Biomechanical measurements in the fast lane

The mechanical properties of cells and their environments strongly influence how biological systems function. They can determine the cells’ shapes, dictate how the cells move, and even affect gene expression. When it comes to investigating those properties, though, traditional biophysical techniques, such as bulk rheological measurements, take a long time and can require large sample volumes. Now Richard Superfine, Leandra Vicci, and their colleagues at the University of North Carolina at Chapel Hill have built a microscope system to speed up the process. Shown here, their shoebox-sized instrument is an array of 12 independent fluorescence microscopes, whose objectives are spaced to work with a standard lab plate with 96 sample wells. Three stepper motors move the lab plate in an automated sequence over the objective array. The package is designed for a technique called passive microrheology, which measures the mechanical properties of a biofluid by tracking the thermal motion of small, fluorescent tracer beads embedded in it. In their demonstration, the researchers confirmed that the microscopes could correctly measure the viscosities of several well-known Newtonian fluids. Then they simultaneously measured 12 solutions of hyaluronic acid, a biopolymer found in extracellular tissue, at different concentrations. The measured viscosities compare well with other groups’ reported measurements. And with the new microscope, the researchers say such measurements can be made nearly 100 times faster than with conventional techniques. (J. Cribb et al., Rev. Sci. Instrum., in press.)