title: In situ mechanical characterization of the cell nucleus by atomic force microscopy.
abstract: The study of nuclear mechanical properties can provide insights into nuclear dynamics and its role in cellular mechanotransduction. While several methods have been developed to characterize nuclear mechanical properties, direct intracellular probing of the nucleus in situ is challenging. Here, a modified AFM (atomic force microscopy) needle penetration technique is demonstrated to mechanically characterize cell nuclei in situ. Cytoplasmic and nuclear stiffness were determined based on two different segments on the AFM indentation curves and were correlated with simultaneous confocal Z-stack microscopy reconstructions. On the basis of direct intracellular measurement, we show that the isolated nuclei from fibroblast-like cells exhibited significantly lower Young's moduli than intact nuclei in situ. We also show that there is in situ nucleus softening in the highly metastatic bladder cancer cell line T24 when compared to its less metastatic counterpart RT4. This technique has potential to become a reliable quantitative measurement tool for intracellular mechanics studies.
authors.affiliation: Department of Mechanical and Industrial Engineering, University of Toronto , Toronto, Ontario, Canada M5S 3G8.
authors.forename: Haijiao
authors.initials: H
authors.lastname: Liu
authors.forename: Jun
authors.initials: J
authors.lastname: Wen
authors.forename: Yun
authors.initials: Y
authors.lastname: Xiao
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.forename: Sevan
authors.initials: S
authors.lastname: Hopyan
authors.forename: Milica
authors.initials: M
authors.lastname: Radisic
authors.forename: Craig A
authors.initials: CA
authors.lastname: Simmons
authors.forename: Yu
authors.initials: Y
authors.lastname: Sun
mesh_terms: D001696:Biomechanical Phenomena; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D055595:Mechanical Phenomena; D040542:Mechanotransduction, Cellular; D018625:Microscopy, Atomic Force / Q000295:instrumentation / Q000379:methods*; D009339:Needles