Detecting early-stage apoptosis using stimulated Raman scattering microscopy

Monitoring apoptosis at the early stage would help maintain the efficiency of the production of recombinant proteins, such as monoclonal antibodies. However, existing methods of monitoring apoptosis are time-consuming and require the introduction of exogenous sensing molecules. In this work, we demonstrated stimulated Raman scattering (SRS) microscopy as a reliable tool to evaluate early-stage apoptosis in a label-free manner. Due to apoptosis-associated hypertonicity, the condensation of proteins in apoptotic cells results in stronger SRS signals than those in healthy cells in the C-H stretching region. We evaluated this optical signature for detecting apoptosis induced by various factors, including staurosporine, hydrogen peroxide, and blue light, across different cell lines such as CHO-K1, HeLa, and yeast. This method is valid for both adherent and suspended cells and can be combined with microfluidics for the rapid assessment of cell viability in drug production processes.