Direct force measurements of biomolecular interactions by nanomechanical force gauge

Without using the laser and optical detection method of an atomic force microscope (AFM), direct force measurements of biomolecular interactions in biological solution are accomplished by a nanomechanical force gauge. The device consists of integrated nanoscale single-crystal Si cantilever and reading scales, which allow the direct measurements of biomolecular interactions by reading the deflection of the cantilever with an optical microscope. The spring constant of the cantilevers was calibrated by measuring the resonant frequency under electrostatic force excitation, and the minimum value among the designed devices shows 80 pN/μm. The piconewton regime dissociation force between a biotinylated bead and streptavidins in an aqueous solution was directly measured with this device.