diverse fields of science, medicine, and engineering in devices capable of probing and manipulating materials at the nanoscale.1 For instance, in cell biology, nano-sized devices can probe cells and subcellular environments with minimal intrusion to perform nanosurgery.2 These activities include modifying cells (via material injection and removal), sensing cell processes (with optical, biochemical, mechanical, and electrical means), and studying cell structure (by manipulation of organelles and molecules).Glass-based nanoprobes, such as glass micropipettes, are currently used to probe intracellular environments. Glass capillaries are pulled into glass micropipettes with predetermined taper geometry and tip dimensions depending on their intended application. For example, glass-based injectors have short tapers with micrometer-sized tip diameters to facilitate fluid transport, whereas glass-based, electrolyte-filled electrodes have long tapers with tip diameters in the hundreds of nanometers. However, there are several issues associated with glass-based cell probes, such as having fragile tips that break easily when encountering a hard surface, being limited to single functions (e.g., injector or electrode, not both), and having relatively large tips that tend to damage cells and organelles easily. These and other issues were reviewed in more detail.
3The advent of nanotechnology has led to the development of new tools for cell surgery, such as nanoneedles for intracellular injection of material and nanoelectrodes for studying cell signaling. Carbon-based nanostructures, such as carbon nanotubes (CNTs), are particularly useful for probing cells because they are nanoscopic in size, have hollow geometry, and have tunable surface characteristics. CNTs are slender (high length to diameter ratio) and thin walled, possess remarkable mechanical and electrical properties, 4,5 and facilitate the transmission and storage of liquids.6,7 Several groups have used a variety of methods to attach CNTs to macroscopic d...