DNA strand displacement based surface-enhanced Raman scattering-fluorescence dual-mode nanoprobes for quantification and imaging of vascular endothelial growth factor in living cells.

Vascular endothelial growth factor (VEGF) is an important over-expressed growth protein during cell proliferation process, which has been regarded as a pivotal biomarker of several cancers mainly including malignant melanoma (MM). The development of accurate quantification analysis combined with imaging technology for biomarkers in complex biological system is significantly essential. In this study, surface-enhanced Raman scattering-fluorescence (SERS-FL) dual-mode nanoprobes based on Au nanoparticles modified magnetic FeO nanoparticles (FeO/AuNPs) were fabricated for in situ quantification and imaging of VEGF in living cells. Dual-mode SERS quantification-FL imaging was achieved through "off-on" mode of SERS and FL signals based on DNA strand displacement strategy. The stellate FeO/Au endowed the great magnetic separation function for SERS quantification-FL imaging performance. Under the optimum conditions, the SERS quantification mode for trace VEGF in cell lysis samples achieved the good linearity in the range of 0.01-50.0 ng/mL with an excellent limit of detection of 2.3 pg/mL (S/N = 3). The FL imaging mode could achieve the selective detection of trace VEGF distributing in living tumor cells. The developed dual-mode SERS-FL method could provide accurate quantification and imaging results, which was highly expected to have broad application for the selective, sensitive and accurate analysis of biomarkers in complex cell or other real biological samples.