Copper Nanosheet-Based Wash-Free Fluorescence Imaging of Cancer Cells.

Near-infrared fluorescence (NIRF) probes greatly facilitate in vivo imaging of various biologically important species. However, there are several significant limitations such as consuming washing steps, photobleaching, and low signal intensity. Herein, we synthesized fluorescent copper nanosheets templated with DNA scaffolds (DNS/CuNSs). We employ them and Cy5.5 of the fluorescence resonance energy transfer (FRET) system, which have a larger Stokes shift (∼12-fold) than the traditional NIRF dye Cy5.5. Based on their excellent fluorescence properties, we employ DNS/CuNSs-Cy5.5 for fluorescence probes in cancer cell imaging. Compared with the free Cy5.5 fluorescence probe, the novel fluorescence imaging probe implements wash-free imaging and exhibits enhanced anti-photobleaching ability (∼5.5-fold). Moreover, the FRET system constructed by DNS/CuNSs has a higher signal amplification ability (∼4.17-fold), which is more similar to that of Cu nanoclusters prepared with DNA nanomonomers as a template. This work provides a new idea for cancer cell MCF-7 imaging and is expected to promote the development of cancer cell fluorescence imaging.