Nanomechanical Probes of Individual Corneal Epithelial Cells

Abstract

Purpose: : A fundamental understanding of the forces acting on the outermost surface of the eye requires input derived from approaches with cellular level sensitivity. This report documents a new approach to this end.

Methods: : Living human corneal epithelial cells have been probed in vitro via atomic force microscopy, revealing the frictional characteristics of the outer surfaces of corneal cells in media.

Results: : Measured shear stresses of 0.40 kPa are amoung the lowest reported values for aqueous lubrication. This is perhaps not surprising, yet the ability to demonstrate the lubricity of single epithelial cell surfaces in contact with a microsphere probe highlights the opportunities for conducting interfacial/solution studies at the cellular level. The mechanical properties of individual epithelial cells have been further probed through nanometer scale indentation measurements. An elastic foundation model, based on experimentally verifiable parameters including cell diameter and thickness, is used to fit the indentation data, producing an effective elastic modulus of 16.5 kPa and highlighting the highly compliant nature of the cell surface. The elastic foundation model is found to more accurately fit the experimental data, to avoid unverifiable assumptions, and to produce a modulus significantly higher than that of the widely used Hertz-Sneddon model.

Conclusions: : The results provide a baseline understanding of the mechanical properties of individual corneal cells and again highlight the opportunities for probing the details of mechanobiology related to the function of the eye surface.

Keywords: cornea: basic science • cornea: epithelium • stress response