While the tip rests on top of some types of cells, we observe an oscillatory motion with amplitudes less than 5 nm. By Fourier transforming the oscillatory signal we find that the signal has a frequency in the kHz range...
... Human hearing ranges from about 20 Hz to about 20,000 Hz. The frequencies observed in the study described above are well within the range of human hearing. Inspired by this finding, we have developed a way to convert the motion data into sound, allowing us to listen to the cells...
... The process of “feeling” a cell with the AFM and interpreting its motion as sound is the basis of Sonocytology. Observing the motion of cells in different situations, i.e. cells under stress, generates different sounds. In fact the state of a cell, if it is healthy or cancerous, can be distinguished by listening to its sound. Sonocytology is a diagnostic tool similar to listening to a beating heart. A doctor can diagnose heart conditions by listening to a person’s heart and comparing its sound with the sound of a healthy heart.
However, not all cells display motions that are oscillatory. We have found that cancer cells display a very noisy motion with no particular oscillations. In turn, the resulting sounds are also quite noisy. In the future we hope to bring our research in sonocytology to the point at which it can be integrated into medical disciplines such as cancer research. “Listening to cells” would allow a fast diagnosis of cancer without the use of drugs and/or surgery. Sonocytology might also make cancer detection possible before a tumor forms, and for this detection only one single cell would be needed....
Atomic force microscopy keeps blowing me away. This latest use, though, strikes me more for its value as a research tool, than for its clinical uses. Would it really be cost-effective to set up an AFM in every path lab, to identify those cancers for which there's no probe, no stain, no histological pattern, already? Then again, this NEJM article suggests some tumors influence endothelial cells in surprising ways -- maybe an AFM can help pin down where the transformations end.
Since any change in membrane properties will likely change the cell's pitch, this process could be useful for studying things beyond cancer, like cholesterol metabolism, viral replication, alcohol absorption, or cytoskeletal remodelling. And more and more researchers are using AFMs.
Sometimes I miss the lab. It would have been nice to hear my chondrocytes sing.