The viscoelastic properties of cells and intracellular transport forces have been studied with micrometer-sized transducers that can handle relatively large forces (tens of nanonewtons). Abdelghani-Jacquin et al. have made magnetic cobalt and iron particles more cell-friendly by plating them with gold in a spontaneous electrodeless reaction to produce a uniform coating. Using thiol chemistry, they then functionalized the particles either by attaching biomolecules directly or by adding a polymer cushion formed of polysaccharides. These beads were used as magnetic tweezers to characterize the local viscoelastic properties of a soft biopolymer film, which showed a purely elastic response when a pulsed magnetic force was applied. They also measured the lateral stiffness, which is related to the shear elastic modulus. — MSL
Langmuir17, 2129 (2001).