Tricolor imaging of MMPs to investigate the promoting roles of inflammation on invasion and migration of tumor cells.

The expression levels of matrix metalloproteinases (MMPs) are closely related to the degree of inflammation which facilitates tumor cells' invasion and migration. A tricolor fluorescence nanoprobe based on high-fidelity gold-selenium (Au-Se) nanoplatform was designed and constructed for simultaneously imaging matrix metalloproteinase-2 (MMP-2), matrix metalloproteinase-7 (MMP-7) and matrix metalloproteinase-9 (MMP-9) to thoroughly investigate the tumor cells' invasion and migration behaviors under inflammation environment. The nanoprobe was assembled by attaching Au NPs with three different peptide substrates respectively labeled with fluorescein isothiocyanate (FITC), 5-carboxytetramethylrhodamine (5-TAMRA) and cyanine 5 (Cy5) via the Au-Se bond. The nanoprobe can specifically respond to MMP-2/7/9, thereby triggering the fluorophores' fluorescence that quenched previously by fluorescence resonance energy transfer (FRET) to realize the MMP-2/7/9's visualization in biological systems. Moreover, as the inflammation stimulated by different concentrations lipopolysaccharide (LPS), the expression of MMP-2/7/9 in SMMC-7721 cells was observed to be significantly enhanced by confocal laser scanning microscope (CLSM) imaging, and inflammation was further proved to intensify SMMC-7721 cells' invasion and migration by transwell invasion and migration experiments. Therefore, the nanoprobe can be used to monitor biomarkers to provide a visual system for the degree of invasion and migration of tumor cells in an inflammatory environment, and also offer a new strategy for the study of the correlation between various active biomacromolecules and specific intracellular pathways in cells.