title: Remote opto-acoustic probing of single-cell adhesion on metallic surfaces.
abstract: The reflection of picosecond ultrasonic pulses from a cell-substrate interface is used to probe cell-biomaterial adhesion with a subcell resolution. We culture monocytes on top of a thin biocompatible Ti metal film, supported by a transparent sapphire substrate. Low-energy femtosecond pump laser pulses are focused at the bottom of the Ti film to a micron spot. The subsequent ultrafast thermal expansion launches a longitudinal acoustic pulse in Ti, with a broad spectrum extending up to 100 GHz. We measure the acoustic echoes reflected from the Ti-cell interface through the transient optical reflectance changes. The time-frequency analysis of the reflected acoustic pulses gives access to a map of the cell acoustic impedance Zc and to a map of the film-cell interfacial stiffness K simultaneously. Variations in Zc across the cell are attributed to rigidity and density fluctuations within the cell, whereas variations in K are related to interfacial intermolecular forces and to the nano-architecture of the transmembrane bonds.
authors.affiliation: Univ. Bordeaux, I2M, UMR 5295, F-33400 Talence, France; CNRS, I2M, UMR 5295, F-33400 Talence, France.
authors.forename: Maroun
authors.initials: M
authors.lastname: Abi Ghanem
authors.forename: Thomas
authors.initials: T
authors.lastname: Dehoux
authors.forename: Omar F
authors.initials: OF
authors.lastname: Zouani
authors.forename: Atef
authors.initials: A
authors.lastname: Gadalla
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Durrieu
authors.forename: Bertrand
authors.initials: B
authors.lastname: Audoin
mesh_terms: D002448:Cell Adhesion; D009000:Monocytes / Q000166:cytology; D055620:Optical Phenomena; D059010:Single-Cell Analysis / Q000379:methods*; D013499:Surface Properties; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D014465:Ultrasonics / Q000379:methods*
chemical_list: D014025:Titanium
keywords: cell adhesion; cell mechanics; photoacoustic; ultrasound