Elastic Scattering Spectroscopy as a Diagnostic Tool for Apoptosis in Cell Cultures

Apoptosis, ldquoprogrammed cell death,rdquo is a cellular process exhibiting distinct biochemical and morphological changes. There is much interest regarding the role of apoptosis in cancer and the response to cancer treatment. Although apoptosis can occur spontaneously in malignant tumors and often significantly retards their growth, the initial response to successful cancer treatment is often massive apoptosis. In typical in vitro studies, current apoptosis detection methods require cell culture disruption via fixation, trypsinization, and/or staining. Our aim is to develop a nondisruptive optical method of detecting and tracking apoptosis in living cells and tissues, initially focusing on cell cultures. Such a method would allow for real-time evaluation of apoptotic progression of the same cell culture over time without perturbation or alteration. We report initial studies on the use of in vitro elastic scattering spectroscopy (ESS) to monitor changes in light-scattering properties of cells due to apoptotic morphology changes. For a sequence of times post treatment, we have measured the angle-dependent scattering at a single wavelength and also the wavelength-dependent scattering at discrete angles, of treated and control cell cultures. A novel polar nephelometer, developed in our laboratory, was used to obtain the angle-dependent scattering for the range of 90-145. Wavelength-dependent ESS measurements were made with a spectrometer, for several discrete near-forward angles. The results indicate that light scattering measurements can reliably discriminate between treated and control cells, correlating well with benchmark assays for apoptosis.