Nanomechanical detection of antibiotic-mucopeptide binding in a model for superbug drug resistance.

The alarming growth of the antibiotic-resistant superbugs methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) is driving the development of new technologies to investigate antibiotics and their modes of action. We report the label-free detection of vancomycin binding to bacterial cell wall precursor analogues (mucopeptides) on cantilever arrays, with 10 nM sensitivity and at clinically relevant concentrations in blood serum. Differential measurements have quantified binding constants for vancomycin-sensitive and vancomycin-resistant mucopeptide analogues.

Mitochondrial displacements in response to nanomechanical forces.

Mechanical stress affects and regulates many aspects of the cell, including morphology, growth, differentiation, gene expression and apoptosis. In this study we show how mechanical stress perturbs the intracellular structures of the cell and induces mechanical responses. In order to correlate mechanical perturbations to cellular responses, we used a combined fluorescence-atomic force microscope (AFM) to produce well defined nanomechanical perturbations of 10 nN while simultaneously tracking the real-time motion of fluorescently labelled mitochondria in live cells.

Investigating the molecular mechanisms of in-plane mechanochemistry on cantilever arrays.

Free-standing cantilevers, which directly translate specific biochemical reactions into micromechanical motion, have recently attracted much attention as label-free biosensors and micro/nano robotic devices. To exploit this mechanochemical sensing technology, it is essential to develop a fundamental understanding of the origins of surface stress. Here we report a detailed study into the molecular basis of stress generation in aqueous environments focusing on the pH titration of model mercaptohexadecanoic acid self-assembled monolayers (SAMs), using in situ reference cantilevers coated with nonionizable hexadecanethiol SAMs.

Non-equilibration of hydrostatic pressure in blebbing cells.

Current models for protrusive motility in animal cells focus on cytoskeleton-based mechanisms, where localized protrusion is driven by local regulation of actin biochemistry. In plants and fungi, protrusion is driven primarily by hydrostatic pressure. For hydrostatic pressure to drive localized protrusion in animal cells, it would have to be locally regulated, but current models treating cytoplasm as an incompressible viscoelastic continuum or viscous liquid require that hydrostatic pressure equilibrates essentially instantaneously over the whole cell.

Estimating the sensitivity of mechanosensitive ion channels to membrane strain and tension.

Bone adapts to its environment by a process in which osteoblasts and osteocytes sense applied mechanical strain. One possible pathway for the detection of strain involves mechanosensitive channels and we sought to determine their sensitivity to membrane strain and tension. We used a combination of experimental and computational modeling techniques to gain new insights into cell mechanics and the regulation of mechanosensitive channels.

Determination of cellular strains by combined atomic force microscopy and finite element modeling.

Many organs adapt to their mechanical environment as a result of physiological change or disease. Cells are both the detectors and effectors of this process. Though many studies have been performed in vitro to investigate the mechanisms of detection and adaptation to mechanical strains, the cellular strains remain unknown and results from different stimulation techniques cannot be compared.

Single cell mechanotransduction and its modulation analyzed by atomic force microscope indentation.

The skeleton adapts to its mechanical usage, although at the cellular level, the distribution and magnitude of strains generated and their detection are ill-understood. The magnitude and nature of the strains to which cells respond were investigated using an atomic force microscope (AFM) as a microindentor. A confocal microscope linked to the setup enabled analysis of cellular responses.