AFM methods for studying the morphology and micromechanical properties of the membrane of human buccal epithelium cell

Abstract

Using AFM methods in air under normal conditions in a wide range of local force effects ({F}_{const}< 40 μN) the relief, functional micromechanical properties (elasticity coefficient K, Young’s modulus E, elastic {Delta h}_{dfrm} and plastic {Delta h}_{stiff} deformations) and adhesive properties (work A of adhesive forces {F}_{adh}={F}_{adh}(x;y)) of the membranes of living adult cells of human buccal epithelium were studied in the presence of a protective layer < 100 nm of buffer solution that prevented the cells from drying. Almost all geometric and functional characteristics of the membrane in the local approximation at the micro- and nanolevels are affected by size effects and obey the laws of fractal geometry. The Brownian multifractal relief of the membrane is characterized by dimension {D}_{f} < 2.56 and irregularities < 500 nm vertically and < 2 μm horizontally. Its response to elastic (≤ 6 nN), active (6–21 nN), or passive (> 21 nN) stimulation ({F}_{const}) is a non-trivial selective process and exhibits a correspondingly elastic (K= 67.4 N/m), active (K= 80.2 N/m) and passive (K= 84.5 N/m) responses. K=K({F}_{const}) and E=E({F}_{const}) depend on {F}_{const}. Having undergone slight plastic deformations {Delta h}_{stiff} < 300 nm, the membrane is capable of restoring its shape. We mapped (E=E(x;y), {D}_{f} = 2.56; {Delta h}_{dfrm}={Delta h}_{dfrm}(x;y), {D}_{f} = 2.68; {Delta h}_{stiff}={Delta h}_{stiff}(x;y), {D}_{f } = 2.42, A=Aleft(x;yright) and {F}_{adh}={F}_{adh}(x;y)) indicating its complex cavernous structure.