Cell breakage techniques

The techniques that have been used to characterise the mechanical properties of microparticles may be classified as indirect and direct. The former includes measurement of breakage in a "shear" device, for example, a stirred vessel (Poncelet and Neufeld, 1989) or bubble column (Lu et ah, 1992). However, the results from these indirect techniques are rather difficult to use since the mechanical breakage depends not only on the mechanical properties but also the hydrodynamics of the processing equipment, and the latter are still not well understood. To overcome this problem, a cone and plate viscometer that can apply well-defined shear stresses has been used to study breakage of hybridomas (Born et ah, 1992), but this is not a widely applied or applicable technique because the forces are too small to break most cells. 

None of these indirect techniques relate the breakage of an individual particle to its mechanical properties. To achieve this, direct techniques are required. These are described later, and their capabilities and limitations discussed. Direct techniques also allow more sophisticated mathematical modelling to be undertaken, which is particularly valuable when the particles are not homogeneous, for example, cells with walls and membranes surrounding cytoplasm, or a liquid-filled microcapsule. 

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