Corneocyte tomography using nanoneedle afm probes

Research output: Contribution to conferenceAbstract

Abstract

Atomic Force Microscopy (AFM) is a powerful multifunctional technique of modern nanoscience with huge potential for advances in biological research. In particular, due to the very small size of the probes, AFM is the best currently available technique for studying nanoscale mechanics. However, the low aspect-ratio of standard AFM probes typically limits these measurements to surface properties. Fortunately, the recent advent of extremely high aspect-ratio ‘needle’ probes now allows the use of AFM for studies of cellular structure deep below the surface.

In our studies1, we employed an Electron Beam Induced Deposition (EBID) technique to grow a nanoneedle on the apex of a standard AFM probe. EBID is a highly versatile technique that can be used for fabrication of free-standing nanostructures and nanotools (e.g. nanoscalpels)2. We fabricated nanoneedles with lengths of ~500 nm and diameters from 30 to 80 nm3. They are composed of mainly amorphous carbon and are stiff enough to withstand forces of 10-6 -10-5 N without buckling.

The experiments were performed on corneocytes isolated from human stratum corneum using a simple adhesive stripping process. Using the nanoneedle probes allowed us to combine imaging of the cell topography with measurements of mechanical profiles beneath selected points on the cell surface, using the nanoindentation method. This method evaluates the forces experienced by a nanoneedle as it is pushed into and then retracted from the cell. The obtained indentation loops yield the stiffness profile and information on the elastic and non-elastic mechanical properties at a specific depth below the surface of the corneocytes. In particular, the local elastic (Young’s) modulus can be calculated. A clear difference between the softer, ~50nm thick external layer and the more rigid internal structure of corneocytes is apparent, which is consistent with the current understanding of the structure of these cells. There are also significant variations in the mechanical properties of corneocytes from different volunteers, in particular volunteers of different age. The small diameter of the nanoneedle allows this ‘‘mechanical tomography’’ to be performed without significant damage to the cell structure and with high spatial resolution, potentially offering an opportunity to detect biomechanical changes in corneocytes because of, e.g., environmental factors, aging, or dermatological pathologies. Furthermore, the nanoneedle probes may permit the localised injection or extraction of material into and out of the cell at preselected positions and depths.

References
1.Beard JD, Guy RH, Gordeev SN, Mechanical tomography of human corneocytes with a nanoneedle. J Invest Dermatol 2013, 133:1565–71
2.Beard JD, Gordeev SN, and Guy RH, AFM Nanotools for Surgery of Biological Cells. J Phys: Conf Series 2011, 286: 012003.
3.Beard JD, and Gordeev SN, Fabrication and buckling dynamics of nanoneedle AFM probes, Nanotechnology 2011, 22: 175303.
Original languageEnglish
Pages55
Number of pages1
Publication statusUnpublished - 2014
EventPerspectives in Percutaneous Penetration 2014 - La Grand Motte, La Grand Motte, France
Duration: 22 Apr 201425 Apr 2014

Conference

ConferencePerspectives in Percutaneous Penetration 2014
CountryFrance
CityLa Grand Motte
Period22/04/1425/04/14

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    Gordeev, S. (2014). Corneocyte tomography using nanoneedle afm probes. 55. Abstract from Perspectives in Percutaneous Penetration 2014, La Grand Motte, France.