Dual-mode tracking of tumor-cell-specific drug delivery using fluorescence and label-free SERS techniques.

We developed a dual-mode detection method for tumor cell specific targeting and intracellular delivery of the chemotherapeutic agent Doxorubicin (DOX) using folic acid functionalized mesoporous silica nanoparticles (FA-MSNs) as carrier systems. In this method, label free surface enhanced Raman scattering (SERS) spectra were utilized to monitor the dynamic release of DOX inside tumor cells in combination with fluorescence images. To investigate the targeting delivery performance of the carrier system, both normal cells (MRC-5) and tumor cells (HeLa) were used as the model cells. The real-time release of DOX from FA-MSNs inside MRC-5 and HeLa cells was monitored. As demonstrated by both fluorescence and SERS results, the DOX loaded FA-MSNs can actively target FA receptor overexpressed tumor cells. Moreover, the releasing behavior of DOX from FA-MSNs in tumor and in normal cells was quantitatively analyzed. Compared with the traditional sole fluorescence or SERS method, this dual-mode detection is more powerful and more accurate, which should have a potential application in drug tracking in living cells.