Label-free immunoassay based on functionalized nanopipettes

Paolo Actis 1Miloslav Karhanek 1Olufisayo Jejelowo 2Nader Pourmand 1

1. University of California Santa Cruz, Department of Biomolecular Engineering, 1156 High Street, MS SOE2, Santa Cruz 95064, United States
2. Texas Southern University (TSU), 3100 cleburne street, Houston, TX 77004, United States


Nanopipette technology is capable of detecting biomolecules based on difference on their size, shape and electrical charge. This unique label-free biosensor is inexpensive, easy to fabricate and versatile. It gives a fast and real time outuput even in small reactions volume (attoliters). At this point, the nanopipette size and geometry, together with the surface chemistry preparation for attachment of an antibody was optimized by both experiments and modeling to result in detectable signals by the nanopipette. In this phase, the goal of the surface chemistry procedure was to prepare nanopipette tip in a way that only controlled amount of the surface is functionalized and used for probe attachment. Preliminary experiments are demonstrating the sensitivity and selectivity of this technique with specific proteins targeting HPV as well as environmental toxins. These results prove that nanopipettes functionalized with apporporiate molecular recognition elements can be used as HPV/toxin sensors. A highly sensitive nanopipette probe can be precisely positioned, unlike other nanosensing technologies, at any subcellular region of a single living cell with submicron accuracy using a micromanipulator. This approach uses a movable sensor on an attached cell, inĀ  contrast to a fixed sensor detecting responses from floating cells. The functionalized nanopipette paves the way for in vivo immunoassay down to the single cell level.


  1. S. Umehara, N. Pourmand, C.D. Webb, R.W. Davis, K. Yasuda and M. Karhanek, Nano Lett., 2006, 6, 2486.
  2. S. Umehara, M. Karhanek, R.W. Davis and N. Pourmand, PNAS, 2009,106,4611

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Presentation: Keynote lecture at SMCBS'2009 International Workshop, by Paolo Actis
See On-line Journal of SMCBS'2009 International Workshop

Submitted: 2009-08-26 20:49
Revised:   2009-08-26 20:50