Micropipet-Based Pico Force Transducer: In Depth Analysis and Experimental Verification

Abstract

Measurements of forces in the piconewton range are very important for the study of molecular adhesion and mechanics. Recently, a micropipet-based force transducer for this type of experiment was presented (E. Evans, K. Ritchie, and R. Merkel, 1995, Biophys. J., 68:2580-2587). In the present article we give a detailed mechanical analysis of this transducer, including nonlinear effects. An analytical expression for the transducer stiffness at small elongations is given. Using magnetic tweezers (F. Ziemann, J. Rädler, and E. Sackmann, 1994, Biophys. J., 66:2210-2216), we were able to determine the force displacement relation of this transducer experimentally. Forces from approximately 10 pN to 500 pN were applied. Theoretical predictions and experimental results coincide remarkably well.

Effect of loading conditions on the dissociation behaviour of catch bond clusters

“…The iteration proceeds until N , 1, which implies the complete detachment of the cluster. For case 4, an axisymmetric model has been developed following the assembly of previous BFP experiments [39][40][41][42][43][44][45]: a pre-swollen, spherical-shaped red blood cell was used as the force transducer; an elastic orthotropic membrane model was chosen to model the composite lipid bilayer of the membrane; hydrostatic fluid elements were introduced to analyse the mechanical response of the fluid-filled cavity inside the cell. The simulations were performed in three phases: firstly, a portion of the cell was aspirated into the micropipette by a suction pressure of magnitude DP.…”

“…In case 4, the cell dimensions were acquired from previous typical BFP experiments [39][40][41][42][43]: the thickness of cell wall h ¼ 20 nm; the cell radius R 0 ¼ 3.53 mm; the micropipette inner radius R p ¼ 0.95 mm; the initial ligand density r 1 ¼ 5000 mm 22 and initial receptor density r r0 ¼ 30 mm…”

Mechanically enforced bond dissociation reports synergistic influence of Mn2+ and Mg2+ on the interaction between integrin α7β1 and invasin

“…Measurements of mechanically enforced bond dissociation were performed as described by Merkel et al (1999), using two beads, coated with invasin and a 7 b 1 integrin, respectively. One bead is attached to an erythrocyte which serves as a tunable biomembrane force probe (BFP; Evans et al, 1995;Evans and Ritchie, 1997;Simson et al, 1998). The beads are brought together and pulled apart to associate and dissociate the binding partners while recording the rupture forces.…”

Cell mechanics in biomedical cavitation

“…The former is due to its excellent capabilities of simultaneous measurements of both deformation and applied force, while the latter owing to its non-contact and cell friendly nature. Other popular methods include compression method which has various formats in terms of its instrumentation such as micromanipulation method and the so-called 'cell-poking' technique [77], micropipette aspiration method [78], magnetic tweezers [79], etc.…”