Determination of cell interaction forces in suspensions with ultrasonic scattering

Theoretical and experimental results show that ultrasonic scattering of cell suspensions is caused mainly by interaction forces between cells. Therefore, the membrane properties of cells, the electrical charge and the viscoelastic properties, but also the antigen-antibody and receptor-ligand bindings, have a strong influence upon ultrasonic scattering. The theoretical calculation of an autocorrelation function of a scattering region containing statistical isotropical distributed scatterers leads to a closed solution of ultrasonic scattering. Two correcting terms can be calculated in addition to the well known Rayleigh´s solution, i.e. the geometry term of the scattering particles and a correcting function dependent on the interaction forces between the particles. Two systems for the measuring of the Doppler-sonographical scattering coefficient were developed, one a recirculating tube system and a Couette-flow cylinder-cylinder system with a sample volume smaller than 0.5 ml. Employing these systems, both the shear rate and scattering coefficient occurring in the flow can be measured simultaneously. It can be shown that with these methods the simple proof of adhesion receptors of erythrocytes, lymphocytes and platelets is possible