Lab on a tip
doi:10.1038/nindia.2010.177 Published online 21 December 2010
Researchers have designed a new endoscope by placing a multiwalled carbon nanotube on the tip of a glass pipette. The tip was made magnetic by filling the nanotube with super-paramagnetic nanoparticles.
The endoscope provides deep cellular penetration, can transport extremely tiny volumes of fluid and is able to record weak signals from cells.
The cylindrical shape, mechanical strength and electrical conductivity of carbon nanotubes make them attractive for cellular probing. Carbon nanotubes displace a hundred to a thousand times less cellular material than glass micropipettes, without causing harm to the cell. To exploit these advantages, the researchers fitted the tip of a glass micropipette with a carbon nanotube. They then made the nanotube magnetic by filling it with magnetic nanoparticles.
When the endoscope tip was brought close to a permanent magnet, the nanotube deflected in response to the magnetic field. This property can be used to generate submicrometre deflections for precise positioning of the tip inside the cell.
The researchers estimate that carbon-nanotube-tipped endoscopes successfully penetrate the cell membrane at least 90% of the time. Unlike with glass pipettes, cells display no visible signs of necrosis in the vast majority (over 90%) of penetrations with the carbon nanotube endoscope. The researchers successfully used the endoscope to inject cadmium selenium quantum dots measuring 6 nm into cervical cancer cells.
Unlike conical pipette probes with similar tip diameters, the carbon nanotube endoscope imparts less mechanical stress on cells when inserted into cells for long periods of time. The tip of the endoscope displaces around 50 times less cellular material than a conical pipette of a similar tip diameter (200 nm).
The unique properties of carbon nanotubes may pave the transition from lab-on-a-chip to 'lab-on-a-tip', the researchers say.
The authors of this work are from: Department of Materials Science and Engineering, Drexel University, Department of Biochemistry and Molecular Biology, School of Biomedical Engineering, Science and Health Systems, Department of Electrical and Computer Engineering, and Drexel Nanotechnology Institute, Drexel University, Philadelphia, Pennsylvania, USA and Department of Chemical Sciences, Indian Institute of Science Education and Research, Kolkata, Mohanpur, Nadia, India.
- Singhal, R. et al. Multifunctional carbon-nanotube cellular endoscopes. Nature Nanotech. doi: 10.1038/nnano.2010.241 (2010)