Determining the mechanical properties of apoptotic cells using time resolved acoustic microscopy

Time resolved acoustic microscopy uses ultra-high frequencies (over 100 MHz) to image cells with a resolution up to 1⃗m. Acoustic microscopy has been used since the 1970's for biological observations, however only recently have technological advances allowed the quantification of the physical properties of cells, such as the thickness, sound velocity, acoustic impedance, density, bulk modulus and attenuation using acoustic microsopy. For the first time, the physical properties of MCF-7 cells treated with a chemotherapeutic agent to induce apoptosis were measured using a 375 MHz transducer. It was found the thickness and attenuation increased after apoptosis, while the speed of sound, acoustic impedance, density and bulk modulus were similar within measured error. Acoustic backscatter measurements showed rapid morphological variations in cells undergoing apoptosis, which correlates to optical observations. This indicates extensive activity is occuring within the cell on a time scale of seconds during apoptosis.