Direct Measurement of Hydrophobic Forces on Cell Surfaces Using AFM

• Published in: Langmuir 2007-11, Vol.23 (24), p.11977-11979
• Main Authors: Alsteens, David, Dague, Etienne, Rouxhet, Paul G, Baulard, Alain R, Dufrêne, Yves F
• Format: Article
• Language: English
• Subjects: Bacterial Adhesion - physiology; Cell Membrane - chemistry; Cell Membrane - metabolism; Cell Membrane - ultrastructure; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; Hydrophobic and Hydrophilic Interactions; Life Sciences; Microscopy, Atomic Force; Mycobacterium - cytology; Mycobacterium - metabolism; Mycobacterium - ultrastructure; Mycolic Acids - chemistry; Permeability; Surface physical chemistry; Surface Properties
• ISSN: 0743-7463; 1520-5827
• DOI: 10.1021/la702765c

Although hydrophobic forces are of great relevance in biological systems, quantifying these forces on complex biosurfaces such as cell surfaces has been difficult owing to the lack of appropriate, ultrasensitive force probes. Here, chemical force microscopy (CFM) with hydrophobic tips was used to measure local hydrophobic forces on organic surfaces and on live bacteria. On organic surfaces, we found an excellent correlation between nanoscale CFM and macroscale wettability measurements, demonstrating the sensitivity of the method toward hydrophobicity and providing novel insight into the nature of hydrophobic forces. Then, we measured hydrophobic forces associated with mycolic acids on the surface of mycobacteria, supporting the notion that these hydrophobic compounds represent an important permeation barrier to drugs.