Cellular analysis based on moving infrared optical gradient fields

A novel, non-invasive measurement technique for quantitative cellular analysis is presented that utilizes the forces generated by an optical beam to evaluate the physical properties of live cells in suspension. Analysis is performed by rapidly scanning a focused, near-infrared laser line with a high cross-sectional intensity gradient across a field of cells and monitoring their interaction with the beam. The response of each cell to the laser depends on its size, structure, morphology, composition, and surface membrane properties; therefore, using this technique, cell populations of different type, treatment, or biological state can be compared. To demonstrate the utility of this cell analysis platform we have evaluated the early stages of apoptosis induced in the U937 cancer cell line by the drug camptothecin and compared the results to established references assays. Measurements on our platform show detection of cellular changes earlier than either of the fluorescence-based annexin V or caspase assays. Because no labeling or additional cell processing is required and because accurate assays can be performed with a small number of cells, this measurement technique may find suitable applications in cell research, medical diagnostics, and drug discovery.