title: Exchangeable colloidal AFM probes for the quantification of irreversible and long-term interactions.
abstract: An original method is presented to study single-colloid interaction with a substrate in liquid environment. Colloids, either in solution or adsorbed on a surface, are fixed by suction against the aperture of a microchanneled atomic force microscopy cantilever. Their adhesion to the substrate is measured, followed by their release via a short overpressure surge. Such colloid exchange procedure allows for 1), the quick variation of differently functionalized colloids within the same experiment; 2), the investigation of long-term interactions by leaving the colloids on a surface for a defined time before detaching them; and 3), the inspection of irreversible interactions. After validation of the method by reproducing literature results obtained with traditional colloidal atomic force microscopy, the serial use of colloids with different surface functionalization was shown on a micropatterned surface. Finally, concanavalin A-coated colloids were allowed to adsorb on human embryonic kidney cells and then detached one by one. The adhesion between cells and colloids was up to 60 nN, whereas individual cells adhered with 20 nN to the glass substrate. A cellular elastic modulus of 0.8 kPa was determined using the attached colloid as indenter.
authors.affiliation: Laboratory of Biosensors and Bioelectronics, Institute for Biomedical Engineering, ETH Zurich, Zurich, Switzerland.
authors.forename: Pablo
authors.initials: P
authors.lastname: Dörig
authors.forename: Dario
authors.initials: D
authors.lastname: Ossola
authors.forename: Anh Minh
authors.initials: AM
authors.lastname: Truong
authors.forename: Monika
authors.initials: M
authors.lastname: Graf
authors.forename: Flurin
authors.initials: F
authors.lastname: Stauffer
authors.forename: János
authors.initials: J
authors.lastname: Vörös
authors.forename: Tomaso
authors.initials: T
authors.lastname: Zambelli
mesh_terms: D002448:Cell Adhesion / Q000187:drug effects; D003102:Colloids / Q000737:chemistry* / Q000494:pharmacology; D003208:Concanavalin A / Q000737:chemistry; D055119:Elastic Modulus; D057809:HEK293 Cells; D006801:Humans; D018625:Microscopy, Atomic Force
chemical_list: D003102:Colloids; D003208:Concanavalin A