Figure 2
From: Acute and chronic demyelinated CNS lesions exhibit opposite elastic properties
AFM protocol for the mapping of mechanical properties of CNS tissue. (A) Schematic representation of an AFM elasticity measurement. The deflection of the cantilever (tipped with a spherical probe) resulting from its contact with the sample is used to derive a force-indentation curve (right panel), with slope proportional to sample elasticity. The force-indentation curves are fitted to the Hertz model for spherical probes55 to calculate the Young’s modulus of the sample, expressed in kilopascals (kPa). Multiple measurements performed in a semi-automated manner over a 90 × 90 µm are used to generate heat maps of tissue elasticity, as shown below. (B) Brightfield image of a 100 µm coronal section from a lysolecithin-injected brain prepared for AFM measurement. Red square indicates the 90 × 90 µm area being sampled centered on the tip of the AFM cantilever, and the resulting map of tissue elasticity. The cortex (CTX) and corpus callosum (CC) are clearly identified as is the needle track left by the lysolecithin injection. (C) Representative force measurements from the cortex and anterior corpus callosum of uninjured contralateral hemisphere. Using anatomical landmarks as reference, larger maps of normal tissue stiffness can be assembled from individual scans. The corpus callosum, cingulum (*) and the adjacent cortical layers are mechanically distinct from each other (CP: caudoputamen, VL: lateral ventricle).
