Mannose-functionalized diketopyrrolopyrrole as AIE-active probes for lectin detection and cancer cell imaging

Considering that many malignant tumors overexpress the mannose receptors (MR) on the surface, mannosylated dyes can target tumor cells by using specific sugar-protein interactions. An AIE-active probe (DPPM) with two mannose groups based on diketopyrrolopyrrole (DPP) core have been developed in our previous work for probing the specific interactions. In order to evaluate the effects of the number of sugar groups on the probes performance and cell imaging, another two glyco-probes based on DPP conjugated with four (DPPF-M) and six (DPPS-M) mannose groups were designed and synthesized. All three molecules are AIE-active and can recognize concanavalin A (Con A) selectively with nanomolar limits of detection. The increasement of fluorescence of glyco-DPPs in NIR region with addition of lectins is attributed to the aggregates induced by sugar-lectin interactions, which has been determined via dynamic light scattering (DLS) and scanning electronic microscope (SEM) analysis. Since the multiple mannose-ligands on DPPS-M, it successfully stains cancer cells which are overexpressed with MRs on the surface such as MDA-MB-231 and MCF-7 cells through interactions between mannoses and MRs.