Detection ofdrug-induced cellular changes using confocal Raman spectroscopy on patterned single-cell biosensors

We report on a cell-based biosensor application that utilizes patterned single-cell arrays combined with confocal Raman spectroscopy to observe the time-dependent drug response of individual cells in real time. The patterned single-cell platform enables individual cells to be easily located and continuously addressable for Raman spectroscopy characterization of biochemical compositional changes in a non-destructive, quantitative manner so that discrete cellular behavior and cell-to-cell variations are preserved. In this study, human medulloblastoma (DAOY) cells were exposed to the common chemotherapeutic agent etoposide, and Raman spectra from patterned cells were recorded over 48 hours. It was found that 87.5% of the cells monitored exhibited a sharp decrease in DNA and protein associated peaks 48 hours after drug exposure, corresponding to cell death. The remaining 12.5% of the cells showed little to no reduction in key Raman biomarkers, indicating their drug resistance. Furthermore, the patterned cell population showed a very similar response to etoposide as confluent cell cultures, as confirmed by flow cytometry. Finally, patterned cells were assessed with TUNEL assay for apoptosis due to DNA fragmentation after etoposide exposure. The results agree well with those from the Raman spectroscopy analysis. This combined biosensor–Raman platform provides a quick, simple way to assess cell responses to chemical and biological agents with high throughput and can be potentially used for a wide variety of biomedical applications such as pharmaceutical drug discovery, toxin tests, and biothreat detection.